Class D amplifier with TPA 3250 board

I don’t often make a big mistakes, but when I do… I do what you are doing. Do the best to mitigate the problem… then sell it. Get what you can. Or throw it in the trash and caulk it up to experience. It was great of you to support a local artisan. Live and learn.

Unfortunately, if you do detailed research you get what you pay for. My amp cost $22K… and well worth it. Incredible performance, from a reputable company that has been around for 50 years. If I had a problem my dealer would come over, give me an interim replacement until he could deliver a fully functional replacement… but then, I am paying for that.

I understand what you're saying. You went to a reputable company, not some guy. Some guy convinced me that he could build a wonderful amplifier for me and that I could see him anytime if I have issues. In essence I paid for the same things you paid for. But the difference between you and I is the reputation and quality. 

In hindsight, I was lured by the prospect of finally experiencing tubes. My experience couldn't be worse and it's hilarious. I notice that my OGY speakers have more bass and fuller midrange with tubes compared to the Yamaha RN402 I regrettably sold. From memory, the differences are subtle but still there. It's like 20% better with tubes (listening to busy tracks where the hum disappears), and that's a huge improvement in audiophile terms. But the quality of the recording and my mood play a bigger part (IMHO).

Perhaps if I use the powered sub, the quality of the amplifier should matter less.

I researched low damping factor amplifiers briefly. It looks like today's transistor amplifiers are built for high damping factor by default. Low damping factor amplifiers are most commonly tubes. A high damping factor doesn't allow a woofer cone to vibrate much. So you get harder upper midrange and less bass with fullrange drivers. That's all theoretical and I'm probably out to lunch on the understanding. 

You got low damping factor pretty much spot on.

Not modern (and no measurements available that I'm aware of), but I have a 20 year old Musical Fidelity X-A1 SS integrated amp that seems to have a very low damping factor as I've used it with many different types of speakers and it mimics the characteristics of a tube amp with "measured" very low damping.

I've had to open it, and the separate power supply, a few times to remedy what was basically shoddy assembly work and discovered that it had wire wound resisters on the speaker outputs (one per channel).

I also have an early 80's Carver SS receiver that also sounds as if the damping factor is quite low (Carver MXR130).

Anyway, hopefully switching to DC on your artisan amp will remedy the hum you are getting.

Also, definitely try the sub you own as doing so should give your single driver speakers a helping hand (making them richer/fuller sounding - more effortless) if the sub settings can attenuate the low frequency output of your single driver speakers.

DeKay

PS:

Couldn't resist and this is not a serious question, but does your amp builders demo/listening room look something like this?

DeKay

@dekay You’ll laugh but the artisan’s workshop had a bunch of noisy neon lights. The artisan told me that he couldn’t hear them anymore.

Thanks for the advice. Musical Fidelity sells the V90 amp new for 350€. The reviews seem kinda mixed. Everyone treats it like a cheap amp. Someone even says that it has a noise floor. 

There's no mention of low damping. I guess I'll give it a pass. I have to wait until Sunday anyways.