Op-amp operating voltages - a question

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Thermionic Idler
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#1 Op-amp operating voltages - a question

Post by Thermionic Idler »

So all op-amps have a range of suitable rail voltages specified on their data sheets, usually up to ±16V or ±18V.

Has anyone experienced changes in sound with different rail voltages within that range?

The reason I ask is that I'm sometimes aware of a slight 'hardness' or shrillness in the upper mids in my system at the moment, similar to when the heater voltages were too high on the 300B's. It's less apparent on vinyl but I still hear it occasionally, and it's more prevalent with less-good digital sources.

This seems to have happened since I ripped out the old linear supplies and fitted the new battery / Silentswitcher power system into the linestage. As part of this change, the operating voltage on the linestage circuit changed from ±10V to ±15V, meaning they are dissipating quite a bit more heat now as they operate Class A.

The Alpha 24 linestage circuit uses three op-amps - the TI OPA1612AID, OPA1632D and OPA1611AID. I know one is rated to ±16V and the other two ±18V. It's possible to alter the voltage from the SilentSwitcher down but you have to work with surface-mount resistors - initially I baulked at that but I'm beginning to wonder if I should just put my big boy pants on and get that voltage down to say ±8V (±10V isn't an option). That will also benefit battery life.

The technical docs suggest that operating voltage shouldn't make a jot of difference but I just wondered if anyone's experienced otherwise?
Deck: Garrard 301 - Audio Origami PU7 - Van Den Hul Black Beauty
Phono: Whest PS30RDT
Linestage: AMB α24/LCDuino
Power amps: 'Newton' 300B PP based on a design by Lynn Olson
Speakers: FF225WK 'Big Met' Metronomes c/o Cressy Snr
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#2 Re: Op-amp operating voltages - a question

Post by jack »

Never noticed any difference - the manufacturer's data also states that noise/performance is independent of supply voltage assuming that the supply is in range.

I've several detailed texts on op amps and their design - I'll have a look to see what the experts say...
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