DSj left channel hum when muted

Audio Components DACs
1

Hi Folks,

Recently I tried DSj straight to a power amp.
Worked much better that with my previous integrated amp.

But, with this config, I had to turn the ATT on, as I already predicted. Without the ATT there is a very loud hiss from the tweeters and hum from the woofers.
With the ATT on, the hum almost disappears (I have to stuck my ear on the woofer to slightly hear it), and the hiss is controlled (audible from 1 meter with absolute silence in the room, but unlisten from the listening position).
So far so good, and sound wise this combo is the best I ever had at home.

A little of background… I always heard, together with the tweeters hiss, some ticks on the left channel without any signal (all tests were made – swap channels at speaker level; swap ICs; swap IC channel), and ended confirming that it was produced by DSj left channel. Nothing audible from more than one meter.
Additionally to this, with the current combo, I discovered another issue with DSj left channel.
With DSj ON and power amp ON > OK (with the bearable hiss described above equal on both channels). But, since the power amp doesn’t have a standby mode, I mute DSj when not listening to any music. As soon as I mute, the hiss from the tweeters decreases (a little hiss remains - must be the amp noise floor), but a more pronounced hum starts just from the left channel (the same with the “ticks” when DSj is on). I also did the same tests, swap channels at speaker level; swap ICs; swap IC channel, etc, and is confirmed that is the DSj left channel output. As soon as I disconnect the left IC (by the way, XLR) the hum disappears.

I didn’t try any FW experiments, due to the latest struggling and fear of DSj FW “bad loads”.

Is there any clue or known issue? @tedsmith @Paul

Thanks in advance.

2

I don’t know of a DS Jr issue that would cause the hum. It’s a good idea to contact support tho.

It could be a ground loop or running an interconnect parallel to a power cord, etc .

2 Likes
3

Many thanks for your input @tedsmith

I don’t have parallel cables (I’m a little OCD on cable management).
The strange issue is it just happens when I mute or put DSj in standby, and only and always with the left channel.
I’m overseas, but I’ll e-mail TJ.

Thanks.

4

Everything suggest is HW related.
Installed Redcloud, same behavior. Snowmass and Windom same behavior.

Also tried single ended instead of XLR with the same results: DSj left channel tweeter “ticking” when unmuted, and woofer huming in mute or standby.

5

Perhaps try switching L and R channels between the DAC and the amp. If the hum stays in the L channel you can figure the problem isn’t in the DAC but in the amp. My guess is ground loop but that usually affects both channels.

6

@cbnbmore thanks for your input.
I tried that already.
It’s indeed the DSj left channel that promotes the hum when in standby or muted.
If I connect the DSj left channel (with XLR or RCA) to the right channel of the amp, the problem appears on the right speaker.