Demo track is a bit random, but basically starts at max gain and goes toward mellower territory. Please disregard any mic-bumping noises. I was playing while knob-twiddling in a very tight space.
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Parts have begun to arrive for the Pelvis amp project! This will be my second Hi-Fi build, and will be somewhat less paint-by-numbers than the last (Pete Millett’s “Engineer’s Amplifier“). First part to arrive: Simple SE PCB from Tubelab.com. So yeah, the power amp will be very paint-by-numbers. This will be an integrated amp, though, and the line stage will be my own strange creation, wired point-to-point. Of course, pretty much all of the design/engineering ideas will be appropriated, but I’ll find a way to put my own spin on it–odd tube choices, tone stack tweaks, who knows? The mind boggles at the possibilities!
Full-sized pictures (incl. schematic) HERE.
Here’s my most recent amp project. It started life as a Wards Airline radio, the cabinet for which now houses the stereo in my living room. The radio didn’t work when I got it, but it made a humming/hissing sound when powered up, so I knew the transformers were working. It sat for a long time in that state while I was busy with other stuff. Finally about a month ago set my previous prototype free and I decided it was time to turn the Airline into a guitar amp.
This is almost entirely a junkbox amp. I did have to stock up on terminal strips, and few tubes—since I wanted to use existing tube socket holes, of which there were several 7-pin-sized and only one 9-pin-sized, I went looking for a 7-pin pentode to use in the preamp. Searching AX84, google images, etc. turned up a couple of guitar amps schematics where the 6AK5/5654 was used. I checked ebay and found out they were cheap, so I decided to try it. I bought a lot of 18. Most of then turned out to be labeled “FAA,” which I took as a sign from the amp gods that I was headed in the right direction.
Anyway, after much trial and error (and lots of re-soldering) here’s what I’ve got: A four tube amp with 5Y3 tube rectifier, 6V6 single-ended power amp. The preamp is one 12AX7 gain stage driving the 5654 pentode, into a direct-coupled cathode follower (the other half of the 12AX7) into Merlin’s BoneRay tone stack. It sounds really nice. Here’s a bit of noodling that illustrates the dirty tone, anyway.
It does pretty nice cleans too, but I haven’t had a chance to record ’em.
You’ll notice a fairly massive heat sink protruding from the chassis. That, along with the mosfet used in the VVR (power scaling) circuit, were salvaged from a power supply after one of our old web servers at work (a Sun e450) was decommissioned. The e450 had FOUR massive power supplies in it, with all kinds of mosfets, rectifiers, etc. So now I’ve got these burly heat sinks coming out my ears—the one you see here was one of the smallest.
The cabinet is the carcass of an old Vox Valvetronix. It’s a bit heavy, being made of particle board, but it’s the right size. I think I’m going to have to customize it a bit, give it some flavor. The aviation theme has me imagining covering it in aluminum and rivets, but that may be a little too ambitious.
The only major new part bought for this amp was the speaker, a Weber Alnico Signature 10S. I was on the fence about buying a speaker given that I had several 10s lying around and this was intended to be a junk box exercise….but I really couldn’t stand the sound of any of the 10s I had, and the Weber was only $40. I’m really glad I did it, it’s a great sounding speaker.
This was the second amp I’ve designed myself, and I couldn’t be happier with how it turned out. I can’t take much credit for all the nifty tricks involved, though—they’re mostly straight out of Merlin’s preamp book and various web forums (mostly AX84).
After years of cursing them for being large and in the way, I have finally wall-mounted my JBL 4311 monitors. Mr. Exell turned me on to monoprice.com. The mounts (intended for flatscreens) were only $20 each! These speakers have been on a shelf right next to each other (and right next to my head) ever since I got them working—nothing like both channels going into one ear! Now I have something like actual stereophonic sound.
So now it’s 1974 up in here. 4311’s were the most popular studio monitor in the seventies. David Bowie used them. Pete Townshend. Frank Zappa. It doesn’t get much beter than this: My original 1985 copy of Welcome to the Pleasuredome on an ’80s Technics table through a halfway-rehabilitated 1965 McIntosh preamp, into a power amp I built out of old TV sweep tubes from the 70s, into the 4311’s.
I got my 4311’s for free after a friend failed to sell them at his yard sale. They weren’t really working, but I found some great info online and was able to replace the rheostats and the crossovers with new/improved parts, and now they sound great. The dustcaps of the tweeters are a little dinged, and their foam surrounds are shot, but that doesn’t seem to affect the sound much, so I’ve decided to move on to obsessing about other things.
“Waitaminute…” I imagine you thinking, “Pleasuredome?? what the?” Maybe it’s one of those things you have to have been into back then, but I’ve always loved it, especially the title track. Not only is it some groovy shit; to me it represents a kind of peak in 1980 high fidelity recording. It’s completely over the top with all sorts of electric, electronic and acoustic instruments, vocal elements, atmospherics. All masterfully recorded (probably written as well) by Trevor Horn on the best studio equipment of the day.
’70s and ’80s records were made before the loudness wars set in, so they have dynamics—they weren’t compressed all to hell. And they were mixed and mastered to sound good on quality hi-fi equipment. Some of my favorite new music, purchased on vinyl and brought home to listen on the living room system, has been pretty disappointing. Too much muddy bass is a common problem. Clearly the target playback is iPod/mp3 or car radio. Some artists (e.g. Jack White) press vinyl as their primary medium, and it shows. The rest of ’em really ought to come up with an alternate master for LPs. ‘Cuz if you’re going to the trouble of buying vinyl, you ain’t playing it back on your goddam car stereo.
Although that would be pretty cool–picture a 14″ wide car stereo with a slot to insert your record. And of course there would have to be a temperature controlled compartment for record storage. Really I’m picturing one of these, with personal assistant / DJ managing the playback and pulling requests from the stacks. And of course some kind of mil-spec shock-mounted tube amp mounted in the back, driving some big-ass 70’s style speakers. And a fucking mural on the side. Not one of these weak decal-based things like you see everywhere promoting products. I’m talking hand-airbrushed, with vikings and polar bears and such. According to my extensive internet research, no one has yet had the guts to do such a thing to a Sprinter. At least not on purpose. I’m sure there are plenty with tasty graffiti on them as a result of being left too long in the wrong neighborhood.
Anyway, I’m off to find some 70s-era vinyl to facilitate the time travel.
I built this amp for P.W. Powers’s 40th birthday. For a long time it didn’t have a name, but today I’ve decided it’s called the Green Manalishi. Maybe I’ll name all my amps after songs! Wait, I’ve already blown that—Brown’s amp is called the Neutron Star, for the insane density of parts it developed despite being only a 4-tube amp.
Anyway, the Manalishi was built with a green theme to it–green magic eye tube, green grill cloth, green knobs, hemp cone speaker. Also Green Manalishi was one of four Judas Priest tunes P.W. and I (along with Dexter Pagan, a fellow Round Table pie driver) covered at an open mike night in the late 90’s. I’d never heard the tune before then, but Dexter was into it, insisted we cover it, and ever since it’s been one of my favorites.
The Manalishi is unfinished, a work in progress. It sounds great, and P.W. digs it, but the magic eye has never done what is was supposed to (pulse, VU-meter style) and the tremolo is not functioning, following several of my attempts to make it work better. I was in over my head when I built the Manalishi. Now I’ve learned enough to get those things dialed in. It’s just a matter of getting P.W. to give it back for a week or so for the update.
 Ten demerits for failing to explain even the basic topology of the amp. The Manalishi is based on the AX84 SEL. It’s single ended, with variable cathode bias for the output tube, which means you can run just about any of the popular octal tubes, from 6V6 to KT88. Power ranges from about 5W with a 6V6 to nearly 20W with the KT88. I gave it to P.W. with a JJ KT77, a current production tube I like a lot. The tremolo was originally a near-copy of the Vibro Champ circuit, but that’s evolving. The magic eye should work something like this when I get it updated. [/edit]
This is an amp I put together for Elijah, who I know from work. I don’t know him well, but he’s a nice guy and a talented musician. When presented with the odd little cab he brought in, I couldn’t not make a little amp out of it.
Electronix-wise, it’s just a Ruby amp, with the “bassman” mod so there’s only one knob (same as was there originally–on the back with the inputs…didn’t get a pic of that). It sounds pretty good. Not much volume–I don’t think the drivers are very sensitive, but a decent clean warm tone. Cranked, with high-output pickups, it gets a little too much transistor-y distortion, all fizz and grit. Elijah’s more of a jazz/blues guy though, so it should suit him.
I’m calling it “BlueGreen Olga” after a Blues Explosion tune. Also because of the grill cloth, which was left over from the
Green Eyed Monster Green Manalishi. I even slapped together a logo/nameplate. Maybe not my finest design work, but it did make it feel complete.