EF 86 VS 5879

[RCGPNY1]

Iv'e recently been getting into pentode preamps. I owned a Divided by 13 RSA 23. The "click" channel was great., and contrary to popular belief, I was able to get a nice clean tone from the low gain input. My question is: can a 5879 be easliy substituted for an EF 86? I like the 5879 better and they seems to be a little less touchy. Thinking of a build with a pentode preamp so what do you think?

[crbowman]

5879 has a different pinout than an EF86 so it's not just a drop in. 5879 apparently needs a larger plate load (470K as opposed to 220K) to approach the same gain level.

Here is an interesting post on the subject:
http://www.el34world.com/Forum/index.php?topic=14205.0

[menger66]

Some guys really like 6u8 also, I have a bunch if you'de like to try one id be glad to donate some for you to try mark

[Turret]

Bump if I may

I'm playing with AC15(ish) design again

My plan is to use AC15 chassis along with stock power amp, and completely rebuild preamp section. I was going to use triode gain stage + top boost unit as a channel 1 and pentode driven channel 2. That would left me with half a valve unused, so I was thinking to use 5879 pentode + simple one knob tonestack and remaining triode to drive the end of this channel

I came out with this (see attachment) - C5, R8 are optional

What do you think? Maybe I should move the tonestack to the end, and drive the front of it with triode? Or use it as a first gain stage perhaps?

I like to make my life extremely difficult. I should fuck this, use EF86 instead, and forget about that triode, but I never build anything with 5879 in past, so it's to tempting

[surfsup]

Why do you have R2 and R3 in series like that? Why not just one resistor?
R1 should probably be at the pin of the tube socket.
I like C5
I'd probably reverse the two tubes as you said.
I'd put a cap across R9
I'd probably put a R between C3/C20 if you leave it as is.

[RCGPNY1]

I owned a divided by 13 RSA23 which had a 5879 channel with a 6 position
tone switch......Plenty of gain! IMHO I liked it better than Vox's I have played with the EF86...just a better tone.

[Turret]

Why do you have R2 and R3 in series like that? Why not just one resistor?

I was to lazy to draw an input jack there, ignore it

R1 should probably be at the pin of the tube socket.
I like C5

Yeah, C5 can be useful with dodgy pentodes

I'd probably reverse the two tubes as you said.
I'd put a cap across R9
I'd probably put a R between C3/C20 if you leave it as is.

Penode->triode->tonestack, or triode->pentode->tonestack?

What I'm after is not the extra drive, so I don't wan't to overdrive it really