I have now built and tweaked this amp. It sounds great! I've built 4 different amps in this chassis and this is by far the most touch sensitive and expressive. It does not have the same degree of overdrive as the HoSo 56 of DaGeezer's but I am using NFB which gives it a better sound to my ears. I have the NFB switchable.
I'm using Tung-Sol 5881's and the harmonics and touch sensitivity with the amp is great. The 5879 does have a very nice fat tone with it. I played the amp with 6V6's also which sounded great but not as sweet harmonics as 5881.
I'm pleased with the amp. It is not as loud as the Carolina Blues Rocket that borrowed alot of Dumblish preamp topology nor does it have the sustain. But the CBR 5879 is far more touch sensitive in playing. It is plenty loud with room to spare to play with the band I sit in with.
UPDATE: 3/25/09 With my guitar on 10, the amp volume (5879) on 7 and the trim pot on 5 ............ I can sustain a note til it feedbacks. This is with the mstr vol (crossline) not engaged but turned off.
I discovered I do like the PAB but on this amp (but for some reason) the treble pot needs to be turned to 10 with the .002 cap paralleled to get the tone I like. I may just leave it as is. Playing along with a CD the boost feature cuts thru very nicely. I initially wasn't sure if I was going to like the PAB.
I compared the 56T and the CBR 5879 side by side playing along with the same song on a CD and without any background music............. The results are:
I would say they are equally touch sensitive. The sustain is about the same on both, so the overdrive is fairly similar. However, the 56T has a more distortion & has a really sweet tone to the distortion. The CBR 5879 is a cleaner sounding overdrive but still sustains great. The harmonics are close to the same with the 56T having a little stronger harmonics (w/some chime).
I think the CBR 5879 has less chime and more warmth to it. I don't use NFB on the 56T and strongly prefer it on the CBR 5879. The CBR has a stronger bass to it with 5881's and a larger 12" speaker compared to the 10" Ragin Cajun on the 56T.
That's probably the best I can describe it and make comparisons. Hope that helps for anyone considering it. I probably would loose the NFB switch and build the "presence" control fixed. I leave the presence control at around 3 and don't adjust it.
With respect, Tubenit
You can find most of these schematic in the "Broken Links" file. Write down the name of what you are looking for and then click on to this Broken Links file list:
http://el34world.com/Forum/index.php?topic=17420.0