[Wayner]

Recently, I have been evaluating a nice tube phono preamp. I had it a month ago, for a few days, then it developed a glitch, and was gone for a couple of week, then it returned.

When I first received the phono pre, I was taken by it's imaging capabilities, but on it's return, it seemed to have been lost. So, I switched back to my usual phono preamp and starting listening to some vinyl. This was on Thursday night. My bride joined me for our usual "beer thirty" and she sat in her usual spot, then commented, "I can't really hear the left speaker". The system is in my studio and our sitting positions were me in front of the left speaker, her in front of the right speaker, in a near field listening environment. This was never an issue in the past as my Dynaco A25XL mods produced fantastic 3D sound, in stereo, in almost any position in the room. That was now gone, as was that nice, refined detail that I had become so used to when listening to vinyl. Something is wrong.

I began swapping between left and right channels, first interconnects, then speaker cables and finally out of a frantic desperation, started swapping tubes! In the end, nothing helped. I was baffled.

Then I decided, if not the electronics, then it has to be the speakers. So yesterday, I took them down to the work bench. I decided to open them up and have a look. After removing the 10" woofer, I folded back the insulation covering the cross-over network and tweeter level control. Everything looked fine, but I decided to give the rotary level control a shot of Caig Deoxit 5 before moving on. I gave the teak wood a nice shot of furniture polish and then repeated the process with the second speaker.

After replacing them back in the studio on their usual perch. I fired up the electronics and put on an album, XTC "English Settlement". Within 3 seconds of music playing I shouted for joy! I had 3D stereo in spades, perhaps better then I had ever heard before. Needless to say, we had an early "beer thirty" yesterday and played about 8 LPs, more then pleased with the sonic bliss we were witnessing.

Now comes the reality. So some dirty or slightly oxidized contacts could do this? I knew the Caig could improve signal transfer, but not to this level. Wow.

The lesson learned is that these tweeter level controls need to be cleaned, perhaps every 6 months. It may also mean that any other device (like a preamp) needs to have it's selector switch or other signal path switches sprayed to maintain signal integrity.

Many vintage speakers have level controls, like JBL, AR, Altec, Dynaco and others. My advice is to get the Caig and start cleaning controls, you might be in for a big surprise.

Wayner 

[rollo]

  Excellent heads up there Wayner. Not only the level controls and switches but those RCA and speaker terminals as well.
   For us having the system in the basement with a slightly higher humidity level, we clean every month. Audio Research in their owners manual suggests cleaning the connections as it affects the top end performance making it bright.
   Funny story, years ago our club had adinner to honor Harry Pearson for a Life Time Achievement award. After his acceptance speech hewas asked "in your experience what was the most important part of getting great sound" The audience on their seats edge waiting for the answer, his answer Pro-Gold.  Yessum clean clean clean.
  Have been doing it ever since about once a month. Again good call 



charles
 

[Brett Buck]

Now comes the reality. So some dirty or slightly oxidized contacts could do this? I knew the Caig could improve signal transfer, but not to this level. Wow.

The lesson learned is that these tweeter level controls need to be cleaned, perhaps every 6 months. It may also mean that any other device (like a preamp) needs to have it's selector switch or other signal path switches sprayed to maintain signal integrity.

Many vintage speakers have level controls, like JBL, AR, Altec, Dynaco and others. My advice is to get the Caig and start cleaning controls, you might be in for a big surprise.

       If you think it makes a big difference on speaker-level signals, try it in microvolt signals in radios!  It's absolutely amazing in things like the bandswitches on a Zenith transoceanic, where you are running these tiny high-frequency signals through multiple sliding contacts. In many cases, I get radios that have been sitting out in barns with literal rats nests in them, that have been rained on for 50 years, etc. The switching tower that selects the frequency band is about the most complicated electrical and mechanical part you will ever see in an electronic device, and it routes the teeny RF signals around through 8-10 contacts, any one of which could prevent it from working at all. A lot of times you will find the entire thing seized up. Spray it with D5, the metal starts looking brand new on contact, and it starts working immediately.

    But I found that the first few applications only start the process. You can shoot it, and the radio will work right away. But if you hit it multiple times over several days, manipulating it, the sensitivity of the radio can go up noticeably. And if you let it sit for a few months, it degenerates materially.  Same thing happens with the tube pins and sockets, particular the old Loctal tubes that have some sort of pin material that seems partially incompatible with the sockets, and turns dark gray in a few weeks.

    So I can easily believe that the controls can go over the hill relatively frequently, particularly on electronics of that vintage. For whatever reason, it doesn't seem to be much of a problem with more modern stuff (like early-70's on) but the older parts definitely seem to degenerate quickly.

    Brett

 p.s.  BTW, I assume we are talking about the D-series contact cleaners. They also make a "Gold" series that is supposed to prevent the sort of degeneration I mentioned above. You use it after you get it clean with D5. I haven't been able to convince myself that it actually keeps it from going over the hill over time, but it might be worth looking into.