WEILIANG, or BRZHiFi... board E600 V1.7

[SoNic]

I got this from Aliexpress. installed under my PC monitor.
My sound card is a SoundBlaster ZxR, with a dedicated headphone amp, with one TPA6120A2 chip. Was doing great for my AKG K701 (62 ohm impedance), but was kind of struggling with my HiFiMan Deva Pro (16 ohm).
I decided to give a try to this E600 amp, because it has two TPA6120A2 chips, in a balanced mode, how the application note recommends them to be used. The Deva can take balanced input too, with the proper 4 pin cable. I have ordered one but it didn't arrived yet.
So I tested it with the unbalanced output. The input is unbalanced anyway, from my PC soundcard.
First, it was having a slight buzz on the RCA input. I was pissed. I had around a small ground loop insolation transformer, put it in on the RCA cables... quiet. That was OK, but it was still bugging me why. Tried a wire between the two cases... not a change.
Eventually I took out the fat, pretty, boutique RCA cables (Monster) and used one of my old cable (from 80's or 90's ?). Holly cow, there was no more buzzing noise!
Yesterday I could not stop listening to music. So much bass, so much airness... I can take it as loud as I want, to ear hurting levels and not a problem. I can't describe how much better sounds that the one chip on the sound card board. Maybe because that also has a passive volume control, that didn't like the 16 ohm at all? IDK.
The board comes with three options of OpAmps, I choose the cheapest one, with JRC NE5532DD. I swapped them with a couple of LM4562NA that I had around. I have done extensive rolling experiments and for me, those are the best sounding. I even used a couple of them inside my sound card (it has sockets for front channels).
The mains is connected trough a fuse holder, in the socket, and the ground wire is connected directly to the case.
I hope the balanced cable comes soon, I can't wait to test it in the proper configuration.

I am happy that for $90, I had such good results. Not sure how it would "measure" if @amirm would measure it, but it sounds good to me.

 

[SoNic]

Pics:

 

[SoNic]

And pic of my sound card SB ZxR output section, with swapped OpAmps:

 

[SoNic]

I got today the balanced XLR to 3.5mm cable and hook it up. Tested, it seems in phase and correctly L-R.
However, I can hear distortions at higher levels bass, in left channel that were not there before. Wonder what's that about... maybe is not wired correctly...

 

[SoNic]

I forgot to revisit the post.
I bought another balanced cable and with that one, no distortions.
With my meter I found the difference - the "good" cable has wired, at the 3.5mm TRS jacks, only the tip and the sleeve (each channel). Sleeve is not connected.
The "bad" cable, has the sleeve connected together with the ring. Bad for HIFIMAN internal headphone connection.

 

[SoNic]

Update on the thread... I was using the amp with a line ground insulation transformer. That's because, when connected to my PC sound card, RCA cables, with volume at max, I could hear a slight (like -60dB?) power hum (60Hz here). It was annoying me that I had to use a transformer between them, so I researched a bit.
All my other equipment (AVR, DACs) had isolated RCA inputs and outputs. This headphone amp has also insulated RCA inputs:

OK, good.

I looked at my other devices schematics (yes, I am a bit of electronics geek) - all of them (Denon, ADCOM, HK) had small capacitors between the mains ground (the middle ground pin of power cord, also the amp metallic case) and the internal board signal ground. Some schematics had such capacitors at every input, some just in one place. Values between 0.1 uF to 1uF / 50V. Hmm... I wonder how is my amp designed. So I opened it.
Cursory glance at power supply, they seem to be separated. Ground from power mains is tied to the case, as it should, no visible connection to the board signal ground...
Oh, WTF is this???

That screw I know is connected on back side to the case. This seems deliberate...
So I used my solder iron and a bit of suction and... I freed the two sides.
Pulled a capacitor from my stash... randomly I got a 0.68 uF (or 680 nF). Soldered it between the two pads.
Now this is how it looks:

Tested the amp without isolation transformer. Max volume... not a noise. Looks like is it connected, lets fire up some music... hmm... better back down that volume a bit before that, I don't want to be deaf.
Whoohoo... loud music blasting from my headphones!

Such a simple fix. I wonder why they soldered those pads together, if they designed the ground separated? IDK... Just know that now I don't need that transformer and I think (placebo?) the bass sounds much better.

 

[Ezees]

Update on the thread... I was using the amp with a line ground insulation transformer. That's because, when connected to my PC sound card, RCA cables, with volume at max, I could hear a slight (like -60dB?) power hum (60Hz here). It was annoying me that I had to use a transformer between them, so I researched a bit.
All my other equipment (AVR, DACs) had isolated RCA inputs and outputs. This headphone amp has also insulated RCA inputs:

View attachment 267133

OK, good.

I looked at my other devices schematics (yes, I am a bit of electronics geek) - all of them (Denon, ADCOM, HK) had small capacitors between the mains ground (the middle ground pin of power cord, also the amp metallic case) and the internal board signal ground. Some schematics had such capacitors at every input, some just in one place. Values between 0.1 uF to 1uF / 50V. Hmm... I wonder how is my amp designed. So I opened it.
Cursory glance at power supply, they seem to be separated. Ground from power mains is tied to the case, as it should, no visible connection to the board signal ground...
Oh, WTF is this???

View attachment 267132

That screw I know is connected on back side to the case. This seems deliberate...
So I used my solder iron and a bit of suction and... I freed the two sides.
Pulled a capacitor from my stash... randomly I got a 0.68 uF (or 680 nF). Soldered it between the two pads.
Now this is how it looks:
View attachment 267134

Tested the amp without isolation transformer. Max volume... not a noise. Looks like is it connected, lets fire up some music... hmm... better back down that volume a bit before that, I don't want to be deaf.
Whoohoo... loud music blasting from my headphones!

Such a simple fix. I wonder why they soldered those pads together, if they designed the ground separated? IDK... Just know that now I don't need that transformer and I think (placebo?) the bass sounds much better.

Great work, my dude. I was looking at a used one of these as a cheap stand-in for my other HP amps (never too many amps, LOL). One of the first things I'd do (if I did get it), would be to change out those rather harsh/threadbare-sounding NE5532s to either cheap (but smoother, IMO) OPA2134s - or better still - Burson V6 Vivids or Sparkos SS-3602s. IMO, you just can't beat discrete opamps (at least with cheap ICs, LOL). Do you have it and do you still like it? Any other mods done???