[doctorcilantro]

I have found a nasty ground loop sounding buzz, but it is actually my dishwasher! On the fence about what to do. One thought is to add a cheaper isolation transformer, but I wouldn't mind my tube gear on regen. AC

The noise floor of my tube amp with shorting plugs is quiet a bit quieter than running DAC in, and dishwasher off. I feel there is still improvement to be made, even after getting the dishwasher out of the picture.

I have a small 100w AC regenerator for my DAC(s)/Preamp.

Problem is I can not connect my tube amp to it.

Considering a larger regenerator or isolation transformer.

Question - does the AC>DC>AC process of the regenerators effectively isolate it from circuit?

thanks for your thoughts!

[Nyal Mellor]

Yes, regenerators work but personally I prefer isolation transfomers for a couple of reasons. One is that they do not have hard current limits like a regenerator and the second is that they are much more reliable. They also have ability to deliver higher instantaneous current than the wall outlet because energy is stored in the magnetic field of the isolation transformer and it is right next to your equipment. If you buy a good isolation transformer you will still have it and it will still be working perfectly in 20 years. Regenerators seem to have a much higher failure rate, witness the amount of B stock PS audio out there.

[doctorcilantro]

I'm a bit isolated in the ME, and worried if I pick up a isolation transformer, I'll be stuck with it. Thus, I have looked at smaller ones since I run a 6watt (pulls 90ish) and 250 subwoofer. Something like the Keces from China.

I see your points, and well taken. Would an Equitech Q-650 or BPT unit be a good buy?

[Big Red Machine]

There is a possibility I may part with my Furman IT Ref 7 unit - 7.5 amps IIRC for cheap.  Older unit that has a non-functioning led light but otherwise works like a champ.  Big and heavy but cost competitive. 

[dBe]

Ah, now I see!  I think i would put the dishwasher on a TX.     Check your email.

Dave

[Quiet Earth]

I think a dishwasher needs a minimum of 9amps to work properly, so that would be an expensive isolation TX to wash your dishes. I bet they would have that audiophile sparkle though....... 

I think I would try to figure out why your dishwasher interferes with your audio gear before I purchased any kind of upgrade gear. Does it interfere when it is plugged in and waiting to run, or only when it is running?

Shouldn't it be on its own AC line anyway?

[Quiet Earth]

The noise floor of my tube amp with shorting plugs is quiet a bit quieter than running DAC in

I'm not sure if that necessarily means you have an AC problem. I think you could say that about a lot of tube amps.

[doctorcilantro]

I'm guessing the dishwasher is on its own line. I live in Middle East but we have 110 here on "camp".

I think my little AC regen did help mitigate the noise. If I switch to USB on the DAC, a relay opens and the noise comes through. If on analog inputs of DAC, the noise goes away. So maybe it is some kind of grounding issue with both house and system?

Also, regarding tube amp noise. I meant with shorting plugs the tube amp noise floor is revealed, correct? If so, when DAC connected, it's louder noise floor. Meaning the tub amp is "quieter" than the DAC?

[jtwrace]

I live in Middle East

WOW, you really did make a big move.   

[doctorcilantro]

WOW, you really did make a big move.   

Yeah, life is good. I don't smoke, but hanging with friends and realized that Marbs are like $2 a pack here lol.

[Quiet Earth]

If I switch to USB on the DAC, a relay opens and the noise comes through. If on analog inputs of DAC, the noise goes away.

Maybe the noise is coming from the computer if it only happens in USB mode. I think your DAC has an earth ground, but I doubt if your Mac mini does. Plug the computer into the same AC duplex outlet as the DAC.

Also, regarding tube amp noise. I meant with shorting plugs the tube amp noise floor is revealed, correct? If so, when DAC connected, it's louder noise floor. Meaning the tub amp is "quieter" than the DAC?

That is correct and exactly what you should expect to hear.


I can't give you any advice about AC regenerators because I have never used one (except for my turntable motor for speed accuracy), but I can tell you a little bit about what to expect and what not to expect from an isolation transformer.

1. Most isolation transformers will give you 14dB of noise reduction across the board. This is a huge amount of reduction terms of noticing a clear difference, but it is not a complete elimination of noise. It is still only 14 dB.
2. If you decide to plug different stereo components into different AC circuits, an isolation transformer will not help you with ground loops. The best way to get a lack of hum when using a balanced AC transformer is to plug all of your gear into one transformer and share the same ground. This is contrary to what most people say, but I find it to be quite obvious in practice. It's what works for me anyway.

[doctorcilantro]

I'm absolutely positive the noise is the dishwasher and I think it's a ground issue, although my DAC has a LPSU with a ground float switch.

If I use shorting plugs on the amp, and don't hear the buzz from dishwasher I guess it must be coming through the DAC though...

[Speedskater]

Does the problem go away when you open the dishwasher's circuit breaker?
Some dishwasher's can be unplugged at their receptacle.

Dishwasher's are one of the types of appliances that are sometimes mis-wired. That's because they are connected by an installer not an electrician.

[doctorcilantro]

If I turn off the dishwasher the buzz stops immediately and noisefloor is acceptable. I'm running through a cheap but solid firman powers trip.

I should test running washer and dryer.

I did try running amp through 100w AC REGEN and buzz was lessened greatly but still there, sound of it changed too actually. That surprised me.

I can't run the tube amp and DAC on that regen as that pushes the units transformer into overload.

[doctorcilantro]

I've asked for an electrician to come check the dishwasher, and I will take a peek at the ground on the AC outlet. But I think I even switched outlets in the room so it's probably a bigger picture with regard to grounding.

[doctorcilantro]

Electricians came and told me to call installer. They work for "camp" I'm on so no big deal, I'll get them back out eventually but I may pull the dishwasher and have a look myself.

I still need to test washer, dryer, and AC in the next few days.

I went to like at fusebox and it turns out it is a 20A curcuit going to living room. Only (3) outlets in there so that means a few lights besides just my hifi equipment.

Pulled AC outlet and it looks and feels solidly grounded.

[doctorcilantro]

Wonder if my amp is part of the issue. I could try a cheater plug.

"Another rather unique feature of our output transformers is that they float.  They have no reference to ground.  This is difficult to do in all but the most stable amplifier circuits."

[doctorcilantro]

I pulled out the dishwasher, and the conduit wiring comes in wrapped in white sheath. It has (3) wires: green, black, and yellow.

These are wired: black/brown (HOT) | white/blue (7-9v) | yellow/chassis (7-9v)

There is also an internal green ground wire coming down out of dishwasher harness that goes to chassis.

I have the breaker off, and curious why the yellow goes to chassis. Doesn't seem right based on what I'm reading but who knows how it is really wired at breaker.

Proceeding with caution.

[Speedskater]

Tell us about the (7-9v) voltage readings?

[doctorcilantro]

I checked each wire from the conduit while energized but disconnected from the the dishwasher.

Once reconnected the same way, but the ground wire tightened, I measured no such voltage on the chassis of the dishwasher. I didn't try to check neutral to ground while reconnected.

I checked polarity of outlet in Hifi room and its ok with .5v measured across neutral to ground.