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Coytee

Preamp question (noise)

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Although I have a Peach, I'm not so sure that is totally relevant.

I'm sitting here, volume turned to zero. I'm hearing what I'd call (mild) static in the right speaker. Much like you could get between FM stations without the squelch turned on (I forget, is that what it was called, or did they call it muting as well?)

Regardless, I swapped right/left channels and the static went to my left speaker.

This is my first tube preamp and I'm wondering if one of the tubes inside is finally starting to give up the ghost?

I don't recall one of Mark's favorite tubes, I think he called it a Rocket? I think the box had a picture of a dude "riding" a tube.

Anyway, although I have another preamp I can insert, what else might I fiddle with to narrow it down to a tube.

If in fact it IS a tube, there are a couple in there to choose from... I guess yank them out, have them tested? Would one over the other be more likely culpret if indeed that is the situation?

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Try tapping lightly on the tubes for the right channel with the eraser end of a pencil. You will know if it is microphonic right away. I had this happen just last week on one of my McIntosh amps. Turned out to be a bad 12BH7. Replaced it and the static went away.

Frank

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Richard, I totally agree with Frank. I had a moment with my Peach on a tube change that I heard the exact same thing. From Mark I learned that I could tell what was going on by switching from Lz to Hz. in Lz only one tube is being used, in Hz the other two come into play.

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Try removing the tubes and reinserting them a couple of times. Even in equipment which receives regular use, it's possible to develop slight oxidation of the tube pins and socket receptacles which can cause such noise. If that cures the problem, pick up a little bottle of Deoxit and put a very thin coating on the tube pins. That should prevent any recurrence for many years You can also try removing the interconnect between the noisy channel and your amp and reinserting that a couple of times for the same reason.

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My preamp has tubes; two for each channel for the phono EQ, and one for each channel of the line stage; so six in all.

I have found that I need to buy about a dozen of these phono EQ stage tubes each year or so (but they are very inexpensive and easy to find). Out of 12, about half will be very nice and quiet. Of those, after a few months in service one may become noisy and need replacing from the "quiet stock" I keep on hand. It's the only way - buy, test listen, identify, and store for when needed.

That's just the way it is with tubes - get yourself a plactic box divided into partitions big enough to hold individual tubes and put a little slip of paper in each one indicating how healty it sounds. When a tube in service starts to go bad, replace it with one from the "quiet" side of the box...

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Pauln said: "I have found that I need to buy about a dozen of these phono EQ stage tubes each year or so (but they are very inexpensive and easy to find). Out of 12, about half will be very nice and quiet. Of those, after a few months in service one may become noisy and need replacing from the "quiet stock" I keep on hand. It's the only way - buy, test listen, identify, and store for when needed."

That's going through tubes pretty quickly. Unless you leave your phono pre on 24/7, that's too much wear and tear from the circuit or the tubes may not be the best match for it. I've had a dozen phono pres or stages and the only one that caused noisy tubes after a few months was an Audible Illusions Mod3A. It went through quite a few nice 6DJ8 variants (6922, ECC088, 7308, etc.) until I inserted Tungsram ECC88's. They were quiet and have stayed that way for over 6 years now (the AIMod3A ended up with my brother-in-law and he hasn't had to change the tubes yet).

To Coytee's problem, you've already determined that you have a bad tube, by all means buy a selection of good ones and see which works and sounds best. I'm not familiar with the Peach but unless the circuit is particularly hard on tubes, you should expect preamp tubes to last at least 5 years with most lasting well beyond that. Have fun

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I'm only speculating a tube issue. I don't know enough about these things to be sure.

That said, I have yanked the Peach out in lieu of the Lexicon so at least I'm back in business. If it is a tube then I have to figure out which one. I happen to have the original tube that Mark sent with the Peach. It's the one that I replaced. I said with a "rocket" above...but it might have instead been a pinched waist? I saw the box earlier and did not see a rocket on it so I'm in error there.

Regardless... I don't have the time now that it's apart to play sleuth. I'll do it later on and replace the original tube to its original place and see what happens.

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I thought I'd post the closure to this question.

The other day, I pulled the case off the Peach. I don't know the names, but there were three spots for tubes. I suppose one was for each channel and the third was the shared tube.

Regardless, I took the shared tube out as it was the pinched waist (or what ever Mark said he really liked). I put his original back in so now I had three identical tubes in there.

Put it back together....and NOW what... I really didn't want to swap things around again, but I had to know.

Plugged CD into it, power and left the case off. Turned things on and the music sounded just fine. That 'fm static' was now gone and I was convinced it was indeed, that shared tube. Ever curious... I turned it off and swapped back to the original (bad) tube and turned it back on.

Works like a charm, not the first hint of hiss, noise or cackle. I suppose this means I simply needed to wiggle the tube in the socket or something like that. Personally, I'm baffled but don't really care!

Works fine and sounds dandy. I pulled it out and took it downstairs since I really didn't want to pull things apart again. I was going to organize some things downstairs (do some more wiring for the HT room and move my temporary location of tunes into the proper closet, making it live for the first time)

Hooked the Peach up to a Crown K2 that I have laying about... to the LaScalas and now I've got some stout tunes down there as well. Now I can get my old Yamaha CR-2040 out for a service call if I want (never been to shop in 30 years) Probably can use some dusting inside.

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