I tried everything I could think of before posting this, but my Aleph J hums with anything connected to the inputs. I have tried different preamps and interconnects with no change. I reconfigured the amp to vertically mount the tranny and have rerouted the incoming AC, and it's still there. I am using shielded wire for the inputs with shield only connected to ground at the RCA input. I tried cutting one of the shields with no change. Moving the input wiring around does nothing to the hum that I can tell. The hum is not super loud but audible from a few feet away from speakers. Too loud to be acceptable.
Hum goes away entirely if I stick a shorting plug in either RCA input. This points to the input wiring, but I can't figure out what's wrong. Thanks for any assistance, and see photos.
Hum goes away entirely if I stick a shorting plug in either RCA input. This points to the input wiring, but I can't figure out what's wrong. Thanks for any assistance, and see photos.
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So I had the exact same problem with a Pass A40 years ago. Tried everything and nothing worked. Not loud but was always there. After reading through Pass papers tried the ground lift with 10 ohm resistor between chassis ground and the ground tab of the RCA jacks. It was like a godsend after fighting this for weeks. Completely quiet.
I have recently finished Aleph J and used standard outboard FW power supply which I use for F5, F4 or M2, all of which work great with no hum. Because I notice some hum with Aleph, I added more capacitance inside the amp and all is good. Seems to me Aleph J has smaller PSRR and just needs better filtered supply.
Well, I added a 10R in line with each input's ground wire to the RCA plug's ground tab, and there is no change to the hum. The hum still goes away when I short the inputs.
I will reroute the rail wires so that they are as short as possible later when I have time. I had already tried the wire connecting both boards GND pads across the amp, but when you say FAT wire, how fat are we talking @zen mod? I used 18ga, but I can find thicker if needed. How does this avoid introducing a ground loop? Seems like I already have the GND for each channel linked at the PS board.
I do not believe the hum has anything to do with the DC rails needing more filtering, as the amp is nearly dead quiet when I short the inputs. I can hear the tiniest, distant hum with my ear right up on the woofer when the inputs are shorted, but I call that good enough. The hum I am talking about is coming from the input wiring, apparently.
I will reroute the rail wires so that they are as short as possible later when I have time. I had already tried the wire connecting both boards GND pads across the amp, but when you say FAT wire, how fat are we talking @zen mod? I used 18ga, but I can find thicker if needed. How does this avoid introducing a ground loop? Seems like I already have the GND for each channel linked at the PS board.
I do not believe the hum has anything to do with the DC rails needing more filtering, as the amp is nearly dead quiet when I short the inputs. I can hear the tiniest, distant hum with my ear right up on the woofer when the inputs are shorted, but I call that good enough. The hum I am talking about is coming from the input wiring, apparently.
Can you show pix of the connection from power supply PCB to the the chassis. And safety ground? Is there a CL-60 PSU to ground?
What happens if you shorten PSU wires and twist them?
Could you go very tight twisted input wires a little longer and play with routing them. I'm thinking try them right against the chassis wall / heat sinks.
What happens if you shorten PSU wires and twist them?
Could you go very tight twisted input wires a little longer and play with routing them. I'm thinking try them right against the chassis wall / heat sinks.
No offence taken
I was just wondering if you did something that was different. NO
I saw someone add small capacitors at the out put of the power supply. NO
Sounds like you just stiffened up the rails ? YES
There is a CL60 from PS PCB groung to chassis safety ground, and I have played with that connection some with no change. I can take a photo later.
I will probably try redoing the DC rail wiring and input wiring a little longer like you suggest. I have tried moving the input wiring around in the amp with no change in noise, so I haven't tried to redo it yet. I may just go unshielded twisted pair since my current input wiring is shielded.
That’s not a ground loop but rectifier hum. Power supply filtering is normally the issue here but your wiring gauge could be the issue.
Alright, here are some photos. I have not twisted the DC supply wires, as the attachment points on the boards are so spread out. The hum is unchanged as far as I can tell, and there may be some additional high frequency noise that wasn't there before.
I did make one change that reduced the hum significantly, not using shorting plugs. You can see it in the photos. I added temporary jumpers from the RCA input ground tabs directly to ground on the PSU. So I think the idea that my wiring, or at least the ground wiring from the amp boards, may not be big enough, possibly introducing some noise.
I focused on the input jacks since the shorting plugs made a difference, and I saw a nice build that was wired this way. There is still a little hum, but I hope that using bigger wire will help, and I haven't tried lifting the input gnd wire on the amp boards to see how this will affect things.
I'll have to order some heavier wire, and the stuff I used is admittedly not that nice. Thanks for all of the helpful suggestions, and I'll report back after I get the wire.
I did make one change that reduced the hum significantly, not using shorting plugs. You can see it in the photos. I added temporary jumpers from the RCA input ground tabs directly to ground on the PSU. So I think the idea that my wiring, or at least the ground wiring from the amp boards, may not be big enough, possibly introducing some noise.
I focused on the input jacks since the shorting plugs made a difference, and I saw a nice build that was wired this way. There is still a little hum, but I hope that using bigger wire will help, and I haven't tried lifting the input gnd wire on the amp boards to see how this will affect things.
I'll have to order some heavier wire, and the stuff I used is admittedly not that nice. Thanks for all of the helpful suggestions, and I'll report back after I get the wire.
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you could try a 'series' ground arrangement in case you have a ground loop.
Connect your PSU ground to one amp channel as normal. Then connect your other amp channel ground to the first channels BOARD'S ground. So you actually only have one wire to PSU ground.
Then you can try the same for the RCA NEG. RCA gnd to RCA gnd, then to one amp channel (or to the PSU).
edit: just to make sure, the end we can't see of the bolt holding through the toroid has nothing connected to it, right?
Connect your PSU ground to one amp channel as normal. Then connect your other amp channel ground to the first channels BOARD'S ground. So you actually only have one wire to PSU ground.
Then you can try the same for the RCA NEG. RCA gnd to RCA gnd, then to one amp channel (or to the PSU).
edit: just to make sure, the end we can't see of the bolt holding through the toroid has nothing connected to it, right?
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