Identifying the cause of distortion in my system

[davmol]

I've been reading ASR for a while nowbut this is my first post. Over the past year I have been building an audio system mainly from refurb and used items on ebay, other than one or two new luxuries (well luxury for my budget anyway )

My setup for desktop listening:

• Topping D50 iii DAC (or Qudelix 5k if on the move / not using USB)
• Topping A50s headphone amp
• Beyerdynamic DT1990 Pro headphones

Recent additions for listening away from desk:

• Wharfedale Diamond 9.1 speakers
• Pro-ject Debut Evo Turntable (with Fosi X2 phono stage)
• Yamaha A-S500 amplifier.

When I first bought the speakers I was listening to them with the turntable via an old micro system that I took from my garage (Onkyo CR515dab) and it sounded good. I wanted a bit more power and also to put that small Onkyo back in my garage, so I found a Yamaha A-S500 refurb unit at a good price and received it last week. I hooked everything up and am getting distortion from the speakers, starting from around 1/3 volume and getting unlistenable by 1/2 volume, which is present whether music is playing or not, and regardless of phono or DAC input selected.

My first thought was cables, so I have tried multiple RCA cables, then I moved between all the various inputs, and also tried plugging the amp into different power sockets / extensions, all with no difference. However, when I use the DAC with the A50s amp and my headphones there is zero noise, or distortion, all the way up to max (with no music playing of course). My assumption then was that the Yamaha was bad, so I was boxing it up to send back and I plugged my Onkyo back in and now notice the noise is also present on the Onkyo, which was a little confusing. I concluded that maybe I didn't notice on my Onkyo at the time because I was listening mainly to vinyl and at lower volume levels.

So, basically, I'm new to this, I now don't think the Yamaha is "bad" given that I can replicate it on the Onkyo, but I don't hear the distortion at all on the A50s, so I don't think there is any issue with DAC / cables etc, which I suppose leaves the speakers, or maybe just that the Onkyo and the Yamaha are not great from a noise / distortion perspective? What else could I possibly check before concluding that both the Yamaha and the Onkyo are both not great at mid-volume and above?

Example of the distortion being heard

 

[Doodski]

Do you have a source on both input 1 and input 2 as used in the video?

 

[Apesbrain]

That sounds like electrical noise being induced into the system from somewhere nearby in the environment. Disassemble your system and temporarily move it to another room. Connect the speakers and see if the noise is still there.

Maybe first, check that something is plugged into the input to which you are listening. Open jacks on the rear panel of the amp can be a path for noise to enter.

 

[tmtomh]

Based on what does and does not create the problematic noise so far, I’d first recommend turning off the turntable and totally disconnecting it from the amp (RCA interconnects and grounding wire), and then see if the noise is still there when you select the DAC as your input on the amp and turn the volume up like in your video.

If that has no effect, then I’d agree with @Apesbrain - move the whole thing to another room and see if the problem disappears or remains.

If it remains, then try different speakers, unless you’ve already tried that.

If the problem exists with other speakers too, then my only other thought would be to try swapping in different speaker cables or maybe gently moving or wiggling the speaker cables and interconnects while you hear the noise to see if that has any impact.

 

[davmol]

Do you have a source on both input 1 and input 2 as used in the video?

I have the D50iii DAC and the Fosi X2 phono connected via RCA into 2 inputs. In the video the Fosi was on line 3 and the DAC on line 2, but I have tried them in every other combination and tried them alone. I am going to take the items to a different room and try it there as per suggestions and will report back.

 

[tmtomh]

One more question: have you tried each of the amps (Yamaha or Onkyo) connected only to a pair speakers with nothing at all connected to the amp's input? As noted above, this kind of configuration could result in significant hum because of having an input active that has nothing connected to it on the back of the amp - but that should produce only (or at least mainly) a mostly constant hum, not the very loud staticky sound you are hearing.

Anything is possible, but if you still hear the same staticky noise and distortion in that scenario, and you hear it with both amps and with another set of speakers (not just those Wharfdales), then in that case I would think it would have to be external interference and/or the speaker cables.

 

[davmol]

With nothing connected other than the speakers both amplifiers are practically silent, regardless which input is selected. Similarly, if they are both connected and I select one of the remaining "vacant" inputs then there is no noise, other than maybe the tiniest hiss at near maximum volume, but my ear has to be right next to the speaker to discern it.

 

[Apesbrain]

Ok, now we know the source of the noise is environmental. It could be "airborne", i.e. radio interference, or coming in via the power cable. If you have a long extension cord, run power back from where you've moved your system to the original power outlet and test for noise.

 

[tmtomh]

With nothing connected other than the speakers both amplifiers are practically silent, regardless which input is selected. Similarly, if they are both connected and I select one of the remaining "vacant" inputs then there is no noise, other than maybe the tiniest hiss at near maximum volume, but my ear has to be right next to the speaker to discern it.

Progress!

Is this with the amps in the original room, or only after you've moved them to another location?

If this is with them in the original room, then that would suggest something being picked up by the interconnects and/or the DAC and Fosi phono preamp and being passed down to the amps and speakers. The DAC, Fosi, and/or their interconnects are acting like a mic or antenna - or at least that seems like the most reasonable guess at the moment.

Since you still have this problem when you've totally disconnected the DAC and use the Fosi, and when you've totally disconnected the Fosi and use the DAC (yes?), that would strongly suggest there's nothing wrong with either one of them. And since you've swapped interconnects and swapped which inputs they're connected to, that would rule out the possibility of oxidization on the RCA connectors and/or the amps' input jacks (for which a few sprays of DeOxit would do the trick).

So the DAC/interconnects and Fosi/interconnects picking up airborne interference seems like the likeliest thing at this point.

The only other variable I can think of is that when you connect anything (DAC, Fosi, or another source component) to the amp's input, that presents a different impedance to the amp than having an active input with nothing connected. But IMHO it would be very strange for that to produce this particular kind of noise/interference, and it would be even weirder for two different sources like the DAC and a phono preamp to produce the identical-sounding noise/interference like it appears they do in your video (except for the level difference which is attributable to the lower input voltage on the phono input I assume).

 

[davmol]

I haven't moved anything yet so anything I mentioned is still with the amp in the normal location. I'm stuck working at the moment and I'm out most of tomorrow, so I'll probably be moving everything around either tomorrow night or Sunday. I will respond back with findings by latest on Sunday evening (I'm in the UK). Thanks for all the suggestions.

 

[davmol]

Interesting development, when someone mentioned "airborne" I figured I would pop the Bluetooth aerial off the D50 DAC to see if it made a difference. That did nothing at all but in the process I accidentally knocked out one of the USB power cables from there dac and the noise reduced to almost nothing. Tried the fosi and it now goes to near max without distortion, so it looks like it might be related to the DAC, or at least the USB connection to the DAC.

I plugged the usb cables back in (I was using separate cables, one for power, one for data) and the noise is back. It seems some noise from each cable separately, but more from the one connected to my dock (data). Very interesting though that I still can't hear any distortion at all through the A50s when I plugged both USB back in. Still silent at max volume, must be a great little amp

So this weekend I will play about with usb cables, usb power adapters / battery banks etc and plugging into different sockets on laptops, hub, dock and see what happens and report back Sunday. Thanks everyone, definitely getting somewhere.

 

[davmol]

So I've been playing around with a lot of USB cables last night and today and made some progress, so here is feedback as promised. As a reminder of my laptop / USB setup:

• Lenovo laptop using standard power block
• Dell laptop powered by USB-C
• Both into a KVM type USB switching dock.
• Switching bock powered by its own DC block.

Onkyo amp (tried with both TS out to RCA, or RCA to RCA, no difference)
With the DAC connected to the Onkyo, the Dell is noisy from about half volume (as per earlier clip). It makes no difference if connecting the DAC directly to a laptop or via the dock, or whether connecting via one USB-C, or with the second USB-C for power. With the Lenovo, if I disconnect the Dell from the dock, all inputs are practically silent / free from noise (all the way to max volume), so this seems to indicate the issue with USB noise is possibly from the Dell (it is powered from the dock DC supply, via USB-C).

Yamaha amp (tried with both TS out to RCA, or RCA to RCA, no difference)
The noise kicks in at lower levels than the Onkyo, from around 1/3 volume it is clearly audible from the phono input, and from just under half volume from the DAC input. Again, if I disconnect the Dell the bulk of the distortion goes away, but unlike with the Onkyo there is still noise when using the Lenovo, from about 60% on the volume dial (which yes would be loud but it is still there). I tried at least 10 different USB cables, a couple of ferrite clips and covering the ground pin on the USB but still the noise is present at higher volumes. I suspect then that the Yamaha just isn't grate at dealing with imperfect signals / noise.

AIYIMA 07 MAX
On Friday, after I had mentioned that the A50s headphone amp displayed no noise or distortion at all, from either laptop regardless of connection, I decided to try out a hypothesis of using a cheap stereo amp that has rated highly here for inaudible noise/distortion (similar to how I chose the A50s, high SINAD?) and I ordered a cheap Aiyima 07 Max. Guess what? No noise, all the way to max volume, from the Dell or the Lenovo, using a single cable. Nothing from the phono stage, nothing from the DAC, complete beautiful silence (until I play the music that is)!

So, I think to conclude, while yes there appears to be a dirty / noisy signal coming out of Topping D50iii DAC (which is a little disappointing in itself), originating from the "dirty USB input" of the Dell, if the amp is capable enough at dealing with that noise then it will not come through the speakers. It is disappointing because the Yamaha had a lot of features that I wanted, with loudness controls, tone controls (sacrilege I know ), multiple inputs, remote control etc, but ultimately I prefer noise free amplification over those features, if I am forced to choose. I am going to return the Yamaha and keep the Aiyima for now, while I figure out where to go to next.

Thanks for all the help!