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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Excuse the doubled post,have no idea why.Tried to delete it but i didn't find how.
Admins,please chime in!
Thanks
Admins,please chime in!
Thanks
Pot at the input,
low output impedance but with pot low you get still all the hum and noise of the pre at the output.
Pot at the output,
much higher output impedance losing high frequency with long cables depending on the level of the pot.
Put it in between 🙂
Mona
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Great!This is what I thought I'd do in the first place but I wasn't sure about the pros and cons (especially the hum issue wich has to be solved separately).
BTW,the volume I intend to install isn't a regular pot but an 24-step log attenuator (ladder).Does this change anything about what you have already said?
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With the input signal applied directly to the input grid, overloading is possible
before the volume control. This is rather likely with the high gain of over 24dB,
so ensure that overload will not happen with the sources used, decreasing the gain if necessary.
before the volume control. This is rather likely with the high gain of over 24dB,
so ensure that overload will not happen with the sources used, decreasing the gain if necessary.
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