I just hooked up a new amp and I'm having a strange noise issue. Only in my right channel, I get this high-pitched whine... maybe around 2khz. My left channel is dead silent.
The problem seems to be an interaction between my DAC and my amp. If the DAC is off, the amp is silent.
The amp is an 84' yamaha, so the cord has no ground. There is a ground screw, though, and I have connected that to my power conditioner, hoping this would solve it... nope.
I've tried plugging the amp straight into the same outlet that the power conditioner is plugged into (into which the DAC is plugged in). That actually did work... but I don't want to run my amp straight into the wall.
I suspect I just need to find a proper place to run that ground wire...
I contacted BlueJeans and they told me that this has happened with a few other people as well. As silly as it sounds, he/she told me that I just needed to 'push harder'. There are these 'tension fingers' that form a tight lock on the RCA connector. These can cause the connector to feel like it is on all the way when really it has a little ways to go.
Unfortunately I sent my cables back... so I have now ordered some new LC-1s to see if this is indeed the solution. Crazy.
I just wanted to add... the cable would only slide down about half way of the connector post on my DAC. At that point the connector would stop because it was hitting the plastic at the back of the space between the outter ring and the inner rod of the RCA connector.
Even if this was it, it still doesn't make sense to me why it would be fine when I run directly to my amp... something to do with not having 2 different signal wires running different amplitudes maybe?
Well I took the DAC out of my system last night and hooked it up to a second system using LC-1 for the output. The same interference noise occured
I had three pairs of LC-1 cable and tried all three as outputs from my DAC to my pre, and they all had the same problem.
If I switch cable, everything is great. If I use the LC-1 to run straight from my DAC to my amp, everything is great. It's only when running LC-1 from my dac to a pre-amp that things get ugly.
Here is my system:
Digital feed from PC via Blue Jeans Digital Coax -> Audio Mirror D2 NOS DAC -> Blue Jeans LC-1 -> Richard Lee Audio Passive Pre-amp -> Blue Jeans LC-1 -> Yamaha M-40 -> Blue Jeans (Belden 5000) speaker cable -> Green Mountain Audio Continuum 1s -> Ears.
For power:
-Computer is on separate power conditioner (this isn't the problem as I experienced the noise with the computer turned off)
-DAC and amp plugged into Furman Elite 15i. DAC is fed by Iron Lung Jellyfish power cable, amp by it's stock power cord.
That's it.
You mentioned the 'loose connection' thing... and I was thinking of something along similar lines. While nothing feels loose, the connectors on the back of my DAC are considerably long. What if the farthest I can push in the LC-1 onto these connectors just isn't enough to make contact with something that is necessary. I don't really understand the details of how this works yet, so this is a shot in the dark...
"Anyone? What is a cable that has a return through the shield?"
- That's cable with only one wire (signal) inside and shield serving as second wire (ground/return). Coax cable is an example (BlueJeans cable is made of coax cable).
Alright... I took the DAC and hooked it up in a separate system on a separate circuit (only using the same LC-1 cable) annnd the noise was still there. Why it would disappear when going direct to my amp (as well as my old integrated) is a mystery to me.
I do have everything plugged into the same outlet. It's all on a power conditioner, actually. I think the confusion there arose when I was switching my power plugs around everywhere to see if that would make a difference.
I tried grounding the DAC to the pre-amp chassis earlier but it didn't seem to make the slightest bit of difference. The screws on my DAC are really small, but I made pretty good contact with them.
So, even though LC-1 cables use shield as a return, I still shouldn't have this problem? What exactly does it mean to use shield as return?
Djembeplay - I'm still not sure that cable was the problem. In general using shield as return is a bad thing but in case of hum or interference we enter the area of "black magic". Bob is right about your problem originating in unit being plugged into different outlets but the certain cables can exaggerate this effect. Why can't you plug everything to the same outlet?
It was caused by the LC-1 using shield as the return? What does this mean? Why was it bad only when connected to my pre-amp? What types of cable should I be looking at as a replacement?
"I just hooked up a long run of crappy RCA cable from the analogue outs of my PC." - quality of the cable is probably not important but this crappy cable probably doesn't use shield as return. Try the same cable from the DAC.
I just hooked up a long run of crappy RCA cable from the analogue outs of my PC. It was the same set-up just with a different source than the DAC... and there is no noise or distortion at all.
So... the problem isn't the cables, but rather something with the output of the DAC interacting with the pre-amp.
It's weird that the DAC sounds excellent when going straight into the AMP.
So, Tvad - I'm going to take your advice and try to ground the DAC to the pre-amp. What is the best way to do this? There is no 'ground' provision on my pre-amp or my DAC, unfortunately.
The thing is... it sounds perfect when I run my DAC directly into my AMP.
OK, so.. here's what I just did:
I didn't use my other amp (integrated) simply because I didn't have the right terminals on my speaker wire. I did, however, use it solely as a pre-amp feeding my amp (whereas the pre-amp I have been using was a little passive w/ volume control).
Using my older integrated as a pre-amp, the noise was MUCH MUCH worse. Again, it was primarily in the right channel.
I switched the RCA's connected at the back of my power-amp, and sure enough, the distortion completely switched channels as well. So, we know it isn't a malfunction on the part of the amp I suppose.
It must be line interference somehow... I really don't get it still.
I'm now going to try connecting my amp chassis to the ground on my temporary pre-amp.
Sooo... actually there is no need for me to run straight into the amp from my DAC... I know it will be perfect. It has been that way for a few days and it was fine. Also, the fact that it goes away with my pre-amp turned up all the way indicates that something is awry in that area of the chain.
WAIT! NO! I was mistaken. Upon closer listening, I do still have some distortion in my right channel... right channel only. And this is only with lower frequencies.
Bob - It makes sense, but why reversing interconnects makes difference? If it's BlueJeans then it's grounded on both ends and reversing it would not make any difference. He says that in one configuration of ICs noise is gone.
Why is it only in one channel - ground loop should affect both channels. Something is fishy here. Could it be defective cable? He mentioned that switching to Monster Cables eliminated noise completely.
Ya, in that early post I had thought that going straight into the wall had worked. It ended up that it repressed the noise quite a bit, but the distortion of lower frequencies was still there and the high-pitched whining had turned into a static 'fuzzy' background.
I'm going to go try some old cheap interconnects I have laying around real quick. I'll report back.
Ya... I'll try the grounding thing and let you know how it goes.
Would this be the same as grounding my amp to my power conditioner? I tried that... and it altered the nature of the distortion, but did not remove it.
Djembeplay - I did not read your posts about cables carefully. If it's Blue Jeans cable and is grounded on both ends, like Bob says, then switching cable direction wouldn't make any difference.
It is difficult to find something in this price range (and I don't have a lot of experience). You might be able to find used AQ King Cobra (previously Python). It is very nice and neutral cable.
Bob - I asked since I've never had coax interconnect. Grounding shield on both ends is really bad, using shield as return is even worse. In addition coax cables, used in video applications, have not the greatest copper since at high frequencies signal travels only on the surface (often silver plated). Blue Jeans cables can still sound great (I don't question that). Capacitance, they are so proud of (12pF/ft) is nothing special (typical for polyethylene) since best cables have 3.5pF/ft and my cable has 5.1pF/ft. In order to get this capacitance foamed teflon in oversized tubes is required but it's expensive.
I am not talking about ground loops. If transmitting end (let say preamp) has ground/case at different potential than power amp's ground/case then it places this potential on the shield. Shield couples this difference (AC) to signal wire (referenced to different GND). When shield is grounded on the amp side then it has exactly the same level as the reference level of the signal wire and doesn't couple anything.
You think so? IDK, it seems weird that just swapping out one of the interconnects fixed everything...
Plus it isn't the typical 60Hz humm.. it's like 2-3 kHz... more of a whine. Also, there is that strange distortion in my lower bass region.
All I can think is there is some sort of interference between 2 BlueJeans cables that are near eachother and have a different magnitude of the same signal going through them (the one after the pre-amp will be attenuated unless it's at full volume).
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