Transistor choice for Tonebender MKII

[nico13]

I would like to build a Tonebender MKII.

I know that the original Tonebender was fitted with Mullard OC81D transistors (or OC75 in some units). As these references are very hard to find now I plan to use equivalents to these transistors.

After searching datasheets I can use AC128 instead of OC81D (AC125, AC126, AC128 or AC151 instead of OC75) but I would like to know if this change would affect the sound comparing to original Tonebender.

Do I have to choose other transistor equivalents (which ones?) for my building to sound as close as possible to the original unit?

[petemoore]

Do I have to choose other transistor equivalents (which ones?) for my building to sound as close as possible to the original unit?
  Read RG's Technology of the Fuzz Face / choosing transistors / also /build it with what you have while you're waiting for the perfect components to become available.
  The ones that sound best sound best, Ge's of same 'ilk'...brand, batch, model # can sound perfectly different and bad...these are 'seconds'.
  You will easily be able to find 'seconds' of the 'originals' in my estimation.
  You'll find the ones that have improved noise and tone characteristics follow...
  ...Gain and leakage are what matters first, after that gain and leakage is what matters most, after that one unit to the next .. slight frequency response differences. IME plenty of frequency response in all good ones, if HF is too much it can easily be tamed.
  Swap 'em 'till you drop or drop 'em...then play the dern thick Fuzz available from good transistors in a tonebender, I don't have 'original' transistors in mine, just the ones that went through the same type of testing the best original tonebenders must have been treated to...extensive tweeking and selection of transistors, that's what gets them in the ballpark for chance at home run.
  Get some Ge's...if you haven't yet, it may be good to get a set or two of matched ones, that way you'll be able to get a great sounding ToneBender by which you can compare TB #2 to.
  ..er...that's how I figured out...I like 'racing' my nearly identical favorite circuits.
 

[drewl]

yeah, if you got em, swap em...
I wanted a good MKII build right from the get go, so I ordered Mousers matced set and damn if it ain't the best sounding pedal I've ever heard.
It gives me a standard that  can measure and try and match what PNP GE's I have or find to what I know sounds great.

[John Lyons]

I assume you meant Smallbear's matched set Drewl?

I recommend the matched sets at SB as well. It's cost a little bit but in the long run it will save you time and you will get a nice good working set of germanuim devices and a good sounding pedal.

John

[drewl]

Yes, DOH! SmallBear!
Sorry, I have to order some stuff from mouser and it was on the brain.
matched set from Small Bear....thank you.
Wonderful world we live in that a place like Small Bear exists for us builders.

[zombiwoof]

Yes, DOH! SmallBear!
Sorry, I have to order some stuff from mouser and it was on the brain.
matched set from Small Bear....thank you.
Wonderful world we live in that a place like Small Bear exists for us builders.

Doh! is right!  After I saw your post I went to the Mouser site and tried to find matched transistors!  No wonder I couldn't find them.  Oh well.....

Al