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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
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
12,418 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.

sns
4,218 posts
 

I use isoproply alcohol and Mr. Clean magic eraser on tube pins. Don't trust most new manufacture tubes, NOS from reputable sellers the way to go. Another issue these days is some manufacturers run tubes hot, higher plate voltages increase tube plate dissipation which shortens life span. Filament/heater voltages can also be a concern, especially with amps that are stated to run a variety of tubes.

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