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Old 9th February 2007, 07:45 AM   #1
febytam is offline febytam  Hong Kong
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Default Aleph P volume

Anyone tried to place the volume control at input rather than original design at output stage? Sound any difference and trade off?
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Old 9th February 2007, 04:45 PM   #2
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This has been discuss quite a bit. Nelson has said the volume control can be either before or after his premaps, but after is better.

Do a search for attenuators or BOSOZ volume controls.

-David
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Old 10th February 2007, 04:00 AM   #3
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This is one of those things you can talk about endlessly, but trying it both ways will tell you what you want to know.
If you have a fixed, unchanging, front end, the impedance presented to the input device will be more-or-less known. The pot at the back will not only reduce the signal, but the noise as well. On the other hand, the circuit may be more sensitive to overload.
Putting a pot at the front allows you to trim a hot signal, but whatever noise the circuit generates will always be there, even if there's no signal.

Grey
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Old 10th February 2007, 06:08 AM   #4
EUVL is offline EUVL  Europe
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> The pot at the back will not only reduce the signal, but the noise as well. ......

All true, and I can confirm that from my own experience.
The disadvantage of a pot at the back is :

1) Your preamp has to swing a long more voltage than the other alternative. Not a problem for Aleph P, but certainly not true for all other preamp circuit.

2) If you have low impedance load (say 100-200 ohms) at the output, then you need thermally stable, high-power resistors in your attenuator of probably quite low values.

Otherwise I am all for pot at the back.


Patrick
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