Amplifier or ground loop problem

[Riccardo.m81]

Hello everyone,
I’ve owned an ASR Emitter II for a few years now, and overall, I’m very satisfied with it. However, I’d like to share something that occasionally happens, in the hope of getting some feedback from others who might have had similar experiences.
From time to time, the sound seems to lose its energy — it becomes dull, lacks sparkle, and shows a noticeable loss of detail and harmonic richness.
In the past, I used to blame the source or the speakers. But just a few days ago, I noticed something interesting: when I disconnect the RCA cables coming from the DAC and briefly touch the positive lead of the cable to the ground (the outer part of the connector on the amplifier), the sound suddenly becomes detailed, rich, and open again.
This wasn’t intentional — I discovered it by accident while switching inputs on the amplifier.
I contacted ASR support, and they suggested checking the grounding of the power outlets and taking some measurements to look for possible anomalies in the electrical system.
I should also mention that I don’t hear any hum or noise from the speakers, even at higher volume levels.
Do you think it’s possible that the issue is purely related to the electrical installation?

 

[jheu02]

Do you have any soldering skills? I would open it up and look for potential cracked solder joints on all your RCA inputs. Physical stress if changing things around can, over time, cause poor connections.

 

[Riccardo.m81]

Yes, but the ASR is still under warranty. I don't think it's a welding problem.

 

[kwayde]

Have you ruled out the cables as being the problem?

 

[stillspin'n]

Impedance mismatch between the amp and DAC, with not enough loading for the DAC?

 

[ConradH]

I've found on several occasions that just unplugging and replugging RCA connectors will improve the sound. They likely get oxidized. Sometimes I use a thin film of Deoxit on them. With lead-free solder now being the norm, I wouldn't say things have to be old to develop problems. If the components were a bit old when soldered (oxidized), or subjected to stress, the joints could easily be defective. This stuff, and cables, can be tough to troubleshoot because it's often subtle and intermittent.

Some trivia about gold plated connectors. It's usually just marketing because nobody wants to plate enough gold to be durable. Also, gold only works with gold-on-gold connections. It does little good (but no harm) if you use a gold plug and tinned jack, or vice versa. Expensive gold-plated machined IC sockets actually have lower reliability than tinned double leaf sockets when used with typical tinned lead ICs. My favorite RCA plug is the cheap garden variety Keystone #567. It will usually equal or beat the fancy expensive ones.