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Tube Preamp Got a Hissy Channel

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Posted on December 24, 2020 at 15:32:19
erik
Audiophile

Posts: 1090
Location: New England
Joined: April 3, 2000



Guys, bought this Chinese/German Vincent sa-t7 preamp about 10 months ago, and a few days back after the warm up the left channel started to make a weird distorted thumping noise, which turned into a permanent loud hiss. Just the left channel. The volume level doesn't affect the noise. I already tried a different power amp and preamp, so the problem is the pre, and it's not tube-related (switched the channels, tried a new set of tubes).

Going to ship it to Audio Advisor under their warranty, but still very curious what that could be.

Any ideas? Appreciate your feedback.

 

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First thing that popped into my mind..., posted on December 24, 2020 at 16:30:29
mlsstl
Audiophile

Posts: 523
Location: Midwest
Joined: September 1, 2015
... was a bad solder joint. Sometimes you can easily see a cold solder joint (the solder is grainy, not shiney) but other times they can be a trial & error bear to run down.

 

FWIW, I found AA to be very good about warranty, posted on December 24, 2020 at 17:03:54
LtMandella
Audiophile

Posts: 1232
Location: CA
Joined: May 27, 2019
Expect you will have the same experience.

If art interprets our dreams, the computer executes them in the guise of programs!

 

RE: Tube Preamp Got a Hissy Channel , posted on December 24, 2020 at 17:14:11
JURB
Audiophile

Posts: 1847
Location: North Ohio
Joined: May 29, 2016
Switch the tubes channel to channel. One pair at a time, when you get to the faulty one the noise will switch to the other channel - if it is a tube which is likely.

 

"Switch the tubes channel to channel", posted on December 24, 2020 at 18:29:44
mlsstl
Audiophile

Posts: 523
Location: Midwest
Joined: September 1, 2015
He says he already tried that, including trying a new set of tubes.

 

RE: First thing that popped into my mind..., posted on December 24, 2020 at 22:15:33
pictureguy
Audiophile

Posts: 13497
Location: SoCal
Joined: October 19, 2008
How about a SPRITZ of something COLD from an aerosol can.....ONE joint at a time?

I'll bet the bad joint will change behavior based on a 'quick freeze'......

This takes time but is non-destructive and can be verified quiclkly with a resolder of the 'noisey' joint.

Is this valid?
Too much is never enough

 

RE: "Switch the tubes channel to channel", posted on December 24, 2020 at 23:41:50
JURB
Audiophile

Posts: 1847
Location: North Ohio
Joined: May 29, 2016
"He says he already tried that, including trying a new set of tubes."

Oops, missed that. I am getting old. I think I am soon to really retire. I am technically semi-retired now, but It is close to time to go all the way.

Damn. But life hasn't been that bad to me. I semi-retired before, like four times and each time it was like another childhood.

Seems like these days I can deal with the technical on a high level but miss the little tings, the obvious things, like those few words from the OP.

 

You can try, posted on December 25, 2020 at 06:33:32
airtime
Audiophile

Posts: 10675
Location: Arizona
Joined: February 4, 2003
Just looking at that preamp it's going to take some real knowledge finding the problem. It could be anything from a bad ribbon cable to a transistor.

If you didn't send it out yet then try is the simple pencil test. Take a NON conducting pencil like object and GENLY poke around the connectors, solder joints, cables, caps, resistors, etc....

Heck, you might get lucky. If not then send it out for repairs.

Addendum: especially check the tube solder joints. they go more often because of mechanical use.

 

RE: You can try, posted on December 25, 2020 at 08:25:20
erik
Audiophile

Posts: 1090
Location: New England
Joined: April 3, 2000
Eh, my man, it's already sealed in the box waiting for Monday shipping. It's fate, I did a search on this piece, nobody's ever complained about its functionality, whoever said negative things was related to the tubes, only I have this kind of problem. Spent so much money on its tubes you won't believe it, but when finally got a sound I was looking for, I got this hiss. I dunno about the transistors, I had an integrated and when one of its transistors died the corresponding channel went dead, this one still works fine, just hisses badly. I guess we'll see.

Thanks for the input though.

 

RE: You can try, posted on December 25, 2020 at 16:10:31
airtime
Audiophile

Posts: 10675
Location: Arizona
Joined: February 4, 2003
There are many regulator transistors that can do that.

I would keep it boxed and send it off for a good once over by a pro.

 

I often "leap before I look"..., posted on December 27, 2020 at 08:19:40
Jonesy
Audiophile

Posts: 2391
Location: Winnipeg, Manitoba
Joined: September 1, 2005
Contributor
  Since:
March 1, 2018
Some of it is old age. Other times I think I know the answer. Thank goodness inmates correct me when I'm wrong!

So on the bright side, even though already brought up, at least your advice was right!

Cheers!

Jonesy




"I know just enough to get into trouble. But not enough to get out of it."




 

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