Nothing seems obviously wrong there.Here's my setup:
Are your RCA grounds isolated from the chassis?
Yes, RCA grounds are isolated from the chassis: properly sized holes, shouldered nylon washers, confirmed with DMM after final assembly. I used 2-conductor foil-shielded Belden wire to the attenuator and wired each channel separately. I can modulate the buzz a small amount by grasping the exterior of the RCA connections - maybe that's a hint that I should try tying the RCA grounds together.
I tested with the transformer white (shield?) wire removed and also with nylon standoffs and nuts/bolts to isolate the board, but the issue persists.
Also note that in my initial pics I had the yellow/orange wires switched. I've since fixed that. The wrong way gave an enhanced 3D effect to the music.
I could wire in a Meanwell SMPS and leave the regulated supply unpowered to see if the toroid proximity is part of the problem here.
Short term workaround to the buzz is to simply open up the pot all the way and control volume at the source - currently a Buffalo II ES9018 DAC with digital volume control and Legato I/V stage.
BK
my solution to eliminate grounding and humming issues was to use 3 lead wires, starting from the (-) from the Weiner power supply board., 2 going to the RCA's (-) L/R inputs of the card and the third wire going to one of the 4 corners of the Weiner card., reference to post 351 or 374. This should resolve the grounding issues for the Weiner card only.
music https://www.youtube.com/watch?v=1iAYhQsQhSY
music https://www.youtube.com/watch?v=1iAYhQsQhSY
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Victory is mine!
After trying many small tweaks and wiring configurations as already described and losing much sleep over the imperfect situation, the real solution was to rig a simple ground loop breaker.
10ohm 5W resistor in parallel with a 0.1uF line safety capacitor between the isolated wiener board and the chassis. See lower left of wiener board.
Sonic bliss with no hum/buzz at any attenuator position with my ear right up to my speaker. Those implementing a one-box configuration might want to give it a try.
BK
After trying many small tweaks and wiring configurations as already described and losing much sleep over the imperfect situation, the real solution was to rig a simple ground loop breaker.
10ohm 5W resistor in parallel with a 0.1uF line safety capacitor between the isolated wiener board and the chassis. See lower left of wiener board.
Sonic bliss with no hum/buzz at any attenuator position with my ear right up to my speaker. Those implementing a one-box configuration might want to give it a try.
BK
An externally hosted image should be here but it was not working when we last tested it.
How does it sound? Goosebumps!!
Special magic synergy with my gear combination or?? Feeding it with high quality signal (full-zoot Buffalo-II or AMB Gamma 1.5) and driving some small nearfield full-range speakers (GR Research LGK). Exactly what the doctor ordered. The bass is quite impressive and I know the amp is partly responsible. I continue to be impressed and can't wait to try the gmarsh wiener PBTL version.
BK
Try the amp with a pair of interconnects using Belden 8402 microphone cable and a set of Switchcraft 3502AAU RCA connectors. Use the white conductor for + and black conductor for - (ground). Tie the braided shield to - (ground) at both ends. Don't worry about ground loops with this configuration. You will be pleasantly surprised with the results and really hear what the TPA311x amps are capable of. Best-Tronics (Best-Tronics Manufacturing) sells the Belden 8402 by the foot or meter. They also carry the Switchcraft RCA connectors.
Given enough interest, sure. In the meantime I've bought parts to build a number of spare cards in case of less than perfect yield, I'll probably have some extra cards to sell when I'm done.
I will say if I get another order of 50+ boards I'll probably get them made at a local electronics assembly shop instead of hand building. This is taking a while
I will say if I get another order of 50+ boards I'll probably get them made at a local electronics assembly shop instead of hand building. This is taking a while