Sabaj A20a 2022 and Topping DX5II stack

[davmol]

I was running Fosi V3 Monos and very happy the sound but never really liked the appearance of them with my WiiM ultra, and even less so after I picked up my Topping DX5II for usb DAC and headphone duties. It was like a messy mish mash of different size and colour components.

So I had been keeping my eye out for something more aesthetically pleasing to go with my silver DX5II and silver WiiM Ultra, and stumbled on a bargain on hifi-express for two Sabaj A20a 2022 amplifiers, and thought they could be a good match. They were discounted due to a couple of minor surface scratches, which aren't even visible when stacked, and the price was so good at £180gbp / $240usd for the pair that I pulled the trigger. On arrival:

Initial impressions were that they sounded brighter than the V3 monos, so I got out the multimeter and level matched to the Fosi output voltage at 1khz, using the volume pots on the Sabaj. Once level matched, with Fosi over RCA and Sabaj over XLR and the DX5II set to simultaneous output, I was able to switch back and forth using the Neohipo ET30 and I could no longer detect any audible difference. Thankfully I could now go back to focusing on the aesthetics!

So no real negatives to speak of on the A20a units, other than maybe an overly bright blue power led. I had read that some people experienced different volume levels from each unit but nothing significant with mine. I ended up trimming -0.01 (left) using the WiiM, which was a slight improvement on the Fosi V3s, which had to be trimmed -0.03. In either case it was nothing to write home about and without measuring the voltage I probably wouldn't even have known.

I did have to turn the volume down considerably on the Sabaj units to match the Fosi. I couldn't see any gain information on the Sabaj tech sheet but the input sensitivity is around 1/4 that of the Fosi V3s, so I assume this could be the reason, and given that the DX5II outputs 5v. I settled on leaving the Sabaj units at max volume and switching the DX5II to preamp mode and shaving 15db off the volume. Then I went back to using the WiiM remote for volume control.

So, here is my final great sounding, good looking, feature packed setup:

Finally, I can rest...

 

[Talisman]

I've always really liked the Sabaj monoblocks from that line.

 

[davmol]

Ok, so the rest is over already

At louder volumes I am hearing some low level background distortion. I also notice if I put my ear close to the tweeter there is a hiss that is present at all times and volumes until the amps are switched off (this is with XLR from the topping D50III). If I switch to RCA there is some kind of interference, which does reduce if I turn down the volume pots on the amps, although the background hiss remains.

I wondered if it's overdriven with the 5v output from the DX5II, vs the input sensitivity of 440mV (I assume that's for RCA input and XLR to be double?). Anyway to test that I connected RCA to the WiiM ultra and cycled through the output voltage from 2v down to 200mV but the interference and hiss was always present. Maybe it could be related to the volume pots themselves?

I connected the Fosi V3 mono back up again, tried RCA input at both gains, and also the XLR input, and there is no interference or hiss present, even at max volume with my ear to the tweeter, and the low level distortion I'm hearing at higher volumes is not present anymore. So, it seems that I might have to switch back to the V3 and demote the A20a to some less important duties, like garage radio.

Maybe I'll send them to Amir for review, just to make sure this isn't all a dream

Here are links to the RCA noise and the hiss present on RCA and XLR regardless of volume.