Hi!! Hello everyone, new member of the forum here, and new in the world of building pedals.
I am writting to you because I need some help desesperately with some noises on a Tone Bender MK1 build that are driving me crazy...
I have built the tagboardeffects layout of the Sola Sound Tone Bender MK1.
I'm using a set of NOS Allen Bradley Resistors and Philips Caps and Some Russian MP41A transistors.
I'm getting good fuzz tones but no matter what combination of transistors I have tried I'm always getting some noises when I touch the strings and even with the vibration of the guitar... here you can check the kind of noises:
https://www.youtube.com/shorts/D4d9eXYYVQ8
Is it a problem with the transistors? I have tried more than 20... Maybe I should check other type of transistors? Everything else seems to be okay...
Hope anyone can help me
Thank you very much!!!
The transistors may be extremely noisy (leaky) and gating (misbiased).
have you tested them for gain and leakage?
Can you give us voltages for both transistors, all 3 pins?
Can you show us your build? Is it in a box?
many of us learned to measure gain and leakage here:http://www.geofex.com/article_folders/ffselect.htm#:~:text=To%20test%20the%20total%20gain,and%20the%20amplified%20base%20current. (http://www.geofex.com/article_folders/ffselect.htm#:~:text=To%20test%20the%20total%20gain,and%20the%20amplified%20base%20current.)
Post a pic of your layout and enclosure.
How have you handled the positive ground in terms of wiring?
Quote from: idy on August 05, 2024, 06:57:58 PMThe transistors may be extremely noisy (leaky) and gating (misbiased).
With a mki and russian germs more likely that they're not leaky enough. Only time i've successfully used russian germs in a mki build was with NPNs which can be somewhat leaky. Russian PNPs are almost all zero leakage in my experience.
Good old AC128s are easier with this circuit.
Quote from: Rob Strand on August 05, 2024, 07:11:19 PMPost a pic of your layout and enclosure.
How have you handled the positive ground in terms of wiring?
Here go some pictures
The drawing schematic is the way I wired all the offboard, the lines crossed out are also wired
(https://i.postimg.cc/DJb34B6X/IMG-4581.jpg) (https://postimg.cc/DJb34B6X)
(https://i.postimg.cc/y3mqvxw6/IMG-4583.jpg) (https://postimg.cc/y3mqvxw6)
(https://i.postimg.cc/2qtf5PQY/IMG-4584.jpg) (https://postimg.cc/2qtf5PQY)
(https://i.postimg.cc/SYFF6C1t/IMG-4588.jpg) (https://postimg.cc/SYFF6C1t)
(https://i.postimg.cc/mcksBbFV/IMG-4589.png) (https://postimg.cc/mcksBbFV)
Quote from: idy on August 05, 2024, 06:57:58 PMThe transistors may be extremely noisy (leaky) and gating (misbiased).
have you tested them for gain and leakage?
Can you give us voltages for both transistors, all 3 pins?
Can you show us your build? Is it in a box?
many of us learned to measure gain and leakage here:http://www.geofex.com/article_folders/ffselect.htm#:~:text=To%20test%20the%20total%20gain,and%20the%20amplified%20base%20current. (http://www.geofex.com/article_folders/ffselect.htm#:~:text=To%20test%20the%20total%20gain,and%20the%20amplified%20base%20current.)
I tested them with Tc 1 for gain and leak but didn't test the voltage...
They have actually little leak and gain.
They are all between 50-90 Hfe and 70-200uA although there is only one with 600uA! :o
Yeah...is in the box... :icon_rolleyes:
Quote from: JustinFun on August 06, 2024, 08:36:19 AMQuote from: idy link= ??? msg=1287806 date=1722898678The transistors may be extremely noisy (leaky) and gating (misbiased).
With a mki and russian germs more likely that they're not leaky enough. Only time i've successfully used russian germs in a mki build was with NPNs which can be somewhat leaky. Russian PNPs are almost all zero leakage in my experience.
Good old AC128s are easier with this circuit.
Yeah they are little leaky except for a couple of them that are around 200 and one that reads 630uA.
I have tried this ones in different positions and the noise is still there with the addition of more background hiss than with the ones with less leak....
Sorry for my English guys... ::) I'm Spanish
Check the metal pot chassis and the input sockets are making a good connection to the enclosure.
Also make sure you keep all the output wires away from input wires. Especially the wires from the PCB to the volume pot. Don't overlook the area around the switch.
Try adding a small capacitor from the input terminal to ground *on the PCB*. Start with say 1nF to see if it has an effect on the problem. Ideally you want to use the smallest value possible.
If that works then could leave it as a solution.
It is possible your transistors have low capacitance and that's causing the circuit to oscillate. You might be able to add small capacitors 10pF to 100pF across the collector and base of Q2 and Q3.
If you can change something which affects the noise then that would be a hint to what is causing the problem.
Another thing to try, add a 100uF electrolytic capacitor across the power rails *on the PCB*.
Quote from: Rob Strand on August 06, 2024, 07:52:50 PMCheck the metal pot chassis and the input sockets are making a good connection to the enclosure.
Also make sure you keep all the output wires away from input wires. Especially the wires from the PCB to the volume pot. Don't overlook the area around the switch.
Try adding a small capacitor from the input terminal to ground *on the PCB*. Start with say 1nF to see if it has an effect on the problem. Ideally you want to use the smallest value possible.
If that works then could leave it as a solution.
It is possible your transistors have low capacitance and that's causing the circuit to oscillate. You might be able to add small capacitors 10pF to 100pF across the collector and base of Q2 and Q3.
If you can change something which affects the noise then that would be a hint to what is causing the problem.
Another thing to try, add a 100uF electrolytic capacitor across the power rails *on the PCB*.
Thank you very much for your answer! Going to get the caps and try your suggestions but sorry for my ingnorance the positions you mean are these for example?:
(https://i.postimg.cc/4mTX7gTJ/IMG-4196.jpg) (https://postimg.cc/4mTX7gTJ)
Also.. where can I put the cap across the collector and base of the transistors? In the same place where the legs go? In the transistor socket?
Sorry again for my ignorance....
"Across the power rails" means from +9V to ground. You could place it on the right side of the layout, top row to the one just below it which is connected to ground. Place it just above the yellow 100n capacitors.
You can place a cap between the base and collector of the transistors anywhere, even below the board. Do not solder them TOO close to the transistors, the heat may destroy them (remove them from socket first!). Look closely at the layout - there is space to add them if you are careful. :icon_cool:
Thanks everybody for the responses, really appreciated!!! :)
Quote from: Rob Strand on August 06, 2024, 07:52:50 PMCheck the metal pot chassis and the input sockets are making a good connection to the enclosure.
Also make sure you keep all the output wires away from input wires. Especially the wires from the PCB to the volume pot. Don't overlook the area around the switch.
Try adding a small capacitor from the input terminal to ground *on the PCB*. Start with say 1nF to see if it has an effect on the problem. Ideally you want to use the smallest value possible.
If that works then could leave it as a solution.
It is possible your transistors have low capacitance and that's causing the circuit to oscillate. You might be able to add small capacitors 10pF to 100pF across the collector and base of Q2 and Q3.
If you can change something which affects the noise then that would be a hint to what is causing the problem.
Another thing to try, add a 100uF electrolytic capacitor across the power rails *on the PCB*.
PROBLEM SOLVED!!! :icon_biggrin: :icon_biggrin: :icon_biggrin:
3nF capacitor from the input terminal to ground on the PCB was the solution!!
I started with 1nF and then 2nf but it wasn't enough and then... solved!
Before that I also tried the electrolitic capacitor and some caps across the base and collectors but it didn't seemed to change anything.
Sounding pretty good althought it seems sometimes the mids get scooped and then come back in like a rotary effect... any ideas on this?
Thank you very much man!!
Quote from: Rnk on August 16, 2024, 06:48:38 PMPROBLEM SOLVED!!! :icon_biggrin: :icon_biggrin: :icon_biggrin:
3nF capacitor from the input terminal to ground on the PCB was the solution!!
I started with 1nF and then 2nf but it wasn't enough and then... solved!
Before that I also tried the electrolitic capacitor and some caps across the base and collectors but it didn't seemed to change anything.
Sounding pretty good althought it seems sometimes the mids get scooped and then come back in like a rotary effect... any ideas on this?
Thank you very much man!!
Cool. 3n is a large value. If I saw that I'd be thinking something is wrong!
Not sure why it has a mid scoop sound. You should be able to set the tone with the Attack pot.
Hi guys, here I am back in trouble again...
I've been trying a lot of combinations of transistors with Ac128, russians... and I always get the same result:
When I use the pedal with my guitar volume from 0-8 it sounds good (or at least I think so...) but when guitar volume is on 10 it sounds crap, completely compressed. (I use log guitar pots).
Also when I pick lightly on 10 it sounds good but if I pick hard, same thing.
It's worse with humbuckers than with single pickups.
Check it out:
https://youtube.com/shorts/M4VX0zsGeC8?si=LmxWimir1r-yMGNa
Any help much apreciated
Thank you very much
But... :o
It's a Fuzz, isn't it..??
Quote from: antonis on December 10, 2024, 06:26:45 AMBut... :o
It's a Fuzz, isn't it..??
My thoughts exactly...
Most fuzzes go nuts at high gain
A high gain silicon fuzz face vs a germanium one is a huge difference.
But the silicon ones has very glassy cleans when backing off volume. Give and take.
Leaky transistors can give a good bias current which makes these old benders clean when backing off volume. WHich means trading gain for leakage might work for the better in 3 transistors circuits.
Russian transistors usually don't have much leakage so that may be part of the problem. Edit, I seen that was said already.
Quote from: Rnk on December 09, 2024, 07:37:53 PMAlso when I pick lightly on 10 it sounds good but if I pick hard, same thing.
It seems to be the input level that is triggering it.
Can you measure the voltages on the transistors.
What I think is happening is the biasing is marginal then once the input level reaches some point one of the stages clips. Then after that the input cap to that stage charges up and you get what is called blocking distortion.
Check the polarity of the 25uF cap between stages 1 and 2.
There are ways to reduce blocking distortion but that requires mods, so it's best to start with the bias voltages.
Quote from: Rob Strand on December 11, 2024, 04:07:01 PMQuote from: Rnk on December 09, 2024, 07:37:53 PMAlso when I pick lightly on 10 it sounds good but if I pick hard, same thing.
It seems to be the input level that is triggering it.
Can you measure the voltages on the transistors.
What I think is happening is the biasing is marginal then once the input level reaches some point one of the stages clips. Then after that the input cap to that stage charges up and you get what is called blocking distortion.
Check the polarity of the 25uF cap between stages 1 and 2.
There are ways to reduce blocking distortion but that requires mods, so it's best to start with the bias voltages.
Here are the voltages:
Q1:
C: -9,12
B: -0,17
E: -0,20
Q2:
C: -5,90
B: -0,16
E: 0
Q3:
C: -5,35
B: -0,08
E: 0
Other transistor combination that I have makes less blocking distortion and the voltages are basically the same except for Q2C which reads -2,34.
Maybe that says something?
I dont know how to check the polarity of the 25uf cap more than putting it in the correct direction according to the layout :icon_rolleyes: :icon_lol:
Quote from: antonis on December 10, 2024, 06:26:45 AMBut... :o
It's a Fuzz, isn't it..??
;D yeahh but it's too much "over compressed" practically unusable but lowering the guitar's volume the tone bender sound appears so something's wrong!
Quote from: Rnk on December 12, 2024, 11:49:39 PMHere are the voltages:
Q1:
C: -9,12
B: -0,17
E: -0,20
Q2:
C: -5,90
B: -0,16
E: 0
Q3:
C: -5,35
B: -0,08
E: 0
Other transistor combination that I have makes less blocking distortion and the voltages are basically the same except for Q2C which reads -2,34.
Maybe that says something?
I dont know how to check the polarity of the 25uf cap more than putting it in the correct direction according to the layou
Well to me the Q1 emitter voltage looks far to low. I'd expect at least 1V, perhaps 1V to 2V (can't remember the exact voltage off the top of my head). It's exactly the type of thing that would cause what you are experiencing.
The reason it is low is probably because Q1 has low leakage. One way around it would be to add a large valued resistor from the collector of Q1 (the negative rail) and the base of Q1. Perhaps 4.7M to 10M.
I'd fix the Q1 bias voltages first.
The Q2 collector voltage seems OK but it does depend on the Attack pot. At one extreme it should go upto 8V or so.
The Q3 collector voltage should be quite a bit higher to be set-up like a true MK1. At the end of the day you can play with that voltage to suit your taste.
Quote from: Rnk on December 09, 2024, 07:37:53 PMHi guys, here I am back in trouble again...
I've been trying a lot of combinations of transistors with Ac128, russians... and I always get the same result:
When I use the pedal with my guitar volume from 0-8 it sounds good (or at least I think so...) but when guitar volume is on 10 it sounds crap, completely compressed. (I use log guitar pots).
Also when I pick lightly on 10 it sounds good but if I pick hard, same thing.
It's worse with humbuckers than with single pickups.
Check it out:
https://youtube.com/shorts/M4VX0zsGeC8?si=LmxWimir1r-yMGNa
Any help much apreciated
Thank you very much
This is pretty much how mine works. Tone Vendor MKI from pedalpcb.
Could be how the design itself reacts to strong input. That is why turning up and humbuckers max it out and it gets more gated or compressed.
I seldom push over 3 o'clock on either pot.
Some even like this sputtery effect.
In a fuzz face it is more control from the volume of the guitar but my MKI not as much.
Probably a contributing factor why they made MK2, MK1.5 MK3s and other.
Mine does this if driven hard, tho it is the silicon version and I have installed a bias pot. So, when it happens, I can dial the bias around to make it do what I want. A little synthy is ok for something, IMO, but I like to dial back the Atari sounds.
.
Quote from: GibsonGM on December 18, 2024, 08:44:12 AMMine does this if driven hard, tho it is the silicon version and I have installed a bias pot. So, when it happens, I can dial the bias around to make it do what I want. A little synthy is ok for something, IMO, but I like to dial back the Atari sounds.
Hi GibsonGM, do you have a schematic? I've tried and failed several time to get a silicon mki to work properly.
It's not a mk1, it's mkII. Haven't seen anyone put Si's in a Ge design without needing to really mess w/the bias resistors; this is pretty much the outcome of that so here is where to start IMO.
I breadboarded mine first, used a lower gain transistor in Q2, I believe...MPSA42 IIRC. Then 3904's. I played w/lots of Q's on the breadboard, putting them in different locations, so you might wish to do the same - I can't be sure WHERE I put the '42, for example! I should've kept better notes. This isn't a 'make it this way' build, you have to tune it to your pref's.
For a bias trim, I replaced the 47k on Q2 with a 4.7kR followed by a 20k trimmer. On MY build, that gave a good range for Q2 adjustment; when all set - after testing pot on Q3 - I replaced with fixed value R. Then I made Q3's 5.6k a 10k bias POT. Test it on your own ckt before assembly; there will be a small range of good bias, you want to be sure you can get into that. You have to get Q2 going, then see if the 10k pot does the job well. I'd like to 'revisit' that, and dial in the range of control better (maybe 5k pot with 2.7k R's on each side), but it does fine for what I do (crackle OK). Experiment with it!
I never did get REALLY close to the posted ideal voltages, but near enough for real tonebender sounds, I think!
**********Edit: looking at build notes now (scrawl). Might have to play with the pot value at Q3 collector, I seem to have ended up with (gasp) 27k in that position! 3.3k and 25k pot. Q2 total Rc came out to 47k, gave 4.5v. Might be totally whacked, but it sounds good ;)
I used a 2N3904, MPSA42 and 5088 for Q's. Probably easier to build stock, then adjust as I did, trying to get a good bias - these notes I'm looking at can't be trusted, may have been "in the middle" at the time.
(https://i.postimg.cc/56yb7CH3/Tone-Bender.jpg) (https://postimg.cc/56yb7CH3)
Quote from: Rob Strand on December 13, 2024, 12:38:56 AMQuote from: Rnk on December 12, 2024, 11:49:39 PMHere are the voltages:
Q1:
C: -9,12
B: -0,17
E: -0,20
Q2:
C: -5,90
B: -0,16
E: 0
Q3:
C: -5,35
B: -0,08
E: 0
Other transistor combination that I have makes less blocking distortion and the voltages are basically the same except for Q2C which reads -2,34.
Maybe that says something?
I dont know how to check the polarity of the 25uf cap more than putting it in the correct direction according to the layou
Well to me the Q1 emitter voltage looks far to low. I'd expect at least 1V, perhaps 1V to 2V (can't remember the exact voltage off the top of my head). It's exactly the type of thing that would cause what you are experiencing.
The reason it is low is probably because Q1 has low leakage. One way around it would be to add a large valued resistor from the collector of Q1 (the negative rail) and the base of Q1. Perhaps 4.7M to 10M.
I'd fix the Q1 bias voltages first.
The Q2 collector voltage seems OK but it does depend on the Attack pot. At one extreme it should go upto 8V or so.
The Q3 collector voltage should be quite a bit higher to be set-up like a true MK1. At the end of the day you can play with that voltage to suit your taste.
I have tried adding the resistor between Q1 collectors and base and it didn't solved it.
It raised the voltage a bit but still happens the same thing
Wow this thing is driving me crazy....
Maybe keep on searching for more leaky transistors for Q1?
You may need to lower that, try 1 meg, even 470k.
Quote from: Rob Strand on December 13, 2024, 12:38:56 AMQuote from: Rnk on December 12, 2024, 11:49:39 PMHere are the voltages:
Q1:
C: -9,12
B: -0,17
E: -0,20
Q2:
C: -5,90
B: -0,16
E: 0
Q3:
C: -5,35
B: -0,08
E: 0
Other transistor combination that I have makes less blocking distortion and the voltages are basically the same except for Q2C which reads -2,34.
Maybe that says something?
I dont know how to check the polarity of the 25uf cap more than putting it in the correct direction according to the layou
Well to me the Q1 emitter voltage looks far to low. I'd expect at least 1V, perhaps 1V to 2V (can't remember the exact voltage off the top of my head). It's exactly the type of thing that would cause what you are experiencing.
The reason it is low is probably because Q1 has low leakage. One way around it would be to add a large valued resistor from the collector of Q1 (the negative rail) and the base of Q1. Perhaps 4.7M to 10M.
I'd fix the Q1 bias voltages first.
The Q2 collector voltage seems OK but it does depend on the Attack pot. At one extreme it should go upto 8V or so.
The Q3 collector voltage should be quite a bit higher to be set-up like a true MK1. At the end of the day you can play with that voltage to suit your taste.
OKAY.. what I've got so far:
On Q3C I have achieved a right voltage (-8,60V) with a lower leakege transistor.
With a 2M resistor from Collector to Base of Q1 I'm getting right voltages on Emitter (-1,30V)
And in combination with a different transistor on Q2 I GOT RID of the Blocking distortion and It's sounding pretty decent right now.
The thing is, the only transistor that got rid of the blocking distortion is a 1600uA leakeage one... that gives me -2,85/-5,65V on Q2C.
If I put a lower leakage one (150uA) I get a desire (-6/-8,5V) BUT the Blocking distortion comes back....
(The 5nF cap from Input to Ground filters all the crazy high freq noises probably caused by all that leakage...)
Any suggestions?
BTW, I got no words to describe how thankfully I am to all of you for taking time on helping me.
Specially you Rob!!!!
Quote from: Rob Strand on August 17, 2024, 12:41:10 AMQuote from: Rnk on August 16, 2024, 06:48:38 PMPROBLEM SOLVED!!! :icon_biggrin: :icon_biggrin: :icon_biggrin:
3nF capacitor from the input terminal to ground on the PCB was the solution!!
I started with 1nF and then 2nf but it wasn't enough and then... solved!
Before that I also tried the electrolitic capacitor and some caps across the base and collectors but it didn't seemed to change anything.
Sounding pretty good althought it seems sometimes the mids get scooped and then come back in like a rotary effect... any ideas on this?
Thank you very much man!!
Cool. 3n is a large value. If I saw that I'd be thinking something is wrong!
Not sure why it has a mid scoop sound. You should be able to set the tone with the Attack pot.
EDIT: 3pF not nf... :icon_redface: :icon_lol:
Quote from: Rnk on January 03, 2025, 05:10:21 PMQuote from: Rob Strand on August 17, 2024, 12:41:10 AMQuote from: Rnk on August 16, 2024, 06:48:38 PMPROBLEM SOLVED!!! :icon_biggrin: :icon_biggrin: :icon_biggrin:
3nF capacitor from the input terminal to ground on the PCB was the solution!!
I started with 1nF and then 2nf but it wasn't enough and then... solved!
Before that I also tried the electrolitic capacitor and some caps across the base and collectors but it didn't seemed to change anything.
Sounding pretty good althought it seems sometimes the mids get scooped and then come back in like a rotary effect... any ideas on this?
Thank you very much man!!
Cool. 3n is a large value. If I saw that I'd be thinking something is wrong!
Not sure why it has a mid scoop sound. You should be able to set the tone with the Attack pot.
EDIT: 3pF not nf... :icon_redface: :icon_lol:
SORRY, It's nf yes... facepalm...
Welcome to the world of trying to tune a MK1 Tone Bender - which can often be both slightly frustrating and very satisfying at the same time. I normally breadboard them first, as you can spend a lot of time tweaking to get good results.
Apart from testing a few different transistors. Try reducing the 470k bias resistor on the base of Q2 - anywhere from 180k to 470k can get things working right (or at least sounding different).
It's not unusual for some settings on the attack pot to not sound great. Occasionally I'll drop down from a B50k to a A25k for this reason (noting the bias resistor value mentioned above). Some versions of the MK1 have a 33k resistor across the 50k pot for the same reason.
Good luck!