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Re: EF86 input tube (wow!)

4/9/1999 10:32 AM
MJ Harnish
Re: EF86 input tube (wow!)
As a follow-up, I tested the channel at practice briefly and it sounds very good but does have a bit too much gain for my tastes. As an experiment I tried a boss DS-1 with the gain set at 2:00 and the level at 12:00 in front of it (it's the only somewhat hi-gain pedal I have access to). With my LP I can get over 2 minutes of sustain from a single note. This is without utilizing any real feedback (other than I'm in the same room with the sound; my back is to the cab and I was 3' away from it) and with the amp at non-deafening levels (you could easily shout over it). It was bizarre to hit a note and have it just go on and on and on. I finally gave up. Next time I'll actually see how long she'll sustain...  
4/9/1999 11:05 AM

How did you hook it up. Oh please, do tell!  
4/9/1999 10:19 PM
MJ Harnish

Well, being the expert that I am I....  
copied the exact circuit from a VOX AC-15. The only difference is that I used a 1 MEG pot instead of the vox's 500k; I still have to find an audio taper; all I've got in my parts bin is a 3 MEG audio.  
I thought this would yield a relatively low gain preamp but was I ever wrong. Part of the difference might be the fact that the EF86 feeds the 2nd gain stage of the 5F6A and then goes on to the tone stack. However, it's not a really buzzy type of high gain; it's very dynamic and not very compressed at all, unlike what you see with some high gain amps.  
I still have to fool with this some more since I hate trying to judge something based on first impressions,but so far the EF86 seems like a really cool choice for a input tube.  
4/9/1999 9:57 PM
Bill Watson

All this talk about EF86s and my problems with the 6SH7. Looks like I'm going to have to do some rewiring to my Clubman clone.
4/9/1999 10:23 PM
MJ Harnish

I think you can change over your clubman to an EF86 with relative ease. From what I can tell (and I've only glanced at the schematic), you just need to reassign the pins since the pinout is different. Take a look at the Vox AC-15 schematic or the svetlana site for how to wire up the EF86. You might have to fool with component values to get it to sound the same but that should be a matter of tweaking.  
4/10/1999 7:04 AM
Bill Watson

Thanks MJ, I'll do that!
4/13/1999 2:24 AM
Markus Torvinen

Hi all!  
I have done all my guitar amps from the first one to this day using EF 86 somewhere in the signal chain. I build also Hi-end valve amps for recording studios and state-of-art music listeners and there EF 86 have also big role: Input stage as a triode -very linear, low noise and unbelievable frequecy response (2Hz-40kHz straight response). I have use it also in some PSU designs as a voltage stabilizer, works nicely!  
Nice trick: You can tune your low end with g2 to ground cap. Usable values are 1000pF-1uF. So you can cut effectively your low end without using passive components in the signal chain.  
Tune your high end: Try series connected 20kOhms resistor and 250pF mica cap across anode resistor. Try different values without fear! You just canīt brake EF 86!  
Tune your distortion harmonics: Try different values resistors as a anode R, cathode R and g2 Resistor. My normal values are Ra: 100k, Rg2: 470k-1M, Rkathode: 1,5k. Usable values are big selection, find your own taste. Decade resistor complex is good to use here!  
Use EF 86 in the end of signal chain. You can wire 4-5 gain stages before EF 86. You will find mesa -sounds very easily.  
Now gotta go to build my parametric eq using EF 86. +-40 dB cut/boost, Hahaa! Porno one! Full valve.  
MArkus Torvinen, Finland

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