OKKO Dominator [traced]
- RnFR
- Old Solderhand
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looks like someone just made Degoop Doctor.
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- batteryacidtea
- Breadboard Brother
Hell yeah! Now that's something to really care about and spend crazy time building and playing!
- DimebuGG
- Solder Soldier
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From the layout, the two Vref's(V/2) are tied together?
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Stifler: Suck my dick - Ron Jeremy
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- RnFR
- Old Solderhand
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I was wondering about the first stage, too. that does not look right.kusi wrote:are you shure about R4 / R5?
regards, kusi
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- bajaman
- Old Solderhand
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Yesplease check R4 / R5 again
R4=R5=10K I do a stupid thing
I was running some potential jfets on my simulator and to get the voltages on your schematic, I had to change the value of R4 from 5k to 10k
Incidentally the correct jfet type is critical to the sound of this pedal - I could not get the correct measured voltages with J201 or 2SK117
It would be great if you could determine what these fets are!
In the meantime my simulations with the 2SK30ATM were right on the button - the same voltages as on the schematic BUT it has DGS not DSG pinouts.
Most of the non linear amplification occurs in this input stage - the 10k loading resistor (R4), draws nearly 4 times the current of the fet when biased on and limits the gain of the first stage by nearly 50%. The distortion due to this badly biased and "slugged" input stage depends very much on the Jfet type and is assymetrical in nature for some types more so for the J201 than the 2SK30
No clipping diodes further down the track either
Incidentally almost any n channel jfet should work for Q2 - it is configured as a buffer stage between the input tone shaping Q1 and the rest of the circuit - the gate is biased at exactly half voltage or 10.8 / 2 = 5.4 volts dc - the source sits at 5.65v dc
cheers
bajaman
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- bajaman
- Old Solderhand
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the rest of the circuit is very similar to the Marshall Bluesbreaker / KOT etc. fopllowed by another buffer (op amp this time) and then a 3 way active tone control with switch selected mid frequency centres.
be kind to all animals - especially human beings
- bajaman
- Old Solderhand
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followed
where did the edit feature go
where did the edit feature go
be kind to all animals - especially human beings
- DimebuGG
- Solder Soldier
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Saruman wrote:are you shure about R4 / R5? - yes
From the layout, the two Vref's(V/2) are tied together? - no
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Finch: A witty saying proves nothing - Voltaire
Stifler: Suck my dick - Ron Jeremy
Stifler: Suck my dick - Ron Jeremy
- bajaman
- Old Solderhand
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BF245A
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- RnFR
- Old Solderhand
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the first stage is still confusing me. this seems like a very odd way to bias a FET. it would obviously bias it close to 1/2 Vcc, but it also seems like you would be shunting a ton of signal to ground through that 10K resistor. I'm aware of what the 10k on the emitter is doing, and why there is gain reduction and distortion there, but why is the collector biased off of the divider like that?
"You've converted me to Cubic thinking. Where do I sign up for the newsletter? I need to learn more about how I can break free from ONEism Death Math." - Soulsonic
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