The Porkchop has landed

[neilium]

Hey,

Thanks to everyone's direct and indirect help, I got this Rocket/AC-15 amp together and sounding ok. There's some things I want to tweak, of course, but the thing works and doesn't hum too much. It has two channels which are internally jumpered. One is basically the Rocket, the second is a take on the 1961 Vox AC15 with a 6AK5 in place of an EF86, and it feeds the grid of the bottom triode of the PI.

The output stage is built around a salvaged Harmon Kardon OT and 2 EL-84's. It sounds a touch "hi-fi" to me. I may be imagining it, but the highs and lows on this amp sound a little hyped to me. It breaks up real early, too; anything past 9 o' clock on either gain control is overdriven.

For a mere 15 watts, it's damned loud! I want to experiment with a conjunctive filter to see if I can smooth it out. As it stands now, It does some fantastic chimey tones, but the bass gets a little goofy at higher values.

The pentode channel hasn't really distinguished itself in any great way from the triode channel. I want to try some different coupling cap values and maybe a smaller cathode bypass cap on it. If that doesn't do the trick, I might chuck it.

The important thing is, it's together and working as it should. Now I just have to make it better.

BTW: 10 x 12" is too small a chassis for a guitar amp. It's what I had on hand, and I thought I could make it work in the smaller space, but it's been a struggle. (Having big hands doesn't help in this situation.)

-neil

[toddyjoe]

Nice work! Now for the important part... soundclips?

[neilium]

Soundclips are on route; the sound right now is too strident in the bass. I'm in tweaksville for a week before I can roll out an mp3 of my second rate guitar playing.

-n

[Omar]

neilium - Very nice work! I love the look. Post more pics when you get a chance. Looking forward to some mp3s as well.

Omar

[neilium]

Omar,

Thanks, for the kind words and your maintenance of this NG. Soundclips are maybe a week away, but things are shaping up with this amp. I've chased down a problem with very strident bass (I replaced the caps around the PI with the values in the schematic as opposed to what I thought should got there...sigh) and tweaked the 6AK5 channel into a satisfying alternate front end. In fact, I'm confident enough that I'm taking it to a gig Friday night.

In the meantime, here's a pic of the front more square.

[Justin]

I really like how your face plate looks. How was it made? Did you have it silk screened?

Justin

[neilium]

Justin,

Nothing that fancy. I designed it in Illustrator, printed it to heavy paper and spray-glued it to a piece of sheet brass. I then did a fake lamination with clear packing tape. (I work in graphics and have made mock-ups of just about everything that can be printed, so this was sort of a busman's holiday.) Next time, I'm going to get it laminated to plastic by professionals. It's pretty clear already that this faceplate isn't going to last.

Speaking of next time: here's the pic I'm not so proud of. I should have known from the start that 12 x 10 is too small, and I considered starting over a couple of times, but I bullied on and promised that I'd not make the same mistake next time. The interior is a bit of a cramped mess, and I'm a little ashamed of my wiring, especially after seeing Omar's latest amp. It hums a little, but that hum is easily swamped by pickup hum.

-neil