D*A*M Forum

Electric Warrior wrote:I forgot, I swapped them so often :D
will measure them tomorrow for you..

Thanks, bro!

OC75 MkII (10K on Q1 base, 47K on Q2 collector)
Battery -9.01
Q1 c -8.50 b -0.038 e 0
Q2 c -0.13 b -0.076 e 0
Q3 c -8.29 b -0.13 e -0.08

OC81D MkII #1 (100K on Q1 base, 100K on Q2 collector)
Battery -9.55
Q1 c -8.51 b -0.06 e 0
Q2 c -0.13 b -0.068 e 0
Q3 c -8.72 b -0.13 e -0.07

OC81D MkII #2 (100K on Q1 base, 100K on Q2 collector)
Battery -9.50
Q1 c -8.76 b -0.062 e 0
Q2 c -0.22 b -0.075 e 0
Q3 c -8.13 b -0.22 e -0.14

Awesome. Really helpful stuff. Thank you so much!

Thanks, Stu! That is some great info!

FUZZTX wrote:What do your transistors measure gain & leakage wise, Electric Warrior? I'd really like to know what vintage units measured, too!

Regarding Q2 collector voltage, mine measures about the same as yours, but I noticed the voltages changes as I turn the "Attach" control up or down?

gains were 96, 135, 68. plenty of leakage: 610µA, 525µA, 525µA

I'm experimenting with some other combinations right now, trying to match Stu's measurements.. some wild results so far

Stu wrote:OC75 MkII (10K on Q1 base, 47K on Q2 collector)
Battery -9.01
Q1 c -8.50 b -0.038 e 0
Q2 c -0.13 b -0.076 e 0
Q3 c -8.29 b -0.13 e -0.08

OC81D MkII #1 (100K on Q1 base, 100K on Q2 collector)
Battery -9.55
Q1 c -8.51 b -0.06 e 0
Q2 c -0.13 b -0.068 e 0
Q3 c -8.72 b -0.13 e -0.07

OC81D MkII #2 (100K on Q1 base, 100K on Q2 collector)
Battery -9.50
Q1 c -8.76 b -0.062 e 0
Q2 c -0.22 b -0.075 e 0
Q3 c -8.13 b -0.22 e -0.14

Cool numbers to have for reference, thanks for sharing!

My most recent MKII build spec'd out like this:
10K on Q1 base, 100K trimmer (set just shy of half...probably around 47K) on Q2 collector
Volume and Attack set full
Battery -9.49
Q1 c -9.12 b -0.010 e 0 (Mullard "Red Head" OC84 2R5 107 hfe 0.04mA)
Q2 c -0.66 b -0.110 e 0 (Mullard "Red Head" OC84 2R5 88 hfe 0.04mA)
Q3 c -*6.81 b -0.40 e -0.29 (Mullard OC84 2T5 78 hfe 0.06mA)
*voltage depends on trimmer...seems to sound good anywhere from 4.80 to ~7v

Stu I am sure like anything sonically there were differences, but of the 3 was there one that clearly sounded better than the other ones?

Electric Warrior wrote:

FUZZTX wrote:What do your transistors measure gain & leakage wise, Electric Warrior? I'd really like to know what vintage units measured, too!

Regarding Q2 collector voltage, mine measures about the same as yours, but I noticed the voltages changes as I turn the "Attach" control up or down?

gains were 96, 135, 68. plenty of leakage: 610µA, 525µA, 525µA

I'm experimenting with some other combinations right now, trying to match Stu's measurements.. some wild results so far

Thanks, man! I'd be interested to hear your results.


Hey Taller76. That is great info to have. Much appreciated and thanks for sharing!

The transistor combination I had in there was pretty nice, albeit a bit dull sounding. Cleaned up ok. Noise was not an issue.
The one I'm putting together now has more midrange honk, clarity and sparkle. Doesn't clean up as well and it tends to be a bit noisier. I consider it much more useable. Has great character
Although the voltages are similar, I believe the transistor gains are not. I'll tweak and measure some more when the room temperature here is back to an average level..

What are you using, EW? OC75's? I've not been able to that midrange tone you are referring to.

Any idea of what good sounding vintage unit transistors have measured?

yes, OC75s. I can get many different tones just by swapping transistors...

David published some hfe measurements: http://stompboxes.co.uk/forum/viewtopic.php?f=10&t=6569