[djembeplay]

Hey everyone,

I and some others over on Audiogon have been working on this one for a little while. I figured I would bring it over here to get some furthar input.

After some intense trail-and-error testing, I've found out that for some reason when I feed my DAC to a pre-amp via BlueJeans LC-1 cable, then to my amp, I pick up tons of interference... not 60Hz hum, but a high whining sound accompanied by a bunch of distortion on my lower frequencies. Also, it's much more intense on one channel than the other.

I have tested this with multiple pre-amps and received the same result.

Now, when I run my DAC directly to my amp via the same LC-1 cable, it sounds perfect - no interference. Also, if I run the DAC to my pre-amp using a different cable (besides LC-1), I get no interference and it sounds perfect.

Someone said something about the 'return running through the shield' in the LC-1, which isn't good apparently and may be causing this... but then I dont know why it would be fine when I run directly to my amp.

Any ideas? Also, the distortion seems to pulse with the signals of the music... not sure if this will help the diagnosis at all.

 

[djembeplay]

Nobody, huh?

 

[SleepyOne]

Have you got lots of cables or electronic devices near you dac/preamp/power amp etc.? I remember KCAG (no shield) has this problem where there are lots of interference.

 

[royalcrown]

I would contact BJC to see what they have to say. I would think they'd have the answer, as they're pretty knowledgeable over there.

 

[NightOwl]

It sounds like your LC-1 cable is picking up interference from somewhere. Since a preamp amplifies lower level signals than an amp, it is much more likely to reproduce that noise than an amp. This could be why the cable connected to the preamp is noisy, but connected directly to the amp is quiet.

The LC-1 is a coaxial cable where the shield also acts as a signal return. It is possible that excessive RFI or EMI being picked up by the shield could be introduced to the signal.

If it is the preamp causing the problem, possibly the source of the noise could be closer to the noisier channel (transformer, ac, etc.). This seems least likely since the problem replicates with different preamps (unless your preamp is located right next to a power bar).

Is the cable that is noise-free a different geometry (e.g. twisted pair with shield) that doesn't use the shield as a return?
If you use the noise-free cable from your dac to your preamp and then the LC-1 from your preamp to your amp, do you still get noise?

Do you have other sources besides your dac connected to your preamp that could be introducing noise to the preamp?

Do you have any sources that could introduce noise located near your preamp (turntable, tape deck, cd player, etc.)? Is your preamp located near a tv set?

Unfortunately solving noise problems can be process of elimination, one thing at a time. Dare I suggest that the easy way is just to use the noise-free cable and use the LC-1 elsewhere or not at all.

 

[djembeplay]

Hey guys,

Thanks for the responses.

I'm still working on this (!!!!!). Crazy.

I am pretty certain the problem lies in the connection between my DAC and the LC-1. If I use another cable coming from my DAC and use a couple bridges to connect to the LC-1, everything is fine. It is only when the LC-1 is directly connected to my DAC do I hear the problem... and, again, that is only when I have my pre-amp in the chain... which is a passive pre-amp, so there is no noise introduced there.

Most... frustrating.. and perplexing... problem... ever.