EF86? What's that sound like?

[Psalm150]

Can someone please comment on the difference between the stock 18w and the version with the ef86? I hear these are sensitive tubes, any problems with using these?

[markh]

Somewhat different sound, more Vox-ish. The EF86s are nortoriously microphonic.

--mark

[jaysg]

I popped for an NOS Amperex somethingorother. Apparently the Svetlanas are not a risk, and certainly cheaper (at least they were - I've been out of the loop lately.)

Like Mark said, it's a chimey Vox-ish sound. If you're building a two channel version, definitely try the Normal channel with one. Glad I did. It offers a little variation.

[Psalm150]

Hmmmmmm...sounds interesting.
So... I just re-wire the normal ch. socket and I'm ready to plug in the Ef86?

[jaysg]

Yeah, that's basically it. Follow the schematic. It's not rocket science. Depending on your board layout, there can be a certain amount of rework. I remember it taking more parts total.

fwiw, I prefer the tone stack on the Trem channel, so that's the one I used. OTOH, Graydon prefers the Normal channel tone circuit, so experiment around with it and decide what you like.

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How come the little face says I'm a Newbie? I'm more of a Geezer at this point.

[sws1]

Was there a smaller number of 18-watts that were made with the EF86? That's not the standard tube, is it?

[Graydon]

Was there a smaller number of 18-watts that were made with the EF86? That's not the standard tube, is it?

That is correct. Marshall 18 watters were only made with ECC83 preamp tubes (aka 12AX7.)

Some of the guys in this group have experimented with installing an EF86 into the 18watt preamp circuit, apparently with good results. It is something that I havebeen meaning to try but never havemade the time. I'd like to try that sometime soon though.

[whiteboyblues2001]

I am about to rewire my trem channel with an EF86. Since the EF86 will give more gain than one stage of a 12ax7, do you get more distortion? I am planning to eventually put a TMB tone stack after the EF86. I am hoping the loss of gain from the TMB tone stack will be offset by the increased gain of the EF86. That way I would end up with the same amount of distortion, but with the added flexibility of a TMB tone stack.

Any comments?

Joe

[markh]

The pentode does not have a whole lot more gain. The bypassed triode gain is around 100 (20dbv) already. What we've found after a lot of experimentation is you need 1.5 to 2 gain stages to make up the large loss imposed by the traditional Fender/Marshall tone stack. See Richie's or Vajra's TMB circuits for examples.

--mark

[jaysg]

: I am planning to eventually put a TMB tone stack after the EF86. I am hoping the loss of gain from the TMB tone stack will be offset by the increased gain of the EF86.
Any comments?

I have a feeling that isn't going to work well. EF-86 tone stacks tend to use 1M pots. There's a ton of gain, but little current drive.