Did you switch the voltage jumper by the tubes? I never had an issue till the tubes hit 1089 hours then I could hear a hiss coming from both channels I figured it was due to the NOS tubes. Before the hiss I was getting the best sound I’ve heard. I have the “Kevins stash” Gold Lions 12v, Brimar NOS, and the Psvanes but personally preferred the Tungsram NOS. I’d like to try the Amperex Bugle Boys. I have another NOS set of Tungsram tubes in now with a third set ready to go!
I did have the jumpers set to 6v and tried both power settings. It was with some high sensitivity speakers so they may have added to the issue. Once I put the 12v tubes back in everything was quiet again. The 6v were some of Uncle Kevvy’s but I don’t remember the manufacturer or model.
It’s strange I didn’t notice a hiss until after I connected the BHK 300’s. So I don’t know if that’s coincidental or I didn’t hear it with the M1200’s. I may go back to the 12v soon just to try with the different amps.
Simple explanation is that the input sensitivity on the 300’s is 1.3 volt and 2.08 volts on the 1200’s. Pretty wide variance and would easily account for the noise as the sensitivity on the 300’s is in the normal range and the 1200’s is high.
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I have a set of 60’s Amperex “Bugle Boys” on the BHK 300’s and I am very pleased. Tried 70’s Mullards and thought them too dark and distant. I am not a tube veteran but I am amazed at the differences in tubes, even in the period of which they are made. Several on this sight have given me good guidance. I think the Gold Lions are no slouch and offer good speed and detail. I sometimes think going back to solid state amps and forget the yin and yang with tubs but what’s the fun in that. 
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I just switched from the stock tubes to a pair of Tungsram PCC88S. I don’t know what they do but the sound has changed and I like it. Hard to express. I think, however, that I’m going to buy myself a spare pair of the Tungsrams - just in case you they are not being manufactured when I need them. Pretty darned good!
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AKAIK Tungsram hasn’t made audio tubes in decades.
Hi
I’m currently using bhk preamp , any buddy knows the output gain of the preamp ? Coz the specification doesn’t mentioned the db gain
The gain spec says 10 db of gain.
Thanks 
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A ways back someone recommended 12AU7A Sylvania/Baldwin tubes offered on eBay. The price was right, so I took the plunge into tube rolling for the first time. Side note… The eBay seller was excellent and the packaging was simply amazing.
After installing the new tubes and turning the preamp back on, there was a continuous rapid pulsating sound for several minutes. About the time I was getting concerned a nuclear reaction was about to occur and my speaker cones were on the verge of disintegrating, the pulse sound just stopped and never has returned. Crisis avoided and back to DEFCON 5!
I have been pleased with the new tubes. I sense an overall lower floor noise over the stock tubes and the music does appear to be a bit more detailed in a positive way. We will call my first experience positive overall and best of all it was a cheap tweak!
Only negative issue I can report on with the new tubes is that I have noticed when adjusting the volume, there is a sound that is much louder and pronounced for each click up or down than before the tube swap. This issue has continued and it is more than week since I swapped the tubes. Not really concerned, but it is annoying especially if the volume was loud to begin with.
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It sounds like the tubes you purchased do not have matched triode sections. The Conn/Sylvania 12au7s I use are very quiet and do not make any noise when adjusting the volume level.
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Any of you thought that the gain of the preamp is slightly inadequate? I always feel that the dynamic swing is somehow can be a bit stronger
If I understand, when you normally adjust the volume there is a clicking noise but when you installed these new tubes the clicking is being amplified by the pre and is heard through the speakers.
This could be microphony. Some tubes react to mechanical noises like a clacking/clicking volume control and also to light tapping on the casework. You might want to consider putting two O-rings on each tube. One at the top of the plate structure and the other at the bottom of the plate.
The Gain of a preamp is what it is depending on the Volume level you have set. The program material is responsible for the dynamic changes. The preamp does not alter the signal only amplifies it.
In technical point of view, the specification of the gain output , some preamp 6 db gain some 12 db and some 16 db , what does it mean ?
That is the maximum Gain the preamp is capable of at full volume.
FWIW re: tube rolling…I’ve reinstalled my 5692s. I’ll just leave them there until they (or I) die lol.
Thx v much
Still loving my recent buy Genalex Gold Lion 12AU7’s,
Head and shoulders above the stock Psvane’s IMO,
and some of the NOS “usual suspects” I took a risk on…
These are the sweet spot.
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