The 5879 seems to be a miniature version of the 6J7 pentode. I think RCA did this because they used 6J7/1620 tubes in a lot of their mixers and mic preamps, and thus wouldn't have to change the circuit design much when "miniaturizing". Thus the triode-connected mu is low (20) and the transconductance is also low. This makes it lower gain than the EF86. However, within these constraints, it is a pretty good sounding tube. I used a triode-connected 5879 as the first tube in my RF-powered 2A3 SE amp, and this amp is one of the best-sounding ones I've made. However, why not use the original 6J7? They are fairly available, and sound good, too.
- John Atwood
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ใครเคยลอง 6j7 แล้วมั่งมันคล้ายกันมั๊ยครับ