What's causing the sound difference between two class D amps.

[Perichoresis]

Hello, I've read the forum for awhile but this is my first post. I was hoping to get some help troubleshooting. I believe that there likely shouldn't be large audible difference between the two class D amps. That said, I am hearing a distinct difference between two setups and I'd like help narrowing down what is most likely causing the difference. The two signal paths are below:

Computer > Aiyima t9 via usb > Kef Q150's

Computer > Aiyima T9 via USB > aux out to Douk a5 > Kef Q150.

The first signal path has a clearer high end and sounds more open in general. The second signal path is stronger in the mids but overal sounds a like there's a cloth in front of the speakers. Also the highs seem attenutated. I am assuming it's not the amps themselves casuing the difference in sound since they're both class D and similar enough that I doubt it's casuing a differnece. Is it possible that the 3.5m to RCA cable or the T9's auxiliary out are somehow attenuating the highs? Any thoughts would very helpful. Thank you.

 

[antcollinet]

The t9 has tubes in it (I assume that is for the preamp part)

God knows what they are doing to the sound quality - and we have no idea what signal the aux out is based on. That could also be haveing an impact.

Without measurements it is impossible to say what is causing your perceptions - even if it is based on real sound differences, and not your (humanities) perceptive biases.


PS - welcome to the forum.

 

[kyuu]

That Aiyama is an unknown quantity, but given what it is I would say it's highly likely that its frequency response is load dependent. On the other hand, we know that the Douk A5 is pretty much load independent. That by itself could result in audible differences. Then of course who knows what the hell those tubes are doing to the sound.

My advice would be to get rid of the Aiyama T9 and use something reasonable.

 

[amadeogt]

The Douk A5 has PFFB (post filter feedback), which makes it load-insensitive. It should deliver a flat response.

The Aiyima T9, as far as I know, does not have PFFB - so its frequency response might change (reinforcing the treble, for instance) according to your speakers' impedance curve.

This is a known issue with class D amps. PFFB fixes it.

 

[kemmler3D]

On the other hand, we know that the Douk A5 is pretty much load independent. That by itself could result in audible differences. Then of course who knows what the hell those tubes are doing to the sound.

Yep this, load dependence in these Class D amps can lead to a few dB change in frequency response:

The big impedance peak in the lower treble on the Q150 might correspond to something you're hearing between the two amps.

The tubes might have something to do with it too, but that would tend to be more subtle than load dependence in this case.

Welcome to ASR!

 

[Perichoresis]

Thank you for for the warm welcome and the responses.

The load dependance of the Aiyima in conjunction with the Kef's impedance curve causing the difference makes a lot of sense. I don't know if it's supposed to correlate exatly but the line indicating the magnetiude of the Kef's impedance curve represents almost exactly what I'm hearing with the Aiyima. Pronounced highs, slightly hollow mids, strong low end. Which I'm percieving as being less vieled in relation to the Douk. So there may not be anything problematic that needs to be solved. It may just be that I've gotten use to a bit of a V curve response.

I also see how the T9's pre-amp section with the tubes causes some unknown factors. I don't think the tubes are actually being used as a real tube preamp in the T9. It's more likely they are being used as a buffer. Regardless, I don't really know what's going on in the pre-amp of the T9. I ordered a Topping E30 ii lite to use as a DAC/Pre-amp rather than the T9. I'll be interested to see if that changes anything.