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Re: 4xEL34 cathode bias ZNFB - done before?

9/18/2000 11:13 PM
Re: 4xEL34 cathode bias ZNFB - done before?
My friend with the 100W Impact, says it measures about 70W output, so I guess You're right!  
Do You (or anyone else?) have a good scematic for an EF86 guitar preamp?  
I'm working with an old (Swedish) mixer amp with EF86's in the two mic channels preamps.  
The owner would like to have it suited for guitar, and it would be interesting to find a good way of keeping those EF86's. The rest of the amp is an ECC83/12AX7 stage with tone controls, and another ECC83 as PI, and two EL34's.  
It has only a 50V output as standard, so I've had to change the OPT.  
I don't have the shematic for it, but I'll try to draw it up. I have one of those amps myselfe too, waiting for some improvements!  
9/19/2000 9:48 AM
Re: EF86 preamps
There's EF86's in the following amps. (There may be others, which I can't remember right now):  
Selmer Zodiac twin 30 and twin 50  
Vox AC15 '59/'60 (can't remember which one, maybe both)  
Vox AC30/4  
Matchless DC30  
Matchless Clubman  
Dr.Z Route 66  
You can find nearly all the schematics at Steve A's excellent site:  
9/19/2000 5:17 PM

Thanks Lion. I'll have a closer look at those shematics!  
And thanks, Steve A., for all the free information!
9/19/2000 12:49 PM
Ray Ivers
Re: 4xEL34 cathode bias ZNFB - done before?
The AC100 is a different circuit; fixed bias from a zener regulator, off the negative tail of the PS HV bridge. I think the AC 80/100 designation resulted from a combination of the actual (80 watts) and intended (100 watts) performance of the amp; it's definitely not a 100 watt output, or at least the one I worked on wasn't. Interesting amp, though.  
Good luck!  
9/18/2000 4:27 PM

Didnīt Matchless make an amp that was similar to the CHIEFTAIN but with twice the power called CHIEF.  
I supose it is a cathode biased class A with 4xEL34.  
I have not seen the schem anywere.  
If someone have it or know where to get it please let me know.  
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