Much thought needs to be applied to one's amp's layout. It is over four times too much, and 400 times itself, is already high !!! The EL84 in a two stage amp would sound best with a common mu of 20 times driver tube ( 20 Xs 19 is 380 times, close enough to 400 times ! )Ī second topic is your layout. That is a gain of 100 Xs 19 or 1,900 times VS the 400 times we find ideal for high end audio. In this guitar amp you have copied, we have a mu of 100 times 12AX7, into a mu of 19 times EL84. So, when using a mu of 4 2A3, it requires a mu of 100 12AX7 or mu of 100 12BZ7 to have an ideal sounding amplification ( four times one hundred = 400 ) as a two stage amp. This 400 provides the most lively and interesting-to-hear long-term music delivery, even though for example, a commonly applied 200 times in a two stage amp would likely " pass a signal OK ". In a two stage amp, we have found from years of building and careful listening, that a gain of both tubes, when multiplied one by the other, is best designed for a total of 400 times. May I offer you some critiques, so that you will learn and improve for the future builds ahead of you ? Part 1, chassis fabrication and planning, power supply:Ĭongratulations on your first amplifier build. More more details on each part of the build, please refer to my 4-part vlog videos on YouTube: I tested each stage as I built the circuit. Riveted on the tag strips for point-to-point wiring:Īnd the finished amp: Power and output transformers were salvaged from a junk valve radio chassis. Started the build by fabricating the chassis from 18 gauge sheet-metal. It is based on the vintage tube guitar amps of the '50 and '60s by Fender, Marshall, etc.Īnd here are some of my notes on the various stages: These being common valves made by BEL is another reason that I decided to go with this circuit. Thus I decided on the AX84 guitar amp circuit found online, more details are available here: īasically, it consists of two preamp stages using one 12AX7/ECC83 and a single-ended output stage using EL84. I was on a tight budget, and my main goal was to learn about tube/valve amp construction through this build, and not necessarily build the best possible amplifier. Earlier this year, I was finally able to start my build which is now complete. Building a tube amp has been a dream of mine for a couple of years.
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