Well this is frustrating ...

[Jamier]

Is that wire romex? If it is it’s not likely be a problem except on the stripped ends which you can check easily. Did you turn off the circuit breaker and pull the duplex out of the wall box?

Jamie

[Deke609]

I'm not worried about the wires so much as I am about the receptacles and receptacle boxes.

[Jamier]

If it is dedicated it only has 2 ends. The duplex in your listening room and the connection at the service panel( unless it is connected through one or more service points, which should also be in metal or possibly plastic boxes).

Jamie

[Jamier]

Derek, turn off the breaker, AND BE SURE it is off, and pull the duplex out and inspect it. It’s possible that the problem could be as simple as a ground wire that’s become detached from the duplex. Not all electricians are as careful as others. Make sure when using the Sideties on a duplex to make a “J” loop on the wire in a clockwise direction so the screw pulls the wire in toward the screw shaft and thus cannot come loose. MAKE SURE you check those wires with a meter before you handle them.

Jamie

[Paul Birkeland]

With preamp on: jagged 60Hz waveform that varies in amplitude by the SII's attenuator setting.

That's a new piece of information.  If the attenuator is all the way down, is the hum nearly inaudible?  Is everything plugged into the same outlet? 

When you figure out what's actually wrong, it's likely to be something incredibly simple. 

Something I've had happen that could cause this would be one of the two connetions on an RCA jack not being connected.  Or, for instance, if somehow you swapped ground and signal hot, that could make a weird problem like this.

[Deke609]

If the attenuator is all the way down, is the hum nearly inaudible? 

Yes, at about -27dB it is barely audible. If I wasn't looking for it, I wouldn't notice it.

Is everything plugged into the same outlet?

Yes. And I've now tried 4 different outlets. 1 off the main panel, 3 off the sub-panel, including the 20A dedicated. All give me hum.

When you figure out what's actually wrong, it's likely to be something incredibly simple. 

That would be nice. I need to take a fresh look at the problem.

Something I've had happen that could cause this would be one of the two connetions on an RCA jack not being connected.  Or, for instance, if somehow you swapped ground and signal hot, that could make a weird problem like this.

I will look. But for that to be the case, I'd have had to make the same error at least twice and at least 1 year apart. B/c I got the same hum with BeePre (built in the last year and tinkered with) and Kaiju (built recently and tickered with), and BeePre and SII-45 (haven't done anything to it in a while - no snubbers, no CLC filters, etc.). And I get it with the Nickel Wonder (built from schematic a while ago; made no mods) w/ Kaiju, SII-45 and a retail-bought SS HP amp.  In mid Sept I had no hum (other than reg dropout in the Beepre) and had never experienced hum.  So I think something has changed ... I just have no idea what.

I'm stumped. THe only thing I can think of is the water leak. But I don't know how that would lead to what I assume is a ground loop somewhere. Or is not a ground loop?

Please keep the ideas coming!!!

thanks, Derek

[Jamier]

Derek, have you tried different interconnects/ cables, including power cables?

Jamie

[Deke609]

Derek, have you tried different interconnects/ cables, including power cables?

Jamie

Yup - four different interconnects, including 2 store bought to rule out me having made the same mistake in building the cables. And different power cords - diy and stock/commercial ones. No difference in hum.

[Deke609]

Does anyone see any clues in the jagged 60Hz waveform that I posted on the first page of this thread?

many thanks, Derek

[Doc B.]

It's not just 60. Looks like 120 and maybe 180 on there too. Just hook a bare wire to your scope input hot and see if it shows the same kind of waveform. Since you seem to hear hum with every piece of gear, that will tell you if every piece of gear is picking up something in the environment.

Also, I don't see anywhere that you have shorted the inputs and looked at the waveform. Turning down the level pot is almost the same thing, but just almost. That will help to determine if the root problem is within the DUT.

[Deke609]

... hook a bare wire to your scope input hot and see if it shows the same kind of waveform. Since you seem to hear hum with every piece of gear, that will tell you if every piece of gear is picking up something in the environment.

Many thanks Doc. Will do.

Also, I don't see anywhere that you have shorted the inputs and looked at the waveform. Turning down the level pot is almost the same thing, but just almost. That will help to determine if the root problem is within the DUT.

So short the preamp inputs and connect to amp and test? Or short inputs of unconnected preamp/amp and test?  Or all of the foregoing?

Many thanks, Derek

[Doc B.]

Start by looking at one piece of gear at a time in order to narrow down where the problem lies. Disconnect the preamp from the amp, short the preamp inputs and look at the output of the preamp. Then do the same with the amp, short the inputs of the amp and look at the amp outputs.

Note that this applies only to Bottlehead products. I don't take any responsibility for the stability or functionality of anyone else's amps with the inputs shorted

[Deke609]

Ah hah! Should have tried this earlier: DAC straight to the SII-45, no preamp. NO HUM! ZIP, ZILCH, ZERO. PERFECT SILENCE!  (And as an intesrting side note, it sounds much better by itself than with the Nickel Wonder in front of it ... which, come to think of it, I think is the reason why I put it in a corner to collect dust in the first place).

So there's something about the interaction of the preamps and the amps. Maybe  I reallly did make the same mistake multiple times. So I think I need to look for possible sources of a difference in ground potentials between preamps and amps. I wonder if the "balanced outputs" mod (+ve and -ve of both speaker out referenced to ground via resistor) might do this? Or interact with the diode chassis ground elevation mod?  I am going to enjoy listening to the SII-45 by itself for a bit and look over schematics and photos of my builds to see if I can spot anything.

Feeling more relaxed now and confident that the riddle will eventually be solved.

Start by looking at one piece of gear at a time in order to narrow down where the problem lies. Disconnect the preamp from the amp, short the preamp inputs and look at the output of the preamp. Then do the same with the amp, short the inputs of the amp and look at the amp outputs.

Many thanks Doc. I will try this tomorrow morning. I'm pretty tired today - at 2 am yesterday I scrubbing/filing heavy gauge ground bus wire in an effort to improve earth ground

Note that this applies only to Bottlehead products. I don't take any responsibility for the stability or functionality of anyone else's amps with the inputs shorted

Hah! I don't care about the other ones. And I'm neither litigious nor the type to blame people for trying to help me (for which help I am thankful and appreciative)!   

I hereby absolve and agree to hold harmless all who post or have posted advice, opinions, suggestions etc., of whatsoever kind, on this thread or other any other on this forum; and for greater clarity, declare that I am solely responsible in law, equity or otherwise for any actions or inactions I have taken or may in the future take, whether in reliance up on or influenced by such advice, opinions or suggestions. Seriously. Not joking.

cheers and thanks, Derek

[Deke609]

That's a new piece of information.  If the attenuator is all the way down, is the hum nearly inaudible? 

Yes, at about -27dB it is barely audible. If I wasn't looking for it, I wouldn't notice it.

@PB: I should clarify that only the attenuator on the SII has this effect. Not the volume pots on the BeePre (pre-dismantling) or the Nickel Wonder. Changing the coarse attenuator on the BP had little effect on the hum: slightly changed the tone, but not the volume. With the Bp attenuators set to minimum volume, I got pretty much the same hum loudness. Same thing with the Nickel Wonder: same hum with volume all the way down as nearly fully open - except that turning it all the way up seemed to shift the hum to one side and change the tone a bit - but I figured this was just weird bahavior of a $10 pot turned too far (literally forcing it to point it wouldn't turn any more). 

And I need to correct a previous misstatement: the hum becomes nearly inaudible at -18dB, not -27dB.

Does the fact that the SII attenuators, and only the SII attenuators, affect the volume of the hum point to anything?

many thanks, Derek

[Deke609]

Last observation for the day: no hum with the Quickie as preamp in front of the SII-45. I assume the same will hold true with the Kaiju. I will try that tomorrow.

Off-topic tangent: the Quickie w/ PJCCS is my son's and I'd never listened to it except connected to my son's Quicksand. It sounds insanely good in front of the SII-45. It beats the pants off the Nickel Wonder - which cost me about 2 X as much in parts (the tiny Hammond nickel transformers alone were $100 or more). Wow! It's no BeePre, but I could understand someone hearing both and deciding they could live with Quickie. Crazy good. And really fun to listen to.

cheers, Derek