36W power stage versus Peavy Classic 30

[d1camero]

Hi all, I am just starting my venture into the 4xEL84 arena.

I was comparing the schematics of the 36W against the Peavy Classic 30 and wondering about some of the differences:

PI Input to ground: 220k on Peavy, 470k on 36W

PI Input to grids: 47k on Peavy, 8.2k on 36W

B+ to grids: either none or 100R on Peavy, 1k on 36W

Cathode: none on Peavy, 150R/100uF on 36W


Since I am not a designer, per se, but more of a "follow the schematic" kind of guy, can those more in the know shed some light?

thanks
Don


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[thinline]

I'm not really familiar with the Peavy circuit, but from those values you posted, I guess:

1) PI Input to ground: 220k on Peavy, 470k on 36W - 470K would hit the power stage harder than the 220K. 220K are the standard Vox/Fender values.

2) PI Input to grids: 47k on Peavy, 8.2k on 36W - same deal as above. The Peavy PI looks to be getting hit harder than the 36W PI.

3) B+ to grids: either none or 100R on Peavy, 1k on 36W - I guess you are talking screen grids here. I don't think the difference in values here makes much difference, it's just to limit the screen grid current.

4) Cathode: none on Peavy, 150R/100uF on 36W - The Peavy is most likely fixed bias, whereas the 36W is cathode biased.

I'm still learning myself, so someone with a bit more knowledge than me might like to confirm my responses?

[krash]

The Classic 30 is a completely different animal. It uses a split-load phase inverter which has unity or less gain, so therefore it cannot drive the power tubes nearly as hard as the 18W/36W can. C30 is also fixed bias with negative feedback. The whole PI+power-amp is a "clean power" type of animal in the C30 and really you're not going to get a whole lot of power tube distortion from it. The 36W/18W in normal form are a power amp distortion kind of thing, way louder and with a completely different distortion character.

That said, I did like my Classic 30 a whole lot. I like it a whole lot better now In fact I still don't know what I am going to do with it in the long run. It's just my test chassis for new ideas at the moment. But it's not really comparable to a 18W/36W type of amp IMHO. Decent little amp with good features and tone for the money. Maybe one of the best sub-$1K combo amps out there if you're into regular rock tone at quietish gig levels.