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ampage archive
Vintage threads from the first ten years
EF 86 pentode project.
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 8/13/1997 4:23 AM |
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Markus Torvinen |
EF 86 pentode project. Hi, My project by using EF 86 preamp- pentode tubes sounds great! It have smooth and tight power amp- like distortion, does anyone have invented it before or should i patented schematic? Markus Torvinen, Tampere, Finland |
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| 8/13/1997 5:05 AM |
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| Dave Harris |
Don't patent it send it to me ! EF86s have been used before in guitar amps. VOX used them in the early AC30 probably because they were in the Mullard hi fi circuits of the day. Vox dropped them because they were unreliable and microphonic when hanging out with guitar speakers. They would not have been used for distortion in those days. The distortion we know and love in old tube amps is just serendipity. The amps were not loud enough so they got cranked ! Do Matchless use EF86s for distortion or just because they were in the VOX, anyone ? |
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| 8/13/1997 10:52 AM |
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| John Martin |
The EF86 is a great tube if you keep the gain within limits. (at least for guitar amps) They can also be operated in triode mode. Pentode preamps/gain stages were very common in early guitar and PA amps. A rough electrical equivelent would be the 6SJ7. In fact, component values used with the 6SJ7 can be applied with great success to EF86 circuits. Another common pentode would be the 5879. Look at early Epiphone, Gibson, and National amp schematics to get a feel for these circuits. I am using the currently manufactured Svetlana version of the EF86, but have samples of Mullard,etc. My 1946 Epiphone has 3 6SJ7s and two 6L6s. When I put my Fender outboard reverb unit in front of the amp it screams. A EF86 driving a 12AX7 driving a push pull pair of EL84s makes a great small amp with all the gain in the world. Or a EF86 driving the triode of a 6BM8, then driving its pentode section, makes a great 3 watt Marshall type amp. etc,etc. More later |
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| 8/14/1997 11:36 PM |
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| Markus Torvinen | What you think about this: Phase splitter(12ax7)-> push-pull EF86 pair-> output transformer-> Power amp (4 X EL84`s)? Sounds great: ef 86`s output transformer distorted little bit. I can`t find words in english to say, how it sounds like. Letīs talk more lately... |
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| 9/2/1997 5:36 AM |
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| Steve Keay |
Hi, Anyone point me to an old Vox schematic with the EF86 pentode?? I'm building an AC30 now and would like to try the EF86 as a channel 2 preamp. Thanks in advance... Steve K |
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| 9/3/1997 1:07 AM |
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| Markus | I don`t have vox schematic but i have lots of my father`s designed ef 86 schematics. But how to mail you, i don`t know? (i can`t send schematics via email) markus |
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| 9/5/1997 10:25 AM |
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| M.Romasco |
Steve go to www.voxshowroom.com they have the AC-30/4 schematic w/ ef86 pentode. It may cost about $15. I can draw you the circuit and fax it to you if you want. Email me w/ fax #. Matt |
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