Vox Tone Bender

[maudlinwaltzer]

Hey all y'all,

I'm new here yes.  Hello.  I am just a noob so be kind.  I am sitting here looking at a Vox Tone Bender, silver case with black face.  When researching the transistors at Fuzzcentral I leaned they commonly had a SFT337 and and an OC76.  The one I have doesn't; rather, a SFT337 and an ATES AC135.  Can some wizard explain what's up with that?  How do the two transistors differ?  Why would this pedal not have a OC76?

Mine looks like this.



Thanks for any help.

[maarten]

Hello Maudlinwaltzer,

Quite usual to replace parts with other parts with approximately the same characteristics. Both OC76 and AC135 are of the germanium type (nowadays hard to find) and both are low voltage, low power and low gain (especially when compared to current transistor types), AC135 being rated for an hfe (gain) of 70 and OC76 of 30 (or less). So probably your AC 135 was considered to be a good substitute for the OC76 at that time - and it probably still is. Kind of difficult to find good information on these transistors, as they were both obsolete long before datasheets were uploaded tot he internet. Maybe somebody else can give you some further information on the difference between these 2 transistors, but to my opinion the difference does not matter.
It must be an old pedal, probably from the seventies at latest, I would imagine (based upon the transistors being used, that is: if they are the originals). Maybe best to keep it in original shape and enjoy it without any modding...
Maarten

[zombiwoof]

I had one exactly like that for several years that I bought when I was a kid from Saul Betnun's in L.A.  I still regret selling it, it sounded awesome.  I'm sure they probably came with a variety of trannies over time, it probably is stock.  Unfortunately when I had it I knew nothing about transistors and such, so I don't know what mine had in it.

Al

[Scruffie]

If you read this - http://www.stompboxes.co.uk/History.html (down the page a bit)

Post 1967 they changed the OC76 is all, still good.

[petemoore]

  The circuit is like an addendum to the rest of the pedal.
  It's not too hard to build up a circuit board for testing Ge's [~4k7 + 10k trimpot to bias them].
  Getting the transistors...another matter, I'd definitely keep that as something to try whippin' [probably a tough fuzz in there, I'd like to hear what it sounds like these days], then if whipped...stick that in your box and take it out for nights on the town or whatever.

[zombiwoof]

  The circuit is like an addendum to the rest of the pedal.
  It's not too hard to build up a circuit board for testing Ge's [~4k7 + 10k trimpot to bias them].
  Getting the transistors...another matter, I'd definitely keep that as something to try whippin' [probably a tough fuzz in there, I'd like to hear what it sounds like these days], then if whipped...stick that in your box and take it out for nights on the town or whatever.

I don't understand much of this post, but I definitely wouldn't mod that vintage Vox.

Al

[petemoore]

The circuit is like an addendum to the rest of the pedal.
  If you're building one of these, the rest of the pedal comprises the lions share of the work, the circuit can be populated relatively quickly and inexpensively.
  Considering the value of the pedal as is, and I'm not referring to simply monetary, modifying this circuit is most easily done with a new circuit board designed to accomodate mods.
  It's not too hard to build up a circuit board for testing Ge's [~4k7 + 10k trimpot to bias them].
  This refers to using a stop resistor, 4k7 or so, seriesed with a 10k trimpot, which provides an adjustable bias easily for whatever transistors will sound good. It's recommended to try transistors that are 'in range' but also varying the Hfe in the Q postitions [lower Hfe in Q1 for instance]. To do this, adjusting the bias is necessary for every swap. 4k7 - 14k7 accomodated and biased smoothly, any of the transistors I wanted to try.
  Getting the transistors...another matter, I'd definitely keep that as something to try whippin' [probably a tough fuzz in there, I'd like to hear what it sounds like these days], then if whipped...stick that in your box and take it out for nights on the town or whatever.
  The transistors in the pedal...performance wise, may be difficult to find comparable replacements for, the other components...well, it's very easy to source HQ components for the rest of the circuit.
 

[petemoore]

  If you feel you need to understand dudes Tonebender better, or whatever it is I typed that you can't seem to understand, you can PM me with specific questions, I would be glad to try to explain more clearly.

[maudlinwaltzer]

Awesome info.  I wanted to make sure it hadn't been modded with something inferior.  But, if in all likelihood it is original or, at least, suitably repaired for the time period, then I am happy.  And yes, it sounds effing wonderful! 

I hear people describe Tonebender's as sounding thin and raspy; mine can kick out some thick and foggy tones.  It's a pure piece of genius pedal.

[zombiwoof]

Awesome info.  I wanted to make sure it hadn't been modded with something inferior.  But, if in all likelihood it is original or, at least, suitably repaired for the time period, then I am happy.  And yes, it sounds effing wonderful! 

I hear people describe Tonebender's as sounding thin and raspy; mine can kick out some thick and foggy tones.  It's a pure piece of genius pedal.

The Vox Tonebender is different than the other Tonebenders, it is closer to a Fuzz Face as far as the circuit goes.  Nothing like "thin and raspy" there!

Al

[Manic Manager]

New as well and trying to start to understand this stuff better. Would the OP be able to add a couple pix of the insides?

I recently picked up one too and I would like to compare them.

thx all!

MM