TRL Dude or Joule 150 MKII for Major Pre Upgrade

It is possible that the power supply ground of the speaker is somehow also connected to the speaker terminals. That could cause some amplifiers to be ground-looped. A continuity test between the ground pin of the AC cord and the speaker terminals would sort that out pretty quick.

Atmasphere, my understanding is that Granny is now using a pair of passive speakers. There should not be power supply for it....

Correct, passive speaker. I ha!ve been working with Vett93 and he has stepped me through all kinds of tests. Thank you for being so patient with me! Through it all I still have the same buzz out of both speakers. The buzz is not present under three conditions we have tested.

1) the Atlas amp turned on and connected to the speakers with nothing else hooked to the amp

2) the Atlas amp hooked to an ic feeding into an RCA socket with the two leads connected and shorted

3) as above with a 1kohm resistor between the RCA ground and center pin.

The buzz is present with any other condition. Here is a recap of what causes a buzz through the speakers.

-Three different single ended preamps turned on or off hooked to the amp. They each caused the same buzz wether they were on or off with or without a source hooked up .

- hooked direct to two different cd players the buzz was the same - no preamp

- cheater plug on amp, then preamp, all xlr inputs on the amp shorted between pin 1 and 3 with purchased xlr connectors having pin 1 and 3 shorted

Vett93 can better explain all the RCA, iec, pin, chassis etc measurements we made concluding all was wired correctly with the amp's input.

Stumped is an understatement. I wonder if a conditioner of passive or active nature is needed to cure other issues?

Through all of this testing all 4 xlr inputs were shorted between pin 1 and 3.

I just read this in my Aesthetix Atlas's manual. " each channel is a balanced bridge amplifier, thus the negative speaker terminal is not a ground, and cannot be connected to a system ground or loudspeaker system with a common ground. Consult your speaker builder to confirm that your speaker does not have internal circuitry with a common ground."

Well, my speaker is passive - Nola Viper Reference. As for what this means above, I have no clue. I can't imagine a passive speaker would have this sort of grounding issue however?

Sounds like Vett93 gave you some excellent suggestions. One additional experiment I would suggest is that besides shorting the two pins on the XLR connectors, you also short the center pin and ground sleeve of the two RCA connectors for the high passed inputs of the amp. If you don't have shorting plugs, you could again use IC's with something conductive inserted at their other end to provide the short.

I would add to your summary, btw, as you mentioned in the other thread where this was discussed, that the noise is present if the preamp is connected to the regular inputs of the amp and the high passed inputs are selected, but disappears if the preamp is connected to the high passed inputs and the regular inputs are selected (while being present if the preamp is connected to the high passed inputs and the high passed inputs are selected).

And yes, the caution about not grounding the negative output terminals of the amp is not applicable if all that is connected is a passive speaker. It shouldn't be applicable with an electrostatic, either.

Best regards,
-- Al