EF86, 6267,,,, Quiet Options~~

[zozoe]

Hi all~~  It's truly amazing how few choices there are for a DECENT EF86,,,, I'm 60/40 in favor of a quite, non microphonic valve over gain performance for my Morgan AC20 Deluxe. Not to say that both factors don't matter, but quiet over gain, by a small margin. What to get in new production, well performing tube, as NOS prices are crazy!??

Thanks in advance.

[xtian]

Can’t offer any experience, but I am offering some for sale on the for sale forum.

[pompeiisneaks]

EF86 are notorious for being microphonic. I just put a few silicone rings on my AC30's that had an odd top end jingly sound coming in and it went away. I know I've seen others shock mount the socket for the EF86 to try to tame that. One other technique that doesn't work too well for a pre built amp is to put a 12AX7 gain stage first and then the EF86, that way it's less prone to harmonics.

They're definitely a challenge. I've heard many people talk about intentionally just buying multiples and tube rolling until they get one that works. Sadly this is not a cheap option.

~Phil

[MakerDP]

Yeah EF86 tubes are often maligned because of the microphonics, but that CAN be greatly minimized. Your "typical" resistor values used for them push them way too aggressively. Merlin goes into some detail on this on his website, and even deeper into the subject in his preamp book.

http://valvewizard.co.uk/pentode.html

I've done his "tamer" EF86 mod on a Matchless DC30 clone (Trinity TC15) with great results. Worth a look and a try.

[beasleybodyshop]

I think increasing the screen grid resistor and lowering the overall gain a bit goes a long way. Also, there are a few Octal varieties of small signal pentode floating around - I forget the model numbers but those seem to be a little more robust in terms of noise and microphonics.

[TUBEDUDE]

5879