Power supply hum transmitted to loudspeakers

normie57

... Is it not almost universal that all amplifiers with power transformers have some low level power supply noise that will cause minimal leakage hum, buzz, or hiss through the loudspeaker with your ear close enough and no inputs to the amp connected?

If you want to test an amplifier, doing so with no inputs connected really doesn't tell you anything. That's not how the amplifier was designed to be used.

Hi Normie,

Noise is a problem with all active devices. It's caused by several things, but what can make it audible is high gain in the system, along with high efficiency speakers.

For some reason traditionally preamps are made with WAY too much gain. PrimaLuna is one of the few makers who make preamps with more reasonable gain amounts, therefore lowering the total noise.

As others have pointed out, what's really important is your peception of it. My system is reasonably quiet, but in the middle of a wind storm or with the heater blowing, it's the least of my problems. :)

E

@normie57

if its a "hum", try this https://emotiva.com/products/accessories/cmx-2

I agree with Cleeds. To make a meaningful test of an amplifier's intrinsic noise level shorting plugs should be connected to its inputs.

Many choices of RCA shorting plugs can be found at eBay, by entering "RCA shorting plugs" into its search box.

Regards,
-- Al

I run high efficiency Lowther speakers. They pick up everything. FWIW... What has helped my system is running everything except the mono amps through an Exact Power SP15 transformer. Also, I've found that I need to keep the SUT away from the other electronics. Well shielded  interconnects & power chords are also a must.