Noise floor from power amp

[headphoneuser123]

I recently got the simaudio 330a to drive sopra no2. I also have the cxa61 and denon x3700h. I found the 330a to sound noticeably better than the power amp from the cxa61(smoother, better bass). However, I am finding that there is an audible noise floor from the midrange and tweeter of the sopra no2 when connected to the 330a(when holding my ear next to the drivers). When I connected the sopras to the x3700h, the static from the midrange vanished and the static in the tweeter became quieter. I found the static to be lower also when using cxa61 connected to the x3700h. Why is the 330a introducing a higher noise floor? It cost ~4k so I am wondering if this is due to the 330a picking up small distortions that the power amps from the cxa61 or x3700h couldn't, or if there is a problem with the amp. Does anyone here have thoughts about this? I am not sure what to think

 

[restorer-john]

The 330A's signal to noise ratio as specified (>100dB) is hardly spectacular. Taken as is, with respect to the rated 125W@8R output, the residual noise would equate to 316uV or 0.3mV. That is very much audible IME, and the likely cause as to why you are hearing noise in the midranges and tweeters.

 

[Slayer]

I recently got the simaudio 330a to drive sopra no2. I also have the cxa61 and denon x3700h. I found the 330a to sound noticeably better than the power amp from the cxa61(smoother, better bass). However, I am finding that there is an audible noise floor from the midrange and tweeter of the sopra no2 when connected to the 330a(when holding my ear next to the drivers). When I connected the sopras to the x3700h, the static from the midrange vanished and the static in the tweeter became quieter. I found the static to be lower also when using cxa61 connected to the x3700h. Why is the 330a introducing a higher noise floor? It cost ~4k so I am wondering if this is due to the 330a picking up small distortions that the power amps from the cxa61 or x3700h couldn't, or if there is a problem with the amp. Does anyone here have thoughts about this? I am not sure what to think

I saw these same complaints on a youtube video I believe. Seems like a lot of money to have an SNR of only 100db. I definitely would reurn it and go with Anthem, more power and wont have these issues.
I see John posted before i clicked reply.

Edit: Anthems SNR is 120db or higher and silent as a mouse.

 

[antennaguru]

Is it really that critical if you can't hear it from the listening position, and you have to hold your ear up to the speaker to hear it?

 

[Chrispy]

I'd be somewhat disappointed to spend that much on an amp and have such an issue but just don't see what makes that amp worth buying in the first place.....why did you choose that amp to begin with?

 

[MZKM]

I'll copy the reply I gave to you on Reddit:

The noise floor is simply higher.

Denon @ 4ohm @ 1W is 85dB; the 330A is 80dB.

Distortion is also higher:

Denon @ 4ohm @ 100W is 92dB; the 330A is 70dB.

______

The 330A's signal to noise ratio as specified (>100dB) is hardly spectacular.

And it's rated that at max wattage; the Denon also achieves that. This is why some companies will also spec it at 1W or so.

 

[restorer-john]

And it's rated that at max wattage; the Denon also achieves that. This is why some companies will also spec it at 1W or so.

S/N is rated at full rated power vs a shorted input residual. Full power can be whatever rating they choose (8/4/2R) in order to give the biggest voltage swing as it is a log ratio between residual noise in uV and available voltage swing over the connected load. Then they publish the best number.

That is why consumers cannot trust S/N numbers. Even 1W figures can be deceptive with no load specified and often no weightings specified.

At the end of the day, the only way to deterine what is real and what isn't, is to measure the residual noise in uV over a specific bandwidth and also examine the spectrum of said noise. Certainly, the Simaudio 330A has a poor S/N and a high residual noise floor if he can easily hear it in tweeters and midranges.

 

[Koeitje]

The reason why the 330A probably sounds better than the cxa61 is probably simply due to power. The CXA61 cannot deliver the power you need for dynamics, and thus you get less bass and it sounds smoother because its not clipping. I experienced the same when I went from a 50 watt 540A to a Marantz PM-16 with 90 watt (per spec, but it was underspecced...more like a 100+). But when I moved to 200W instead of 90W there wasn't a noticeable difference, because both amplifiers were powerful enough.

If you want both a lower noise floor and similar power there are plenty of alternatives.