Lucias_D
New Head-Fier
- Joined
- Dec 20, 2006
- Posts
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I have some questions about ac/dc op amp based amplifier coupling, with some pertaining to the cmoybb
First I would like to discuss the types (physical construction) of capacitors used in coupling, and it's measured effect on sound quality. Does anyone have directed reading or personal findings on types of capacitors (electrolytic, mylar, polystyrene, teflon, etc..) regarding this question? Most notably I'm tackling THD or floor noise, and associated coloration of the waveform. If I had a scope I might try a bunch of different caps and try to take some measurements but I'm quite limited over here. I'm limited to my DMM and ears.
Secondly, JDS Lab's on there cmoybb modifications page highly recommend using a DC coupled signal path when using a "Line Out" input source. Does anyone know why this is? What is it specifically about a line level signal that would benefit from DC coupling in contrast to AC coupling?
Maybe this benefit is because of the specifically recommend caps in the bill of materials for this amp. From this thinking I would theorize that if 'high quality' [read: transparent audio] caps were used in this specific ac coupling in place of resistors (DC coupling), there would be no benefit to going the DC route.
Lastly, has anyone tried using trim potentiometers to 'equalize' DC offset in op-amp based headphone amplifiers or specifically the cmoy/cmoybb. Outcomes?
This forum has been an invaluable resource for many situations I've encountered. Thanks for all those dedicated to helping others!
First I would like to discuss the types (physical construction) of capacitors used in coupling, and it's measured effect on sound quality. Does anyone have directed reading or personal findings on types of capacitors (electrolytic, mylar, polystyrene, teflon, etc..) regarding this question? Most notably I'm tackling THD or floor noise, and associated coloration of the waveform. If I had a scope I might try a bunch of different caps and try to take some measurements but I'm quite limited over here. I'm limited to my DMM and ears.
Secondly, JDS Lab's on there cmoybb modifications page highly recommend using a DC coupled signal path when using a "Line Out" input source. Does anyone know why this is? What is it specifically about a line level signal that would benefit from DC coupling in contrast to AC coupling?
Maybe this benefit is because of the specifically recommend caps in the bill of materials for this amp. From this thinking I would theorize that if 'high quality' [read: transparent audio] caps were used in this specific ac coupling in place of resistors (DC coupling), there would be no benefit to going the DC route.
Lastly, has anyone tried using trim potentiometers to 'equalize' DC offset in op-amp based headphone amplifiers or specifically the cmoy/cmoybb. Outcomes?
This forum has been an invaluable resource for many situations I've encountered. Thanks for all those dedicated to helping others!