The Amp Garage

am back after a long hiatus... put the soldering iron down for a bit and went of to north india on a holiday. this amp has been a bit of trouble, but i'm not giving up yet. before i pulled the PPIMV, the amp stopped working altogether. i assembled the circuit back as per the stock soultone schematic...

Oh dear! And way too early, too. RIP Ted.

this little amp has made quite a bit of progress, and i'm coming to the end stages (yeah, yeah, i've been slacking a bit...). a quick question: the output stage has an octal and a noval socket wired in parallel for output tube flexibility. however, as advised, i've wired a 2k2 resistor to g1 on each...

sorry for the long delay... i figured out what the problem was. i had forgotten to install the 470k grid bias resistors that shunt to ground on the output tubes! since then, the redplating has stopped and currents have stabilized well. right now, the draw is about 45mA per tube. a new problem rears ...

RIP Michael. I grew up listening to his music, doing ridiculous dances to smooth criminal and beat it at the age of 4 or 5.... i'm rather upset. he was an amazing talent as a musician, recording artist and performer, and i'm lamenting that i missed his only concert here in mumbai back in the day. De...

i'm thinking of making a 6U8+6C4 based "propah tube saturation" overdrive pedal, with an output tranny, dummy load, etc.

hey drew,

will take photos of the innards today (forewarned, it's a rat's nest in there, but the amp is actually quite silent). will draw up a schem right now.

ok, i tried checking the voltages across the newly installed hundred ohm resistors... i had to be fairly quick about this, because the redplating was quite nasty quite fast this time, and i didn't want to kill goldpin E84Ls on a current test.... the cathode currents, as far as i could measure them, ...

hmmmm.... you guys are making me think, a hitherto unexplored domain... :D will measure the voltages and cathode current using the one ohm resistor method tomorrow. i'm not sure why it's only one EL84 that redplates though. for the 5 minutes or so that it works, it sounds great, so i'd love to have ...

so... i pulled the EL84s and measured the DC resistance of the windings to the center tap, and there's a whopping difference of almost 40 ohms, with one side measuiring 195 ohms and the other 149 or so. i'll be chewing the winder's brain out shortly. i also checked the spare trannies i have from ano...

hey structo,

thanks for chiming in.... will splitting the cathode resistor help even if the OT primary is not symmetrical?

importing OTs is forbiddingly expensive... which is why i get mine custom wound locally.

ok, it's done, i need to shout HALP! i had a pair of "sacrificial" BEL EL84s that i put in. everything was working fine right off the bat - never had that immediate success before, so i was rather pleased... until! the sound started to deteriorate - sounded like bad biasing and i noticed that one of...

OK, not too many questions this time, but some amp pictures for y'all from sunny Bombay. the circuit is pretty much stock 2061x from the infamous layout doing it's rounds on teh intertubes, with a couple of modifications: 1. switchable tube or diode rectification using the mesa boogie dual rect circ...

Hey Andy, thanks for stopping by and the tips... wow, i'm almost scared of the black metal can thingy now :D i've heard about pentodes having a lot of gain, but didnt expect transconductance to be in the order of thousands... i've never used a pentode as a preamp or line stage before. i suppose that...

Mark, thanks for the encouragement. i realise that the design (not the design per se, but the switching) is quite complex and could put people off quite a bit. for some other considerations... has anyone used a 6SJ7 going into a cathode follower? schematics i see, particularly of the octal fatness, ...