tube screamer: hooking up the diodes to ground vs. bias

[fatfoohy]

Hello Internet!  I've noticed, the TS 808 has the diodes hooked up to the 4.5 volts, and so does the son of a screamer, however, both versions of the tube reamer, are hooked up to ground. Could somebody explain to me why? and what the difference is between the two is. thanks in advance!

Fatfoohy

[earthtonesaudio]

None go directly to any DC reference.  They are part of a voltage from the op-amp's output to "ground" or "Vref" or wherever.  The (-) input sees the divided voltage, and so the output gain increases to make the inputs equal.

[fatfoohy]

oh, alright, i kinda get what you mean, so what is the reasoning behind either?

[GibsonGM]

Since you're dealing with an AC signal, and Vref it connected to ground thru a filter cap, there's no difference.  The signal simply sees Vref as ground.   As it would "-" or "+".  Remember, there are caps connected across power supplies for filtering, and AC sees that as a short.
The cap in the connection blocks Vref from actually being part of what's going on in the loop....

[earthtonesaudio]

If you use a polarized cap, that's one case where it actually matters.  In that case, tie the cap to either supply (usually ground) and get the polarity correct.

[GibsonGM]

Good call.