Aleph J illustrated build guide

So after sneaking from the sleep ing baby a few times I've tested several things and still have no idea why the transformer is humming. First, I disconnected each amp board from the power supply and can say with certainty that the transformer hums regardless of which channel amp board is attached (L or R). Next I tested for shorts of of the power supply board. None. Then I noted that there is no hum when NEITHER amp board is attached. Fourth I disconnected the transformer from the rectifiers and there was no hum. I also completely disassembled the transformer mount from the transformer. I can confirm that iI used a gasket on either side of the transformer and that none of the mounting hardware is touching the chassis except for the L-bracket. Next I tested the voltages in the power supply. At the time of testing i was getting ~125vac at the wall, ~19vac at the secondaries, ~25vdc after the rectifiers and ~25vdc after the amp board. These all look correct based on others findings on the forum. I built this power supply at the same time as the one in my M2x with performs without a hitch or hum. I should also note that both channels bias without any problems. So what should I consider my next steps??? I'm really stuck here. Thanks,
 
Then I noted that there is no hum when NEITHER amp board is attached.


Could be a case of loose windings; all good with no current, but the windings start to vibrate / buzz when under the load. Nothing you can do, apart from potting the whole thing, or returning the transformer to the manufacturer. For this very reason, I think I read somewhere that Nelson uses a correctly specified wiring (VA rating), but wound on core specified for a higher induction rating (300VA wire thickness, but 400VA-specified core, for example)

You could test the above theory if you have something like 10-20 ohm / 50-100W resistors; just load the secondaries, connect the transformer to mains and listen closely <- this is pretty much what you proved already when you connected the amp PCB's (which loaded the transformer)

I test all my transformers with a resistive load at secondaries, BEFORE they go inside the amp chassis... unfortunately, this is still no assurance that the transformer will not start buzzing down the road.. at some point... this is why, for my personal use, I decide to use fully potted transformers. They cost more but they stay quiet.
 
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The most recent posts are: 5211, 5208, 5161, 5160, 5155, 5153, 5144$, 5142$, 5093, 5091. The posts with $ have photos. The string of posts goes back further, but I believe you can search my post history for those. Basically I’ve been fighting with this build for months and I’d like to finish it. The first set of problems I’ve had were related to bias problems and blown MOSFETS. Now that the amp biases and the MOSFETS are replaced the transformer hums when the power board is attached to the amp boards. Thanks
 
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6L6

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Float the purple? I highly doubt that will work but it will take very little time to try, so you may as well eliminate that variable.

Do they warrantee for hum? No idea. I personally am a interstellar vortex of attracting transformers that hum (regardless of brand), have been for years and years, so I have always just bought replacements.
 
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Jim, should I just buy another? Does Antek warranty against this by any chance?

Also, one thing I haven’t tried I just realized is floating the transformer ground (purple wire). Any chance that will work?

Thanks

Contact Antek. I've used quite a few of them with no problems. I have no doubt they would replace it, anyone can make a bad one now and again.

Whatever, keep at it! This is one amp that is well worth the trouble.

I think most here use the 400VA model, as it can be had with shielding. I have used their 500 VA model on most everyone of my builds, never hit a bad one and they all run quiet.

As cheap as they are and as worth it as this amp is, I would order another...

M2, F6, Aleph J all use them, all my preamps use them, (50 VA model on preamps). The BA3 uses a SumR from a group buy for F5 turbo. My F5 used 2 300VA units, as dual PS.

Russellc
 
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im not really sure about this or if it was previously mentioned, but it appears you have both sets of primaries and secondaries all wound together. Have you tried separating them and more importantly, have you verified you've got the right red/black and blue/grey pairs for each so you arent wiring one side of one winding to the other? I'm far from an expert but I thought that would create issues.
 
Pechelman, I braided the wires to reduce clutter and noise. You may be able to see where I marked one pair with silver bands Near the heat shrink before braiding. This is true of the primaries and secondaries. I believe they are correctly sorted, however how would you suggest I check if I did so? Continuity test? Thanks
 
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It's an easy check.

Set your voltmeter to continuity beep check or resistance if you dont have that.
with the power off and transformer leads disconnected, check for very low resistance or continuity between red/black and then blue/grey. If it beeps you have found the pair. If it's open, it's a different winding.

All the leads are is one continuous wire wrapped around an iron core.
 
One quick thought: would the amp even work if I had misaligned the primary and secondary wires to the transformer? Please recall, as noted above, that the amp biases correctly and that the proper voltages are coming out of the amp board. Would this be the case if I had miswired the transformer? Thanks, and I will report back on the tests.
 
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It's just something to check. Since you can bias the amp and set offset correctly, it's likely the transformer.

I'm sure like myself, you checked the pairs when you assembled, but sometimes....

Get a hold of Antek, I'm sure they will stand behind it. I'd order one as soon as I could, and hope they back it up. Whatever, cost of transformer is reasonable, and you are going to need it!

Russellc
 
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freejazz00,

I have a little used Antek AS-4218 that worked perfectly, to include no hum.
It was pulled when I converted to dual mono power supply for my AJ.

You could have it for a nominal fee + $15.00 to cover USPS Medium Box Priority shipping.
PM me if you want it.
 
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