Diode clipping on ground or bias

[liagasg]

I've noticed that on hard clipping stages :
1. There are designs that connect one side of the diodes to the signal, and the other side of the clippers to ground (like MXR Distortion +)
2. There are designs that connect one side of the diodes to the signal, and the other side of the clippers to ground or Vbias (Marshall's Drive Master)

What's the difference? Can I just use whatever option I want in a design, or there are more parameters to be taken in consideration?

[R.G.]

It all depends on the electrical qualities of your bias voltage.

A bias voltage is supposed to be very low impedance, like ground, but moved a few volts away.  Most bias voltages are decoupled to ground with big electrolytic caps to keep their AC "grounded-ness" good.  To the extent that a bias voltage is tied to ground by good, low impedance capacitances, it will be fine to connect clipping diodes to it.

I guess another way to say this is that if your bias voltage is well done, it doesn't matter.

[samhay]

I would imagine that you would only really want to connect clipping diodes to Vbias if the signal you want to clip is swinging either side of Vbias - i.e. if it is DC coupled between op-amp stages.

It looks like there has been a revision of two of the Marshall Drive Master schematic
compare here http://www.gmarts.org/?go=217 vs here: http://www.aronnelson.com/gallery/main.php/v/Renegadrian/a_mdm.gif.html

[liagasg]

So, if the clipping stage is between op amps is a good idea to connect them to Bias or connecting the to Vbias is the only way?

Yes, I've noticed the difference between the two schematics. DO they sound the same?
http://www.circuitstoday.com/diode-clippers

[samhay]

It depends if the op-amp stages are DC coupled - if there are no series capacitors between them, then they are DC coupled. If so, then I would clip to Vbias.
No idea how the circuits sound, I have not come across them before.