Class D amplifier with TPA 3250 board

FYI:

Here’s a review of the Atoll.

https://www.tnt-audio.com/ampli/atoll-in80_e.html

DeKay

Are the OGY 8 ohm or 16 ohm?

If 16 ohm they may not sound right with a Class D amplifier.

I have Sharp SD-EX111 (Class D amplifier section) that does not mate well (sounds odd/off) with any of my 16 ohm single driver speakers, but it sounds good with my 8 ohm single drivers.

All my drivers are vintage (Elac, Stephens-Trusonic, Coral et cetera).

I've read that whatever causes this has been remedied with some of the new (more expensive) Class D designs, but not certain if this technology has trickled down to the less expensive gear.

DeKay

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

Not familiar with your Bluesound Node +, but it still could be a gain issue.

Aside from that do you have any other musical source gear that you can try (with the amp) besides the Bluesound, as the hiss may be caused by it (the Bluesound) and a gain/other issue)?

If not, I would try the product I suggested (or something like it) before tossing a 2K US$ unit back to it’s builder without a refund.

I listened to your speakers (YouTube) and though this is not the best way to audition speakers they seemed fairly bright with little bass/mid-bass to me (this is coming from someone who has been using wide band single drivers since 2002) and I would suggest implementing your unused subwoofer at some point.

All my single driver speakers mate best with single ended tube amplifiers and/or PP tube/SS amplifiers that have a very low damping factor as I do not use subwoofers.

DeKay

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

PS:

Damping factor will not be much of a concern at all if the low frequency duty is taken over by your subwoofer.

I do not used subs (just 8" single drivers running full range) which is why low damping makes my speakers sound fuller/better.

I tried a sub years ago (Gallo TR2) which I liked, but due to my using a high level connection (speaker wire in/out) the sub’s crossover was fixed @ around 100 Hz (needed to go lower and didn’t want to fuss with splitting the signals from my basic/budget preamplifier in order to use the low level inputs).

If I lived where you do I would be investing my money in a nice 2CV or DS.

DeKay

Glad to read/hear it, and...

I told you so (regarding the sub;-).

DeKay