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The latest "What to build" question lol

axpro

Member
Messages
628
Hey guys,

I have been jamming with a couple guys lately, and the amp i use (a homebrew JCM800 hi gain mod) doesn't cut it. It's got massive bottom end, and sounds great for metal, but we tend to skew a little cleaner, and into blues rock. I used the low gain input, but it sounds a bit crap... It's an amp i rarely played for a couple years, so it may have suffered some failure...

Anyways, I have a Traynor YBA1 that i already modded into a JCM800. But I am thinking more along the lines of a cleaner amp, maybe something that can eventually work it's way to breakup.

The easy answer is a plexi, or bassman or YBA-1. Since the amp is designed to be that in the first place. But I like to tinker. Has anyone built one based on a Matchless Chieftain Reverb, but "sans reverb"? It seems easy enough, 2 parallel sections, some interesting looking tone controls, and a post PI master and cut control (I tend to put cut controls in all my amps anyways)

Any other ideas? LOoking for a warm "generally clean" sort of vibe that would take pedals well.

Thanks!
 

Silent Sound

Member
Messages
5,042
I built a half Matchless DC30, half Marshall Plexi (2203) once. Actually, those were just the preamp sections I used. It was a cathode biased 6V6 and I was only mildly inspired by those two designs. I drew from the EF86 side of the DC30 and switched the EF86 to a 6AU6. It turned out really nice though! The 6AU6 gave it a great, warm clean tone, and the Plexi side provides some great distortion! I've been thinking about building another with a JCM 800 2203 preamp instead of the Plexi to give it a touch more gain, but with the extra inverting gain stage, I'd need to swap up the other side to keep them out of phase so they'll mix properly at the PI. That's the down side to that design, how they converge at the PI. The upside is using both channels at once gives you an extra option that's a lot of fun! Kind of a pseudo 3rd channel. By using the Plexi version of the 2203, I was able to keep the first stage as a parallel stage (mimicking jumpering the inputs), instead of cascading them to keep the signal from inverting at the PI since the other side of the preamp was inverting. The Chieftain uses the same method of combining signals at the PI. I prefer this method of channel switching as it doesn't require any relays. You can just hook up both channels, and then ground out the one you're not using at the gain control on the input of each channel.

I kept the PPIMV and cut control, but instead of linking them directly to the opposite sides of the signal post PI with a single pot, I used two dual ganged pots and tied them to ground, and then threw in a pair of 0.1uF coupling caps before and after them to keep DC off the pots. They work great, though I don't really use the cut control. Apparently presence and resonance controls don't work real well with this setup though. But having the regular master volume before the PI and a PPIMV help to let you balance the volumes of the two sides, while controlling the overall volume of the amp without messing with the volume balance.

So if you're looking for a warm clean tone to go with the JCM800, I'd say maybe consider something along those lines. You could use a JCM 800 (permanently mounted through the HI input) and maybe a Fender Twin Reverb style (normal channel) other channel. That would give you on inverted and one non inverted preamp section to combine at the phase inverter and keep them in phase. Or you could just do what you want and not have the option to run both channels at once. Having both Hi and Lo inputs on the JCM 800 would provide some issues with flipping phases on the inputs.
 

donnyjaguar

Member
Messages
4,201
If I run my Strat SSS into my JCM800 its pretty good for getting the boogie and blues on. If you're decked out for metal, I'm guessing your guitar is a humbucker and maybe a bit much?
 

00JETT

Member
Messages
550
You can get some fantastic tones by dropping a gain stage in a Jcm 800 style build, I messed with this for a while when I needed lower gain tones from my 2204ish build. Dropping the cold clipper and paralleling v1 A&B while keeping everything else the same just drops the gain nicely for a lower dial range. Messing with the voltage and filtering can soften it up too.
 

axpro

Member
Messages
628
If I run my Strat SSS into my JCM800 its pretty good for getting the boogie and blues on. If you're decked out for metal, I'm guessing your guitar is a humbucker and maybe a bit much?
Yeah, I play mostly PRS guitars, and I don't like the humbucker cleans.... I really don't like most humbuckers clean to be honest, but I get easily annoyed by hum so I am stuck between a rock and hard place. A couple of my guitars have some Seymour Duncan 3+3 split coils in the neck position, and they sound pretty good, And one has the Eric Johnson pickup in the neck which is good, but most have regular stock PRS humbuckers, which are GREAT for almost everything.... I use models with 5 way switches, and the tones are good, but switching them is problematic during a song. All my PRS guitars are older stock, so none have a blade switch. I might do some custom wiring and wire the necks parallel with a 3 way toggle, Parallel HB's sounds good to my ears.
 

axpro

Member
Messages
628
Back to amps, I ended up kinda half assing together a Matchless-ey amp. I used the preamp stages of a Matchless lightning for inspiration (kinda like a Marshall topography, but with a parallel first stage) Master volume is pre phase inverter at the moment, I don't have a spare dual ganged pot for a Larmar PPI Master at the moment. Has a cut control to tame some of the high end and I am using some Groove Tubes 6l6GEs since i had them laying around. Sounds pretty big and clean, and when i crank the preamp volume it gets a little nastier. I think a Post Phase inverter master might be a little better, but for now, this is working. Going to try it with a few pedals today
 

axpro

Member
Messages
628
Okay, i think I have it dialed in. Lowered the gain somewhat in the preamp, changing the cathode resistor of the parallel first stage to a 2.7k (from the 1.5 stock) and using a 1uf bypass cap. Also switched the preamp tubes with 12ay7's. I keep the volume cranked (if i had a good push/pull volume, i'd install a bypass) and it sounds nice and big and round... still using GE6l6 model groove tubes for the output section, and a 12ax7 in the PI. The ay7's give it a little bit darker soul and with the volume drop you end up pushing things a little harder, it sounds pretty good with my PRS CE22 in parallel positions... not a fan of series humbuckers clean... But i figure if I can use the parallel position for my clean, and add a pedal for my main dirty sounds, when i need a quick boost for a solo, i can turn the volume one notch to full series HB and get a little gain boost. When i crank it up, even with the ay7's it gets a little gritty. I could probably pull off some early AC/DC or Alice Cooper, but I'll need a pedal for anything more aggressive than that.... or i could just use my other head that is the "METAL MACHINE" lol

for a "Big Clean Machine" it sounds good. I'll hopefully get to try it with the band this week
 

Geeze

Member
Messages
2,429
Have you thought of running KT66's? I've used them in place of 6L6's and preferred the smoother tone with the current production Gold Lion KT66's. I have them in a JTM45ish amp and it is magnificent, punchy and LOUD!

Russ
 

axpro

Member
Messages
628
Have you thought of running KT66's? I've used them in place of 6L6's and preferred the smoother tone with the current production Gold Lion KT66's. I have them in a JTM45ish amp and it is magnificent, punchy and LOUD!

Russ
I tried kt66s before when this amp was more of a JTM45, the jcm800 and didn't find a huge improvement, but of course I had an issue with the cathode follower i missed for several build variations.

I think i have a pair of kt66s here somewhere, but i don't think they are gold lions.

The amp is at my buddy's place, we are supposed to jam tomorrow, the attempt last week was thwarted by sick band members!
 




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