Sabaj A20h Balanced Headphone Amplifier Owner's Thread

[Shinrei]

Today the remote control stopped responding even when I changed its batteries. That's a shame since I find it easy to change the gain when switching between headphones and IEMs.

However, when I search for a replacement I find this description: 'Sabaj Audio Amplifier Remote Control, suit for Sabaj A2 A3 A4 WP1 D4.'.

Would that work with the A20h?

Link

 

[Roland68]

Today the remote control stopped responding even when I changed its batteries. That's a shame since I find it easy to change the gain when switching between headphones and IEMs.

However, when I search for a replacement I find this description: 'Sabaj Audio Amplifier Remote Control, suit for Sabaj A2 A3 A4 WP1 D4.'.

Would that work with the A20h?

Link

Did you press the "B" button to activate the remote control for the A20h?

 

[Shinrei]

Did you press the "B" button to activate the remote control for the A20h?

No I didn't, but after I did it works again. Thank you very much!

 

[bsdinis]

I just found something really weird, I am picking up FM radio interference but only on 3 separate volume spectrums, between -99dB and -85dB, between -3dB and -1dB, and at 0dB.

Between -99dB and -85dB is the strongest, I can no longer hear it when I increase the volume to -84dB.
Between -3dB and -1dB it's still there but not as noticeable due to the higher noise floor, I can no longer hear it when I decrease the volume to -4dB.
At 0dB it's a bit lower, but still there.

I am using the single-ended output and the FM radio interference can only be heard on the Left channel.
It doesn't matter which input is selected on the amp.
It doesn't matter which gain setting is used, although it is the only thing that seems to have any effect on the volume of the FM radio interference.

I am using a Topping D10 Balanced with very short 30cm XLR>6.35mm cables without any adapters, the interference only goes away when I unplug both cables even though it can only be heard on the Left channel.
There is nothing connected to the amp's single-ended input.

Touching the Topping's chassis or its USB cable or moving the stack seem to alleviate the problem, but what is the explanation for this phenomenon and what can be done to mitigate it? And why exactly only between -99dB~-85dB, between -3dB~-1dB and at 0dB?

The radio station that I'm hearing is transmiting on 103.40MHz or 105.00MHz, not sure which one, or maybe on both.

 

[IAtaman]

I got one as well a few days ago and just had the chance to listen to it today. From day one have a few issues with it:

• While on H1, which I assume is the medium gain setting, -32db is quiet and -31db is loud. Almost sounds like it is changing gain. Am I doing it wrong?
• They were ok with most headphones but while listening HD600s via balanced pentacons, got this weird cracling noise on the left channel, not too dissimilar to a RF interference @bsdinis has decribed above.

 

[Veri]

I tried two A20h from Amazon and returned both because of intermittent and annoying interference type noise and pulsing. Wanted to like it but oh well, plenty of good amps to be had nowadays.

That's weird. Which headphones? I don't think I've ever noticed this on mine.

 

[IAtaman]

I had the same noise on the left channel again today with 6.5mm connectors and Edition XS. Noise disappears when you pass -32db so maybe be linked to gain or the relay volume control?

Edit note : Did some testing, at least the noise I am getting seems to be related to the mobile phone. When I use the Macbook to do phone calls the noise appears. If the phone is a certain distance away from the amp, and the volume is below -32db, then the noise appears on the left channel. Tested with a variety of cables and headphones, noise is always there regardless of the cable, connector or the headphone used. Tested with 2 different DACs, still the same.

If I increase the volume above -32db or move the phone, the noise goes away. If I move the phone to the right side of the amp, the noise goes away. When the phone is on the left side and you move it closer to the amp, first noise stays the same, then it starts to get lower below 10cm. Weird. Reminds me of the good old days your speakers would let you know your phone is about the ring before they actually did.

 

[Swtoby]

I had a similar noise problem with the a10h amp. Anytime it was very close to something with wifi would seem to cause it: Roku, wifi extender, etc. The only solution that worked for me was to move it away from those devices.

 

[Veri]

DCA Aeon RT. Maybe it's a mismatch because they are problem free with every other amp I use them with.

Mm they're a lot more sensitive than the stuff I use with mine though. Maybe it's a lower-ohm, sensitive headphone problem. not sure.

 

[IAtaman]

Mm they're a lot more sensitive than the stuff I use with mine though. Maybe it's a lower-ohm, sensitive headphone problem. not sure.

It is not, unless you consider HD600 a sensitive headphone. I belive it is a shielding issue.

 

[IAtaman]

I opened my unit up (to be honest I mainly bought it to play with anyway). Just 4 screws and the back part comes out with electronics once you unplug a few ribbon cables, and you are left with an empty outer shell. The outer shell and back plate is all metal but they are powder coated (I think) and are not conductive. I scratched some of the paint at the corners of the back plate and outer shell in an attempt to form some sort of a Faraday cage to protect against EMI. It did not help with long term corrosion resistance probably but initial tests with the phone are promising - so far no noise.

 

[IAtaman]

I opened my unit up (to be honest I mainly bought it to play with anyway). Just 4 screws and the back part comes out with electronics once you unplug a few ribbon cables, and you are left with an empty outer shell. The outer shell and back plate is all metal but they are powder coated (I think) and are not conductive. I scratched some of the paint at the corners of the back plate and outer shell in an attempt to form some sort of a Faraday cage to protect against EMI. It did not help with long term corrosion resistance probably but initial tests with the phone are promising - so far no noise.

I thought I will use it again while I am at the desk and the noise is back. Scraping the paint from the corners of the back plate and outer shell did not fix it. Well it might have fixed lack of corrosion problem but the noise is still there.

 

[AudioFans]

I thought I will use it again while I am at the desk and the noise is back. Scraping the paint from the corners of the back plate and outer shell did not fix it. Well it might have fixed lack of corrosion problem but the noise is still there.

I found that it sometimes makes a low-frequency hum and that the sound disappears when you touch the metal part

 

[bsdinis]

I was finally able to return my first A20h. I just received the second unit and so far I haven't been able to hear any interference from FM radio stations, the noise floor is also a lot lower on this one.
The leaking between inputs is more noticeable, I can clearly hear the balanced input when the amp is on IN2.

 

[Veri]

I was finally able to return my first A20h. I just received the second unit and so far I haven't been able to hear any interference from FM radio stations, the noise floor is also a lot lower on this one.

Interesting. I could definitely not reproduce these things so it must come down to certain parts/replacements used in certain batches. At least I'm not crazy
Input leakage might be a thing on these though, yes. Right now, I'm only using 1 input in my current (final?) set-up though..

 

[bsdinis]

I just found something really weird, I am picking up FM radio interference but only on 3 separate volume spectrums, between -99dB and -85dB, between -3dB and -1dB, and at 0dB.

Between -99dB and -85dB is the strongest, I can no longer hear it when I increase the volume to -84dB.
Between -3dB and -1dB it's still there but not as noticeable due to the higher noise floor, I can no longer hear it when I decrease the volume to -4dB.
At 0dB it's a bit lower, but still there.

I am using the single-ended output and the FM radio interference can only be heard on the Left channel.
It doesn't matter which input is selected on the amp.
It doesn't matter which gain setting is used, although it is the only thing that seems to have any effect on the volume of the FM radio interference.

I am using a Topping D10 Balanced with very short 30cm XLR>6.35mm cables without any adapters, the interference only goes away when I unplug both cables even though it can only be heard on the Left channel.
There is nothing connected to the amp's single-ended input.

Touching the Topping's chassis or its USB cable or moving the stack seem to alleviate the problem, but what is the explanation for this phenomenon and what can be done to mitigate it? And why exactly only between -99dB~-85dB, between -3dB~-1dB and at 0dB?

The radio station that I'm hearing is transmiting on 103.40MHz or 105.00MHz, not sure which one, or maybe on both.

My second unit does in fact still pick up interference from FM radio stations that can only be heard on the Left channel, exactly like I described in this previous post.
Between -99dB and -85dB, between -3dB and -1dB, and at 0dB.
The position of the headphone's cable affects the reception, I can barely hear the radio station when the cable is resting on my desk but if I stand up or lift the cable in the air the interference gets stronger.

 

[bsdinis]

It's not as strong as in my first A20h, but it's still there at the same exact volume steps.

 

[bsdinis]

On my second A20h I can hear the microcontroller inside the amp when I use the remote control. And what's weird is that it's much more noticeable when the headphone's cable is positioned in a way that it picks up interference from FM radio stations. And just like the FM interference, the beep can be heard more clearly at any of those 3 problematic volume steps.
It sounds like a beep, very faint.
If I press a button on the remote I hear the beep.
If I hold a button on the remote the beep repeats at a rate of about 10Hz, but only the first sounds like a real beep, the rest sound almost like a beep, I don't know how to explain.
If I block the IR emitter on the remote, hold a button and then unblock the IR emitter I don't hear the first (true) beep, I just hear the almost-beeps, at the same rate of about 10Hz.

 

[Madhatter]

You would achieve more. if you build the Netzfiler from the diyaudio forum and use it with the supplied power supply.
Or buy a Mean Well LPS-50-15, wire it up neatly, and build it in a case with the filter. It also beats most "audio" power supplies, even at $500.

Hi Roland68, which netzfilter have you tried? Thx

 

[Joel]

FYI, my A20h is on its way to Amir for testing. It will probably still be a few months.