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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Re: Questionable posted by rickl on September 29, 2004 at 11:48:30:
Hello ,
Sorry , the 6SC7 is unsuitable for concertinas driving triodes , Ra too high . For a single valve , you need something like a dissimilar triode such as 6EM7 or 6GL7 that has mu 68 , Ra 45k and mu 7 Ra 1k respectively . I used a 6EM7 with NimH battery bias and a CCS top load for the input stage with 10k loads for the 6EM7 beefy section . I can't remember the gain and clean P-P swing I got from this setup but it was more than adequate . The valves I really like for the concertina stage are the 12B4A and 6BL7 (paralleled) and should be low Ra , medium mu for optimum performance . Triode strapped EL84 also work well . For the input stage 6072 may be a suitable candidate for a 'clean' sound but may not have enough gain if you don't use a pre-amp . The decisions regarding valve choce are mainly dictated by the amount of HT available . You need to have approx HT/3 on the anode of the input valve . The input valve needs to be biased in such a way as to meet this requirement and have enough headroom to drive the grids of the output valves to full power . Hope this helps :)cheers
...FB
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Follow Ups
- Re: Questionable - fatbottle 12:10:56 09/29/04 (4)
- Re: Questionable - rickl 14:10:24 09/29/04 (3)
- Not questionable at all... - serus 15:02:28 09/29/04 (2)
- Re: Not questionable at all... - rickl 20:54:59 09/29/04 (1)
- Preamp - serus 21:54:34 09/29/04 (0)
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