18Watt.com

I think you also get better tone out of a dedicated tone cabinet, combo cabs are just for convenience imho.

Finished mine yesterday. Sounds great, except need to reduce the el84 cathode cap from 18watt value (500uf) to 250uf like in a ac15, and a couple small tweaks, but it sound great, maybe the fact that I used original Celestion Blue (Vox Silver Bulldogs) speakers for playing, in a 2x12 cab... Guess that helps, but sound really great though.
Anyway, Yea in a head cabinet it sounds pretty good. I had to take the tube shield off of it as it rattled, and it really only is as Microphonic as a bad 12ax7, so its pretty reasonable. And no problems with it right on top of the cabinet. I played it through a little 1x12 with a WGS reaper in it and that was great too. It squeals with my tele, when you dime it, so I gotta try some other guitars too, as It's just that that guitar is a little microphonic itself, as the pickups arent potted. but they are pretty good.

The 5879 pentode is a nice alternative to the EF86. We've used this in V1 in numerous builds including the HoSo56 which originally had EL84's.

http://www.el34world.com/Forum/index.php?topic=6176.0" onclick="window.open(this.href);return false;

and in overdrive sections of amps like this one:

http://www.el34world.com/Forum/index.php?topic=9636.0" onclick="window.open(this.href);return false;

With respect, Tubenit

I've got the AC15 EF86 preamp as a second channel in my 18 Watt head. Works fine except for the EF86 in there at the moment has gone noisy (it crackles) and needs replacing. I've never had microphonic issues with it.

Hello

another very good option is to use a used EF804 from Telefunken. The differences to the EF86 are very small and it is a really very stable tube with less micro phonics than the today available 12AX7A, even selected. I have build some custom amps with that tube and the sound is really wonderful.

Best regards
Ingo

Tubenit,
That tweed OD special schematic looks really interesting, I liked the tone, slightly interested in building one now. That would be cool.

Also, Ingo, You mentioned the EF804, is that a direct replacement for the EF86 pinwise? Does it have the same gain properties? Like would it be less gain kind of like the difference between a 12ax7 and a 12ay7 or is it similar?

I looked for the EF804 and found that it's a tube the sellers are very proud of. i.e. $$.

KennyO

I use EF806S which is a direct replacement for EF86 and they sound fantastic.

The EF806s isn't too cheap either, but definitely would be nice to experiment a little further. I'm hoping to build another AC15 soon, so when I get another EF86, I'll have to try another variant or two...

I got a new tung-sol ef806, so Ill see what that will do in a head. A little off topic, bit somewhat realivant... dose anyone know of a good way to tone controll schematic? I was thinking of the matchless/orange style rotary tone controll, although with the right coupling cap I would be happy no tone controlls. Just gain and volume.
I will be using mearlins values for the ef86 section, which Im sure Ive seen zaphood refrence at one point

My favorite for a single knob simple tone control so far, is like a tweed deluxe... Look up the schematic for the 5e3.

Isaac Stuckey wrote:Tubenit,
That tweed OD special schematic looks really interesting, I liked the tone, slightly interested in building one now. That would be cool.

Also, Ingo, You mentioned the EF804, is that a direct replacement for the EF86 pinwise? Does it have the same gain properties? Like would it be less gain kind of like the difference between a 12ax7 and a 12ay7 or is it similar?

Hi Isaac

The EF804 from Telefunken is a long living version from the EF86 and is less microphonic. It is a direct replacement pinwise and has the same electric values as the EF86. Even this tube is more expensive, it´s worth a try

Best regards
Ingo

That's very cool, will have to try one of those eventually.

I'm curious about them too, but the JJ EF806S is $30 compared to the EF804 for $70...and I'm happy with the EF806S. I think it's funny that I don't want to spend that much on tubes considering what some people pay for NOS.

Is your EF806s basically the same thing as Ingo described?

Yes. Direct replacement for EF86, and supposedly less microphonic. So far I've only built them in heads and they sound amazing. I built a combo version I need a cabinet for, I'll see how that does with the EF806S.

Cool, will look into that once I get around to building another AC15 clone.

I built the EF-86 mod that is included in the Tube Depot's 18 watt "kit."
Pretty easy change for the original "Normal" channel 12AX7.
Buy a new socket, much easier just to rewire from the ground up

I'm familiar with the tube because of the QUAD preamps I had for years. (The Brits love these tubes)

I mounted the socket with rubber "O" rings between it and the chassis and included the "rf" cap. One thing I do use is a tube shield which holds the tube rather tightly in the socket. This may help cut down on the microphonics. Since the tube is a high gain, I never would have used it without a shield.

I've also added one with both the "small" rotary tone control (6 positions) and the "large" control (from W***r with 12 positions.

Good shielded cable from the inputs is a must.
Don't use an inexpensive tube - the RFT EF86 is pretty decent in my amp
Haven't tried EF806 that is sold as a replacement, probably will try the JJ one just to see.

saransk wrote: I mounted the socket with rubber "O" rings between it and the chassis and included the "rf" cap. One thing I do use is a tube shield which holds the tube rather tightly in the socket. This may help cut down on the microphonics. Since the tube is a high gain, I never would have used it without a shield.

I've also added one with both the "small" rotary tone control (6 positions) and the "large" control (from W***r with 12 positions.

Good shielded cable from the inputs is a must.
Don't use an inexpensive tube - the RFT EF86 is pretty decent in my amp
Haven't tried EF806 that is sold as a replacement, probably will try the JJ one just to see.

That's interesting, I was going to use rubber o-rings also. I love the tone of the EF806, but it is a little microphonic when the head sits on top of the closed-back cabinet...which I guess should be expected. I know a lot of people say to just not put the head directly on top of the cab, but real-world situations, that's not always an option so I'm trying to work around it.

I already use tube shields, but I'm going to try the o-rings out and see if it works better. I'm curious also about the EF804 if it really is less microphonic than the EF806. For almost triple the price, it better be.

I'm also curious about an octal substitute like the 6SJ7 or RCA 5693. I don't know what it would sound like, but if it sounds similar to the EF86 but without the microphonics, that would be awesome and much less expensive.

First post!

My view is if you like the sound of the EF86 then you should use it. I was reading an interview with DrZ the other day and he uses them even though they are microphonic. He was saying that if you tap the tube lightly with a pencil you can hear how microphonic it is. His solution is to find the least microphonic tube and put that into the first preamp stage. As every EF86 IS microphonic, this seems like a decent enough solution to me. You have to say that Dr Z is pretty clever and probably designed his circuit a bit better than we could to help minimise microphonics.
I really liked some of the other suggestions with fibre washers.