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PostPosted: Thu Dec 28, 2017 6:30 am 
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Sgt Pepper wrote:
Could be dirty tube sockets.


Highly unlikely

-- 28 Dec 2017 14:33 --

sasquatch wrote:
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


I dunno....with a few hundred volts lurking ....

Just the op cleaning the sockets could give him a jolt if he didn't drain the caps

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PostPosted: Mon Jan 01, 2018 8:07 am 
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Location: Sturgeon Falls, ON, CA
I’m almost certain that it only happens when the unit reaches a certain “temperature”. Upon start up, dead silent . After about 8-15 minutes of play it does the crackle sometimes a squeal it will last maybe a minute or so .. then silence for the remainder of the play session no matter how long it plays it has gone for as long as 2-3 hrs without a sound . Seems it’s within that critical time of heat / expansion that it acts up . I’d take it to a tech but theirs no authorized BAT dealers in my area . This really blows .


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PostPosted: Mon Jan 01, 2018 10:06 am 
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Sounds to me like static build-up due to very low humidity in your space (home). The major clue being "lately". It is very cold and your furnace is working overtime blowing hot, dry air around. Try placing your pre-amp on a rubber mat or running a humidifier. If your system or cabling is on a synthetic/wool carpet you can build up significant charge to cause a crackling sound in the very high gain circuitry of your pre-amp section. You cam also try rubbing down all your cabling with 'bounce sheets' or spraying with a mist of water to see if the crackling dissipates.

If this is indeed the cause, you need to increase the humidity or provide a 'drain' to discharge the excess charge to true earth ground.

J.


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PostPosted: Mon Jan 01, 2018 10:16 am 
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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



Yes, 'Crack", 'Fentanyl' and other substances ae known to (occassionally) 'crackle up' things. (Kidding)

It may very well be the BAT's (excellent) volume attenuation 'circuit (resistor -ladder style) ?
Contact current BAT ownership -with this inquiry.

(To test, and if BAT has a 'Pass-trough/Home-Theater" input/function feature, engage (carefully of course) and control volume by/via te processor -or simiilar. This would effectively by-pass BAT's own volume attenuator).

pj


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PostPosted: Mon Jan 01, 2018 11:22 am 
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Location: mtl, QC, CA
Had the same problem with my Red Wine audio Isabella tube Pre. Pick-up a set of tattoo tip cleaning brushes from E-bay & use the smallest brush to clean the sockets with contact cleaner & De-oxit. Use the same fluids to clean the tube pins (contact to clean, De-oxit to condition) with a tiny (artist) paint brush. You must do this periodically. Have not had this problem since. You could also do the same to all connectors/contact points in your sound system. Have done this recently, & sound quality has gone up a notch.


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PostPosted: Mon Jan 01, 2018 11:41 am 
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People sure like scrubbing sockets....

K...understand the type of socket, what might be underneath the socket and if socket just needs to be retensioned (or replaced)

Again...consider there could be a few hundred volts on the caps

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PostPosted: Tue Jan 02, 2018 5:16 pm 
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The two times I’ve had crackling on a tube amp it was:
1) A failing resistor around the bias circuit
2) Unclean tube socket that resulted in arcing across pins

The arcing could be seen when taking the tube out and inspecting the socket. Do you see blackened spots there?

-- 03 Jan 2018 02:18 --

Oh and the people saying it’s the tube...he changed right to left and it didn’t follow, ipso facto, not tubes


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PostPosted: Tue Jan 02, 2018 6:13 pm 
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Some valid advice from some members.
Based on your description of the preamp problem(s), microphonic tubes may be a factor, but you stated that inserting previous tubes , same problem persists. Therefore, problem might be a dirty volume pot.... even if problem is in one channel. Spray Deoxit Gold ! If this does not remedy problem, it's possible a failed cap, resistor is present in that channel. Hope your situation clears up! :wink:


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PostPosted: Wed Jan 03, 2018 5:33 am 
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“Binky”
Would unplugging the main power cord and leaving at rest overnight drain the caps enough to be able to attempt a cleaning of the tube sockets ? Or if anyone else knows this feel free to chime in... thanks ... M


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PostPosted: Wed Jan 03, 2018 10:43 am 
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It should...assuming there are bleed resistors.

Myself, amp warm, unplug with switch on...tubes will dissipate....

But always check with a meter!

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PostPosted: Wed Jan 03, 2018 4:57 pm 
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Thanks Binky
Something worth mentioning here. This particular preamp was not in use at least very little for the last 1-2 years. I pondered on the idea that maybe things just needed to be “used” or broken back in for lack of a term . I say this because it seems the more I play this preamp the less it’s doing that bloody crackle . Today turned it on after about 30 minutes use it made a faint static sound then that was it . About 5 hrs later , and still no sound . Maybe the audio gods took one for the team here .


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PostPosted: Thu Jan 04, 2018 5:15 am 
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Location: Hamilton, ON, CA
malthuse wrote:
The two times I’ve had crackling on a tube amp it was:
1) A failing resistor around the bias circuit
2) Unclean tube socket that resulted in arcing across pins

The arcing could be seen when taking the tube out and inspecting the socket. Do you see blackened spots there?

-- 03 Jan 2018 02:18 --

Oh and the people saying it’s the tube...he changed right to left and it didn’t follow, ipso facto, not tubes


maltuse: These are excellent suggestions/recommendations.

OP -take note.

pj

-- 04 Jan 2018 13:18 --

deuce07 wrote:
Thanks Binky
Something worth mentioning here. This particular preamp was not in use at least very little for the last 1-2 years. I pondered on the idea that maybe things just needed to be “used” or broken back in for lack of a term . I say this because it seems the more I play this preamp the less it’s doing that bloody crackle . Today turned it on after about 30 minutes use it made a faint static sound then that was it . About 5 hrs later , and still no sound . Maybe the audio gods took one for the team here .


Perhaps try to leave unit on (24/7) for 2-3 days -possibly can help determine if it is a "heat" related condition/fault ?

pj


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PostPosted: Thu Jan 04, 2018 5:39 am 
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deuce07 wrote:
Thanks Binky
Something worth mentioning here. This particular preamp was not in use at least very little for the last 1-2 years. I pondered on the idea that maybe things just needed to be “used” or broken back in for lack of a term . I say this because it seems the more I play this preamp the less it’s doing that bloody crackle . Today turned it on after about 30 minutes use it made a faint static sound then that was it . About 5 hrs later , and still no sound . Maybe the audio gods took one for the team here .


Cap could be reforming itself due to lack of use.Keep the electrons flowing.
Also it seems it has some sort of digital volume/balance encoder control so try to refrain from squirting it.

Gary


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PostPosted: Thu Jan 04, 2018 6:11 am 
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Leaving on for 2 or 3 days straight is a bad idea in my opinion rotary coders can be washed out and a cap shouldn't take that long to reform

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PostPosted: Thu Jan 04, 2018 7:03 am 
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Original post said :

he put sovtek 6922 and changed to an old set of 6922 tubes and had the same issue.
Have you 100% sure about theses sets of tubes? Gas, emission? Transconductance?
Of course the tubes best tests are inside your BAT preamp.
Might be all together rushing noise that sounds like cracking or frying .

All my tube DAC and preamp are always on went I'm home and have time to listen. Most of theses hifi units are made to be 24/7 by design.
If you have an intermittent problem , the tech at service will have to provoke the problem by having it working a long period of time to have a solution, either tubes, caps, or bad solder, bias, or resistor.

good luck.


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