steinchen
100+ Head-Fier
- Joined
- Jan 6, 2005
- Posts
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Unfortunately one of my audio sources (Creative Audigy 2 ZS) has a quite high dc offset (some tens of millivolts). With a gain of 10 in my headamps this would result in some hundred mV on the output of the amp. Therefore I got to use coupling capacitors in my amps.
On my PIMETA i soldered (large) Wima MKP 0.22uF with short wires under the pcb (C1L, C1R).
For my PPA I'm planning to put the coupling capacitor between the pot and R1, too. Means cutting the traces on the bottom side of the pcb and mounting the caps directly to the pot bridging the cut. Hope this is correct so far. I'm planning to use large high quality caps (Wima MKP or Mundorf).
With R2=1M the corner frequency (-3dB) of the resulting high-pass should be 0.5Hz with a 0.33uF cap. Would this be overkill ? The PIMETA reference from tangent is 0.7Hz with a 0.22uF cap. Would a smaller (even if higher quality) cap result in degraded sound quality due to phase distortion ? Should I use the largest cap possible ?
Furthermore I thought about putting a switch parallel to the cap, my CD-player has almost no dc offset, so I could bridge the cap depending on the source, but I'm afraid of noise pickup etc.
Are there other ways to deal with dc offsets from the source ? Maybe a high-pass-filter between source and amp outside of the amp ? Or an active circuit between R1 and the + input of the opamp making caps obsolete ?
On my PIMETA i soldered (large) Wima MKP 0.22uF with short wires under the pcb (C1L, C1R).
For my PPA I'm planning to put the coupling capacitor between the pot and R1, too. Means cutting the traces on the bottom side of the pcb and mounting the caps directly to the pot bridging the cut. Hope this is correct so far. I'm planning to use large high quality caps (Wima MKP or Mundorf).
With R2=1M the corner frequency (-3dB) of the resulting high-pass should be 0.5Hz with a 0.33uF cap. Would this be overkill ? The PIMETA reference from tangent is 0.7Hz with a 0.22uF cap. Would a smaller (even if higher quality) cap result in degraded sound quality due to phase distortion ? Should I use the largest cap possible ?
Furthermore I thought about putting a switch parallel to the cap, my CD-player has almost no dc offset, so I could bridge the cap depending on the source, but I'm afraid of noise pickup etc.
Are there other ways to deal with dc offsets from the source ? Maybe a high-pass-filter between source and amp outside of the amp ? Or an active circuit between R1 and the + input of the opamp making caps obsolete ?