RESOLVED - Noisy at the highest coarse setting

[Urbansandz]

I finished the Bee2Quiet upgrade last night and I'm getting quite a lot of noise at the highest volume on the coarse switch. Taking it down one notch on coarse seems to eliminate most (maybe all) the noise but I'm still getting some odd distortion on the lower levels but not the noise. I'm setting aside the lower level distortion for the time being and focusing on the noise at the highest level. It's kind of a sizzle/buzz sound. I thought I'd poke around on the coarse switch to see if I'd find anything and I resoldered the 7 and 1 positions to see if that resolved anything, but it did not. Then I thought I'd double check the resistor. It's a 2135J. You can't see it too well in the attached picture, but you can kind of make it out at the 1-2 position. That code didn't correspond with any of the resistors identified in the manual, but I did pull it from the provided folio of resistors in the kit. Is it possible that I have the wrong resistor there? The codes on most of the other resistors don't match up either, but I made sure to pull them from the correct ohm spot in the folio and just figured that the model codes had changed. I couldn't find any information about a DALE 2135J resistor. You can see in the photo that the 4/5 position is a 2133J. The 8/9 and 2/3 position are 1151F, which matches up. The 3/4 position is a 2421J.

 

[Paul Birkeland]

With the fine switch turned up all the way, you can measure the resistance values of the resistors on the coarse switch while they are soldered in place. 

If you have the coarse switch turned up all the way and you're playing music through your system, is that a realistic listening level? If you have a high gain amplifier and super sensitive speakers after the BeePre, then there may not be anything wrong here, and you may find that you never get near that level on the attenuators.

 

[Urbansandz]

Thanks Paul. I should have given more thought to my original message. The resistance measure at the end of the coarse rotary install measured correctly at both measurement spots, so it's all good there.

I guess I'm just wondering what is normal for noise at the highest coarse and fine setting. Currently for me at the highest volume I can hear the buzz from 20 feet away and maybe more (I ran out of room). At the 2nd highest coarse setting and highest fine I can hear it clearly from my listening position at 3 feet, but it's hard to make out at about 7 feet. At the 3rd highest coarse level (-18db) and highest fine I struggle to hear it against the background noise at my listening position 3 feet away and at the 4th highest level (-27db) I can only hear it if I get my ear about 7 inches away. Realistically, I probably would not be listening higher than -18db, but I'm really just wondering if these noise levels are something I should try to troubleshoot or not. I tried poking around with a chopstick and didn't locate any issues. Is there anything I can do to potentially reduce the noise further? Any common sources of noise I should consider?

I should add that at the two highest coarse levels I get pops when switching inputs, particularly at the 2nd and 3rd inputs, but never at the first. This occurs while my DAC is on the third input with no other inputs. When I remove the DAC inputs I don't get a pops when moving the selector through the range of inputs.

For context I have the Kaiju with the DC filament supply as my amp and 92db speakers. The Kaiju with the DC filament supply is very quiet.

 

[Paul Birkeland]

If you have your DAC output level maxed out, is this noise intrusive? 

The popping only with the DAC connected is a bit odd, you could try connecting a clip lead between the metal chassis of your DAC and the chassis of the BeePre to see if that helps.

 

[Doc B]

Yeah, kinda sounds like a ground loop between the preamp and the DAC. Does the DAC use a three prong plug? Is it connected to a PC or laptop of some kind? Are the DAC and the preamp plugged into the same AC mains circuit?

 

[Urbansandz]

I resolved the pops. It was an issue with the cabling of my subwoofer and was occurring whether the RCA cables were plugged into my DAC or not. 
The high volume noise, however, persists. I went back through and re-soldered various spots that I thought could be causing an issue, but to no avail. I need to go through the troubleshooting in the manual for buzz/hum. What's the best way to check if I have a ground issue in the preamp?

Thanks for the help.

 

[Paul Birkeland]

You can poke around with a chopstick in any area with black wires to see if any of them are loose.  You have to do this with the preamp running and playing music into something, though I wouldn't recommend doing this with your main system.  There are a pretty good number of devices these days with an AUX input and a speaker that will do the job though.

 

[Urbansandz]

I poked around with a chopstick and I was unable to find any issues.
I measured the resistance between chassis ground and the ground tab on the outputs and it was about 23 ohms is that to be expected or is that indicative of an issue?

 

[Paul Birkeland]

That indicates that the 22 Ohm resistor between audio ground and the chassis is in its proper place. 

 

[Urbansandz]

I installed the output upgrade, which completely eliminated all noise.