Hi all,
Got a Music Angel preamp on repair and upgrade.
I noticed that the vol pot is placed at the very end of the signal chain ie. between the 2,2mF cathode condensators and the output RCA's (see the first pic).Not a very common procedure,isn't it?....or?
On another Marantz 7 clone I saw (the MingDa MC-7R,pic 2),the volume pot is placed at the beginning (between the input selector and first tube's grid - through a 0,22mF,of course) wich looks like a more appropriate topology.
The tubes in the MA on my bench are 6N2P and 6N1P (not 12A*7 's and the heaters are wired accordingly) .
What are the pros and cons of having the pot at the preamp's output instead of input?
TIA!
Cheers,
S
Got a Music Angel preamp on repair and upgrade.
I noticed that the vol pot is placed at the very end of the signal chain ie. between the 2,2mF cathode condensators and the output RCA's (see the first pic).Not a very common procedure,isn't it?....or?
On another Marantz 7 clone I saw (the MingDa MC-7R,pic 2),the volume pot is placed at the beginning (between the input selector and first tube's grid - through a 0,22mF,of course) wich looks like a more appropriate topology.
The tubes in the MA on my bench are 6N2P and 6N1P (not 12A*7 's and the heaters are wired accordingly) .
What are the pros and cons of having the pot at the preamp's output instead of input?
TIA!
Cheers,
S
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"What are the pros and cons of having the pot at the preamp's output instead of input?"
Pro, If you know the added output impedance still can drive the loads that is to be connected, you get to adjust the output level.
Con, The added output impedance will limit the type of load the preamp could drive. aka: Bad idea if you don't know the output load.
Pro, If you know the added output impedance still can drive the loads that is to be connected, you get to adjust the output level.
Con, The added output impedance will limit the type of load the preamp could drive. aka: Bad idea if you don't know the output load.
Just some thoughts, although at line levels, and without pentodes, they might be irrelevant for your situation.
In the old days, they often advised not to place the pot at the input of (very) low level stages (like a high impedance microphone input) because irregularities in the pot could/would cause crackling that would get fully amplified if the pot would be situated at the entrance.
If the first stage(s) create noise (mostly when using pentodes) but there's also a surplus of gain, than placing the pot after this or these stage(s) would keep the noise somewhat lower.
In the old days, they often advised not to place the pot at the input of (very) low level stages (like a high impedance microphone input) because irregularities in the pot could/would cause crackling that would get fully amplified if the pot would be situated at the entrance.
If the first stage(s) create noise (mostly when using pentodes) but there's also a surplus of gain, than placing the pot after this or these stage(s) would keep the noise somewhat lower.