Guys, I searched a lot for something like this and it seems nobody did this for dummies. So being one myselff I decided to post something :icon_mrgreen:
First of all here is the theory behind this:
http://www.geofex.com/Article_Folders/ffselect.htm
Here you have the pcb and layout for the circuit noted in the above link
https://mega.co.nz/#!gt5hibYI!9vbFakCUUPgjxATjofUDmreCp7Lp6QfwLrRtNXxaFEw (https://mega.co.nz/#!gt5hibYI!9vbFakCUUPgjxATjofUDmreCp7Lp6QfwLrRtNXxaFEw)
Download and burn. You have to hand pick a resistor that is closest to 2.2M, and with a muti turn pot, dial 2,472 (or 2,47 if your DMM goes off range)
Populate the board.
After that hook up everything as per the diagram in the first link. The board silkscreen tells you were you have to connect everything anyway :icon_biggrin:.
When your done, pinch your Germanium Tranny on the socket, paying attention to the pinout.
Set your DMM to DC Voltage in the 2v range and read the value. Write it down
Press the switch at the board. Write that down
Load that values in this spreadsheet . (idea taken from here http://www.diystompboxes.com/smfforum/index.php?topic=102014.msg910364#msg910364)
https://mega.co.nz/#!Jxp1DSQJ!P0kSoyHGug41b3j-6kr3oYj9TxempQMUc4q9Jbjw7es (https://mega.co.nz/#!Jxp1DSQJ!P0kSoyHGug41b3j-6kr3oYj9TxempQMUc4q9Jbjw7es)
First column first reading, 2nd column 2nd reading.
The leakage current and hfe will appear at 3rd and 4th columns respectively
Thats all.
Tell me if there is any error in the steps and I'll correct it.
Regards!
Awesome! I'll give it a go when I can get to a computer that can actually run the spreadsheet.
If the voltage supply is different from 9V, can that be input and will it compensate?
I think if you mess with the 9v power supply that will mess with the 4uA calculations. That needs to be exact 9v for accuracy.
I just copied the formula from the topic above, (http://www.diystompboxes.com/smfforum/index.php?topic=102014.msg910364#msg910364)
Maybe DiscoVlad could clarify it.
If you are asking about the spreadsheet, it is made dinamicaly so if you change the 9v at the Psupply section it will change the other values.
You don't really need to use a pot to get exactly 2,472 Ohms, R.G only uses that value because it works out that you just take the voltage you measure and multiply it by 100 to get the gain, which is easy to do in your head. The formula you use in your spreadsheet calculates the gain in a different way so there's no need to use the exact value you can just use a 2.4k resistor.
Hi Slacker!
Great news. I was just re reading Rg article and I can't realize why he picked that resistor value
In fact, that resistor is just an excuse to use the voltimeter at the DMM and then calculating the current with the Ohms law.
There you can just stick the DMM in series and use the current measurement function setted in a lower multiplier...
There is a tutorial on FSB that is very good for beginers.
I would link to it but apparently that is forbidden on this site. Search for "RG's Tester for Idiots" and you should find it.
http://tinyurl.com/k5j5f5t
Quote from: slacker on April 28, 2014, 03:34:38 PM
You don't really need to use a pot to get exactly 2,472 Ohms, R.G only uses that value because it works out that you just take the voltage you measure and multiply it by 100 to get the gain, which is easy to do in your head. The formula you use in your spreadsheet calculates the gain in a different way so there's no need to use the exact value you can just use a 2.4k resistor.
Grab a few 30k & a few 2k7 resistors and bingo...
(http://i216.photobucket.com/albums/cc305/davent/IMG_5802_zpsf28c0b05.jpg)
Quote from: Arcane Analog on April 28, 2014, 07:14:23 PM
There is a tutorial on FSB that is very good for beginers.
I would link to it but apparently that is forbidden on this site. Search for "RG's Tester for Idiots" and you should find it.
Yep. I read that post.
you have to use a breadboard, and lift one end with each transistor. Definitely not practical for a batch of 70 germaniums as I tested :D
That and the risk that lifting things the resistor could disconnect something else, so you have to recheck, and a large etc.
Also, the leakeage is not calculated. You have to compare your results with a table.
This way you build the circuit, measure, load the spreadshet and voila. It goes as accurate as your election of components and power supply. :icon_cool:
Quote from: Carlos Best on April 28, 2014, 11:15:50 PM
Quote from: Arcane Analog on April 28, 2014, 07:14:23 PM
There is a tutorial on FSB that is very good for beginers.
I would link to it but apparently that is forbidden on this site. Search for "RG's Tester for Idiots" and you should find it.
Yep. I read that post.
you have to use a breadboard, and lift one end with each transistor. Definitely not practical for a batch of 70 germaniums as I tested :D
That and the risk that lifting things the resistor could disconnect something else, so you have to recheck, and a large etc.
Also, the leakeage is not calculated. You have to compare your results with a table.
This way you build the circuit, measure, load the spreadshet and voila. It goes as accurate as your election of components and power supply. :icon_cool:
No - you do not need a breadboard to do that method - you can usealigator clips and make the setup very easy - almost like an Atlas. I would say your setup is actually harder to fit transistor legs into a tiny PCB. That is simply agravating. On the physical end of things, breadboarding and aligator clips would be far easier on the head and faster.
I am not sure you have addressed it or not but your setup does not ensure that you are getting the proper voltage to the transistor either.
Leakage is extremely easy to calculate when you use the components listed. The chart he posted is for reference.
If you are going to test a lot of germanium without an atlas, one of these or something similar is much better than a breadboard or a PCB with tiny sockets.
Quote from: Arcane Analog on March 23, 2013, 01:41:25 PM
I am sure the 'experts' use their vastly superior Atlas tester but I highly recommend making something like this if you aim to test any decent amount of germanium:
(http://img.photobucket.com/albums/v89/Troublestarter/Tester_zps7ff18474.jpg)
You can watch the transistor fluctuate and/or settle which gives you indications on the device's quality that an Atlas cannot. I own an Atlas and I rarely use it other than for rough sorting.
Calculating leakage is easy.
Quote from: Arcane Analog on March 23, 2013, 12:22:16 AM
I can try to offer a simple response.
First, if using the RG method, you must regulate your power supply to an even 9V. A simple pot works well for that as it can dump the excess juice from your adapter or battery and make it easy to hit the 9V that RG specifies - along with the 2.472K and 2.2M resistors.
Measure your transistor for leakage with the tester and the old multimeter:
0.345V
As a side note, a lot of people use uA to note/discuss leakage: uA = microamps - mA = milliamps - 1000 uA = 1 mA
0.345V divided by 0.002472 = ~139.6uA of leakage
Flip Switch for the 'total' gain reading:
1.666V
So take the 'total' gain reading and subtract the leakage:
1.666 - 0.345 = 1.321V
Take that number and multiply by 100 for your 'true' gain.
1.321 x 100 = 132
Hope that helps.
To quote RG...
Quote from: R.G. on May 12, 2013, 10:57:44 PM
Openoffice spreadsheets will save as an excell (.XLS) spreadsheet. Do "Save as" and pick the appropriate file format.
However, I still philosophically object to using a nuclear spreadsheet to squash a fly. It's very nearly the level of arithmetic that can be quickly done in your head.
I found some small spring actuated terminal blocks with a .10" spacing, added a second Emitter connection on the other end so no awkward lead re-arrangements to accomodate the different pinouts.
Also added an adjustable regulator, feed in 12vdc and trim to 9v.
(http://i216.photobucket.com/albums/cc305/davent/IMG_6123_zps5fa9abab.jpg)
dave
Arcane,
I didn't want to start a controversy
My setup works, and is virtually hasle free for a beginner. No calculations, and they obviusly can ommit the pcb and use a breadboard, or alligator clips or they bare hands to twist the wires.
There are a lot of ways to do it better, but this works very well.
Here are two test rigs, one RG Keen, the other from Smallbear. There's a slight modification you can do, adding a spdt with the comon to the base, to connect it to the emitter for pure leakage measurement, and the other to the 1M or 2.2 M resistor to ground.
(https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-prn2/t1.0-9/q79/s720x720/1483071_10152425624393384_455072078479920927_n.jpg)
(https://scontent-b-ord.xx.fbcdn.net/hphotos-prn2/t1.0-9/q82/s720x720/1554627_10152425621553384_3818774421277904077_n.jpg)
No controversy. I am simply stating your setup with the floating PCB and small sockets look terribly awkward and cumberson for measuring quantity.
Edit: Are you sure your calculations are compensating for supply voltage?
(http://4.bp.blogspot.com/-5AbBWIHSj_8/UCZU-ZAaN1I/AAAAAAAACMI/-usJ1b_vxHg/s1600/Germanium+Transistor+Tester.png)
This layout is more friendly and provides a switch to avoid moving those clips around. Add a trimmer to trim the DC to 9V exactly. Slap it all in a box with proper srping sockets to avoid fighting with the transistor leads and you are in business.
http://tagboardeffects.blogspot.ca/2012/08/germanium-transistor-tester.html
Quote from: Arcane Analog on April 29, 2014, 07:20:37 PMEdit: Are you sure your calculations are compensating for supply voltage?
His calculations take the supply voltage into account, a different supply voltage gives different operating conditions eg; the base current will be different so the calculations give the correct results for those operating conditions.
R.G's method will give the wrong result in the same conditions because it assumes 4uA base current.
Using a different supply voltage might not give the same answer as using exactly 9 volts, depends how much the gain varies with different base currents. The calculations don't attempt to adjust the answer to compensate for this if that's what you meant.
Whatever method you use so long as you use about 9Volts, about 2M2 and about 2K47 the result is probably close enough for rock 'n' roll.
In my gallery there are WIn, OSX and HTML helpers to automate calculations that include different PS voltages and bias resistors.
As you know hfe is not constant but a function of the collector current.
For example, some of my power germs like AD1xx have 2x more gain if base current is 50% higher than 4ua as in RG test.
This is the HTML script, wiring is missing but you can download it from the 2nd link and put both the page and gif in the same folder,
http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=43773&g2_GALLERYSID=1d31f3ccf9bb60f827f1ad6a04067a56 (http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=43773&g2_GALLERYSID=1d31f3ccf9bb60f827f1ad6a04067a56)
http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=43770&g2_serialNumber=1 (http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=43770&g2_serialNumber=1)
mac
My Spidey sense is tingling...
Quote from: Carlos Best on April 28, 2014, 03:01:39 PM
I think if you mess with the 9v power supply that will mess with the 4uA calculations. That needs to be exact 9v for accuracy.
I just copied the formula from the topic above, (http://www.diystompboxes.com/smfforum/index.php?topic=102014.msg910364#msg910364)
Maybe DiscoVlad could clarify it.
Do I have to?
As I recall, the original reasoning was that 4µA is the approximate base current of FuzzFace transistors, and that the testing circuit is only for an
EASY quick and dirty way of finding transistors that sound "good"
in a FuzzFace. There's really no benefit to being completely anal about component values here (±1% tolerance on a 2M resistor is a ±20kΩ range).
Remember that Ge devices are incredibly temperature sensitive compared to Si transistors! The current gain, and base/collector currents all change with temperature. These effects have been ignored in the calculations -> They complicate things unnecessarily and a simple device selection circuit sitting on a test bench in no way reflects conditions found on a stage. Be aware that the effect exists though.
The Power supply only needs to be 9.0V to make the calculations with a 2472Ω resistor easier to do mentally (Use a bench supply, dial in 9V). Obviously if you're trying to test at eg. 18V it's going to throw things out of whack, but ±0.5V from a battery doesn't/won't make that much difference.
Quote from: slacker on April 28, 2014, 03:34:38 PM
You don't really need to use a pot to get exactly 2,472 Ohms, R.G only uses that value because it works out that you just take the voltage you measure and multiply it by 100 to get the gain, which is easy to do in your head. The formula you use in your spreadsheet calculates the gain in a different way so there's no need to use the exact value you can just use a 2.4k resistor.
Regarding the spreadsheet formula: No it doesn't, it calculates it the same way as R.G. did, but in a general way that uses the measured value of
any 2.4k resistor instead of a specially selected 2472Ω one.
Quote from: slacker on April 30, 2014, 03:37:37 AM
Whatever method you use so long as you use about 9Volts, about 2M2 and about 2K47 the result is probably close enough for rock 'n' roll.
Exactly!
Sorry if my tone seems a bit annoyed, people seem to get really hung up about component selection when in a majority of cases (for 9V effect pedals at least) it doesn't matter anywhere near as much as people think it does. :)
You can get a perfect 9v supply and perfect resistors... but you can't get a stable temperature :)
And another thing to keep in mind is that Vbe is not constant, it also affects the *100* factor ;)
The general formula for any set of resistors and power supplies is,
hFE = [Vnc - V]*Rb/[Vcc - Vbe]/Rc
where Vnc is the collector voltage when Rb is Not Connected,
and V is the value when Rb is connected.
RG tester set Rb/[Vcc - Vbe]/Rc = 100, supplying a base current similar to a FF.
As leakage goes to zero, silicons, Vnc tends to Vcc. You can use the formula to measure silicons as well.
mac
Quote from: DiscoVlad on April 30, 2014, 10:34:59 PM
Sorry if my tone seems a bit annoyed, people seem to get really hung up about component selection when in a majority of cases (for 9V effect pedals at least) it doesn't matter anywhere near as much as people think it does. :)
I have a powersupply that has nearly 10V and i suspect that there are many supplies similar out there. I would prefer to use 9V and stick with the 2M/2K4 as opposed to fudging it. Finding a 2M and 2K4 resistor and making the supply 9V is too easy. Testing at or close to room temperature is a no brainer.
If you are going to bother testing germanium you might as well put the effort in a do it right.
Quote from: Arcane Analog on May 01, 2014, 11:21:07 AM
If you are going to bother testing germanium you might as well put the effort in a do it right.
It's not really a case of doing it right, it's about deciding what level of accuracy is useful for your purposes. R.G's method using the notional values over states the gain by about 1% and that's likely more than good enough for anyone. If you don't need that level of accuracy then you can be looser with the values used, for example 1 Volt out either way on the supply voltage gives a ~10% error, if that's good enough for your purposes then there's no need to tweak it.
I wonder if the original makers of Fuzz Faces, Tonebenders, etc. (Vox, Fender, etc) squabled about this kind of stuff....
I mean really... do you think they worried about "Exactly 9VDC" or "2.472K ohm resistors" when they built the things?? ::)
Just get it as close as you can and audition by ear and be done with it! 8)
Quote from: Govmnt_Lacky on May 01, 2014, 12:38:11 PM
I wonder if the original makers of Fuzz Faces, Tonebenders, etc. (Vox, Fender, etc) squabled about this kind of stuff....
I mean really... do you think they worried about "Exactly 9VDC" or "2.472K ohm resistors" when they built the things?? ::)
Just get it as close as you can and audition by ear and be done with it! 8)
All said.
Regarding that I was wondering if the new fuzz faces from dunlop take hfe matching into account
Quote from: Govmnt_Lacky on May 01, 2014, 12:38:11 PM
I wonder if the original makers of Fuzz Faces, Tonebenders, etc. (Vox, Fender, etc) squabled about this kind of stuff....
I mean really... do you think they worried about "Exactly 9VDC" or "2.472K ohm resistors" when they built the things?? ::)
Just get it as close as you can and audition by ear and be done with it! 8)
If you are going through the motions of building a tester, why would it be anything but close? Is getting a 2k4 and a 2M2 resistor and 9V hard to do?
When you are building certain types of Fuzz pedals, including a few you listed, you need to measure them properly if you want them to work properly. Getting them to sound good is a completely different thing. The original builders used certain types of transistors in certain circuits because they inherently had the characteristics required to make the pedal work and sound good. If DIYers want those designs to work well and do not use the original transistor they need to ensure the transistor has the appropriate HFE or the right amount of leakage, whether that be low or high leakage, to work. That, or modify the circuit. Put the wrong transistors or the wrong values in certain fuzzz circuits and you might not even get signal to pass. I have circuits where I want the leakage to be within 25uA +/- of my target.
Edit: For that matter, there are circuits using silicon transistors that have to be measured for the pedal to sound right. Auditioning by ear can be a nightmare if you do not know what you are doing or if you are using untested transistors.
Quote from: Arcane Analog on May 01, 2014, 05:35:15 PM
The original builders used certain types of transistors in certain circuits because they inherently had the characteristics required to make the pedal work and sound good. If DIYers want those designs to work well and do not use the original transistor they need to ensure the transistor has the appropriate HFE or the right amount of leakage, whether that be low or high leakage, to work. That, or modify the circuit. Put the wrong transistors or the wrong values in certain fuzzz circuits and you might not even get signal to pass. I have circuits where I want the leakage to be within 25uA +/- of my target.
Edit: For that matter, there are circuits using silicon transistors that have to be measured for the pedal to sound right. Auditioning by ear can be a nightmare if you do not know what you are doing or if you are using untested transistors.
My point is....
Do you honestly think that Vox, Fender, or other Fuzz marketers actually had a group of people that weighed and measured EVERY Germ transistor for gains, leakage, and loss prior to putting them into their circuits? I seriously doubt it. The fascination of getting the "perfect" matched set of transistors is something that was created out of hype and nostalgia. I know this may be a taboo thing to say but.... really..... do you think one of the above companies wasted THAT much time doing this. Hardly!
As for getting the right sound..... Isn't it well known that Hendrix used to audition new batches of Fuzz type circuits.... Often going through dozens of them.... until he found the one that sounded right? If the transistors were matched and the circuit was built around them as you elude to... then he could have just walked in, tested 2 of them, and known that they had the IDENTICAL properties and moved on.
This is why I suggest auditioning by ear. Pick what sounds best and right to YOU. Don't be so concerned about gains, losses, whatever! Just go for it! 8)
My point is that they were picky about their transistors in that they designed the circuits around the transistors. So yes, they were picky, but they did not need to be picky in the same way you are describing. They did not need to be picky the same way someone using a now hard to source germanium device would be. What you are not grasping is that some circuits need lots leakage, need high/low HFE or need a combination elements to work. Try building a good sounding MKI without paying close attention to your transistors.
You see it all the time on these forums. A prime example is "Why isn't my MKII working? I used all the recommended HFEs!" A common answer is "Do you have enough leakage in Q1?" There is a reason OC75s were used in MKIIs. They have lots of leakage and they bias up perfectly with stock values giving ~8V at Q3C. Try getting that to happen with near zero or low leakage germanium devices using stock values. You can swap out transistors until the end of time and it will not make a lick of difference if your devices are not within the correct tolerance for the circuit you are working on or you do not modify the circuit.
It is not always nostalgia as in your Fuzz Face example - which by the way, if the builder had simply measured the transistors, Hendrix would not have had to go through a large number of crappy pedals to find a good one. That is case in point - thanks for the analogy. Starting with proper transistors is better than blindly swapping them out. Or, you could pick out a set by simply swapping them out only to find that the pedal no longer works or sounds decent when he temperature goes up/down a few degrees. It might have been a good idea to properly measure the leakage, champ. Now you have a pedal that only works properly when the temperature is the same as when you did your blind taste test.
Taking the extra few minutes to properly test your transistors is all about getting a circuit to actualy work properly and not fizzle, gate out, fart or sound extremely thin and harsh. Many fuzz circuits are not paint by the numbers modulation effects where you follow the picture and everything works out. You need to properly measure your transistors, let them settle, listen, etc if you want a decent pedal.
Actually, on Small Bear's site, he has a very good explanation of how to measure germaniums, it's adapted from the GEO method. I found it the easiest to understand. It's in the section of articles on the site.
Al
Quote from: slacker on May 01, 2014, 12:33:54 PM
Quote from: Arcane Analog on May 01, 2014, 11:21:07 AM
If you are going to bother testing germanium you might as well put the effort in a do it right.
It's not really a case of doing it right, it's about deciding what level of accuracy is useful for your purposes. R.G's method using the notional values over states the gain by about 1% and that's likely more than good enough for anyone. If you don't need that level of accuracy then you can be looser with the values used, for example 1 Volt out either way on the supply voltage gives a ~10% error, if that's good enough for your purposes then there's no need to tweak it.
I did not say you had to use RG's values to do it right but if you are using RG's values why not use all of his values. I would say that there are circuits where 10% difference may give you trouble.
If a person is willing to invest in the germanium, the parts for the build and building a tester it does not make any sense to deviate from the values provided unless you have the knowledge to compensate.
Quote from: Arcane Analog on May 01, 2014, 10:50:19 PM
It is not always nostalgia as in your Fuzz Face example - which by the way, if the builder had simply measured the transistors, Hendrix would not have had to go through a large number of crappy pedals to find a good one. That is case in point - thanks for the analogy.
I understand some of the points you are making but.... how is the statement above contradictory to the point I was making? In fact, you just amplified the point I was making......
The builders, in fact, DID NOT measure the transistors. That is why he auditioned them.... which was the point I was trying to make.
I was NOT implying that the proper transistors should not be used. In fact, I am in favor of it. What I was trying to imply was that the reason for all of this hoopla regarding weighing and measuring Germs is because of hype and the quest for the perfect sound. Which was mostly because the artists took the time to PICK out the pedals that sounded good. The actual "measuring" was a result of the modern quest for tone..... not because it was the way it was always done.
In the spirit of this, I would say do what sounds good to you. Don't focus on getting EXACTLY 200uA of leakage OR that 70-80Hfe. If it sounds good to you... then ROCK IT!
Hope that is a better explanation ;D
Quote from: Govmnt_Lacky on May 02, 2014, 12:25:40 PM
Quote from: Arcane Analog on May 01, 2014, 10:50:19 PM
It is not always nostalgia as in your Fuzz Face example - which by the way, if the builder had simply measured the transistors, Hendrix would not have had to go through a large number of crappy pedals to find a good one. That is case in point - thanks for the analogy.
I understand some of the points you are making but.... how is the statement above contradictory to the point I was making? In fact, you just amplified the point I was making......
Your statements do not make any sense in the context of the thread and you left out the part of the quote that explains why it does not make any sense. The topic of conversation here is the importance of measuring transistors. You advocate for simply relying on the "just trust your ears" method which suited Mr. Hendrix. That is not good advice nor a good practice - quite the opposite. It is apparent that you have little to no experience with germanium devices.
Let us use the particular case of a Fuzz Face. I can work with that but I would say there are many fuzz designs that are a hundred times more picky about the devices used than is the Fuzz Face - which is pretty damn easy to select transistors for.
If you simply plug in transistors to your Fuzz Face which sound good at your testing time without any other control measures those transistors may be leaky devices which sound terrible with a few degree temperature swing. You sound awesome in the basement but you sound like crap on stage.
What's the problem? I swapped out a hundred transistors yesterday, picked two amazing devices and they sounded great! Now they sound terrible! Well, you used leaky transistors that sound good at room temp or in a cool environment but sound terrible under the stage lights or outdoors in the sun. That 250uA in the basement quickly became 500+uA in the heat. If you had of measured the transistors first you eliminate the leaky transistors and stick with the on spec devices which will be much more likely to tolerate temperature swings. You then audition the devices that are on spec. Put another way, you can have a great sounding set of leaky devices that become poor sounding devices when the temperature changes a few degrees. In fact, you could very well go from "sounding great" to a pedal is no longer passing signal at all. Auditioning is important but you need to screen the transistor first. I would go as far to say that if you could only chose one method of selection that a builder will have a better chance of success simply measuring the transistor to ensure the values are on spec. For a great sounding pedal that is relatively stable it is essential to do both tests.
Even if the builders in Hendrix's day auditioned the transistors for sound they would still have pedals that sounded poorly when Mr. Hendrix took the stage at Woodstock. If the builders in Mr. Hendrix's time had of properly measured the devices he could grab one off the shelf and have an excellent chance of selecting a great sounding pedal that stays great sounding when he leaves the music shop. In other words, if you measure the transistors you have a greater amount of success for a good pedal and you eliminate a completely avoidable scenario. If a builder simply does your "trust your ears" test you could still end up with a poor sounding pedal the very next day.
The scene becomes even more important with other designs. Try swapping out untested transistors in a MKI or MKII that have "zero" or low leakage. The popular Russian transistors are great for Fuzz Faces but nearly useless in Q1 of a MKII. If you had of measured the devices first you would not have wasted your time plugging them into the pedal and swapping them around. Perhaps you improperly determine you have made a mistake in your build as it is misbiased or not passing signal. If they are all zero or extremely low leakage devices you will never get a good sounding pedal. You may never have anything but a useless pedal that does not pass signal.
Is testing germanium import? Only if you like your pedals to work properly and sound good.
Just want to point out that properly working AND sounds good is an assumption and that sounds good is 100% subjective. Obviously there are specs that when stayed within guarantee that certain audial issues won't rear their ugly heads but there is a limit where one must stop measuring and start trusting their ears regardless; the ears always win at the end of the day because their satisfaction is the entire reason for the product to begin with. Tell any musician who doesn't like what they hear "well I measured it and it is in spec" and see what happens. :)
That being said the trick is to know when which one of the above matters and which one to give precedence to. Doing that well is key. One can spend countless hours taking measurements and be off by a mile as far as the ears go and vice versa. The last thing one wants to do is get hung up on being too like "Spock Logical" and miss the magic; it's good to be both left and right-brained about this and not get too caught up in the minutia. 2 cents.
Quote from: Govmnt_Lacky on May 01, 2014, 09:48:56 PM
My point is....
Do you honestly think that Vox, Fender, or other Fuzz marketers actually had a group of people that weighed and measured EVERY Germ transistor for gains, leakage, and loss prior to putting them into their circuits? I seriously doubt it. The fascination of getting the "perfect" matched set of transistors is something that was created out of hype and nostalgia. I know this may be a taboo thing to say but.... really..... do you think one of the above companies wasted THAT much time doing this. Hardly!
No. They certainly did not. If they did, they would have not had a bunch of crappy pedals and made Hendrix wade through a bunch to find a good one as you mention below. This is why testing is important. If they tested them all Hendrix would have been able to grab and go.
Quote from: Govmnt_Lacky on May 01, 2014, 09:48:56 PM
As for getting the right sound..... Isn't it well known that Hendrix used to audition new batches of Fuzz type circuits.... Often going through dozens of them.... until he found the one that sounded right? If the transistors were matched and the circuit was built around them as you elude to... then he could have just walked in, tested 2 of them, and known that they had the IDENTICAL properties and moved on.
You said yourself they did not test Fuzz Face transistors. If they did, Hendrix could have walked in and discovered there was little difference in them. What I said was that certain circuits matched transistors to the circuit or designed around them. I never said they did that with the Fuzz Face although low leakage devices were certainly used. They could have weeded out the bad ones testing them. The prime example for a circuit design based on the transistor are the MKI and MKII Tonebender. They need certain amounts of leakage to get the pedal to function properly.
Quote from: Govmnt_Lacky on May 01, 2014, 09:48:56 PM
This is why I suggest auditioning by ear. Pick what sounds best and right to YOU. Don't be so concerned about gains, losses, whatever! Just go for it! 8)
If you only audition by ear you can easily end up with the Hendrix effect.
Quote from: karbomusic on May 02, 2014, 01:41:18 PM
Just want to point out that properly working AND sounds good is an assumption and that sounds good is 100% subjective. Obviously there are specs that when stayed within guarantee that certain audial issues won't rear their ugly heads but there is a limit where one must stop measuring and start trusting their ears regardless; the ears always win at the end of the day because their satisfaction is the entire reason for the product to begin with. Tell any musician who doesn't like what they hear "well I measured it and it is in spec" and see what happens. :)
That being said the trick is to know when which one of the above matters and which one to give precedence to. Doing that well is key. One can spend countless hours taking measurements and be off by a mile as far as the ears go and vice versa. The last thing one wants to do is get hung up on being too like "Spock Logical" and miss the magic; it's good to be both left and right-brained about this and not get too caught up in the minutia. 2 cents.
Which is why I said this:
Quote from: Arcane Analog on May 02, 2014, 01:11:55 PM
Auditioning is important but you need to screen the transistor first. I would go as far to say that if you could only chose one method of selection that a builder will have a better chance of success simply measuring the transistor to ensure the values are on spec. For a great sounding pedal that is relatively stable it is essential to do both tests.
It is important to read all of a post - especially so when you quote one line of many.
Quote from: karbomusic on May 02, 2014, 01:41:18 PM
Just want to point out that properly working AND sounds good is an assumption and that sounds good is 100% subjective. Obviously there are specs that when stayed within guarantee that certain audial issues won't rear their ugly heads but there is a limit where one must stop measuring and start trusting their ears regardless; the ears always win at the end of the day because their satisfaction is the entire reason for the product to begin with. Tell any musician who doesn't like what they hear "well I measured it and it is in spec" and see what happens. :)
That being said the trick is to know when which one of the above matters and which one to give precedence to. Doing that well is key. One can spend countless hours taking measurements and be off by a mile as far as the ears go and vice versa. The last thing one wants to do is get hung up on being too like "Spock Logical" and miss the magic; it's good to be both left and right-brained about this and not get too caught up in the minutia. 2 cents.
AWESOME! Agree 100% ;D
Quote
It is important to read all of a post - especially so when you quote one line of many.
Either properly working = sounds good or it is subjective. I don't see where multiple subsequent paragraphs are required to address that as written. However, no dog in the fight, as I said, just pointing out what I felt was a discrepancy. I don't get the argument passion for such a small thing to address to be honest. Carry on!
Quote from: karbomusic on May 02, 2014, 02:06:57 PM
Quote
It is important to read all of a post - especially so when you quote one line of many.
Either properly working = sounds good or it is subjective. I don't see where multiple subsequent paragraphs are required to address that as written. However, no dog in the fight, as I said, just pointing out what I felt was a discrepancy. Carry on!
Properly working = passing signal, not noisy, not hissy, good range on the fuzz pot, etc. This is objective.
Sounds Good = subjective.
Sounds good and working properly are two distinct features. A pedal can sound great but have little temp stability, range on the fuzz pot, etc.
Quote from: Govmnt_Lacky on May 02, 2014, 02:04:34 PM
AWESOME! Agree 100% ;D
Quote from: karbomusic on May 02, 2014, 02:06:57 PM
I don't get the argument passion for such a small thing to address to be honest.
I am curious. Have either of you ever built MKI Tonebender or an FZ-1?
@arcane analog
I don't get where you're pointing at. Your almost obsessive praise for accurate measurement contradicts the overall given fact
that leakage is temperature dependent. With fixed variables it's quite easy to determine the result but temperature is like weather... Who knows if Hendrix's tech didn't have a stack of FFs at the gig to choose the best for the evening. Good measurement at a well known place makes it a bit more predictable but it's still a guessing what happens on stage a week later. I'd say go for a ballpark value and cope with a bias pot (maybe with external measuring points) in risk to loose this one sweet spot with the output cap, it' all compromise. Leakage, bias, whatever, I'd like to hear a sound guy say "this place shouldn't take more than 257 people or the resonance frequency about 300Hz gets unpleasant". If you know the weakness and can't make it predictable make it adjustable within a range, typical engineer's advise...
Quote from: deafbutpicky on May 02, 2014, 06:14:19 PM
@arcane analog
I don't get where you're pointing at. Your almost obsessive praise for accurate measurement contradicts the overall given fact
that leakage is temperature dependent. With fixed variables it's quite easy to determine the result but temperature is like weather... Who knows if Hendrix's tech didn't have a stack of FFs at the gig to choose the best for the evening. Good measurement at a well known place makes it a bit more predictable but it's still a guessing what happens on stage a week later. I'd say go for a ballpark value and cope with a bias pot (maybe with external measuring points) in risk to loose this one sweet spot with the output cap, it' all compromise. Leakage, bias, whatever, I'd like to hear a sound guy say "this place shouldn't take more than 257 people or the resonance frequency about 300Hz gets unpleasant". If you know the weakness and can't make it predictable make it adjustable within a range, typical engineer's advise...
A huge point about measuring them first is that they are temperature dependent! Leakage will increase with the temperature - that IS pridictable. Why would you start with a device that has a lot of leakage or not enough leakage? The result IS pridictable and it makes no sense not to make sure you are using the right tools. It is very apparent that anyone that does not think starting off with a good idea about the transistors they are using do not know much about germanium based circuits. That is like saying getting the proper voltages on your pedal or using established voltages as a reference on a circuit is not important. It makes zero sense.
Do you think Small Bear would have a lot of happy customers who pay for transistor sets if they decided to stop measuring the device before they sell it for a specific circuit? Does Small Bear waste their time when they audit they transistors for gain and leakage?
I am saying eliminate the leaky/unstable germs first and then pick them by ear. Have you ever watched an unstable transistor in a test circuit? Measure first, then listen. If you do not think measuring devices is a key component you do not have a lot of experience on the subject matter.
I am saying if you are working on a circuit that needs leakage, you have to measure the germanium device to make sure it will work before you audition the device.
Go look at the main page and see how many people have problems with their fuzz because they have not used the right range of transistor. How many times have I read a post by Lucifer's Trip explaining "leakage is more important than HFE for Q3 of the Buzzaround" or "you do not have enough leakage for your MKIIs Q1" or "you do not want 4.5V on your MKs Q3 collector". There is at least one thread a week with someone having trouble because they try to plunk a random device into a circuit. This is because the person does not have the insight or has relied on someone who does not have the insight. I appreciate the fact that most of the people in this thread rarely use germanium and when you do it is probably a Fuzz Face or Rangemaster. Try building something a little more difficult and then explain to me that measuring is not all that important. Go build a MKI with low leakage transistors and tell me how much fun you are having getting rid of the noise and fixing the decay.
QuoteWhy would you start with a device that has a lot of leakage or not enough leakage? The result IS pridictable and it makes no sense not to make sure you are using the right tools. It is very apparent that anyone that does not think starting off with a good idea about the transistors they are using do not know much about germanium based circuits. That is like saying getting the proper voltages on your pedal or using established voltages as a reference on a circuit is not important. It makes zero sense.
That's the whole point, getting a "good idea" about the transistors is not getting a grasp of the environment they're used at.
Quote
Have you ever watched an unstable transistor in a test circuit? Measure first, then listen. If you do not think measuring devices is a key component you do not have a lot of experience on the subject matter.
yes, but measuring gives you an idea about the range to make it work with, it's not absolute.
Quote
I am saying if you are working on a circuit that needs leakage, you have to measure the germanium device to make sure it will work before you audition the device.
Again, this is not about the quality of measurement as it will be not so necessary to determine absolute values as they would change anyhow with two more light bulbs on stage. Go easy, make a range of possible values and deal with it.
Be honest and tell me how many and what kind of germaiun based circuits you have built.
Quote from: deafbutpicky on May 02, 2014, 07:33:39 PM
QuoteWhy would you start with a device that has a lot of leakage or not enough leakage? The result IS pridictable and it makes no sense not to make sure you are using the right tools. It is very apparent that anyone that does not think starting off with a good idea about the transistors they are using do not know much about germanium based circuits. That is like saying getting the proper voltages on your pedal or using established voltages as a reference on a circuit is not important. It makes zero sense.
That's the whole point, getting a "good idea" about the transistors is not getting a grasp of the environment they're used at.
Quote
Have you ever watched an unstable transistor in a test circuit? Measure first, then listen. If you do not think measuring devices is a key component you do not have a lot of experience on the subject matter.
yes, but measuring gives you an idea about the range to make it work with, it's not absolute.
Quote
I am saying if you are working on a circuit that needs leakage, you have to measure the germanium device to make sure it will work before you audition the device.
Again, this is not about the quality of measurement as it will be not so necessary to determine absolute values as they would change anyhow with two more light bulbs on stage. Go easy, make a range of possible values and deal with it.
Arcane....
The fact that you have built dozens... hundreds... or thousands of Germanium-based transistor Fuzz circuits gives your points some merit HOWEVER.... they are not absolute.
I say this because the ONLY hard data or "facts" that you can point to is based on how the final product SOUNDED TO YOU! By that basis alone your argument is subjective and not absolute.
Heck... even RG Keen still recommends using your ear as the final decider! and I would doubt it very much if you have more time dedicated to this than he does.
Quote from: Govmnt_Lacky on May 02, 2014, 08:26:50 PM
Arcane....
I say this because the ONLY hard data or "facts" that you can point to is based on how the final product SOUNDED TO YOU! By that basis alone your argument is subjective and not absolute.
Are you reading any of my posts? FORGET SOUND. Just getting some circuits to work - to even get it to pass a signal or sound like crap - revolves around choosing the right device. Some circuits are 100% dependent on leakage to function. So no - you are wrong. I have plenty of hard "facts" that state OBJECTIVELY that transistor selection is essential. There is nothing subjective about making the pedal function. It may not be hard to get a Fuzz Face up and running but there are others that are ten times more difficult.
I have also said that post selection process, it is necessary to test them for sound. You seem to ignore that I have said that in almost every post. Not once did I say you should not listen to the transistor.
It is fine a dandy to type a post saying just use your ears. The reality is that does not always work. I encourage you to go build a MKI. Try it at least once. You will have a new appreciation for germanium transistors after that build.
If you need to know, I've build several SI and GE FFs and diode related , and am to get a Darlington FF high gain device to work under changing conditions, only problem is a heat fan opposed to it makes it squiggle too much to my likes at now, what about you...
Quote from: deafbutpicky on May 02, 2014, 08:54:40 PM
If you need to know, I've build several SI and GE FFs and diode related , and am to get a Darlington FF high gain device to work under changing conditions, only problem is a heat fan opposed to it makes it squiggle too much to my likes at now, what about you...
Exactly. From your posts it was extremely obvious that you have very little experience with germanium. With all due respect, building a few Fuzz Faces cannot give you a good grasp on the subject. Making a Fuzz Face work and sound good is pretty damn easy.
My experince comes from reality - not supposition.
Enlighten me/us, your previous posts didn't..., my experience comes from measuring vs sound and this topic is
about measuring; what do you do to hit the sweet spot within a range?
Again, there seems to be confusion about hitting a certain sound or sweet spot. That is not really where I was going per se. Perhaps everyone is still associating the builing a Fuzz Face with building all fuzz circuits.
I have posted examples already. Circuits like the MKI, MKII, MKIII, FZ-1, all need some minimum or specific ranges of leakage and/or HFE to work properly or to not sound like garbage without getting crazy and heavily modifying the circuit. Then again, slapping trimmers on them will only make things worse in some cases. To dial them in or tame them to be useable you need a certain interaction between leakages and HFEs and those interplay with the other transistors. Not so much the MKII but getting a decent MKI that does not craclke and fizzle or have a terrible decay can be insanity. For such simple parts count they can be extremely tough to dial in. If you are going about it blindly without taking measurements and/or transistor type into consideration you will probably drive yourself insane.
I 100% agree that testing them for sound is essential. I happen to believe measuring them beforehand is just as important and it will help in the long run.
Quote from: Arcane Analog on May 02, 2014, 09:37:23 PM
Again, there seems to be confusion about hitting a certain sound or sweet spot. That is not really where I was going per se. Perhaps everyone is still associating the builing a Fuzz Face with building all fuzz circuits.
I have posted examples already. Circuits like the MKI, MKII, MKIII, FZ-1, all need some minimum or specific ranges of leakage and/or HFE to work properly or to not sound like garbage without getting crazy and heavily modifying the circuit. Then again, slapping trimmers on them will only make things worse in some cases. To dial them in or tame them to be useable you need a certain interaction between leakages and HFEs and those interplay with the other transistors. Not so much the MKII but getting a decent MKI that does not craclke and fizzle or have a terrible decay can be insanity. For such simple parts count they can be extremely tough to dial in. If you are going about it blindly without taking measurements and/or transistor type into consideration you will probably drive yourself insane.
I 100% agree that testing them for sound is essential. I happen to believe measuring them beforehand is just as important and it will help in the long run.
^Emphasis added. I don't think anyone would really disagree with the value you are trying to get across. Where it gets sticky for anyone is when the words "sounds like" show up in an objective description.
I do understand you are considering the usual expected sound those products were designed to make and within that confine I agree with you. Since much of what makes a guitar sound good from the pedal, to the amp, to the cab, deals with the exploitation of failures and shortcomings, using the word measure and sounds good together can get a bit tricky (as evidenced in this thread) even when you are right. It's the very reason we see so many people end articles and advice with "use what sounds best to you" because it varies that widely even outside of what you or I might think sounds even remotely functional or completely wrong.
Just think of the great sounds that likely exist for no other reason than as a result of not doing it right; I do get the point you wanted to make though; just adding thoughts we can chew on. Now, allow me to make an offering as well as show that I'm not against measuring. Here is the test circuit I built right after getting my first batch of Ge's. I've got that puppy calibrated to exactly 9V and within 1 ohm :icon_biggrin:
(http://wallsonic.com/public/posts/GeTester.jpg)
A MKI sounds like garbage when you have a howling, crackling, sizling mess with a weak or no guitar signal mixed in.
A MKII sounds like crap when you have 90% hiss and 10% fuzz and you are not entirely sure you can hear any guitar.
A MKIII or FZ-1 sounds like garbage when you have only 2-3 seconds of sputtering sounds and then it gates out completely.
I have already said several times that I am not talking about tuning it to taste or finding a sweet spot. I am talking about getting the pedal to function so you can play your guitar through it and hear your guitar without uncontrolable hiss, gating, etc. If you cannot digest that I cannot help you.
You can try to split hairs and save some face and say well "we might like those sounds." Why don't you try to building one first before providing your opinion. Have you even played or heard any of the circuits? It amazes me that people jump into these threads and offer advice or information without any practical experience to back it up. It provides only misinformation.
Next time you build one of those testers you might want you use aligator clips or spring loaded sockets. As I have pointed out several times those tiny sockets are going to lose tension extremely fast and you will have your transistor flalling out very easily.
Double post.
QuoteYou can try to split hairs and save some face and say well "we might like those sounds."
It wasn't a save face situation for me, one must be in a "win/lose" mindset for that to even enter their mind which I certainly am not. I offered some additional thoughts, take them, leave them, ignore them as is life. I don't know how much nicer and agreeable I could possibly be so it appears this is not the discussion for me if interpreted as it is above.
Quote
Next time you build one of those testers you might want you use aligator clips or spring loaded sockets.
Not really, it works as-is for my needs.
You can lead a horse to water but you cannot make it drink.
Quote from: Arcane Analog on May 03, 2014, 09:26:19 AM
You can lead a horse to water but you cannot make it drink.
... and sometimes they drink the Kool Aid and don't know any better or are resistant to trying something else! ::)
This really is going nowhere. Good luck to the OP in his endeavors.
Quote from: Govmnt_Lacky on May 03, 2014, 11:58:13 AM
Quote from: Arcane Analog on May 03, 2014, 09:26:19 AM
You can lead a horse to water but you cannot make it drink.
... and sometimes they drink the Kool Aid and don't know any better or are resistant to trying something else! ::)
This really is going nowhere.
You should take your own advice. I have done everything covered in this thread and on this and other boards extensively if not exhaustively. Have you? Judging by your comments I think not.
I test first, audtion second. Can you trust your ear to find leaky germs?
(http://img.photobucket.com/albums/v89/Troublestarter/TestersL_zpsde8b9c8d.jpg)
It will certainly be hard for you to go anywhere with this when you do not read/comprehend what I wrote several times. I still do not think you have grasped the difference between subjective and objective observations.
Fun thread
Problem: Touching the transistor under measurement doubles reading
I built the RG Keen tester on perfboard a while ago and was quite unhappy with the voltage measurement dropping for minutes on end. Now I just found the time to have go at a batch of AC128K I bought of ebay in January .
I wonder if somebody experienced that touching the tranny shortly (like a quarter of a second and in a perfectly healthy state, no fever whatsoever) whilst measuring upsets the reading quite strongly. I know that the leakage is heavily temperature dependent. But a squeeze of the solid metal housing (the AC128K are bold square things with a built-on heatsink) shouldn't change the temperature that much that the reading doubles from .654V to about 1.2V within second. Is that possible and if yes would such a transistor be a good friend on a stage?
I just waited about 5 minutes and the reading settles now at around .89V in contrast to .654V previously. Same transistor nothing moved. That is quite unsatisfying. I find myself looking at ebay offers for an Atlas DCA55 whilst waiting for the tranny to calm down. Frowning at the same time at the 24 others in the box waiting to be assessed.
QuoteProblem: Touching the transistor under measurement doubles reading
Heisenberg Uncertainty Principle, you change what you measure :)
It's unlikely that in a blink of an eye you can transfer so much energy to double the reading.
But some germs, like 2N1114 have the base connected to the case. Touching it alters the reading. This is no the case.
mac
I see.
Maybe that's why you shouldn't built Fuzzfaces and the like if you don't fully understand quantum physics.
What musician wants a Schrödinger's cat-pedal on stage where you can see if it is alive not until you plug it in your amp and stomp the switch? However, I guess I'll just refrain from touching the transistor and see to it that there are none of my probing fingers left in the enclosure when I'll finally box it.
Strange still, though.
Quote from: Arcane Analog on May 02, 2014, 09:37:23 PM
Again, there seems to be confusion about hitting a certain sound or sweet spot. That is not really where I was going per se. Perhaps everyone is still associating the builing a Fuzz Face with building all fuzz circuits.
I have posted examples already. Circuits like the MKI, MKII, MKIII, FZ-1, all need some minimum or specific ranges of leakage and/or HFE to work properly or to not sound like garbage without getting crazy and heavily modifying the circuit. Then again, slapping trimmers on them will only make things worse in some cases. To dial them in or tame them to be useable you need a certain interaction between leakages and HFEs and those interplay with the other transistors. Not so much the MKII but getting a decent MKI that does not craclke and fizzle or have a terrible decay can be insanity. For such simple parts count they can be extremely tough to dial in. If you are going about it blindly without taking measurements and/or transistor type into consideration you will probably drive yourself insane.
I 100% agree that testing them for sound is essential. I happen to believe measuring them beforehand is just as important and it will help in the long run.
I am still a huge noob and use a cheap chinese tester but already found out you have to experiment and test for upper and lower limits on transistors for fuzz circuits ..that is what "matching" means I think lol
RG's article has some good info in it.
His test circuit is nice and simple and does the job. If you study how it works you will learn something about transistors as well.
The other good thing is many people use that circuit so when they quote Hfe and leakage (Iceo) everyone is on the same page.
Quote from: lars-musik on May 08, 2015, 01:13:47 PM
I know that the leakage is heavily temperature dependent. But a squeeze of the solid metal housing (the AC128K are bold square things with a built-on heatsink) shouldn't change the temperature that much that the reading doubles from .654V to about 1.2V within second.
did the case feel cold when you touched it? if so, you were transferring heat to it. you could always lag them with styrofoam.
I have a box with a cat on, I don't think it has a cat in. I'll open it up, and look inside .....
Don't look! That's the most imoprtant part if we are talking and thinking about Schrödinger's cat and Schrödinger's pedal respectively.
Once I had strange readings while testing FETs for a P90.
I realized it was me, the desk and the breadboard altering the readings because of an EM interaction.
I did the reading on another place and no problems.
Check if it's not a breadboard thing.
QuoteWhat musician wants a Schrödinger's cat-pedal on stage where you can see if it is alive not until you plug it in your amp and stomp the switch? However, I guess I'll just refrain from touching the transistor and see to it that there are none of my probing fingers left in the enclosure when I'll finally box it.
I don't remember to have put a cat inside my Fuzz Face. But I put a couple of germs in it.
All I can say is that Schrodinger was right. Every day I switch it on I don't know how it's going to sound. Some days I don't know if there is a germ inside at all!!! :) :)
mac