Tonebender Transistor Help

[Wilhelm5]

Hey guys, I'm new to effect building and I'm having a bit of a hard time trying to decide which PNP Ge Transistors I should use for my sola sound tonebender MKIII build. Does anyone know what transistors were used in the actual SS tonebender mkIII? I'd like to stay as close to the original sound as possible. I've read through several forums and build reports and have seen everything from the russian made gt402V and gt108V to oc81's.  2N404's and AC128's have been listed as being used as well. This is all somewhat overwhelming. If anyone has any advice on which transistors to go with to keep me as close to the original tone as possible, I would greatly appreciate it! Thanks!

-Wil

[garcho]

EDIT sorry, MkIII, guess I need new glasses...

links are now fixed (linked to Mk3, not 2)


MkIII page

[garcho]

don't get too hung up on type. it's gain and leakage that will get you the "right" sound. read GEOFEX technology of the fuzz face et al. and maybe try with some cheaper Ge's and experiment with measurements and stuff. even if you get the perfect part number you might not get the perfect part.

oh, yeah, and WELCOME to the forum!

[Wilhelm5]

Excellent info! Thanks for the help garcho! The MkII (and crucial MKIII page addition) narrowed down my list, and the gain/leakage advice should allow me to experiment with a few combinations socketed to fineness and personalize the tone. This should definitely get me pointed in the right direction. Thanks again!!!

[Dooter]

When I built my first Tonebender MkII, I read the 'Technology of the fuzz face ' article and selected three low leakage tranny's of gain approx 100. Whilst the pedal sounded fine (and was bought by a guitarist in a Thin Lizzy trbute band - the pedal received compliments and enquiries from audience members) I later read an article that said the Hfe gains should be lower for this pedal (40-60). This was a revelation as I had made and sold plenty Fuzz Faces and finding low leakage tranny's of gains 80-120 is a pain in the butt. My stores had built up lots of tranny's that I had rejected - but hold on... I had lots of tranny's in the 40-60 Hfe range! Perfect for the next Tonebender. The one I have on my own board has 3 matsushita 2sb328's of gains about 50 and it sounds fantastic. More organic, musical, versatile and responsive than the one with 100's in it. Lower gains also work fine in Rangemaster treble booster clones too (60-80 Hfe) as do higher leakage than would be tolerated by a fuzz face circuit.

Hope this helps.

[Wilhelm5]

Thanks for the tip, Dooter! I too read that lower gains seemed to better suit these builds. Specifically at Q1 and Q2. A slightly higher gain of 100-120 Hfe is suggested for Q3. In your opinion, is there anything to be "gained" by sticking three tranny's in there with similar gains? Again, I'll probably buy a few, socket, and test to get a feel for what I'm looking for, but I definitely appreciate all the tips because, well, I don't want to spend too much money in buying a ton of transistors right now. My brother bought a Big Muff pi, but I'd rather build my own fuzzbox A) for the satisfaction of stomping on something I put together, and B) To have a nice sound without throwing the bank at a pedal just for the name. I'd eventually like to build up stock down the road and turn box building into a hobby (I've heard it's addictive), but right now I'm looking to just build what I need, gain experience, and keep some $ in my pocket.

Side Note: I'm digging the content on this forum. So many interesting topics and things to learn!

[Guitar Poppa]

Hello Wihelm and everybody

I'll try to be synthetic, addressing three levels where you'll find as well some of your questions and some of the first answers on this thread ...

On types of transistor...
Your questions are welcome, even if the type of transistor is not the most important in the Tone Bender Mk3 circuit...
To be very synthetic : there are 4 families of germanium transistors, each with a specific sonic comportment ...
--- Audio preamplifiers like OC75, 76 etc., AC125 /126, SFT320-323, russian MP41A, MP42b etc. produce a rather bright or hi-mid sound, as well when clear or saturated... Some older of them, like OC71, MP40A are less trebly, and produce a more lo-mid body...
--- Audio amplifiers (500mW to 1w) like OC81, AC128 etc., Russian GT402s, and equivalents may produce a more creamy texture, with particular dynamics...
--- Radio Frequency preamplifiers like OC44, AF124, GT308b and GT313b etc. are very reliable and plain, but almost too good to give its dirty juice to a fuzz.
--- Computer and switching transistors like OC43, OC140, 2N404A and many other give a very homogeneous saturation, but warmer and living than RF trannies...
This are first markers answering your question... But : they are not the most important, as wrote Garcho

On Gain and leakage
--- The different types of transistors will express their musical identity only if they are well suited to the circuit in which they must operate.
Regarding the TB Mk3, the first two transistors Q1 and Q2 form a pseudo-Darlington assemblage, which is equivalent to a single high gain transistor. To built it, very moderate gain (<80) transistors will be more than sufficient and recommended. The high sensitivity of this stage requires low leakage models : less than 250μA measured with the method of RG ... The russian MP40A, 42b, GT313A, GT308A, for example, will be perfect. 2N404A if well choosed...
--- The third transistor Q3 is used in a special way, without bias resistors on its base. It must therefore be biased by its own leakage current (this trick is very common in germanium circuits). It may have a relatively high leakage current: 500 to 900μA. This is common in preamplifiers and amplifiers transistors in the OCxx / ACxxx families. the OC75 / AC125 family will give a sharper fuzz, and the OC81 / AC128 family a rounder and creamy sound. The gain is relatively unimportant in this case : 80-180, for example...

On adjusting the circuits
--- Vintage analog electronics is the art to obtain precise effects with imprecise components ... As in the antique mechanics, this often requires adjustments. Many people believe that old pedals were perfect. I used them in my youth, I can say that most were less or more rotten. A good circuit and selected transistors are not always enough. Most of the time, you have to adjust certain resistance values, until you find the best sound and the best dynamics.
--- The resistors of 220k and 47k that polarize Q1 and Q2 can be slightly modified to get the best when you play softly and when notes end ... The 18k on the Q3 collector can have great consequences on the texture, at full level of fuzz. Connect, play, listen and note your impressions for each trial... Come back the day after rested in ears, ans take it one more time... And so on...

One day you will have the best you can at this moment, that's all I hope to you !

See my website if you want more about the germanium world...
http://guitarpoppa.com/?cat=32

[Wilhelm5]

That's exactly what needed to hear, Guitar Poppa. I was trying to figure out a way to explain the tone I was hoping to achieve without posting youtube videos of TB mKIII demos, and you nailed it square on the head. I'm aiming for a creamier, warm, rounded fuzz rather than a distorted, biting fuzz.

Thanks for your input and for giving me a better understanding of how the transistors work relative to one another and to the complementary components (resistors, capacitors, etc...) You guys are great!

[mac]

Matsuhita 2SB172,175,176
Toshiba 2SB54,56
HItachi 2SB77

mac

[Tony Forestiere]

Matsuhita

I see what you did there. 

[smallbearelec]

As Guitar Poppa points out, you should expect to have to tweak the biasing to get the best possible result from the devices you have. For this reason. get a breadboard. It can be as simple as this small strip:

http://smallbear-electronics.mybigcommerce.com/breadboard-strip-with-power-bus-small/

or larger and tricked-out for serious prototyping like this:

http://smallbear-electronics.mybigcommerce.com/kit-build-an-idea-board/

Happy experimenting and construction!