A couple of boards.

[RRJackson]

I'm putting one of these in a chassis tonight and thought I'd take a shot of the pair of them just to show what I'm up to. Split-cathode JTM45-style boards, obviously. 2 uF and .68 uF, so neither input is strictly Bassman/JTM45-y. Trying out some 5-watt plate resistors. Other places you'll probably notice components that seem like overkill, but in most cases it was a matter of what I had on-hand. You'll notice that changed a bit between the two boards. As always, the community here has been a huge source of inspiration and really the thing that has made me want to do some experimentation.

http://www.flickr.com/photos/r_jackson/8222456698



-Rob

[julkke]

Those 5 watters look huge on the board. Nicely done!

[RRJackson]

Those 5 watters look huge on the board. Nicely done!

Thanks! I had to grind down the leads a little to get 'em into the turrets. If you look close the leads on those things are like coat-hanger wire.

-Rob

[julkke]

Those 5 watters look huge on the board. Nicely done!

Thanks! I had to grind down the leads a little to get 'em into the turrets. If you look close the leads on those things are like coat-hanger wire.

-Rob

I see you didn't use them on the PI turret with four component leads

[RRJackson]

I see you didn't use them on the PI turret with four component leads

Astute observation.

-Rob

[Reeltarded]

Fatness!

I recently packed a JTM45 combo with big Piher cats and mustards with 4 stages instead of the trem.

[RRJackson]

Fatness!

I recently packed a JTM45 combo with big Piher cats and mustards with 4 stages instead of the trem.[/url]

See, that's beautiful. That's a lovely vintage-y, historically accurate reimagining.

Mine is more like a kid at a tech school's project after finding an old schematic. And then ignoring a lot of the values in the schematic.

Seriously, though...that's beautiful. Very nice work.

-Rob

[Reeltarded]

It's a Bogmeron JTM 2204 heh

I want to hear your amps channel comparison when you get those done. I need to build something a little cleaner than the last two pants on fire amps.

Your resistors look like an action figure visiting a maternity ward. lol.. "Ahhhm Ahnold.. Nies doo meeetchu.."

[RRJackson]

It's a Bogmeron JTM 2204 heh

I want to hear your amps channel comparison when you get those done. I need to build something a little cleaner than the last two pants on fire amps.

Your resistors look like an action figure visiting a maternity ward. lol.. "Ahhhm Ahnold.. Nies doo meeetchu.."

I'll tell you what I'm shooting for and then when it isn't what I got we can both have a laugh at my expense.

To me, the JTM45 is pretty much the ultimate amp, but I'll come back to that.

BTW, I grew up on the 800s. Everyone I knew who played guitar owned an 800 of some flavor or another. When someone says, "Marshall" the image that usually comes to mind is still an 800. And they had that "Marshall crunch" that is kind of the definitive rock guitar sound of the era I grew up in. But if you look at them on a scope...wait, here:

http://www.flickr.com/photos/r_jackson/8225306954


Each line in the grid is 1000 Hz. So this is a guitar solo and the sound extends all the way up to around 7000 Hz. See the areas where there are parallel lines about a thousand Hz apart, the longest one is near the end. That should not be six narrow-band tones, but it apparently is.

So here's what's going on, IMO. 99% of the signal should be in the range from the bottom of the graph to the first line, but it's not because the distortion is adding all those artificial harmonics and wall of harmonic crunch up top. Those parallel lines are harmonic overtones and at least the first three are as strong as the fundamental.

My guess is that the distortion is completely shaped by the .68 cathode bypass cap suppressing the fundamental.

So then, getting back to the JTM45, I came to the JTM45 late. I'd always been a 100-watt master volume guy and then in the late 80's I engineered some recordings for a guy who used a Princeton and kind of fell in love with it and the way a small amp can get a really compressed unpredictable thing going on. In the mid-90's I bought a Budda Twinmaster and completely loved it until the first time I played with a really loud drummer and couldn't even hear it. So that brought me to the JTM45. It's loud enough to play in any rock ensemble, but it does the kind of unpredictable stuff that you get from smaller non-master-volume amps. It's not a bedroom amp, by any stretch of the imagination, but you don't have to be insane to turn it way up, either. Although it's still too loud for most club owners, but what isn't?

BUT...the distortion doesn't really have that "Marshall crunch." It has a much meatier, more satisfying thing going on most of the time, but I'm always wondering about how to get that very Marshall-y sauce.

My guess is that jumpering the channels on this will get me a blend of the Plexi-ish trebly "Marshall crunch" with a nice foundation of the JTM45-ish sound with a little less "fartiness." Of course, that's just a guess at this point. I may know tonight or tomorrow, though. At which point I'm either going to be really happy or drinking a lot. Or maybe even both.

Sorry for writing a book. Too enthused...

-Rob

[Reeltarded]

Enthused is good, that is life for ya.

Until last year I mostly played 68-72 amps since 1980. The few amps I had worked on never worked out, and the rare really good amps always changed over time. I pulled apart 16 basketcases to live the dream of making things sound like what I was thinking.

I totally hear ya.

I never thought I would like the flavor of electricity so much, I was scared. I lay in bed thinking about switching now. haha

Enthused is awesome.

[RRJackson]

Enthused is good, that is life for ya.

Until last year I mostly played 68-72 amps since 1980. The few amps I had worked on never worked out, and the rare really good amps always changed over time. I pulled apart 16 basketcases to live the dream of making things sound like what I was thinking.

I totally hear ya.

I never thought I would like the flavor of electricity so much, I was scared. I lay in bed thinking about switching now. haha

Enthused is awesome.

Wow, that's really cool. I think I'd be terrified at the prospect of rebuilding classics, but building them from scratch is really interesting to me. There are a couple of amps I've played over the years that stuck in my head and I figure I'll experiment until I'm either on the trail of what gave them their sound or I've become so frustrated that I black out when someone brings up the topic. Either way, I haven't got to where I'm goin' yet and still have a lot of curiosity unsatisfied.

-Rob