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PostPosted: Tue Dec 26, 2017 4:42 pm 
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Tapped on tubes definately hear in speakers , rocked tubes in their sockets and you can hear crackling . If it is a dirty socket my confusion lies in why would it only do it occasionally ?..


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PostPosted: Tue Dec 26, 2017 5:31 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.


He actually said the unit shut right off when he adjusted the volume....

deuce07 wrote:
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: Wed Dec 27, 2017 4:34 pm 
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Almost 3 hrs of listening and it’s dead quiet ... thing has a mind of its own !!


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PostPosted: Wed Dec 27, 2017 5:09 pm 
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deuce07 wrote:
Almost 3 hrs of listening and it’s dead quiet ... thing has a mind of its own !!

Now tap on the body not the tubes...

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PostPosted: Wed Dec 27, 2017 5:34 pm 
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Hi, I would check;
- redo all solder joint on tubes sockets. It could be also on all joints in the audio paths.
- check to volume control pot if cleanable ( I'm thinking if it is a pot or not, like otherwise a stepped level chip?)
- coupling caps like the Jensen are reported to be problematic in the past.
-voltage regulators , seems to be near the tubes..


Again this is just like an estimation, without schematics, and it would have to be taken at a tech for tests on long term basis.
good Luck


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PostPosted: Wed Dec 27, 2017 5:42 pm 
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Chipmunk1957 wrote:
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.


Bad joint won’t make a tube go microphonic

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PostPosted: Wed Dec 27, 2017 6:01 pm 
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deuce07 wrote:
Tapped on tubes definately hear in speakers , rocked tubes in their sockets and you can hear crackling . If it is a dirty socket my confusion lies in why would it only do it occasionally ?..


On 9 pins usually a pull and reinsert is all u need to clean.

Hearing the tap is a microphonic tube, crackling sounds like a shorting/failing tube.

However, with the tube replace and tube swap I’m gunna say bad socket.

Tighten sockets and if those cheap finger spring types check for a bent one....been there...

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PostPosted: Wed Dec 27, 2017 6:03 pm 
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BinkyTheCat wrote:
Chipmunk1957 wrote:
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.


Bad joint won’t make a tube go microphonic

It did on my Opera.
Badly soldered connection was repaired and the microphonics ceased.

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PostPosted: Wed Dec 27, 2017 6:17 pm 
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How?

It's the tube creating the microphonic effect not the connection.

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PostPosted: Wed Dec 27, 2017 6:20 pm 
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BinkyTheCat wrote:
How?

It's the tube creating the microphonic effect not the connection.

The bad joint was on one of the sockets which caised bad bias to the tube this microphonics.

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PostPosted: Wed Dec 27, 2017 6:31 pm 
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This is an extreme case of a microphonic tube...

https://www.tubedepot.com/what-is-a-microphonic-tube

In no way is a bad solder joint going to make a tube microphonic.

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PostPosted: Wed Dec 27, 2017 7:20 pm 
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Ok...

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PostPosted: Wed Dec 27, 2017 7:28 pm 
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I think you're confusing mechanical noise with an actual microphonic tube.

The ironic thing is when looking at a microphonic tube that is in essence mechanical noise lol!

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PostPosted: Thu Dec 28, 2017 5:07 am 
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Chopstick time.
If you're comfortable start poking(flexing) main circuit board,components etc...might reveal itself.
Possible bad plate resistor,cold solder joint, anything really.
Oscillation could sound like microphonics.

Gary


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PostPosted: Thu Dec 28, 2017 6:23 am 
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Could be dirty tube sockets.


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