Class D amplifier with TPA 3250 board

Do you hear hiss when the amp is hooked to the speakers, turned on, with NO source (including preamp) connected?

While sometimes hiss is connected to an amp that simply doesn't have a very good S/N ratio, it is just as often connected with a mismatch between input sensitivity and gain levels between sources, preamps and the amp.

If you have no hiss while just using the amp only, add components back one at a time and see when hiss returns. You might be able to fix the problem by decreasing the input sensitivity of the amp, reducing the output of the source, or using resistors in between the two to reduce gain.

I have an all tube system. With very efficient speakers you have a lot of great options. I highly recommend finding a a great amp made by a company, not an “Artisan”… a company that knows how to design and manufacture great tube amps… Audio Research, Conrad Johnson, Cary, VAC, or budget… Rogue. There are more… but they will be completely noiseless and sound fantastic.

The OGY are 8 Ohm 15W. 

I heard the Unison Research Simply Italy in a shop and it was perfect. I was blown away.  I wanted to save money by having the artisan build a clone. Now I feel like an idiot. Another shop recommends Fez Audio but I didn't have a chance to go there and audition. I'm trying to prioritize Euro brands over Chinese.  

The amp was clearly defective at the analog inputs. They were all noisy. So when I plugged the speakers in, the noise gradually built up over 10 seconds and reached about 40db. It didn't matter which input was selected or if music was playing.

Today the amp is (supposedly) fixed. I have to drive over to the artisan and retrieve it. 

Thanks for the kind replies. It's funny how you guessed ASR instantly. Yeah I'm not too stubborn on getting a class D amplifier or tubes. I just drank the cool aid wanting to believe that a 60€ amplifier with a TPA 3255 would satisfy my needs. I like Atoll because they're easy to find on the used market around 500€. I am more familiar with class A/B and know it's just fine. Class D is more expensive for some reason, unless you go for the really cheap TPA boards. 

News update: I got the amplifier back. It still has a hiss. But it disappears when music plays. It's still a little bit louder than I'd like and you can still hear that hiss on very quiet tracks. It's way more manageable now.

I'll buy an A/B amplifier some day. Nothing too fancy. Or a good class D if the price is right. 

You could experiment with something like this (inline attenuators) between your music source and the integrated amp inputs.

What is the rest of your system?

http://www.rothwellaudioproducts.co.uk/html/attenuators.html

DeKay