Troubleshooting help: single channel static after C4S,ImpSw install

xander14 · 2064

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Offline xander14

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Just finished my 2.1 C4S & Imp switch kits and need some advice on how to diagnose some static/popping/hissing that I'm getting strictly in the left channel of my headphones.  Using the 32ohm setting with HiFiMAN planars.

The problem did NOT exist when I finished the stock build, so I know it should be limited to the upgrades.  The problem didn't follow the tube after a swap, so it's the circuit and not the tubes.  Tried switching to balanced using a speaker taps-->4pinXLR, and nothing changed, so thinking it seems like nothing to do with the output re-wirings.  Tested the different impedance levels, none of which have made a dramatic difference, though I THINK the static got just slightly quieter on the lower settings.

I have taken a thorough look at what I think is every joint I soldered for the upgrades and re-flowed more than a few wherever they looked like they could use it, and still no change, so I think I'm now down to a bad component.

The only thing that could be more demoralizing at this point would be to start uninstalling & checking resistors & whatnot only to still not find the source, so I need a little direction from somebody as to what the most likely culprit might be.  From the descriptions in the manual, seems like it's going to be a resistor, but there's 2, maybe 3 of the associated sounds described there instead of just one, so I really don't know.



Offline Paul Birkeland

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How are your voltages? 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline xander14

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How are your voltages?
They're all mostly where they're supposed to be, including the extra two referenced in the C4S manual.  Most within about 5%, a few that push 15-20%: 

- The A7/B7 & A8/B8 pairings (as well as up on the C1/2 & C4/5 pairings on the upper terminal strip) are sort of pushing it -- they both read something like -3.6 on the 7 and 2.5 on the 8, but I've seen other people on here shrug that off as acceptable. 
- B3 reads 15.5, so also sort of straying from the manual reading (19) there. 
- On the C4S board, OA reads basically exactly what it's supposed to at 76, whereas OB is a hair off, around 66 I think.

But that's basically it...

  :-\



Offline Paul Joppa

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The voltages look good. Most likely it's the C4S. Because the voltages are good, I'd say the C4S is basically good; perhaps there's an iffy solder joint on the board. The center leg of the MJE-350 is the most common culprit since it absorbs heat really well, cooling the solder too fast and causing a "cold solder" joint. But inspect them all!

Paul Joppa


Offline xander14

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So I reinforced/reflowed many of the C4S joints, and still no difference. Uninstalled the board & replaced it with the stock resistors, and the static was gone, so it's definitely the C4S board.

Uninstalled the 4 resistors on the board & measured the resistance, and all 4 checked out perfectly...

Any suggestions as to how best to proceed?  The only thing I can think to do would be to completely disassemble & reassemble the entire thing, but I don't know if I even have enough room on the clipped leads to do that...



Offline Paul Birkeland

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So I reinforced/reflowed many of the C4S joints, and still no difference.

Now that you have them installed, I would reflow them all.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man