No crackle? That is not ok.

And should have used the second opamp as output for proper melting.

Most JFETs are symmetrical and work both ways. You can find a note in many datasheets that drain and source can be switched, see here.

There are several possible adjustments to decrease volume.

- R25 bigger
- R15 smaller
- R26 bigger
- Insert a resistor between C16 and the volume pot

The last one is superfluous as well.

Ah ok, that is the input impedance with the amplifier running open loop, when no feedback is applied. We never do that (unless building a comparator or Schmitt Trigger), so that value alone doesn't give the actual impedance. By applying feedback, the open loop impedance gets multiplied by the open l...

What makes you think it is low impedance? Sure you wouldn't use it as an electrometer input stage due to its bipolar input, but I don't see the problem with audio.

Well, take a wild guess :D. There are two that don't make any sense at all, one which might but really doesn't either, and one that is connected to other parts that have something to do with driving the LED, which determines the compression. R8/R9 are for DC biasing. R4 is part of the feedback netwo...

1. You can put a capacitor in front of the 10k in the sidechain, try 47nF or 100nF.
2. I'm not gonna look up that layout, but I would try a LED in parallel to the other one. It should have roughly the same forward voltage. Also put a small resistor in series with both of them.

Both Pin 1/7 should be at 0V. Do you have the correct from voltage from the charge pump? Also, try another opamp.

Like Phil said, as drawn it will put out a negative voltage. I think it's just mislabelled in the schematic out of habit. The voltge is only used for the tube heaters, but the tube doesn't care if it's negative or positive 12,6V. Both stages are common cathode, so heater-cathode voltage isn't an iss...

Yes, you can build it without the transformer. But it's not in the circuit to provide isolation (as drawn it doesn't), it is there to form the sound. In comparison to an overdriven guitar sound, transformer distortion is very subtle, its contribution might be minimal anyway. These little transformer...

Latest post on Zeptobars: https://zeptobars.com/en/read/Ti-CD4046 ... -VCO-zener

Now that's a proper PLL gutshot .

In addition to what Phil said: you can't change the polarity of the signal at that point. It would upset the phase relation of the mixer in front of the BBD, as well as the mixer of clean signal and effect signal at the output.

6. When you are working in the kitchen, you can clean up after every step of the process, or you clean everything once when you are finished with cooking. The end result is the same. 7. The 150R increases the output impedance. But the complete term is R5 + each "half" (depending on the pos...

1. Many old effects were not TB. People weren't as obsessed as today about real copper paths™ and probably thought more like "hey a free volume control included, cool". 2. Yes it's a failure, I rambled about that a while ago in another thread. Unfortunately the Memory Man set the bad prece...

Broken switch.

Leave it out. That power supply section drawing is a mess. If it's a standard silicon or schottky diode, it doesn't do anything. If it is a zener, then the 10R resistor is definitely wrong. I don't see any reason why the supply voltage should be dropped at that point. It will run fine on 9V or 12V.

Increasing the resistor will increase the level, true. But your numbers are off, because you are ignoring the 47n capacitor to ground. Its impedance is roughly 3,4k at 1kHz. So the level drop is less than you state, and doubling the resistor won't give double the volume. The problem is by changing t...

Read here first: http://www.geofex.com/Article_Folders/mosswitch/mosswitch.htm You want low Rds_on and need to watch the current/max power dissipation specs. The power can be calculated with the Rds and the current drawn by the effect. Although in reality this is probably only of theoretical interes...

Sure, PM me your address and I'll send you a couple, I have more pcbs than I'll ever build in a lifetime. Same goes for anyone else interested of course. Unfortunately I don't have any more of the duals at the moment. I tested the single opamps in a Rat, Hotcake and OD250, and they do offer some ton...