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variable positive and negative volts

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Posted on August 30, 2020 at 01:23:30
glue tech
Audiophile

Posts: 119
Location: western new york usa
Joined: March 27, 2014
Hi all,
I have a phono which can run in dc at various voltages. I experiment with different power supplies. I have one i have yet to try that lets you independently vary the positive and negative volts. My phono is a cheap op amp based unit. Can i expect any benefits from varying positive and negative voltage slightly?

 

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RE: variable positive and negative volts, posted on August 30, 2020 at 02:19:20
Duster
Audiophile

Posts: 16463
Location: Pacific Northwest
Joined: August 25, 2002
Please provide a link to, or the make/model of the particular power supply, glue tech. TIA

 

RE: variable positive and negative volts, posted on August 31, 2020 at 07:19:44
glue tech
Audiophile

Posts: 119
Location: western new york usa
Joined: March 27, 2014
The power supply in question is an elenco precision xp 620. The phono section is an ART dj pre II. The ART can run from 7-12 volts DC and 9 to 12 ac. Im running it right now on the 7.5 setting of a similar cheap variable dc power supply but with fixed voltage settings and no way to vary + and -. I've had a look at the manual for the Elenco and now know how to wire it so i can experiment for myself. This was my main concern. Just trying to get the most out of this cheap phono i like, mainly because its cheaper than a good switch and i'm setting up a three arm system. With the gain turned all the way down on a good dc supply, it sounds pretty good if you can get the gain elsewhere. Works with high output mm and my fairly sensitive headphones just fine. Just wondering what if any theoretical advantages there might be to varying +and- volts, especially with op amps.

 

RE: variable positive and negative volts, posted on August 31, 2020 at 14:26:07
Duster
Audiophile

Posts: 16463
Location: Pacific Northwest
Joined: August 25, 2002
The Elenco product is a lab PSU. There may be a science-based application where varying the voltage of each polarity is advantageous, but I know of nothing in the audio realm that encourages end users to do such a thing, especially for a low-level device such as the pro audio ART phono preamp. Precision voltage regulation, including the relationship of the two polarities is vital for a device that handles a phono-level signal. I would not opt to use the Elenco product for the purpose, with fiddly knobs for variable adjustments of each polarity, glue tech.

 

RE: variable positive and negative volts, posted on September 13, 2020 at 12:40:12
LtMandella
Audiophile

Posts: 735
Location: CA
Joined: May 27, 2019
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RE: variable positive and negative volts, posted on September 18, 2020 at 04:04:28
Ugly
Audiophile

Posts: 2838
Location: Des Moines, WA
Joined: August 22, 2006
I think it is usually a good idea to increase voltage on op amp based preamps when you can.

Most op amps seem to distort a bit less, per their specs, if you can give them higher voltage. You may also stand to increase your overhead, which can be important for low distortion during high amplitude parts of the music.

Though each device within the circuit will certainly have some rated voltage limit that you should never exceed, so be careful with that. The op amps may or may not be the limiting factor when it comes to max safe voltage. It is always good to check the schematic first.

 

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