question about ef86 front end preamp

[brownnote]

This is my take on a ac15/dc30/18watt hybrid.
There are clips on my site if you want to check it out...it's a rockin little amp.

[nwobhm]

Here's my layout for an 18watt EF86 Lite. It sounds pretty darn good to me without an extra gain stage.

I built Dartonion,s ef86 LITE. It's got plenty of gain unless your looking for mesa type gain.

[nwobhm]

Here's my layout for an 18watt EF86 Lite. It sounds pretty darn good to me without an extra gain stage.

I built Dartonion,s ef86 LITE. It's got plenty of gain unless your looking for mesa type gain.

[wsaraceni]

not looking for tons of gain. just looking for something different. i really need a low wattage amp for the living room. i'm planning single ended, and even use an attenuator on top of that.

[Alexo]

I haven't found data sheets for EF86 that give the handy little chart for different resistor values and levels of gain, but looking at the 6AU6 mini-pentode chart, which is probably similar to en EF86's, you see that it is very easy to get gain from 100 on up to 300! Compare that with the other high-gain standard, the 12AX7 which will usually give you a gain of 40 to 70.

Pentodes have pretty high output impedances, so they are not considered good candidates to drive a tone stack, as you will lose a lot of signal, I think that's why a lot of designs use the coupling cap selector method.

[dartanion]

A simple low insertion loss tone stack like in the Lite design quells this concern. I wouldn't try to run a TMB tone stack with a single EF86.

[wsaraceni]

im really going simple with this. hoping for a volume, tone, and built in attenuator. volume, tone, attenuator bypass, and attenuation setting knobs only hopefully.

[Alexo]

What attenuator scheme are you thinking about?

[wsaraceni]

havent gotten that far yet. after i found out that i made a few errors on my express clone, i have to fix that before i dive into this project. im wondering if something similar to the "bedroom" level on the airbrake would work well. with a Single ended amp you could probably get away with just 1 resistor, a capacitor and the funky pot (rheostat maybe...i forget what it's called). i'll just put it inline with the speaker and have a bypass switch instead of a rotary knob. just need to figure out which value and wattage resistor to use.

[kapa21]

when amps use an ef86 preamp, are they generally just the 1 tube in that channel. when i look at a matchless dc30, for example, i see that the ef86 goes into a rotary switch and then direct into the PI section. is that normal for an ef86 channel in most applications? are there any other amps with schematics that use this tube in a preamp?

thanks
bill

Hi!
This is very nice forum and read alot, but this is my first post. Thanx everybody for very useful posts.

Here is link about ef86 amps. I´ve made c5 and h5 and they sound very good to me. One El84 SE is very goog bedroom amp, but driving enough it´s loud enough to play with band. And have gain to load PT to distortion.

http://www.kolumbus.fi/risto.kivioja/Ri ... /index.htm

-Kapa

[dartanion]

Those Rikstone amps look interesting. However, they should update their schematics as the show the grid in the screen position. It's numbered right, just schematically in the wrong place. The grid is normally positioned above the cathode.