2. amps-preamps
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Tubes and microphonics

I want to know when microphonics affect the sound.
I have a Sonic Frontiers Line 2SE Preamplifier. I tried many tubes like Valvo, Siemens, Reflector 6H23NEB.
Recently I bought two matched pair of Amperex 6922PQ White Label Made in USA. I think that the Amperex are better than the others, but I could see that they are less silent.
When I knock the cover of the preamplifier I can hear the knock clearly in the speakers. That not happen with the others tubes. The 6H23NEB are the most silents.
I think that Amperex have more gain than the others. But I don´t know when that is critical to the sound.
Please let me know your experience with your tubes and preamplifiers.
Thanks,
Pablo
elduende14
13 responses Add your response
jax2
3,031 posts
 
Pablo - the 6922/E88CC family are very microphonic, as you probably know. You may want to try some tube dampers to help out with that. I've used Herbie's and Mapleshade and either works very well. Tubes in preamps are usually very sensitive to vibrations and will amplify them (as they are prone to) at the speakers. It's more of a surprise that you do not hear the knocking on the cover with other tubes, than it is that you would with the Amperex. Anyway, give the tube dampers a try if it is a problem. Herbies are inexpensive and effective.

Marco
aball
2,016 posts
 
Herbie's worked great for me when I had a VK-3i.
jsawhitlock
302 posts
 
Pablo, I own the SFL-2 and use Amperex PQ tubes and you'll find the best position for your best tubes are in LVS2 and V2 and LVS1 and V1 are the next best position. I have two sets of red labled Herleen Holand tubes that I tried and installed the first pair in LVS1 and V1 then the next pair into LVS2 and V2 positions and got noise when tapped on tubes as you described so I swithed the LVS1 & V1 pair with LVS2 & V2 pair and no more noise. I now use Amperex PQ in LVS1, V1, LVS2, V2 positions and the red lable Herleen Holand Amperexes in the remainig positions and all is quiet, also as mentioned above the Herbies tube dampers work great.
yioryos's avatar
yioryos
723 posts
 
Guys
Can anybody tell me their opinion for the Amperex PQ orange label USA late 60's early 70's production?Need for the SF SFD 2MK2 Dac.
Elduende 14,sorry for highjacking your thread
Marco you should know any comments?
Thanks
George
jax2
3,031 posts
 
Sorry George, no experience with that specific tube that I can recall. Mostly compared the German tubes in that family. My favorites in the application I was using them in were the Siemens CCa's.

Marco
s23chang
617 posts
 
Siemens 7308 is dead quiet.
yioryos's avatar
yioryos
723 posts
 
Thanks guys
Marco the NOS Siemens CCa must be expensive ,no?
George
jax2
3,031 posts
 
George - Unfortunately, yes, they are quite expensive and sometimes counterfitted or sold in less than desirable condition for large coin. If you go that route definitely go with a reputable resource. Expect to pay $75-150/tube (crazy!). Alternatively, in current production (or NOS if you like) I'd give a try to the Russian Rocket tube, I think they are 6H30 and are drop-in for most 6922 applications, but take care in which variety of that tube you use. I think BAT uses them in their gear. Worthy of a listen and much cheaper than NOS. YMMV and check on the application with your specific piece of gear.

Marco
rwwear
2,846 posts
 
I could be wrong but, I don't think the 6H30s can be used as direct replacements for the 6922s without some adjustment.
jax2
3,031 posts
 
I could be wrong but, I don't think the 6H30s can be used as direct replacements for the 6922s without some adjustment.

You are quite right, my bad. It is a 6H23 that I was thinking of. Thanks for picking out the mistake.

Marco
elduende14 OP
51 posts
 
Marco,
the Reflector (Russian) 6H23NEB are very good tubes (much better that the standard Sovteks)and they ultra low noise (an excellent tube for Audible Illusions preamplifiers) but the Valvo 6dj8 and the Amperex 6922PQ are really better. Unfortunally I tried the Siemens E88CC but for me the Valvo and the Amperex are better.
You can contact to Mr. Chris Johnson at Partsconnexion. He sell the 6H23NEB at 45u$s(matched pair) and the Valvo 6dj8 at 75u$s (matced pair).
The Amperex PQ are really difficult to find but for me they are the best.
Thanks for all for your answers.
jax2
3,031 posts
 
Just one clarification Pablo - The Siemens I liked best were the E88CCa. They are not the same as the E88CC. You can see the entire range of various brands and pricing here to give you some idea of the relative price range. I never heard the Valvo or Amperex, and even if I had it would have been in a different piece of gear so the differences between tubes would not correspond exactly to your experience with your SF2SE (nor, of course, would my preferences necessarily correspond with your own). I would always encourage others to roll their own and make their own judgements where these things are concerned. Just sharing my own experiences here. YMMV.

Marco
eldartford
4,262 posts
 
All tubes are microphonic, but some tubes are more microphonic than others. And it makes a difference where in the amplifier circuit the tube is used.

A severe case of microphonics is certainly bad. However, it may be the case that a trace of microphonics contributes the "warm" sound that characterizes tube electronics.
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