Op Amp Max Supply Voltage

[Doctor B]

Long-time listener, first-time caller...

Been looking at some of the recent class-D wonder-amps (fosi, aiyima, smsl, topping, etc) and noticed that the 2 main "tweeks" are 1.) roll the op-amps and 2.) get the 48V power supply. I thought the power supply advice seemed logical and was pretty universal, both on audio (expert) discussions and in buyer (laymen) reviews. When looking into recommended op-amps (e.g. opa2134, lm4562, etc) I found a spec called "supply voltage MAX". Most, if not all, of these op-amps are rated in the 30s, even the stock NE5532 (30V). I'm thinking Max Voltage doesn't mean what I think it means. Is it "safe" to use a 48V power brick with these? I'm assuming yes, since even the makers of the amps match 48V power supplies with there amps, but maybe someone can explain why this is OK?

 

[SIY]

Long-time listener, first-time caller...

Been looking at some of the recent class-D wonder-amps (fosi, aiyima, smsl, topping, etc) and noticed that the 2 main "tweeks" are 1.) roll the op-amps and 2.) get the 48V power supply. I thought the power supply advice seemed logical and was pretty universal, both on audio (expert) discussions and in buyer (laymen) reviews. When looking into recommended op-amps (e.g. opa2134, lm4562, etc) I found a spec called "supply voltage MAX". Most, if not all, of these op-amps are rated in the 30s, even the stock NE5532 (30V). I'm thinking Max Voltage doesn't mean what I think it means. Is it "safe" to use a 48V power brick with these? I'm assuming yes, since even the makers of the amps match 48V power supplies with there amps, but maybe someone can explain why this is OK?

Putting aside the fact that "rolling" opamps is generally a terrible idea (which may explain its popularity among the hucksters), the voltage on board may be regulated down to safe limits. What you need to do is measure the actual voltages at the opamp power pins and choose the substitute accordingly.

The smart move is not to play in the first place.

 

[Zapper]

@SIYis correct. The input voltage is regulated down to a lower voltage for the op-amps. The TI reference design uses a two step regulator for the op-amps, which operate from a single +12V supply:

First a LM5010ASD buck steps down the input voltage to 15V, then a LM2940IMP-12 LDO is used to generate a cleaner 12V supply, which is further filtered by an LC filter, which includes 10uF and 0.1uF caps at each op amp.

Of course the commercial products based on the TPA3255 may differ in implementation.

I also agree that there is nothing to gain by "rolling" op-amps.