OC81D question - Tonebender MK II

[mikemaddux]

I see that OC81D is the recommended tranny for this circuit HFE at 70 70 100 for q1-q3.

But, the OC81D does not seem to have that high of gain.....according to datasheets.....

And I see theres a bunch of people that have built them using OC81D's.........so did these people use low gain trannys?

[petemoore]

I see that OC81D is the recommended tranny for this circuit HFE at 70 70 100 for q1-q3.
  And...the leakage ?
  Recommended..sure, if they sound good.
But, the OC81D does not seem to have that high of gain.....according to datasheets.
  Datasheet [in the case of Ge transistors] won't tell of leaky transistor or of gains ranging from X to Y.
  And I see theres a bunch of people that have built them using OC81D's.........so did these people use low gain trannys?
  That'd be ok too, mainly has to do with leakage being low enough for suitability [some tonebenders rely on Q1 having "X" leakage in order to bias IIUC], yupp leakage and gain numbers.
  The OC's and other Ge's are suitable for trying out if the leakage and gain are 'good'...depends on what you consider 'good'.
  The brand on the side can for the most part be disregarded if what you want is a few transistors suitable for a TB, I'd say start with more pieces than you need and find the values that suit your build/ears/pickups etc.

[mikemaddux]

I know its all subjective, but I think most of us are looking for gain and leakage numbers for a starting point to go through our batches......

but thats kinda OT......the original question is how do you get 100 hfe out of a tranny that only specs out at max 40 hfe (i've seen up to 60 hfe OC81D's - never higher)

[mac]

I used germs in the range 40-70 with excelent results.
I should be more concerned about leakage. If they are leaky good luck trying to bias it, inparticular Q2

Question: the magic set 70-70-100, that reminds me of the 90-60-90 cm of a perfect girl, is a real measure or just a guess?

mac

[jrod]

From what I've heard the OC81D's commonly sold on ebay are garbage. And getting real ones that are good are very, very expensive.

Anyhoo, from what I have read, especially on the DAM forum, the new OC81D's (like on ebay) are low gain. However, the old Mullard branded ones were higher gain, from what I understand. So, people who have used them in their builds have either used the low gainers or have been lucky enough have good NOS ones. The lower gain ones probably are ok in Q1 position, at least.

This is what I believe anyway.

[zombiwoof]

From what I've heard the OC81D's commonly sold on ebay are garbage. And getting real ones that are good are very, very expensive.

Anyhoo, from what I have read, especially on the DAM forum, the new OC81D's (like on ebay) are low gain. However, the old Mullard branded ones were higher gain, from what I understand. So, people who have used them in their builds have either used the low gainers or have been lucky enough have good NOS ones. The lower gain ones probably are ok in Q1 position, at least.

This is what I believe anyway.

If you're talking about the DSI OC81D's, I don't think anyone has said they are "garbage", what has been said is that it appears most of them are in a low gain range (Small Bear got a sample of them and they were all around Hfe 30 or so).  I haven't heard anything from anyone who has even used them yet, as most people would want them for ToneBenders and if they can't get them in the right gains they aren't going to be able to use them.  They look fine to me, but the gain considerations are important.  I would really be interested in hearing from someone that has used them successfully, and can report on how they sound in a ToneBender clone.  Same thing for the other DSI offerings, I hear they also have OC44's available.

And you can find "real" Mullard OC81D's on Ebay from time to time, the problem seems to be that there are now some fakes going around, and one respected pedal builder even unknowingly used some in his pedals (but he did tell people about it when he found out, and offered to fix the pedals he sold that had them in them.)
Al

[Scruffie]

From what I've heard the OC81D's commonly sold on ebay are garbage. And getting real ones that are good are very, very expensive.

Anyhoo, from what I have read, especially on the DAM forum, the new OC81D's (like on ebay) are low gain. However, the old Mullard branded ones were higher gain, from what I understand. So, people who have used them in their builds have either used the low gainers or have been lucky enough have good NOS ones. The lower gain ones probably are ok in Q1 position, at least.

This is what I believe anyway.

If you're talking about the DSI OC81D's, I don't think anyone has said they are "garbage", what has been said is that it appears most of them are in a low gain range (Small Bear got a sample of them and they were all around Hfe 30 or so).  I haven't heard anything from anyone who has even used them yet, as most people would want them for ToneBenders and if they can't get them in the right gains they aren't going to be able to use them.  They look fine to me, but the gain considerations are important.  I would really be interested in hearing from someone that has used them successfully, and can report on how they sound in a ToneBender clone.  Same thing for the other DSI offerings, I hear they also have OC44's available.

Al

I've used low gain mullard OC45 (40-60 hfe give or take) in a Tone Bender MkII and while it did sound different, it still sounded good and I think those DSIs were used in a reissue of the Tone Bender MkII recently, there is nothing wrong with them par se but they probably wont give the same sound as the original OC81Ds of which I have a set of originals (all around 80-120 hFe) they are slightly leaky but the Tone Bender requires leakage to work properly anyway and they play in the circuit just fine and give a different character.

Also regards the datasheets for OC81Ds the only ones I have ever seen show them as drivers for the OC81 but don't mention there hFe and even then, the OC81 is listed as Greater than 45 hFe, I have some OC81s too with no D Suffix and while i've had low gain ones (60 ish) i've also had higher.

I'd suggest just trying them (The DSIs) You'll probably be happy with the result and who knows what gains you might get when buying off ebay anyway, could be low or high.

[zombiwoof]

From what I've heard the OC81D's commonly sold on ebay are garbage. And getting real ones that are good are very, very expensive.

Anyhoo, from what I have read, especially on the DAM forum, the new OC81D's (like on ebay) are low gain. However, the old Mullard branded ones were higher gain, from what I understand. So, people who have used them in their builds have either used the low gainers or have been lucky enough have good NOS ones. The lower gain ones probably are ok in Q1 position, at least.

This is what I believe anyway.

If you're talking about the DSI OC81D's, I don't think anyone has said they are "garbage", what has been said is that it appears most of them are in a low gain range (Small Bear got a sample of them and they were all around Hfe 30 or so).  I haven't heard anything from anyone who has even used them yet, as most people would want them for ToneBenders and if they can't get them in the right gains they aren't going to be able to use them.  They look fine to me, but the gain considerations are important.  I would really be interested in hearing from someone that has used them successfully, and can report on how they sound in a ToneBender clone.  Same thing for the other DSI offerings, I hear they also have OC44's available.

Al

I've used low gain mullard OC45 (40-60 hfe give or take) in a Tone Bender MkII and while it did sound different, it still sounded good and I think those DSIs were used in a reissue of the Tone Bender MkII recently, there is nothing wrong with them par se but they probably wont give the same sound as the original OC81Ds of which I have a set of originals (all around 80-120 hFe) they are slightly leaky but the Tone Bender requires leakage to work properly anyway and they play in the circuit just fine and give a different character.

Also regards the datasheets for OC81Ds the only ones I have ever seen show them as drivers for the OC81 but don't mention there hFe and even then, the OC81 is listed as Greater than 45 hFe, I have some OC81s too with no D Suffix and while i've had low gain ones (60 ish) i've also had higher.

I'd suggest just trying them (The DSIs) You'll probably be happy with the result and who knows what gains you might get when buying off ebay anyway, could be low or high.

Wouldn't the "D" suffix imply a device that was sorted to a higher gain range (within the gain range of the specific device)?.
If so, I don't see how DSI could put "OC81D on them, if they are mostly in a lower range.  They should have just called them OC81's.

I tried emailing the guy selling the DSI OC81D's, asking about what gain ranges they typically fall into, and he didn't even reply to me.

Al

[Masuto]

hi guys heres my 2 cents..
less than one year ago i built two tonebenders mkii, with my early page boots and yardbirds lps at hand to get in the mood and ear..
-ordered 3 oc81d from ebay guy based in eastern europe (i kinda remember) for my best friends build
-ordered the matched equivalent trio from smallbear and waited ages for them to get through. they had a schem of the pedal and two resistors but no clue as to what to do with them (later i realised they were to bias the trannies...
well..mine sounded ok. my friend keeps coming back to me to tell me just how brilliant the oc81d build sounds.
i am going to build another oc81d for myself. end of story

[tonyharker]

The D on the OC81D means driver, and they were optimised (chosen) to be used as a transformer driver for a push pull output stage as in the Deacy amp.  It is NOT a gain indication.