Author Topic: Tracking down noise  (Read 882 times)

Offline S Clark

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Tracking down noise
« on: September 20, 2021, 06:15:12 PM »
I had a low level noise in my main system for a good while... couple of years.  I thought it was an issue with a tonearm.  Looked at finding someone to polish or replace bearings.  Over time, the low level noise became more intrusive and sounded like a dirty volume pot in my Dodd pre... only randomly and without the volume being touched.  But finally I desoldered and put in a new Alps.  It was a pain in the ass, and fortunately Rich H was available to guide me to the correct replacement.  But that wasn't it.  And then  :duh, I decided to replace the 6H30DR tube... success!!!  For a day or two.   
Time to call the pros.  I talked with Charlie Cocci, who has most of the schematics for Dodd gear.  We decided to replace a board, and Charlie had an extra on hand to send me.  A week later it arrives.  The unit is plugged in but the case is off and I start to look at the board.  It's got a pin connection that I touch... and the noise appears.  I wiggle it again, and the noise appears.  I wiggle another pin connection, and the noise appears.  I call Charlie, and after a liberal spray of Caig De Oxit and a good scrubbing with a set of brushes for tube sockets, the noise is gone. 
A year or two has gone by, and all it really needed was to take the internal connectors loose, clean them, and put them back on. 
This has been a hard lesson learned.  Corrosion is insidious.  Take the case off your gear occasionally and clean all contacts.  It will be on my list of annual things to do. 
“In the end, we will remember not the words of our enemies but the silence of our friends.” Dr. Martin Luther King, Jr.

Offline Nick B

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Re: Tracking down noise
« Reply #1 on: September 20, 2021, 07:39:06 PM »
That’s quite an adventure/ordeal and over quite a long period. Glad you had the persistence to get it resolved. How long have you had the Dodd?
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Offline S Clark

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Re: Tracking down noise
« Reply #2 on: September 20, 2021, 08:07:15 PM »
How long have you had the Dodd?
Probably 6-7 years. I've got one of his first battery preamps in my other system that I've had since around 2006.   They are excellent gear. 
“In the end, we will remember not the words of our enemies but the silence of our friends.” Dr. Martin Luther King, Jr.

Offline malloy

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Re: Tracking down noise
« Reply #3 on: September 21, 2021, 11:16:26 PM »
So, it was dirty and loose pins in the tube sockets?

The amount of troubleshooting you performed is indeed something. To summarize the list of suspects: Tonearm bearings > Volume Pot > noisy tube > new board > pins

This would have made me go mad, but of course, things like these you just cannot 'let go', that is why you are in the hobby.

Reminds me of a smaller ordeal I had after having my amp serviced. One channel would go dead, but of course the fault only showed itself when I was listening and never at the repair shop!

Offline BobM

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Re: Tracking down noise
« Reply #4 on: September 22, 2021, 05:32:22 AM »
I agree that your diligence is commendable. The first, very first thing to do with any troubleshooting problem is to isolate the true source of the noise. To go from a turntable to an amp as the source means you didn't successfully perform that first exercise. Something as simple as identifying that the noise happened on both a turntable and a CD player would confirm that the noise was indeed somewhere after the source component in the chain.

I'm glad you finally found the problem without having to fully replace your amp. I don't know if I would be as successful a sleuth to open it up and check the pins and connections, but that was indeed a stroke of genius. Clean connections ... who would have thought they mattered (sic)?  :duh
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Offline rollo

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Re: Tracking down noise
« Reply #5 on: September 22, 2021, 01:46:00 PM »
  Great advice thank you. Never would have thought that. Before the flood I grounded every component to a star ground then to Earth ground OMGoodness. DEAD quite when I thought it was quiet to begin with.

 

charles
contact me  at rollo14@verizon.net or visit us on Facebook
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Offline Nick B

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Re: Tracking down noise
« Reply #6 on: September 22, 2021, 02:15:34 PM »
  Great advice thank you. Never would have thought that. Before the flood I grounded every component to a star ground then to Earth ground OMGoodness. DEAD quite when I thought it was quiet to begin with.

 

charles

Charles,
How does that all work including your use of the Gigawatt?
Van Alstine SET 120 Control Amp
Supratek Chardonnay preamp
Fritz Carrera 7 BE speakers
Border Patrol SEi dac
Auralic Aries Mini & Mojo Audio lps
Audio Envy & Wywires cables
Roon, Tidal, Qobuz
PI Audio UberBUSS

Offline P.I.

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Re: Tracking down noise
« Reply #7 on: September 22, 2021, 09:28:09 PM »
During my studio days we would fastidiously clean connections at least once a month.  Measurements were done with an O-scope or an Audio Precision analyzer.  The tech that had the APA told a story of going in to a studio here that had been running for years.  They never pulled the cards in their 24 track to clean the contacts. 

"Dude, they are gold plated and don't need cleaning." 

Uh huh... sure.

Pulling the cards, cleaning and treating with Cramoline and cleaning the routing through the patch bays and channel ribbon connectors yielded a 20dB increase in SNR.  That is HUGE!
"A man with an experience is never at the mercy of a man with an argument." - Hilmar von Campe

Offline rollo

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Re: Tracking down noise
« Reply #8 on: September 28, 2021, 08:52:04 AM »
  Great advice thank you. Never would have thought that. Before the flood I grounded every component to a star ground then to Earth ground OMGoodness. DEAD quite when I thought it was quiet to begin with.

 

charles

Charles,
How does that all work including your use of the Gigawatt?

  Ran the ground to the screw for the cover plate of outlet for Gigawatt.

charles
contact me  at rollo14@verizon.net or visit us on Facebook
Lamm Industries - Aqua Acoustic, Formula & La Scala DAC- INNUOS  - Rethm - Kuzma - QLN - Audio Hungary Qualiton - Fritz speakers -Gigawatt -Vinnie Rossi,TWL, Swiss Cables, Merason DAC.