Ef 86 Most Reliable???

[michaelcauley]

Hey Guys , My Brownote 18 ef86 is very microphonic real bell like sound when you tap the inputs or the tube,Can anyone reccomend what higher grade brand I should get,Tung sol gold is about 33.00 about twice the cash then the electro harmonx i have in there now,Is a more expensive tube going to do the trick,And I did try the rubber O ring slidding it down to the base of the tube against the socket,No fix. Thanx Boys

[zaphod_phil]

Stephen Cohrs at Trinity swears by Amperex Bugle Boy EF86s. He says he's never had microphony problems with them. You could also try using an EF83 or 6BR7, which are both low-microphony pentodes. EF83s are pin compatible with EF86s, while 6BR7s aren't, so a little socket re-wiring would be required for those.

About the silicon rings, you're meant to use two of them per tube, placed over where the mica spacers make contact with the inside of the glass.

There's some more advice on reducing EF86 microphonics in http://www.18watt.com/modules.php?name= ... 8&start=15

You can also try Valve Wizard merlinb's EF86 preamp component values, which run the EF86 at a lower gain, so you get less microphony and need less attenuation after - see www.freewebs.com/valvewizard/Pentode2.jpg (left hand schematic)

[snoof]

I've had good luck w/ dario miniwatts. Though they can be spendy...

[krx]

You can also try Valve Wizard merlinb's EF86 preamp component values, which run the EF86 at a lower gain, so you get less microphony and need less attenuation after - see www.freewebs.com/valvewizard/Pentode2.jpg (left hand schematic)

For what it's worth, the sound is not the same at all using the Valve Wizard values. IMHO, if you're going to make the gain that low, you'd be better off putting in a 6SJ7 which sound great and are only $5 each NOS.

I'm not going to give away all my secrets, but the key is to get the screen voltage a little lower and then adjust Rk to get the current back to where it should be so it doesn't sound overly thin and compressed. Doing this won't make a badly microphonic tube usable but it will reduce noise levels and help prevent the tube from going microphonic.

[dotfret]

Lots of people, like me, use E80F or EF806S as exact replacements. Worth paying the serious money, those are 10 000 hour valves. They don't wear out in a hurry.

You should always use the full can screen on EF86 types to reduce microphony.

[Norbert]

I've had good luck with Philips Miniwatts. Less microphonic than some 12ax7s. Also the Amperex work well, from the one I've tried.

[Rockn]

The best ones you will ever get are the Genalex Z729/EF86. I ran across these by accident in an old tape recording amp. I got three of them along with 4 Hammond amps for $85 as the guy did not know what he was selling. Savage Audio took two of them in trade for some equipment. There are also military spec versions of these tubes, but I can not remember the models off the top of my head.

[snoof]

You should always use the full can screen on EF86 types to reduce microphony.

could you expand on this?

[krx]

You should always use the full can screen on EF86 types to reduce microphony.

could you expand on this?

I think he just means the regular miniature tube can retainers. I don't see (or hear) how that makes much difference though since the EF86 already has an internal shield and the can shouldn't affect microphony.

Some people like to shock mount their EF86 sockets or use tube damping rings... In my experience, the best thing is to get some audiophile feet for your head. They improve the sound of the whole amp by isolating it from mechanical vibration. I like the ones at Herbie's Audio Lab (google it). He has a very generous money-back guarantee in case they don't work out for you.

[dotfret]

That's what I mean - don't run them naked, cover up!

Very old EF86 are very susceptible to microphony - the designs with only one mica plate. Hey, but they sound good!

[snoof]

I understand it now, thanks guys. the phrasing just threw me.