diytube.com

A forum for EL84 based "18 watt" guitar amps. Users have to register, but it's free, and may take a day or two to get "let in".

http://www.18watt.com/index.php

It's interesting to compare what constitutes a decent EL84 audio amp, as to what constitutes a good 18W guitar amp... There ARE differences...

/ed B in NH

And of course, under the heading of 18 watters, there is the AX84 URL:

http://www.ax84.com/bbs/index.php

No registration neede, just jump in and enjoy...

/ed B in NH

yeah apparently these 18 watters are really popular in the guitar amp world.


I got sent some docs a little while ago and contemplated making one in the future.

This is one of the nicest layout docs I've seen so far

http://www.schematicheaven.com/marshall ... layout.pdf


http://www.schematicheaven.com/marshall ... _schem.pdf

I notice the big differences between these designs and the "hifi" amps, is small interstage coupling caps, no NFB, lower B+ (around 325V) and use of a a 130 ohm cathode resistor for the pair of 6BQ5s, which harks back to the 1950-1960s tube manual data. The tube combinations seem to be 12AX7 / ECC83 and 6BQ5 / EL84 almost exclusively.

I posted an article over at 18W about the use of "non standard" tubes like 6GK6 and the various siblings, like 8BQ5, 10BQ5, 10GK6, 16GK6 and the alleged 29GK6. I dunno just how much "18 Watters" tend to experiment, or if they prefer to stick to tried and proven designs.

/ed B in NH

It took me a while to figure it out - but the amp is a significant part of the electric guitar sound (or more specifically, the distortions from the amp - all going back to Leo Fender being a businessman, not a musician). An electric guitar through a "hifi" amp simply sounds terrible.

I think the folks at 18Watt are more oriented towards reproducing the original sound of that classic amp. AX84 is more oriented towards experimentation - getting "classic" sounds in new ways (and often at lower power - good for those of us playing at home).

Rich

Those layout and schematic diagrams are the exact same ones shown on the "18 Watt" site. There is anso a "minimalist" version which forgoes the tremolo and tone controls and uses a parallel wired 12AX7 as the input VA, and has only a volume control between it and the LTPI.

It also specs the 261M6 power trannie, and just like I recently discovered, a couple of posters over there found that this particular trannie throws a really "mean" AC induced magnetic field.

I'm starting to see that guitar amp and hi-fi amp designs follow two divergent tracks...

/ed B in NH