I have been using 6j5 tubes in my pre for a while now the problem is microphonics even with tube dampers. So I tried the 2C22's and there was just too much tube rush coming from them. So now I am thinking 7N7 or back to the 6F8G's which are not as linear but not microphonic either!!!
What is "tube rush"?
Do you mean like a brown noise? Usually that's caused by oscillation or heater cathode leakage in my experiences... Some times flicking the tube hard with your finger stops it - that tells you something is loose 🙂
Do you mean like a brown noise? Usually that's caused by oscillation or heater cathode leakage in my experiences... Some times flicking the tube hard with your finger stops it - that tells you something is loose 🙂
I’m interested in your statement that a 6F8G is not as linear (presumably as 6J5). When I look at the tube datasheets I believe I see identical performance curves and data. Could you provide more information to explain your assessment?
No I can not only what I was hearing, can you show me the curves you are talking about.
Below are links for datasheets published by Tungsol for 6J5, 6F8G and 6SN7 tube types. The operating characteristics, plate curves, etc all look identical to me. There are minor differences in inter-electrode capacitances. Could this be what you hear?
http://frank.yueksel.org/sheets/127/6/6J5.pdfhttps://frank.pocnet.net/sheets/127/6/6F8G.pdfhttps://frank.pocnet.net/sheets/127/6/6SN7GT.pdf
http://frank.yueksel.org/sheets/127/6/6J5.pdfhttps://frank.pocnet.net/sheets/127/6/6F8G.pdfhttps://frank.pocnet.net/sheets/127/6/6SN7GT.pdf
Maybe go backwards in history and try a 6C5, this was the predecessor to 6J5 which replaced 6C5. I picked up a caddie full of NOS ones that never left their boxes, seem similar enough to 6J5. It has the old cylinder anode shape, interesting looking tube. Came in metal, gt with metal base and st shape. My understanding is that it was one of the first tubes actually marketed for audio, then got replaced by 6J6.
https://th.bing.com/th/id/R.e2c9284...BcsD1rCvO5itoA+UDhsM5Mk=&risl=&pid=ImgRaw&r=0
https://frank.pocnet.net/sheets/127/6/6C5.pdf
6L5 or 6P5 might be worth a try too, and be careful I believe pin 1 on 6C5 attaches to the metal base so check that your amp isnt using that pin for anything but ground.
https://th.bing.com/th/id/R.e2c9284...BcsD1rCvO5itoA+UDhsM5Mk=&risl=&pid=ImgRaw&r=0
https://frank.pocnet.net/sheets/127/6/6C5.pdf
6L5 or 6P5 might be worth a try too, and be careful I believe pin 1 on 6C5 attaches to the metal base so check that your amp isnt using that pin for anything but ground.
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That would be my choice. I once did a shootout of several 6J5 types and I remember this came out on top with the 2C22. Lovely tube.
The 6L5 is a forgotten tube and almost the same as a 6J5 with slightly less Gm and Mu. The 6C5 is also forgotten and is a 6J7 that has been triode connected withing the tube. The advantage to the 6C5 is that it still has the 6J7 shield around the plate (see the photo above). Obviously, the 6F8 is just as linear as the 6J5 and the 6SN7 since the internals are the same. The 6P5 is a 76 with an octal base and is similar to the 6L5.
The 6L5 has a gain of 17, so closer to a 6J5, as opposed to the 6P5 with a gain of 12. Not a bad tube, but if microphonics are an issue, maybe not the best choice. Also not as good-sounding IME as the 6J5.
Thanks for the links, maybe it was my hearing that day. I am gonna install the 6F8G tubes again and listen.
The 6F8G, the early TungSol 6SN7 and a handful of early 6J5G and 6SN7 types have cylindrical plates, as do many other early tubes like the 6K5G & 6F5G types. Since it is a different construction from the ladder plates of the later tubes, it seems plausible that there is a subtle difference in sound.
I dug out my old shootout of some 6J5 types and though the 6L5 did well, seems others did better.
Very good:
CV1932 Mullard clear glass – neutral/smooth, neutral timbre, very good detail, clean
CV1932 Raytheon silver glass - neutral/smooth, neutral timbre, very good detail, clean
6J5GT VT-94D Kenrad – neutral, quite fat timbre, very good detail, airy
6J5GT Raytheon - neutral, quite fat timbre, very good detail, airy
Good + :
6C5G - Smooth, delicate, fat timbre, micro detail. Measures well
6J5GT Pinnacle – neutral/hard, neutral/thin timbre, very good detail, clean, clear treble
6L5G – neutral/hard, neutral/thin timbre, very good detail, percussive, voices recessed
Good – :
6J5G Brimar - Smooth, loss of detail (round plate)
6J5 - neutral/hard, neutral/thin timbre, good detail, percussive, voices recessed
6C5 - neutral/hard, neutral/thin timbre, good detail, percussive, voices recessed
Not rated:
6J5G type ? Raytheon – hard, thin timbre, good detail, percussive, voices recessed
6J5GT CV1067 - neutral, thin timbre, average detail, clear, bland
Very good:
CV1932 Mullard clear glass – neutral/smooth, neutral timbre, very good detail, clean
CV1932 Raytheon silver glass - neutral/smooth, neutral timbre, very good detail, clean
6J5GT VT-94D Kenrad – neutral, quite fat timbre, very good detail, airy
6J5GT Raytheon - neutral, quite fat timbre, very good detail, airy
Good + :
6C5G - Smooth, delicate, fat timbre, micro detail. Measures well
6J5GT Pinnacle – neutral/hard, neutral/thin timbre, very good detail, clean, clear treble
6L5G – neutral/hard, neutral/thin timbre, very good detail, percussive, voices recessed
Good – :
6J5G Brimar - Smooth, loss of detail (round plate)
6J5 - neutral/hard, neutral/thin timbre, good detail, percussive, voices recessed
6C5 - neutral/hard, neutral/thin timbre, good detail, percussive, voices recessed
Not rated:
6J5G type ? Raytheon – hard, thin timbre, good detail, percussive, voices recessed
6J5GT CV1067 - neutral, thin timbre, average detail, clear, bland