Questions for ToneBender´s gurus

[percyhornickel]

Hi, I have breadboarded a MKII using trimmers for Q2c and Q3c. I really don´t know how sucessful I am because I could get good sound with this voltages:

Q1 4.1V USING 10K RESIST
Q2 8.4V USING 100k TRIM
Q3 1.5V USING 20K TRIM

There´s no way I can get 4.5V in Q3, I am using the leaky transistor that I mentioned in other post:

2SB492-1   hfe 75 / 0,627 mv leak
2SB492-2   hfe 70 / 0,485 mv leak
2SB492-3   hfe 85 / 0,647 mv leak

Are my voltages right?

Another question: with attack in min I still get distortion, even I took out the 5uf cap from the attack part and the distortion is there, the pot just increases the level from that point I guess.

Is this a volume controled circuit?, with fuzz face I get almost clean sound with min attack...   ..not the case with my TB.

I would like to see come comments about it.

Thank you.
 

[Big Monk]

Hi, I have breadboarded a MKII using trimmers for Q2c and Q3c. I really don´t know how sucessful I am because I could get good sound with this voltages:

Q1 4.1V USING 10K RESIST
Q2 8.4V USING 100k TRIM
Q3 1.5V USING 20K TRIM

There´s no way I can get 4.5V in Q3, I am using the leaky transistor that I mentioned in other post:

2SB492-1   hfe 75 / 0,627 mv leak
2SB492-2   hfe 70 / 0,485 mv leak
2SB492-3   hfe 85 / 0,647 mv leak

Are my voltages right?

Another question: with attack in min I still get distortion, even I took out the 5uf cap from the attack part and the distortion is there, the pot just increases the level from that point I guess.

Is this a volume controled circuit?, with fuzz face I get almost clean sound with min attack...   ..not the case with my TB.

I would like to see come comments about it.

Thank you.

Can you post the schematic you followed and any parts substitutions?

Your voltages are WAY off the mark and I have tons of suggestions for you but I'd want to see what schematic you worked from and know exactly what is on the breadboard before I give advice.

[Radical CJ]

As above, would need to see a schematic of exactly what you've put together. But I would note that many people prefer a voltage north of 4.5 for Q3. I think mine is more like 6.5, but I'm sure there is a range of opinions on that. Should definitely be higher than 1.5 though.

[percyhornickel]

Ok thanks for the answers, I used the Fuzz Central Sola Sound MKII schematic:

http://fuzzcentral.ssguitar.com/mkII/mkIIschematic.gif


I spend the afternoon reading so interesting posts in here and took some ideas from electric warrior and I could set the bias:

Q2c  -017
Q3c  -v4.5

Some people set Q3c bias at -8.xv for sweet point, some others says -4.5v, my case -4.5.

I just set the trimmer for Q2c and let the Q3c with 8.2K without any trimmer, so it can work properly with the 470 ohms resistor once Q2 is biassed.

I sounded a litler gated (maybe because the lots of leakage in my transistors) so I changed the 100kr Q1b resistor for a 20k pot and setted the "sustain" I liked so much this add so I can change better the Vc of the input buffer and helped a lot with the gatered sound. I think I will put and outside "sustain" control once fitted in the enclosure.

Now it sounds very nice I think, can I still say I have a Tonebender MKII? I hope so...

I would love to read some other sugestions and thank you.

P.H.

[Big Monk]

Ok thanks for the answers, I used the Fuzz Central Sola Sould MKII schematic:

http://fuzzcentral.ssguitar.com/mkII/mkIIschematic.gif


I spend the afternoon reading so interesting posts in here and took some ideas from electric warrior and I could set the bias:

Q2c  -017
Q3c  -v4.5

Some people set Q3c bias at -8.xv for sweet point, some others says -4.5v, my case -4.5.

I just set the trimmer for Q2c and let the Q3c with 8.2K without any trimmer, so it can work properly with the 470 ohms resistor once Q2 is biassed.

I sounded a litler gated (maybe because the lots of leakage in my transistors) so I changed the 100kr Q1b resistor for a 20k pot and setted the "sustain" I liked so much this add so I can change better the Vc of the input buffer and helped a lot with the gatered sound. I think I will put and outside "sustain" control once fitted in the enclosure.

Now it sounds very nice I think, can I still say I have a Tonebender MKII? I hope so...

I would love to read some other sugestions and thank you.

P.H.

Electric Warrior knows his stuff. With leaky units like you are using, he's suggested in many forum posts to have the resistor from base to ground on Q1 at 10k ohm and the collector resistor for Q2 at 47k ohm, which is how the originals with OC75s were set up.. It looks like you incorporated at least the base to ground resistor on Q1 by implementing a trimpot.

I would bump Q3c up to between 7.2-8.2 vDC. You'll be surprised how much better it sounds. The 4.5 vDC value is a hold over from the days when people didn't know any better on this circuit and thought it was simply a Fuzz Face with an additional gain stage.

Also, you are reading positive values for voltage, not negative, correct? I'm curious as to the value of the trimpot used on Q2c. With leaky transistors like yours, i'm surprised it was not a struggle to get it to 4.5 vDC.

Overall, it's how YOU like the sound but I could never bond with anything lower than 6.5 vDC.

[percyhornickel]

Electric Warrior knows his stuff. With leaky units like you are using, he's suggested in many forum posts to have the resistor from base to ground on Q1 at 10k ohm and the collector resistor for Q2 at 47k ohm, which is how the originals with OC75s were set up.. It looks like you incorporated at least the base to ground resistor on Q1 by implementing a trimpot.

I would bump Q3c up to between 7.2-8.2 vDC. You'll be surprised how much better it sounds. The 4.5 vDC value is a hold over from the days when people didn't know any better on this circuit and thought it was simply a Fuzz Face with an additional gain stage.

Also, you are reading positive values for voltage, not negative, correct? I'm curious as to the value of the trimpot used on Q2c. With leaky transistors like yours, i'm surprised it was not a struggle to get it to 4.5 vDC.

Overall, it's how YOU like the sound but I could never bond with anything lower than 6.5 vDC.

Ok "as soon as my wife left the house" I will try to raise the Q3c to 7.2-8.2 vDC and test the sound..   ..(I´d could do it while she is sleeping too but I like to test with volume !!!!).

Glad to read the originals with OC75s were set up like I amtrying to do, so I can say I made a ToneBender.

And yes, I am reading positive values.

I will let you know the results.

P.H.

[rankot]

I've built TB MkII too, and I have a problem with oscillations. I have used Russian transistors:
Q1: MP20 hfe=69 leak=110uA
Q2: MP20 hfe=54 leak=110uA
Q3: GT308B hfe=62 leak=25uA
It seems that oscillations can be tamed with proper biasing, but when I do it, my voltages are not as expected. I will post them soon.

[Big Monk]

I've built TB MkII too, and I have a problem with oscillations. I have used Russian transistors:
Q1: MP20 hfe=69 leak=110uA
Q2: MP20 hfe=54 leak=110uA
Q3: GT308B hfe=62 leak=25uA
It seems that oscillations can be tamed with proper biasing, but when I do it, my voltages are not as expected. I will post them soon.

What schematic did you use? Any major parts substitutions from that schematic? When you say "oscillations", what do you mean exactly?

[Radical CJ]

I've built TB MkII too, and I have a problem with oscillations. I have used Russian transistors:
Q1: MP20 hfe=69 leak=110uA
Q2: MP20 hfe=54 leak=110uA
Q3: GT308B hfe=62 leak=25uA
It seems that oscillations can be tamed with proper biasing, but when I do it, my voltages are not as expected. I will post them soon.

I have previosly put together a Tonebender style circuit using USSR MP somthings (can't remember offhand which exact number), hfe was around 60. The circuit didn't self osillate, but did hiss. I solved the issue with a 1n cap from the base of Q1 or Q2 to ground. It was then good enough to be worth boxing up.

However, on reflection the attack knob is subtle and best near full, so could gave been switched to a fixed resistor, and then instead an external pot to bias Q3 between 4.5 and 8 V would have been more useful.

[Big Monk]

I've built TB MkII too, and I have a problem with oscillations. I have used Russian transistors:
Q1: MP20 hfe=69 leak=110uA
Q2: MP20 hfe=54 leak=110uA
Q3: GT308B hfe=62 leak=25uA
It seems that oscillations can be tamed with proper biasing, but when I do it, my voltages are not as expected. I will post them soon.

I have previosly put together a Tonebender style circuit using USSR MP somthings (can't remember offhand which exact number), hfe was around 60. The circuit didn't self osillate, but did hiss. I solved the issue with a 1n cap from the base of Q1 or Q2 to ground. It was then good enough to be worth boxing up.

However, on reflection the attack knob is subtle and best near full, so could gave been switched to a fixed resistor, and then instead an external pot to bias Q3 between 4.5 and 8 V would have been more useful.

A 1kC pot broadened the range of the Attack pot for me, but ultimately there should be a considerable amount of range and variability when the unit is biased right. Personally, I find it useful all up and down the dial.

[duck_arse]

percyhornickel - if you have built a circuit with pnp transistors, and with positive ground, all your voltages should read negative. for consistency, we ALWAYS put the black meter probe to ground [no matter pos or neg ground, always ground] - and we ALWAYS ground the sleeve of our jacks, so that's a good place to put your black probe to avoid confusions. and when you post those voltages, you should include the minus sign.

[Big Monk]

percyhornickel - if you have built a circuit with pnp transistors, and with positive ground, all your voltages should read negative. for consistency, we ALWAYS put the black meter probe to ground [no matter pos or neg ground, always ground] - and we ALWAYS ground the sleeve of our jacks, so that's a good place to put your black probe to avoid confusions. and when you post those voltages, you should include the minus sign.

I missed this. In a separate thread, he had listed these as NPN and I neglected to look them up. These Sanyo units are in fact PNP. Good catch and sorry to have confused the matter!

[percyhornickel]

percyhornickel - if you have built a circuit with pnp transistors, and with positive ground, all your voltages should read negative. for consistency, we ALWAYS put the black meter probe to ground [no matter pos or neg ground, always ground] - and we ALWAYS ground the sleeve of our jacks, so that's a good place to put your black probe to avoid confusions. and when you post those voltages, you should include the minus sign.

Ok thank you to clear this point, this is my second pnp build and I not that familiar with this. Next time black probe right to +9V!!!.

[rankot]

I have fixed oscillations - it was a high pitched sound from 500-1500Hz, depending on bias trimmer position. The problem was with my voltage inverter, I used 10uF MLCC for an output capacitor after LT1054 and it was obviously not suitable for that purpose - once I replaced it with 100uF tantalum, oscillation was gone and I was able to bias pedal correctly.

Now, regarding bias, this is what I get with my transistors - I set it by ear, e.g. the sound I like the most:
Q1: MP20 hfe=69 leak=110uA Vc=-7.87V
Q2: MP20 hfe=54 leak=110uA Vc=-0,34V
Q3: 1T308V hfe=62 leak=25uA Vc=-7.35V

I tried to set Q3c to -4.5V, as suggested in FuzzCentral article (http://fuzzcentral.ssguitar.com/mkII.php), but it was not loud enough, and setting Q3c to more than what I settled at the end was a little bit farty, so I let it go like this.

I will add 10p capacitor (C15) across Q3 base and collector, just in case.

This is the schematic I used:


Parts with * are just placeholders, I didn't install any of them, only R2. Do I need it at all?

[percyhornickel]

I have fixed oscillations - it was a high pitched sound from 500-1500Hz, depending on bias trimmer position. The problem was with my voltage inverter, I used 10uF MLCC for an output capacitor after LT1054 and it was obviously not suitable for that purpose - once I replaced it with 100uF tantalum, oscillation was gone and I was able to bias pedal correctly.

Sorry about my silly question but what is the "oscilation"? isn´t there a sound where I could here how it sounds?. I just know how is a gatered sound in this circuit but I have no clue about oscilation.

[antonis]

https://www.youtube.com/watch?v=n_MgszRlalk

[rankot]

Sorry about my silly question but what is the "oscilation"? isn´t there a sound where I could here how it sounds?. I just know how is a gatered sound in this circuit but I have no clue about oscilation.

This one I had was a little bit overdriven sine wave. So just find any sine wave and listen to it, that's it.

[percyhornickel]

Rankot / Antonis thank you for make this clear to me, I haven´t experimented any ascilation until now I guess.

I tried to bias Q3c around -7.5v/-8.5V but the sound is too gatered, so I feel a better taste around -4.5v to -6.5v like vintage units, maybe because the big leak of my transistors, don´t know.

Did you know what voltage it is typical for the Q1c?, I put a 20k pot and I set this for -1.5v/2.1V.

Please let me know if I am wrong

Thank you.
P.H-

[Big Monk]

Rankot / Antonis thank you for make this clear to me, I haven´t experimented any ascilation until now I guess.

I tried to bias Q3c around -7.5v/-8.5V but the sound is too gatered, so I feel a better taste around -4.5v to -6.5v like vintage units, maybe because the big leak of my transistors, don´t know.

Did you know what voltage it is typical for the Q1c?, I put a 20k pot and I set this for -1.5v/2.1V.

Please let me know if I am wrong

Thank you.
P.H-

Just to be clear, there are no vintage units with 4.5 vDC on Q3c. That's a holdover from when people though a Tonebender was just a Fuzz Face with an extra gain stage.

Try swapping the transistors around in each position until you get a combo you like at a higher voltage.

Q1c should be seeing basically the same voltage as Q3c, maybe a touch higher.

[percyhornickel]

Ok Big Monk, here my last update:

Q1b - Changed the 20k pot for 10k resistor as suggested by electric warrior / turns out the pot wasn´t working fine.
Q2c – Change the 100k trimmer for 50k pot and set bias / 50k trim helps easily to set bias / the 100k trim is in the trash too.

My new readings:

Q1c -7.45v (higher than Q3c as you said)
Q2c -0.22v
Q3c  -7.33V
This thing now sounds great!!!!

...And yes, the -4.5V is for fuzz face so fuzz central and some others are wrong I guess.
I have in separate breadboards the silicone FF and TB, the germanium FF is in a pcb already. They all sounds great even with hambuckers.

Thank you all, I really appreciate your help.

P.H.