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What contributes to the gain in an AC30? I got an amp with a Fender poweramp clone, and ive built in an ac30 top boost preamp. However, the gain is really suffering. Does the el84 quad add a lot of distortion? Keep in mind that I dont have all the matching parts to achieve ac30 'tone', Im just concerned about gain. any help?
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The EL84 is the highest gain power tube in common use and the AC30 has no feedback in the power amp keeping the gain at max.WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
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Cathode bias adds some compression, which may br percieved as "gain".Comment
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It takes twice as much signal drive to the grids of the 6V6s and more for 6L6s to make full power as it does for EL84s.Originally posted by EETStudent View Post
Still, an AC30 preamp should have enough to drive the 6V6s into clipping.Comment
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If one wanted to figure the output the preamp needed to drive a given set of tubes, what specs would look for in the data sheet? Like, for a pair of 6V6s or EL34s or something, what would you need to calcualte to find the preamp output level needed?Comment
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A good tube datasheet should give the AC grid voltage needed for rated power output. Just make sure to check if it's RMS, peak, peak-peak, or what, and whether it's between one grid and ground, or differentially between the two grids in a push-pull amp.
Generally, the peak voltage to drive one tube works out about the same as the bias voltage, since power tubes are set up to clip by going into grid current. So roughly 10V for EL84s, 20V for 6V6s like Bruce mentioned, and 35-50V for 6L6s, KT88s, 6550s etc. It's twice this for a pair of tubes, if you think of it differentially between the two PI outputs."Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"Comment
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OK, that makes sense. Thanks, Steve!Comment
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What Steve said and also... most push pull EL84 amps don't need any more then 28vac to 32vac (peak to peak) from the phase inverter... this is from my real time experience.Originally posted by CitizenCain View PostComment
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Thats 28vac grid to grid on a single power tube?Comment
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That's the p-p V between the g1 grids of a push pull arrangement. Peter.My band:- http://www.youtube.com/user/RedwingBandComment
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Ok just so Im clear. Placing one probe on g1 of one tube, and placing a second probe on g2 of the other, you read 28-32vac maximum in the particular configuration.Comment
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Yes, and with that much drive, you will pretty much turn a pair of cathode biased EL84/6BQ5 tubes inside out.Originally posted by EETStudent View PostComment
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