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September 27, 2021, 06:55:34 AM

Author Topic: Random crackling in left channel, getting worse  (Read 461 times)

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Offline fung.chan

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Random crackling in left channel, getting worse
« on: July 16, 2021, 02:14:15 AM »
Hi everyone, hope you're all staying safe. I bought a Crack around a month ago after reading about it and researching it for a week straight, everyone had good things to say so here we are.....after finishing the amp I tested it straight away and was thoroughly blown away, until about 3-4 hours after listening, I heard a slight crackling in the left channel. It got progressively worse, I thought it needed burn in, so I left it on for 8 hours overnight with music playing softly and a very gentle breeze to help keep it cool. The next day I had a quick listen and the crackling was still present. I thought it still needed burn in so I put about 20 hours of actual listening on it, somedays it sounded totally fine, a couple of days it crackled as soon as it warmed up and the crackling would come and go totally at random.

The crackling is only in the left channel and sounds like dust on an old vinyl, the right channel didn't have any crackling until after I tried to fix it (get to that in a bit)

I spent an entire night troubleshooting and took the following notes:
1/ Crackling does not change volume when volume knob is adjusted.
2/ Crackling does not change if RCA cable is plugged, unplugged or swapped over.
3/ Crackling does not change with different source device (Sony ZX300 and Samsung Note 9).
4/ Crackling does not change if connecting my Sennheiser HD600 via (official) single ended or balanced cables with a convertor.
5/ Changed power cable, still crackles.
6/Used different powerpoints in the house, with and without a filtered powerboard, still crackles.
7/ Tried two other 12AU7 tubes from my xDuoo TA-20 amp, still crackles.
8/ Tried different headphones altogether (Focal Elear, single ended and balanced to SE convertor), still crackles.
9/ Wiggling and tapping tubes while amp is on makes no noises or popping. so I'm guessing things aren't loose.
10/ Tapping all over the amp produces no pops or additional crackling either.
11/ The crackling isn't radio interference as I tried three different places in my medium sized house, as per point 6.
12/ Crackling only occurs when Crack is fully warmed up (when music plays at regular volume).
13/ Unplugged and plugged in both tubes numerous times in case of corrosion in terminals or tube pins, still crackles.
14/ I have tightened the transformer screws as suggested in other forum posts.
15/ I have reflowed ALL solder joints TWICE, some of them three times, especially connections pertaining to the left channel, from the black RCA jack, to the volume knob, to the tube sockets, to the headphone jack.
16/ The two red LEDs on the 12AU7 socket light up and do not flicker, even when tapped
17/ I have tightened the screws on the 12AU7 socket clamp as suggested in forum post.

Regarding point 15, I have done the following:
a/ Every single solder joint has been reflowed. Every single one. Twice.
b/ Both tube sockets have had all their solder reflowed three times.
c/ Every solder was done by tinning the soldering iron, then applying heat to both the component/cable and the hole it's going through, then letting it heat up for a second and applying solder.
d/ None of the solder joints are loose, or cracked, I have wiggled every single one of them with needle noise pliers.

Guess what? Now the crackling in the left channel is even worse, and now both channel hiss whenever it crackles too! What have I done wrong, I'm at wits end. The only thing I could not test was swapping out the big tube, could it be damaged, or have I heat damaged something?

Offline pofofo

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Re: Random crackling in left channel, getting worse
« Reply #1 on: July 16, 2021, 05:36:41 AM »
Holy crap. It sounds VERY similar to a problem Im currently got with my S.E.X. amp. I´ve started a thread about it and are still trying to find out what it is. I´ll follow in this thread also.

Offline Paul Birkeland

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Re: Random crackling in left channel, getting worse
« Reply #2 on: July 16, 2021, 05:38:44 AM »
Can you post some build photos?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline fung.chan

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Re: Random crackling in left channel, getting worse
« Reply #3 on: July 17, 2021, 11:56:05 PM »
Hi Paul, here you go, I'd like to add the soldering looked much better the first time around  :'(


Offline fung.chan

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Re: Random crackling in left channel, getting worse
« Reply #4 on: July 17, 2021, 11:58:22 PM »
Continued

Offline fung.chan

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Re: Random crackling in left channel, getting worse
« Reply #5 on: July 17, 2021, 11:59:49 PM »
Continued

Offline Paul Birkeland

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Re: Random crackling in left channel, getting worse
« Reply #6 on: July 18, 2021, 04:53:09 AM »
What kind of solder are you using?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline fung.chan

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Re: Random crackling in left channel, getting worse
« Reply #7 on: July 18, 2021, 05:13:37 AM »
Hi,

Duratech 1mm 60% SN, 40%PB, 2% Flux 2%, resin core.


Offline Paul Birkeland

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Re: Random crackling in left channel, getting worse
« Reply #8 on: July 18, 2021, 06:31:50 AM »
To help pinpoint the problem, plug in a pair of very inexpensive headphones and poke around the circuit with a wooden chopstick until you're able to activate the noise, then that can help you focus your efforts.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline fung.chan

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Re: Random crackling in left channel, getting worse
« Reply #9 on: July 20, 2021, 02:45:13 AM »
Hi

I just poked around everything with a pair of really cheap headphones connected:

- All cables along their lengths and solder joints.
- All the big capacitors and their legs and solder joints.
- All four white capacitors and their legs and solder joints.
- All the tube socket pin solders and the pins themselves, both tube sockets.
- All the little brown capacitors with the coloured stripes.
- Both RCA jacks.
- All three power socket pins.
- Both power button pins.
- All the solder joints on both sides of three four terminal strips.
- All the pins on the PT10, including the little black cable for terminals 15-16.
- All the little black rectifier with the silver bands.
- Both red LEDs and their legs and the associated pins they're soldered to.

None of the above seem to make any noise when being poked.

I did notice one thing though, when I flipped the amp upside down in the stock wooden cabinet(rubber feet have been installed so there is a space), it ran hotter, and the crackling now happens in BOTH channels, and more frequently, with the cheap headphones.

When I flipped it back over and connected the HD600s again, the crackling happened less, and only in the left channel....


Offline Paul Birkeland

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Re: Random crackling in left channel, getting worse
« Reply #10 on: July 20, 2021, 07:32:45 AM »
Can you post a recording of this crackling?  It could be interference from a nearby wireless device, and reorienting the chassis may have changed how it's being picked up.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline fung.chan

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Re: Random crackling in left channel, getting worse
« Reply #11 on: July 22, 2021, 12:04:00 AM »
Hi Paul, please find the files attached. They were recorded with a Zoom H4n recorder, on a fabric couch with the headphones walled in by big cushions. There is a bit of background hiss which is unfortunately how the Zoom is.

In the file crackles, the crackling starts immediately in the left channel. This was pretty much within a couple of minutes of powering the amp on.

In the file High pitched whining, you can hear some really high pitched whining at 15 seconds onwards. This was taken about an hour after power on (I left the recorder running for 3 hours+ and chopped out what you can hear.

For some reason (and I find this weird I'm sorry), I can't, on a forum about sound and music, upload an mp3, but it will allow me to upload an mpg, which is normally a movie....anyway, the below worked on my PC, if it doesn't play, simply rename the extension to .mp3 and you're good to go.

Offline Paul Birkeland

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Re: Random crackling in left channel, getting worse
« Reply #12 on: July 22, 2021, 05:58:41 AM »
I don't hear anything on the high pitched whining recording.

The crackles you're hearing could be from a cold solder joint, tube socket pins that are a little dirty, or a tube that needs to run in for 50-100 hours.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline charnich

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Re: Random crackling in left channel, getting worse
« Reply #13 on: July 23, 2021, 01:19:45 PM »
I had the exact same problem when building my crack. It turned out to be the "input" or small tube was bad. I replaced it and problem was resolved. I can't guarantee that is your issue but it was sure mine. Best of luck.
« Last Edit: July 24, 2021, 10:20:45 AM by charnich »
Chuck Nicholson

Offline Doc B.

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Re: Random crackling in left channel, getting worse
« Reply #14 on: July 24, 2021, 05:58:04 AM »
Time for my annual "high pitched oscillation is 90% of the time due to oxidized tube pins" post.
Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.