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 Post subject: Help crackle on preamp
PostPosted: Tue Dec 26, 2017 2:17 pm 
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Location: Sturgeon Falls, ON, CA
Looking for some opinions on the following issue :
I have a Bat vk30 preamp , lately There has been a crackling sound from the left speaker. I swapped the right tubes with the left , no fix . This sound is very intermittent can go for an hour or more without anything then it appears . Worth noting , the tubes are less than a month old (sovtek 6922). Another puzzling part to this is if the preamp is on any given imput( without any signal from that imput . Ie it’s off) the occasional crackle still appears . Now hears the odd part the other day I was listening , I got up touched the preamp , it suddenly got a bit louder, when I adjusted the volume it shut itself off . I waited a few seconds , turned it back on and it continued to work . I’m puzzled and floored at what may be going on here . I cleaned out the tube sockets with a little bit of alcohol on a “gum” tooth pick but no fix . Lastly I found 4 of the sovtek tubes to
Be extremly microphonic . Did the tap test and those four were really loud through my speakers . Amplifier is a bryston 14b sst, vpi scout table, bryston digital player and Dac for digital side . Again doesn’t matter what imput I use ( the inputs can even be turned off ) still does it on occasion .
If any of you have had similar experiences , opinions would be great to hear ... cheers ... Moe


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PostPosted: Tue Dec 26, 2017 2:33 pm 
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Assuming you didn't replace the tubes because they were shot, have you tried swapping the prior tubes back in?

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PostPosted: Tue Dec 26, 2017 2:40 pm 
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Yes installed the old tubes still doing it . Ive only aquired the preamp before xmas used, seller told me it was checked and the old tubes needed replacement


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PostPosted: Tue Dec 26, 2017 3:00 pm 
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I have had this issue with a previous Opera Consanance i ran a few years back.
Same crackling in one channel and tubes microphonic.
Took it to the shop and turned out to be a badly soldered connection.

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PostPosted: Tue Dec 26, 2017 3:08 pm 
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Chipmunk do you remember if it was socket joint that was loose or another part ie resistor,cap or something similar ...

Thanks


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PostPosted: Tue Dec 26, 2017 3:11 pm 
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1. You need to take it to a good tech.

2. Was it shipped?

3. It's possible the seller made his problem yours or it got bounced on it's way to you.

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PostPosted: Tue Dec 26, 2017 3:19 pm 
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If possible take it in and get it checked once you've eliminated the obvious stuff.
I had a vk31se and was warned by a Bat dealer that since they run so hot, that they were having issues with them.
Probably nothing serious, but best to let a pro look before it is.


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PostPosted: Tue Dec 26, 2017 3:23 pm 
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deuce07 wrote:
Chipmunk do you remember if it was socket joint that was loose or another part ie resistor,cap or something similar ...

Thanks

It was a bad solder on one of the tube sockets but not something easy to find. My Opera got bounced in shipping.

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PostPosted: Tue Dec 26, 2017 3:34 pm 
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When you adjusted the volume the noise went away? Could be a noisy volume pot. I have a similar problem occasionally with my ARC SP 14 preamp. With no source on, scrolling the volume up and down solves the issue. You could also try some deoxit in the volume pot. Try this before you ship it off to the repair shop.


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PostPosted: Tue Dec 26, 2017 3:40 pm 
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MENDEL24 wrote:
When you adjusted the volume the noise went away? Could be a noisy volume pot. I have a similar problem occasionally with my ARC SP 14 preamp. With no source on, scrolling the volume up and down solves the issue. You could also try some deoxit in the volume pot. Try this before you ship it off to the repair shop.

That would not explain the other symptoms like new tubes becoming microphonic.
Just saying.

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PostPosted: Tue Dec 26, 2017 3:51 pm 
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It seems volume doesnt affect it at all. The volume seems fine , man this is a real head spinner. Im thinking of ordering the "CAIG deoxit vaccum tube survival kit" and try cleaning the tube sockets again , it may or maynot help ( their ppretty damn small) and made from porcelin .anyone use this deoxit ?


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PostPosted: Tue Dec 26, 2017 3:55 pm 
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to me it sound like a bad capacitor.


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PostPosted: Tue Dec 26, 2017 4:06 pm 
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deuce07 wrote:
It seems volume doesnt affect it at all. The volume seems fine , man this is a real head spinner. Im thinking of ordering the "CAIG deoxit vaccum tube survival kit" and try cleaning the tube sockets again , it may or maynot help ( their ppretty damn small) and made from porcelin .anyone use this deoxit ?

Did it start out of the blue or has it been happening more and more.
And if you tap on the amp when its playing does it crackle?
If yes its a poor solder.

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PostPosted: Tue Dec 26, 2017 4:16 pm 
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It started shortly after tube replacement . Maybe 10-20 hrs later. Ive been listening as we write here for almost 1 hr ...dead silent ...then suddenly crackle and needle across the record sound .... Then it goes after i hit mute no noise . Cancel the mute and its there but very faint .


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PostPosted: Tue Dec 26, 2017 4:23 pm 
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deuce07 wrote:
It started shortly after tube replacement . Maybe 10-20 hrs later. Ive been listening as we write here for almost 1 hr ...dead silent ...then suddenly crackle and needle across the record sound .... Then it goes after i hit mute no noise . Cancel the mute and its there but very faint .

Did you tap on the preamp to see if it coincides with your tapping.

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