I've got a question about replacing the attenuator in the following circuit from a Denon pra1100 preamp. I like the preamp, and it sounds good. I am curious about changing out the attenuator, however it uses a 4 gang pot that is really 2 different pots with different resistance. The first pair, is atte50k and sits before the flat amp and tone controls. The second pair is 5k and sits before the buffer.
My question is, why is there a 5k attenuator before the buffer?
Because the attenuator pot is 2 different resistance, a replacement pot is not available that I can find. Maybe I should leave it as it is, but I can't understand why it is there, or needed... Could it be replaced with a resistor in the middle of the range? say 2.5k in line, and 2.5k to ground?
Thanks for the info... I'll probably leave it alone, but I was toying with the idea of putting a higher quality attenuator in, say a 50k alps blue velvet, just to play around with it.
My unit doesn't seem to have the cd direct input or relay 601.
Here is the circuit diagram.
My question is, why is there a 5k attenuator before the buffer?
Because the attenuator pot is 2 different resistance, a replacement pot is not available that I can find. Maybe I should leave it as it is, but I can't understand why it is there, or needed... Could it be replaced with a resistor in the middle of the range? say 2.5k in line, and 2.5k to ground?
Thanks for the info... I'll probably leave it alone, but I was toying with the idea of putting a higher quality attenuator in, say a 50k alps blue velvet, just to play around with it.
My unit doesn't seem to have the cd direct input or relay 601.
Here is the circuit diagram.
Attachments
I think that scheme is to optimize gain structure for lowest noise.
It is interesting. I wouldn't change it. If you must change the pots, then try to assemble two pots together if you can. If you look closely, some pots can be disassembled and reassembled with mix and match parts.
Edit: If you can figure out how to piggyback two Blue Velvet pots together, then that might be very worthwhile. If you look, they're held together with small screws. Take one apart and see what's up.
It is interesting. I wouldn't change it. If you must change the pots, then try to assemble two pots together if you can. If you look closely, some pots can be disassembled and reassembled with mix and match parts.
Edit: If you can figure out how to piggyback two Blue Velvet pots together, then that might be very worthwhile. If you look, they're held together with small screws. Take one apart and see what's up.
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I would seriously consider removing the output buffer/servo and replacing the opamps with something nice, high current, low offset. Don't see the discrete fet output raising the performance of a good opamp anyway.
If it were mine, I'd add a tone bypass switch, starting from before the balance control,
and ending at the 5k volume control.
Don't increase the value of the 5k to more than 10k, if at all.
Some people like tone controls. Many commercial applications of tone controls do more harm than good. Some are terrible. A few are good. My Luxman receiver has subjectively nice tone controls and I've never done a single thing to them, not even cleaning the pots.
Old tone controls can introduce a lot of problems. Potentiometers wear out. Add switches (or relays) to the mix and there's more opportunity for failure. Old line level switches and relays that are never actuated are destined to go bad.
Old tone controls can introduce a lot of problems. Potentiometers wear out. Add switches (or relays) to the mix and there's more opportunity for failure. Old line level switches and relays that are never actuated are destined to go bad.
There is a tone bypass switch, and it is set to bypass nearly all of the time.
My idea was to replace the primary 50k attenuator with a higher quality unit, and replacing the 5k with fixed resistors, middle of the range, say 2.5k. I can't replace both because they are in line, and run off the same knob. When 50k is adjusted, the 5k is also adjusted.
Interesting idea about replacing the buffer. My primary amp I use with this preamp is a honey badger badger amp.
My idea was to replace the primary 50k attenuator with a higher quality unit, and replacing the 5k with fixed resistors, middle of the range, say 2.5k. I can't replace both because they are in line, and run off the same knob. When 50k is adjusted, the 5k is also adjusted.
Interesting idea about replacing the buffer. My primary amp I use with this preamp is a honey badger badger amp.