Preamplifier power supply


Hi folks, should a preamplifier have a BIG (that is: an overkill power supply) to sound dynamic and authoritative? I'm asking this because some experts would say "yes" while others would say "no". Recently a well known audio journalist (Anthony Cordesmann?) said that the preamplifier doesn't have to have a big power supply because it doesn't have to deliver lots of energy (in the form of current). A preamplifier can sound "dynamic" even with very modest power supply --> for example the built in preamplifier in the Benchmark DAC. But some manufacturers rely on a truly overkill power supply in their reference preamplifiers: MBL, First Sound Audio, BAT, VTL, LAMM, Mark Levinson. So who is right?

Chris
dazzdax
Hi Chris . . . it's a mistake to so superficially "analyze" both the engineering decisions and marketing motivations behind any consumer product . . . it's true that there are many questionable design and engineering practices behind many specialist audio products - but simply looking at the size of the "power supply" (what does that include?) is akin to starting a thread with a title of "What's the proper diameter of a woofer?" . . .

. . . and if it's a mains transformer and filter capacitors you're looking at -- let's just say that dramatically oversizing these components is a pretty ineffective way of ripping off the consumer.
Kirkus, I'm not saying that an oversized power supply is all you need. I was trying to find out why some experts keep telling that a big power supply is essential, even with preamplifiers. Why do you think manufacturers are making two (or four) chassis preamplifiers with the entire power section occupying an entire chassis? Spectral preamplifiers for example have a power section that is bigger than some power amplifiers! You can't deny that this is way overkill. So what are the benefits of such a design?

Chris
I see what you're asking.

Power-supplies are commonly separate from the main chassis usually either for UL approval (when pre-fabricated wall-warts are used) or to reduce magnetic coupling from the power transformer into the audio circuitry. In the latter case it may be actually cheaper to produce a separate chassis than to apply the correct parts and engineering time to eliminate the interference when these parts are in close proximity.

Truly low-noise circuit designs usually require low signal impedances, which means more signal current, which means more power-supply current, which can easily lead to a bigger supply . . . and everything runs warmer, so it has to be spread out more for heat dissapation. Also frequently, internal grounding mistakes can cause supply ripple currents to be injected as hum into signal grounds . . . and if the cause of the hum isn't well understood, then it may be solved simply by heaping on more power-supply capacitance and reducing the ripple current.

There are also standard core sizes that transformers are made in . . . and other electrical characteristics (like load regulation, EM field output, and leakage reactances) that are related to the size of the core and the winding methodology. Again, it simply may occur that to acheive other engineering goals . . . bigger ends up being the cheaper/simpler way to get better.

You might also run into issues where these products are sold in countries that have different power tolerances (50Hz runs hotter and requires more capacitance), or tropical climates where a lower temperature rise is requires.

So, in the end, it's these and a thousand other factors. In the end, just like underwear . . . it all Depends.
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Elizabeth is just flat out wrong on this and apparently doesn't understand the importance of a component's power supply.

Some of the finest line level amplifiers use large, even massive power supplies to ensure dynamics are reproduced accurately.

They include Blue Circle, Plinius, Marantz, Tom Evans, Pass, Atma-Sphere, First Sound, and on and on.