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Strange Behavior for New Tubes in Preamp

 A while back I had a tube get noisy in my Van Alstine T-10 RB pre-amp. It uses two of the JJE88CC and I ordered a new pair of their stock silver pin JJE88CC directly from Audio by Van Alstine. The new tubes arrived quickly and sound great and the noise (high pitched squeal) is gone. 

In the meantime I have consulted the AVA website and this pre-amp can also use: 6922,  ECC88, 6DJ8, 6CG7, and 6N1P tubes. I confirmed these numbers with someone at AVA and they said that using these numbers will not void my warranty, as long as they are 6 volt tubes.   After some research and asking questions I ordered a balanced and matched pair of JJE88CC Gold Pins, a pair of 6922, and a pair of matched 6N1P Voshkod Rockets. 

I used an interdental brush dipped in CAIG D5 cleaner, then tapped to remove excess to clean the tube sockets, even though my preamp is just shy of a year old. I install the Gold Pin JJE88CC and wait as they warm up. This is when things get weird. As they are warming up the slight noise (that sounds like steady static) gets louder and louder. At first I have to put my ear to the speakers to hear it but after 20 seconds I can hear the noise in my listening position eight feet away. It increases in volume each second until I shut off the preamp. This is with the preamp volume turned completely down. I thought maybe there was D5 cleaner residue causing trouble in or near the sockets but I had carefully used a blower and thought I did a good job removing residual cleaner.  So I re-installed the stock JJE88CC tubes I received from AVA and everything sounds like normal. Normal has been a slight static noise with my ear close to the speakers.

Today, after a week of using the same stock JJE88CC tubes, I try again the new Gold Pin JJE88CC tubes and same thing.... with the preamp volume turned clear down the noise starts out barely audible but builds until it can be heard across the room... at which time I shut off the preamp.  I let the tubes cool and remove them. I install the new Voshkod Rocket 6N1P and they sound great with the normal hiss that I'm used to if I put my ear to the speakers.

I let the preamp cool and replace the two 6N1P with the two new 6922. Same increasing loud noise but sounds more like a slightly crackly static instead of a steady monotone static or hiss.

I'm fairly new to tubes so I hope you folks have some ideas why it effects just the gold pin JJ and the 6922. Thanks.

foamcutter
atmasphere's avatar
atmasphere
12,414 posts
 

I used CAIG D5 to clean the tube pin sockets because the JJ tube seller (Eurotubes) recommends it in the FAQ on their website.

@foamcutter I've had customers damage equipment by using excess 'cleaners' or the like on tube pins and sockets. 

Depending on what's in it, the residue can migrate across sockets and cause a Voltage drop to occur between contacts of the socket or the tube itself. Sometimes if the sockets are contaminated in this manner the only solution is replacing the sockets. If the sockets are on circuit boards the boards themselves can be contaminated too. Noise is only one of several problems than can be introduced in this manner. 

One time I was able to solve this by taking the preamp to a car wash, the manual high pressure kind, and thus was able to clean the boards properly. After that I let them dry for about a week before attempting to power up. That worked but for obvious reasons could have gone wrong in many ways!

Gold pins have nothing to do with it.  

Now the good news: Normally Caig D5 is not a problem. I use it to clean dirty sockets, but I always use a paper towel or the like to remove excess and get the socket completely dry. If I spray the pins of a tube I have a paper towel handy to immediately remove excess. I also use it to polish the tube pins a bit. 

 

foamcutter OP
86 posts
 

Thanks atmasphere. My procedure seems similar and I was trying to be cautious. I sprayed the D5 into it's lid and dipped the tip of the interdental brush into the liquid, then tapped it on the lid to remove excess. I also used a paper towel to remove any excess from the socket assembly as I went. When I was done with each socket assembly I dried the brush and used it to help dry each pin socket, drying the brush between sockets. Then I used a squeeze type air blower to dry each pin socket and the assembly. I also let the preamp air out before using it. By this time I was not seeing any sign of cleaner. 

I called AVA yesterday afternoon but did not get an answer. I'll try again today.

As I'm fairly new to tubes, I have a question for anyone: If the noise problem is due to the cleaner or cleaning process, why don't I have the same symptoms with all the new tubes?  Thanks.

atmasphere's avatar
atmasphere
12,414 posts
 

@foamcutter Right now we don't know where the noise is coming from. It could be that you just had bad luck changing out tubes that were just as bad as the ones that got replaced.

If I were you I'd clean those sockets and tube pins with isopropyl alcohol. 

triton20trx
86 posts
 

@nwres +1

I have never liked JJ tubes.   NOS tubes from Brent all day long.  Never disappointed 

foamcutter OP
86 posts
 

Thanks for the comments.  @atmasphere I will clean the pins and sockets with isopropyl alcohol this weekend.

@triton20trx I don't have an answer.  I have talked with two different people at AVA on two different occasions and both people explain that a group of listeners at AVA chose the JJ over the other tube possibilities for sound quality and reliability. 

Myself, I like the rich, open and detailed sound of my AVA equipment with the factory tubes. So far the 6922 and gold pin JJ were both noisy and have not worked out. The brief day or two that I listened to the 6N1P was encouraging but I would want  to hear them again for at least a week before making a judgement. I'll try cleaning the pins and sockets with alcohol and report back here.

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