Ge's ...how were the originals tested?

[tacobender]

Anyone know how the original builders tested their tranies? Sorry if this has been covered before, im looking for a way to test my Ge's that doesn't involve building a gizmo more complicated than the pedals im making. I had considered a peak component analyzer, but was told they are not accurate for Ge gain/leakage. Anyone here got the 411 on this? Sorry if this topic has been beat into the ground but i gotta know, as my horn is still pretty green. Thanks.

[MaxPower]

http://www.geofex.com/Article_Folders/ffselect.htm

How's that?

[greaser_au]

Anecdotally, the original builders didn't do much of this kind of testing, they just built usable pedals (using their 'normal' manufacturing processes).  The big name players cherry-picked for pedals that  sounded best - leaving the unselected ones for the mere mortals.

Greater minds have offered us some very simple methods to sort transistors, and what the requirements are for each position of the popular Ge pedals for a better-sounding result.  If you don't want to/can't  spend the time to select your component sets and audition them, the best advice you can get from anybody would be to pay the premium for a matched set or two from someone like SmallBear who *has* spent the time to sort them out for you.

david

[Calambres]

...I had considered a peak component analyzer, but was told they are not accurate for Ge gain/leakage...

Can you shed some light on this, please?
I've got a Peak DCA-55 and always thought that the Ge gain/leakage measurements were correct...

[tacobender]

http://www.geofex.com/Article_Folders/ffselect.htm

How's that?

...thats great, just need to upgrade my dmm, and read this article a few dozen times until i can fully wrap my brain around it, until then i guess smallbear can supply my fix.

[tacobender]

Anecdotally, the original builders didn't do much of this kind of testing, they just built usable pedals (using their 'normal' manufacturing processes).  The big name players cherry-picked for pedals that  sounded best - leaving the unselected ones for the mere mortals.

Greater minds have offered us some very simple methods to sort transistors, and what the requirements are for each position of the popular Ge pedals for a better-sounding result.  If you don't want to/can't  spend the time to select your component sets and audition them, the best advice you can get from anybody would be to pay the premium for a matched set or two from someone like SmallBear who *has* spent the time to sort them out for you.

david

i guess thats why some of the originals do sound a little funky.

[pupil]

I have used RG Keen's transistor method to sort endless amounts of germaniums.

Lately, I decided to buy a Peak DCA55 and have found it very accurate. The leakage reads shy of what I get using RG's method, but I believe this to be a function of the different collector emitter voltage used in each test, not because it is an inferior testing method. To get a similar measurement to RG's test I multiply the DCA55 leakage value by 1.7 and it consistently comes very close.

[Electric Warrior]

Anecdotally, the original builders didn't do much of this kind of testing, they just built usable pedals (using their 'normal' manufacturing processes).  The big name players cherry-picked for pedals that  sounded best - leaving the unselected ones for the mere mortals.

That's pure speculation. We don't know how builders in the 60's selected their transistors, but that doesn't mean there wasn't a testing process of some sort. In case of the Fuzz Face Arbiter might simply have bought the transistors in matched pairs. As these use carbon comp resistors that may drift a lot it's hard to tell how many duds there were orignally.

I once played a Fuzz Face that had a wrong resistor value on one of the collectors (I guess someone didn't pay attention at the factory). Didn't sound any good. Once the owner replaced the resistor with with the correct value it sounded great. Go figure..

There are always better, worse or just different sounding pedals in any kind of production environment. Especially when you use germanium transistors.

[greaser_au]

That's pure speculation. We don't know how builders in the 60's selected their transistors, but that doesn't mean there wasn't a testing process of some sort. In case of the Fuzz Face Arbiter might simply have bought the transistors in matched pairs. As these use carbon comp resistors that may drift a lot it's hard to tell how many duds there were orignally.

I once played a Fuzz Face that had a wrong resistor value on one of the collectors (I guess someone didn't pay attention at the factory). Didn't sound any good. Once the owner replaced the resistor with with the correct value it sounded great. Go figure..

I DID say 'anecdotally'...  This (further piece of anecdotal evidence)  supports the speculation/urban legend - a) that they made good ones and bad ones, and b) their testing was less than stellar...  

There are always better, worse or just different sounding pedals in any kind of production environment. Especially when you use germanium transistors.

Agreed. the widespread manufacturing tolerances, drift with time, and extreme thermal characteristics are some of the reasons why germanium devices went out of favour for general use (thus they are no longer mass-produced and are somewhat rare now).

In modern mass production, though, it would be reasonable to assume that the engineering would be such that the resulting variation from unit to unit would be so much less than it was in the '60's. 

david

[Thecomedian]

Anecdotally, the original builders didn't do much of this kind of testing, they just built usable pedals (using their 'normal' manufacturing processes).  The big name players cherry-picked for pedals that  sounded best - leaving the unselected ones for the mere mortals.

Greater minds have offered us some very simple methods to sort transistors, and what the requirements are for each position of the popular Ge pedals for a better-sounding result.  If you don't want to/can't  spend the time to select your component sets and audition them, the best advice you can get from anybody would be to pay the premium for a matched set or two from someone like SmallBear who *has* spent the time to sort them out for you.

david

I bought a smallbear FF kit because it would've been nearly the same price to pay for "matched pair" on e-bay or anywhere else for the same transistors, except they also come with resistances selected for proper ohmage to make the circuit sound good with the the transistors that were paired together.

[Electric Warrior]

If the transistors were selected to work well in a fuzz face circuit, why would you need to swap resistors?  

I DID say 'anecdotally'...  This (further piece of anecdotal evidence)  supports the speculation/urban legend - a) that they made good ones and bad ones, and b) their testing was less than stellar...   

It doesn't mean the transistors were not tested or matched, though. It just means that the final tests that happened after assembley were not very good.

[karbomusic]

If the transistors were selected to work well in a fuzz face circuit, why would you need to swap resistors?  

Probably variance due to the fact that Ge transistors are what they are. I've purchased three different matched sets in the past year (reliable source) and in two cases I had to either replace one of the transistors or adjust resistor values.

It doesn't mean the transistors were not tested or matched, though. It just means that the final tests that happened after assembley were not very good.

I'd put my money on they were not individually tested anywhere near the specs we use in this forum; they probably passed some broad lot test at best. Call it a mass manufacturing hunch. I have also found it much better to just order as many Ge transistors as I can and match them myself at build time. I've not found a better method thus far and I don't see how any manufacturer could have pulled that off to that accuracy on a production line.

[Electric Warrior]

If the transistors were selected to work well in a fuzz face circuit, why would you need to swap resistors?  

Probably variance due to the fact that Ge transistors are what they are. I've purchased three different matched sets in the past year (reliable source) and in two cases I had to either replace one of the transistors or adjust resistor values.

Germanium transistors are what they are? What do you mean by that? The Fuzz Face circuit is very forgiving. It will take anything from low gainers with high leakage to high gain silicons without any mods. Building one with stock values is not hard. If you had to replace transistors or adjust resistor values to make it sound good, you don't have a reliable source.

I'd put my money on they were not individually tested anywhere near the specs we use in this forum; they probably passed some broad lot test at best. Call it a mass manufacturing hunch. I have also found it much better to just order as many Ge transistors as I can and match them myself at build time. I've not found a better method thus far and I don't see how any manufacturer could have pulled that off to that accuracy on a production line.

Testing for hfe and leakage and matching up transistors is rather simple. And it's possible that they bought them prematched.
The Fuzz Face is one of the easiest germanium fuzz circuits to make, really. It lends itself to a larger scale of production. The MKI and MKII Tone Benders need a lot more skill and tinkering.

[karbomusic]

Germanium transistors are what they are? What do you mean by that? The Fuzz Face circuit is very forgiving. It will take anything from low gainers with high leakage to high gain silicons without any mods. Building one with stock values is not hard. If you had to replace transistors or adjust resistor values to make it sound good, you don't have a reliable source.

They are what they are that I thought everyone knew; very wide in spec variance and somewhat fragile across the board. The source was small bear and I don't slight them, and I disagree with being very forgiving (to a point that is). I'm no aficionado but I spent months on the FF circuit via ears, eyes (oscilloscope and FFT), multiple amps, guitars and gigs and there is a relatively small window where it is truly ideal. Of course ideal is subjective but I'm comfortable with my rendition of what that is. It has a long history of duds and those historically searching for one that sounds great should be evidence of this. That being said there is a very wide window of varying disgusting tones (many of which I love) but that's another debate.

Testing for hfe and leakage and matching up transistors is rather simple. And it's possible that they bought them prematched.
The Fuzz Face is one of the easiest germanium fuzz circuits to make, really. It lends itself to a larger scale of production. The MKI and MKII Tone Benders need a lot more skill and tinkering.

In a production environment the way we test (the small bear and keen methods)  would, from a profit perspective very painful comparatively but I agree that we simply don't see eye to eye on this point. It is surely very easy to build but just throwing parts together does not a great FF make. Again, I'm happy to stand by my statements as purely subjective opinion but I still stand behind them for the time being. However, if you can point me to anything that alludes to them testing each transistor to similar standards I am certainly open to changing my mind. With the stories of their variance historically, something must give, either people aren't telling the truth or they varied and weren't so easy to get right.

[greaser_au]

Germanium transistors are what they are? What do you mean by that? The Fuzz Face circuit is very forgiving. It will take anything from low gainers with high leakage to high gain silicons without any mods. Building one with stock values is not hard. If you had to replace transistors or adjust resistor values to make it sound good, you don't have a reliable source.

Will every build sound good with the transistors that set up properly at the stock values (and then we're back to my original point)?  I assume this is why you see so many layouts with an internal (or even EXTERNAL) bias pot. Reputable suppliers have been sorting and auditioning for their idea of good sound, and supplying transistor/resistor sets that hit that 'sweet spot'  to give the paint-by-numbers builder the best chance of success, and to reduce their discard rate.  If it works, that is good engineering, and even better business practice in my opinion!

You are absolutely correct in that we really don't know what the original manufacturers did. We have stories that are anecdotal/apocryphal and most are probably even complete BS. My own 10 years experience in a commercial electronics engineering  & manufacturing environment (and the stories of the FF product variability) gives a good idea -which may  be completely wrong- of what they likely did, however.

david

[Satchmoedie]

I have been using RG Keen's method, and I have a curve tracer or two kicking around. The little Leader curve tracer does a nice job for $50, supply your own O Scope. Originally they were tested for leakage much the way Keen shows. One of the older transistor testers I have checks both HFE and leakage, but it takes a bunch of C batteries, in multiple holders, supplying multiple parts of the circuit. Some day I may get around to converting it to AC power, but there are multiple floating grounds to deal with in it. I would probably be better off making my own from scratch.

[Electric Warrior]

Will every build sound good with the transistors that set up properly at the stock values (and then we're back to my original point)?  I assume this is why you see so many layouts with an internal (or even EXTERNAL) bias pot. Reputable suppliers have been sorting and auditioning for their idea of good sound, and supplying transistor/resistor sets that hit that 'sweet spot'  to give the paint-by-numbers builder the best chance of success, and to reduce their discard rate.  If it works, that is good engineering, and even better business practice in my opinion!

It will probably not work with all transistor types, but with many it would be no problem at all.

You see so many layouts with bias pots because someone once said that a good fuzz face should have a collector voltage of 4.5V for Q2. A bias  pot in that spot is not particularly useful, though. More like a glorified tone control. It's marketed as a tool to make up for temperature changes, but I don't find it all that useful for that either.
Also many people believe they need those pots because of the bad reputation germanium has. Beginners might even be insecure about their abilities and believe they need them because everybody's talking about them.

I suppose most people, including some reputable suppliers, are painting by that number now.
In the past I often got the impression that smallbear uses that approach for the OC75 sets for MKII Tone Benders. People report a ridiculously wide spread of gains in those sets. Low for Q1, medium for Q2, high for Q3. Very consistent. And it consistently doesn't work too well in the stock schematic. With the supplied resistor values the voltages are way off - but again, very consistent, as they're set deliberately. Q3's collector alway measures around 4.5V (whereas vintage units and clones with stock values measure between 7.5 and 9V there).
When I built my MKII clone I tried trim pots on all collectors. And guess what? Bringing down the voltage that far made it sound thin and buzzy and brought the volume down considerably.. Sticking to the original recipe made things far easier for me.

Painting by numbers may work in many cases, but it's also important to try different setups, use your ears and listen.

They are what they are that I thought everyone knew; very wide in spec variance and somewhat fragile across the board. The source was small bear and I don't slight them, and I disagree with being very forgiving (to a point that is). I'm no aficionado but I spent months on the FF circuit via ears, eyes (oscilloscope and FFT), multiple amps, guitars and gigs and there is a relatively small window where it is truly ideal. Of course ideal is subjective but I'm comfortable with my rendition of what that is. It has a long history of duds and those historically searching for one that sounds great should be evidence of this. That being said there is a very wide window of varying disgusting tones (many of which I love) but that's another debate.

A wide variance in spec is rather useful for many fuzz builds. The main issue with germaniums is that they're very sensitive to temperature changes. Sometimes a pedal is the greatest fuzz in the world, other days it's a dud. Thus the long history of duds and Hendrix searching for the ultimate tone only to find out that his pedal didn't sound that hot in a different environment.
And yeah, ideal is subjective. There can be many great tones with very different transistors and different voltages.

I believe Arbiter did a far better job with these than you concede to them. There are many nice sounding germanium Fuzz Faces out there.

[greaser_au]

The paint-by-numbers approach is what many builders need- a verified layout (What!!???, no schematic??? grrrrrr! move on to the next topic), a PCB, a kit, whatever. They are just not equipped to deal with the tweaking and tuning required- something that just works is the requirement.

When Ge trannys were cheap and plentiful, a high discard rate wasn't a big deal (though I doubt that very many were discarded at all), but now they're getting scarce and expensive - anything that works for the kit builders, AND can reduce the discard rate has to be a Good Thing(TM), surely? 

david