Jet City 100H Marshall Voicing Mod

[CTN]

The Jet City 100H's stock sound is a thicker version of a Marshall kinda thing. It's got a ton of lows and big growly low mids to complement smoothed out mids and highs. Sounds great.

But sometimes, all that low/low-mid grunt can be a bit much. Sometimes, you just want a classic marshall upper mid kinda thing going on without the huge low end. So I modded my amp to allow me to switch between the stock voicing and a voicing with reduced/tightened up lows and low mids.

Here's where it goes: the slope resistor at R24. As you might be able to see, R23 is kinda discoloured, probably on its way to being burned out for whatever reason, so I took this opportunity to replace that too.




Between the two points where R24 is, I installed a DPDT, ON-ON mini toggle rated for 5A @ 120V. Leads go from each end of the R24 solder pads to the center lugs of the switch. and on the outer lugs, soldered a 47k resistor (stock value) and a 33k resistor. They're both 1 watt resistors with a tolerance of +/- 1%. Here's what it looks like:



(and yes, that black wire IS soldered properly, but in this pic it looks like a crappy solder joint cuz there's a tiny bit of rosin at the top of the solder blob that looks like a hole in the solder pad from this angle)

Other side of the panel. I love the flat toggles.




And the sound?

In a word, good! I find it's very useful to have it set up on a toggle like this where you can switch between the stock resistor value and the 33k. The 33k resistor tends to reduce and tighten up the 100H's ample lows and low-mids. This has the added benefit of letting the amp's naturally Marshally sounding midrange and high end to shine through - doesn't sound thin, bright or harsh though. It's just enough to make the amp sounding more like a Marshall but still retains the essential Soldano character. I played all my guitars through it, toggling back and forth, and on both channels. The voicing switch definitely is more noticeable on the OD channel because of how it thickens up and adds more and more lows/low-mids the more gain you add. On the clean channel, it's still noticeable, but not as much. The stock resistor is great for adding some beefiness and more of a full range kinda sound to bright guitars and helps single coils sound deep, rich and warm. The 33k resistor is fantastic for low tunings and darker sounding guitars/pickups. All in all, I'm happy with this mod.


Also, bonus picture! Changed out the cheap stock LED assembly for a sturdy Fender style pilot light assembly which uses actual proper incandescent bulbs! No circuit modification required, just had to enlarge the mounting hole on the chassis.




Also sometime next week I'll record some clips with my current tube complement (TungSol 12ax7s in V1,2,3, JJ in V4, EHX in V5) to illustrate the difference in voicing. I should also (hopefully) be receiving a couple of JAN GE NOS tubes next week, a 5751 and a 12au7, which I intended for the V1 and PI positions, respectively, but I'll do some clips of both in a number of different positions to find the best configuration.

Once I get those new tubes in and I've settled on a combination, the chassis will go back in the headshell and I'll get a pic of how the amber lamp (ambalamps!!!) matches up with the grill cloth on the baffle.

[Surgeon]

Re: Jet City 100H Marshall Voicing Mod

Very cool, simple mod. Glad it works nicely! Makes the amp a bit more tweakable, which is great!

[vinta9e]

Re: Jet City 100H Marshall Voicing Mod

Nah, to me the Jet City sounds like a Soldano with cheap iron. I've heard a friend make a statement a Soldano is a bit Marshally sounding but to be honest, I can't make it out in my head, they seem two completely different animals to me.
Definitely agree with you about the pushy low mids though. For low tuned chugga chug, I quite liked the combination of the slightly tighter SL60 spec together with the depth mod. That was a single channel HR50 though, so a similar circuit but not quite the same.

Ambalamps rule. I remember the blue led flashing @ 50Hz (cause our current is slower than yours!) on a JCA20H. It was barely noticable but already quite irritating.

[CTN]

Re: Jet City 100H Marshall Voicing Mod

Very cool, simple mod. Glad it works nicely! Makes the amp a bit more tweakable, which is great!

Definitely! this plus the depth mod which I did a year ago makes the amp even more versatile than it was stock

Nah, to me the Jet City sounds like a Soldano with cheap iron. I've heard a friend make a statement a Soldano is a bit Marshally sounding but to be honest, I can't make it out in my head, they seem two completely different animals to me.
Definitely agree with you about the pushy low mids though. For low tuned chugga chug, I quite liked the combination of the slightly tighter SL60 spec together with the depth mod. That was a single channel HR50 though, so a similar circuit but not quite the same.

Ambalamps rule. I remember the blue led flashing @ 50Hz (cause our current is slower than yours!) on a JCA20H. It was barely noticable but already quite irritating.

Well they are different animals for sure, but the sonic influence is pretty similar imo/ime. But the circuits are like 98-99% the same as the Hot Rod 100 so meh. In a live situation with the volume up it's hard to tell the difference, especially with nice tubes.

Also, regarding the iron...I don't know too much about the effects of transformers and whatnot, but I do know that Mike Soldano himself spec'd out the transformers and they went through several prototypes before he finally gave his approval.

I think my amp is from the 1st or 2nd production run, and they featured faulty LED pilot lights - they would eventually just stop working. Wasn't even a normal 3mm or 5mm LED which I could buy at any electronics supply store, it was some goofball assembly that you couldn't even remove from the housing. Jet City eventually realized they goofed and were providing free replacements to anyone who wanted them but it was still blue LEDs, not just white LEDs with a blue jewel. I wanted to change the colour completely, so the fender style assembly was a better option, and also an upgrade in terms of reliability. Got a whole box of replacement bulbs too, just in case.

[DankStar]

Re: Jet City 100H Marshall Voicing Mod

you're a pretty handy guy!

[vinta9e]

Re: Jet City 100H Marshall Voicing Mod

Well they are different animals for sure, but the sonic influence is pretty similar imo/ime. But the circuits are like 98-99% the same as the Hot Rod 100 so meh. In a live situation with the volume up it's hard to tell the difference, especially with nice tubes.

I don't know, and don't mean to argue with you even though my point of view is actually quite different. I had heard one of the earliest Marshalls (was it a JTM) was basically the same circuit as a Fender Bassman; and that's what the SLO was based on, too. So there is a merit in what you've just said, it's just that I cannot hear them being similar.

I'd say that in a live situation, the amp cranked loud and cooking, means all of its substance is exposed. If it farts, burps, chokes or otherwise misbehaves, it will only be more noticable when loud, won't it?

As for the similarities, I would almost bet my money on the PCB layouts being exactly the same among the Jet City 100H and the Hot Rod 100+, and the two using exactly the same schematic. I don't have any personal experience with the 'plus' to confirm that, only single channel Hot Rods. I wouldn't be surprised if the Jet City and the Soldano are 100% the same circuit only made from different grade parts. To be honest with you, I think the Mercury Magnetics iron is the sh!t. A friend of mine swapped a 5150's output transformer for one of those and the difference it made in tone and dynamics was immense.

To me, the fender, the marshall and the soldano are archetypes, or I could call them "reference flavors of distortion". Oh, then there's the notchy engl sound which is unlike any of the above. But whatever amp tone I hear, I always relate to these.

To me, contemporary Marshalls only sound good on youtube; the most authentic Marshall tones I know of, come out of amps made by Curt Granger; a recto boogie reminds me of a big and slow bubble-bottom sumo-overweight soldano with a messy haircut or harsher treble; Mark series have a smooth top end and a focused, prominent midrange with a hot-rodded Fender aftertaste; a 5150 is a less sophisticated, blue collar soldano; a Framus Cobra is a tighter one with an umlaut; a VHT/Fryette is like a rabid marshall that's been fed razors; The Bogner xtc is a spongy crossing of a marshall and a marshmallow, the Uberschall is like the most badass mutant DSL100 turning into fur-coated godzilla; the Cameron CCV is like a polished, hi-def, modded superlead, and way trendier than ipods last year; Splawns are like snarling cousins to Aldrich-modded Marrrrshalls; KT88 Barons are almost like more sophisticated 5150s with good definition and a pinch of Engl's smooth tightness (caught my ear!); Diezels are much like the Cobra but twice the definition and twice the price; and last, but not least, the Elmwood Modena sounds like a plush grizzly which is just too good to be true.

[CTN]

Re: Jet City 100H Marshall Voicing Mod

you're a pretty handy guy!

lol not really, it's just that unrelenting tinkering bug + soldering iron = modding almost everything I own. hahahaha

[CTN]

Re: Jet City 100H Marshall Voicing Mod

I don't know, and don't mean to argue with you even though my point of view is actually quite different. I had heard one of the earliest Marshalls (was it a JTM) was basically the same circuit as a Fender Bassman; and that's what the SLO was based on, too. So there is a merit in what you've just said, it's just that I cannot hear them being similar.

I'd say that in a live situation, the amp cranked loud and cooking, means all of its substance is exposed. If it farts, burps, chokes or otherwise misbehaves, it will only be more noticable when loud, won't it?

As for the similarities, I would almost bet my money on the PCB layouts being exactly the same among the Jet City 100H and the Hot Rod 100+, and the two using exactly the same schematic. I don't have any personal experience with the 'plus' to confirm that, only single channel Hot Rods. I wouldn't be surprised if the Jet City and the Soldano are 100% the same circuit only made from different grade parts. To be honest with you, I think the Mercury Magnetics iron is the sh!t. A friend of mine swapped a 5150's output transformer for one of those and the difference it made in tone and dynamics was immense.

To me, the fender, the marshall and the soldano are archetypes, or I could call them "reference flavors of distortion". Oh, then there's the notchy engl sound which is unlike any of the above. But whatever amp tone I hear, I always relate to these.

To me, contemporary Marshalls only sound good on youtube; the most authentic Marshall tones I know of, come out of amps made by Curt Granger; a recto boogie reminds me of a big and slow bubble-bottom sumo-overweight soldano with a messy haircut or harsher treble; Mark series have a smooth top end and a focused, prominent midrange with a hot-rodded Fender aftertaste; a 5150 is a less sophisticated, blue collar soldano; a Framus Cobra is a tighter one with an umlaut; a VHT/Fryette is like a rabid marshall that's been fed razors; The Bogner xtc is a spongy crossing of a marshall and a marshmallow, the Uberschall is like the most badass mutant DSL100 turning into fur-coated godzilla; the Cameron CCV is like a polished, hi-def, modded superlead, and way trendier than ipods last year; Splawns are like snarling cousins to Aldrich-modded Marrrrshalls; KT88 Barons are almost like more sophisticated 5150s with good definition and a pinch of Engl's smooth tightness (caught my ear!); Diezels are much like the Cobra but twice the definition and twice the price; and last, but not least, the Elmwood Modena sounds like a plush grizzly which is just too good to be true.

Fair enough, can't account for the different way people hear things, but to me Soldanos sound like JCM 800s on steroids with muscle in the low mids.

As far as the volume thing goes...I dunno. At low volumes, my amps sounds good, but compressed. At high volumes it becomes quite different. The mids open up a lot, the lows get a tiny bit more focused and really hit you in the chest, the highs stay smooth.

The PCBs/layouts/circuits between the JCA100 and the Hot Rod100+ are nearly identical yeah. I've played the hot rod 100+ and the hot rod avenger, and both sounded pretty much the same as my JCA100, albeit a bit tighter and more focused. Could be down to the quality of the caps, resistors, and transformers, but honestly it's a pretty subtle difference.

Of that gargantuan list, I've only played the recto, 5150 and splawn quick rod, and I'd say your descriptions are pretty much bang on. I hated the recto. sounded like shyte to my ears. I love the 5150 for its tightness, grunt and massive amount of gain on tap - such that you don't really need to use all that much to get great high-gain sounds. And the quick rod was great too but felt a bit constrained...like it was trying to be polite instead of letting loose.

[xxxplorer]

Re: Jet City 100H Marshall Voicing Mod

Kinda like the 'tight' switch on Egnaters hehe. I have a similar switch on my Eggie Seminar amp that I put in.

[Maynardo]

Re: Jet City 100H Marshall Voicing Mod

All you changed was the slope resistor in the tone stack?, I would've changed the first bypass cap from 1uF to 0,68uF also for a more "Marshally" tone, cool mod tho

[Maynardo]

Re: Jet City 100H Marshall Voicing Mod

Kinda like the 'tight' switch on Egnaters hehe. I have a similar switch on my Eggie Seminar amp that I put in.

I thought that switch was always about changing the value in the first coupling cap :s

[misterwhizzy]

Re: Jet City 100H Marshall Voicing Mod

I did the depth mod on my JCA20H, and I added a switchable bypass cap on the second gain stage. I think it's the second gain stage, anyway, but I'm too lazy to go find the schematic again. It's crazy how much one component change can make in the feel and sound of an amp. And these guys appear to be great modding platforms. The fact that this mod does little on the clean channel bugs me, because I don't have that wonderful OD channel. I guess that's what I get for being an early adopter.

[CTN]

Re: Jet City 100H Marshall Voicing Mod

All you changed was the slope resistor in the tone stack?, I would've changed the first bypass cap from 1uF to 0,68uF also for a more "Marshally" tone, cool mod tho

Interesting...why do you say that?

Also, on this schematic, is it C32?

[CTN]

Re: Jet City 100H Marshall Voicing Mod

I did the depth mod on my JCA20H, and I added a switchable bypass cap on the second gain stage. I think it's the second gain stage, anyway, but I'm too lazy to go find the schematic again. It's crazy how much one component change can make in the feel and sound of an amp. And these guys appear to be great modding platforms. The fact that this mod does little on the clean channel bugs me, because I don't have that wonderful OD channel. I guess that's what I get for being an early adopter.

yeah, definitely good for mods. Get a 22H!!!

Also, you are pretty much the only reason I am getting a 12au7 for my PI

[misterwhizzy]

Re: Jet City 100H Marshall Voicing Mod

yeah, definitely good for mods. Get a 22H!!!

Also, you are pretty much the only reason I am getting a 12au7 for my PI

I don't know if the 12AU7 is necessary when you've got an amp with so much headroom. In a 20-watter, I think everything you can do to open it up helps, and that definitely did the trick.

I've thought about getting a 22H, but then I might have to go back to the drawing board. Redo the depth mod. Redo the poweramp bandwidth mod. Redo the choke mod. Fortunately, it has a loop, so I wouldn't have to do that again, and the overdrive channel would probably take care of me having to redo the bypass cap mod.

Seriously, it sounds really great when it comes to the overdrive on it. If I were to get a new amp, I'd get something just for clean tones and run those bad boys in stereo.

Or I'd get another 20H and turn the preamp into a JCM800. Or do the Friedman mod on it. Maybe I should check Craigslist... Thanks for nothing, dude. ;-)