Guitar Gear Forum

Just be careful, eh? We want you here so you can figure it all out and tell us what we're doing wrong

GRIMESPACE wrote:Just be careful, eh? We want you here so you can figure it all out and tell us what we're doing wrong

Sure thing! Hey is there a way to add a toggle switch to the front of the amp to switch between channels instead of using the foot switch?

I've thought about doing that as well. I'm pretty sure it's an easy thing to do, but I think you would have to designate the panel switch as a 'master', such that it would have to be in one position to allow the footswitch to function. Not a big thing, and I'm pretty sure the Blackstar head I bought (and then returned so I could get my JCA) had a similar setup. I'll look at the schematic in a bit too see if I can diagram it out. Not sure how the led power would function...

Well, I did the slope resistor mod! It went well!

This is where it goes - R24. As you might be able to see, R23 is also kinda discoloured (note, English spelling, because I'm Canadian), 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 which is what Edge 11 suggested. 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. Kudos and much gratitude to Edge 11!


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.



Once I get those new tubes in I'll play around with them and once 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 (I am seriously fuckin giggling like a fool right now) matches up with the grill cloth on the baffle.

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, and as I mentioned earlier, I'll do some clips with the new tubes as well.

CTN wrote:Well, I did the slope resistor mod! It went well!

This is where it goes - R24. As you might be able to see, R23 is also kinda discoloured (note, English spelling, because I'm Canadian), 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 which is what Edge 11 suggested. 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. Kudos and much gratitude to Edge 11!


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.



Once I get those new tubes in I'll play around with them and once 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 (I am seriously fuckin giggling like a fool right now) matches up with the grill cloth on the baffle.

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, and as I mentioned earlier, I'll do some clips with the new tubes as well.

Nice work! Can this also be done on the 22h?

@CTN: Holy crap, dude - THAT is how a mod gets done and documented. Outstanding work! Thank you so much for the detailed descriptions and photos.

So, in the end, is it totally worth the effort? It's certainly well within my skillset to do that kind of mod, but I don't want my panel turning into swiss cheese unnecessarily. I've already got 2 extra holes that I didn't end up using near the input jack. How does this mod do with lower-gain / crunchy settings? I would love to be able to get a less bass-heavy (almost muddy) tone just by flicking that switch - is that the magic bullet, then? I'd very likely do exactly as you did - set it up on a switch so I can return it to the stock value for comparison and flexibility.

REALLY looking forward to those clips!


@Jase: I'm looking at the schematics that Edge has on his mod thread at the 'other' forum (I keep trying to get him to put them up over here - maybe I can talk him into letting me do it), and it looks like the slope resistor is labeled R26 on the 22h. That's also confirmed on the last pages of that thread (there's a bunch of new guys tearin' it up over there - good reading, if you haven't seen it yet), where they're recommending a 39k. Not sure if that'd be better match with the 22 than the 33k that CTN was told to use for his 100. I'm guessing it'd be worth trying both to see which you like better.

I did some experimenting with my footswitch tonight to see about wiring in a front panel channel selector. Interestingly, when the switch is open, the amp is in OD mode. It's only when the switch shorts the two conductors that it kicks back into the Crunch channel. That means, with the footswitch disconnected, the circuit is open, and therefore the amp will default to OD. The LED is wired on the opposite side of the switch. I think I know of a couple ways to go about doing the panel-operated switch, but I'm going to run it by the guys at HCAF to see what they think first.

Just finished biasing my amp and doing the Depth mod. HOLY CRAP Batman!, what a difference a couple of $ worth of components and some time makes. Love it.
For tubes i'm using JJ's in the power stage and V1 thru V5 goes: Sovtek 12ax7LPS, Tung-Sol, JJ, JJ then Electro Harmonics last but not least.
I've put some chrome dome knobs on and made a metal grill, but here's a daft question: I love the look of this thing "naked" ie. not in the box. If I were to make a bottom for the chassis is there any reason I could'nt leave it like this?
I'm not in a band, don't gig and it never leaves the house. Just a silly idea, but hey.
If I can figure out how to put up fotos I show you how it's looking so far.........

Photobucket account is how I host my pics. Click the image, click the img tag, post in the box here. Pretty easy, once you get the hang of it. Glad to hear things worked out well with the updates. Pretty amazing difference, eh? I don't know of any reason you couldn't leave the amp with a closed bottom. You just have to worry about heat and glass breakage issues from the tubes, but that'd be about it, I guess.

Hope this works....

Jase: I honestly don't really know...I understand that the 22h has a somewhat different preamp layout than the 50H/100H/100HDM, so I'm kinda in the dark about whether it'd work the same, but like Grimespace said, have a look around on HCAF and maybe ask Edge11 about that. Btw, those silver knobs look KILLER! Also, cute dog

GRIMESPACE wrote:@CTN: Holy crap, dude - THAT is how a mod gets done and documented. Outstanding work! Thank you so much for the detailed descriptions and photos.

So, in the end, is it totally worth the effort? It's certainly well within my skillset to do that kind of mod, but I don't want my panel turning into swiss cheese unnecessarily. I've already got 2 extra holes that I didn't end up using near the input jack. How does this mod do with lower-gain / crunchy settings? I would love to be able to get a less bass-heavy (almost muddy) tone just by flicking that switch - is that the magic bullet, then? I'd very likely do exactly as you did - set it up on a switch so I can return it to the stock value for comparison and flexibility.

REALLY looking forward to those clips!

I think it's worth it. But I also don't think it was all that much effort, especially if you have some practice soldering to a PCB.

I had a bit of an "oh shit..." moment when I had just finished the mod and thought to myself "oh shit...what if this sounds like crap, and I've gone and defaced my amp for nothing?!" But fortunately, that isn't the case. The change in voicing is subtle with low and mid gain stuff. As I said before, it's really noticeable when you get into the higher gain territory on the OD channel, but even with low/mid gain, the shift is there. I love that it tightens up the amp as a whole. It's not like VHT/Fryette kinda dry tightness mind you...it's still got that thick wet soldano/marshall distortion, but the flabby lows/low-mids are reigned in. And if you find that the switch castrates the lows too much, you can just add some rumble back with the depth knob! Might be right up your alley. What you could do to test it out with your rig/guitars is do the circuit mods, and "audition" it before drilling holes into the chassis, and if you dig it, then you can commit to it, if not, then just replace the stock resistor (or a new 47k 1% 1 watt resistor). Alternatively, just use longer lead wires and put the switch near your input jack in one of the existing holes!

So what is it exactly about the effects loops that make them "incompatible" with some effects pedals/units? Serial and fixed range? Parallel only? What gives? I have some BOSS and Jet City pedals en route and want to make sure they're going to work correctly.

Thanks in advance!!

This is the only Jet City product I own.


It's very cool, but I never use it. Someone needs to buy it from me

racerevlon wrote:So what is it exactly about the effects loops that make them "incompatible" with some effects pedals/units? Serial and fixed range? Parallel only? What gives? I have some BOSS and Jet City pedals en route and want to make sure they're going to work correctly.

Thanks in advance!!

Billy knows a helluvalot more than I do about this, but my understanding is that that loops are typically -10db (low-level, like what comes out of the guitar) or +4db (line-level). I've also read that the 22h has a 0db loop, which is meant as a compromise. The higher the number, the hotter the signal. An effects pedal, which is designed to take a minimal input (like what's coming out of a guitar) can't deal with the line-level signal, and cuts off (clips) a portion, creating harsh distortion. Some pedals are designed to accept a pre-amped signal (like a chorus that doesn't clip when slammed by a distortion with a boost on it's input) and may work fine in a loop. Other cheap, low-bandwidth pedals can't deal with it and clip and/or suck the life out of everything.

The JCA loop is serial / in line with the signal path. The list on the first page should give you a good start on what works. Not necessarily a definitive list, and doesn't include the many pedals that don't work - I'm consolidating comments from the first round of people that tested pedals back on the HCAF thread to help with that. Also, it's been stated that most (if not all) rack effects work pretty well with the JCA.

Devin wrote:This is the only Jet City product I own.


It's very cool, but I never use it. Someone needs to buy it from me

Like it - please tell us about it, then put it on the spam thread and git yer profit

CTN wrote:I think it's worth it. But I also don't think it was all that much effort, especially if you have some practice soldering to a PCB.

I had a bit of an "oh shit..." moment when I had just finished the mod and thought to myself "oh shit...what if this sounds like crap, and I've gone and defaced my amp for nothing?!" But fortunately, that isn't the case. The change in voicing is subtle with low and mid gain stuff. As I said before, it's really noticeable when you get into the higher gain territory on the OD channel, but even with low/mid gain, the shift is there. I love that it tightens up the amp as a whole. It's not like VHT/Fryette kinda dry tightness mind you...it's still got that thick wet soldano/marshall distortion, but the flabby lows/low-mids are reigned in. And if you find that the switch castrates the lows too much, you can just add some rumble back with the depth knob! Might be right up your alley. What you could do to test it out with your rig/guitars is do the circuit mods, and "audition" it before drilling holes into the chassis, and if you dig it, then you can commit to it, if not, then just replace the stock resistor (or a new 47k 1% 1 watt resistor). Alternatively, just use longer lead wires and put the switch near your input jack in one of the existing holes!

Probably gonna run by the electronics store on my way home. Gotta try this one!

Would something like an Ebtech Line Level Shifter help with this?

Not sure, but I know that there was talk about those things in the hcaf thread. I don't think there was any final verdict. It'd be great to know, if you give it a try!

I just posted several links to useful JCA-related threads on the 'other' forum in the 3rd posting of this thread. I'm intending to expand this list - if any of you have things to add, let me know!

oh dear. A dude on the duncan forum suggested also changing the first bypass cap (C32 on the 50h/100h) from the stock value of 1uf to 0.68uf for a more Marshall sound. Apparently the 0.68uf pushes the mids more whereas 1uf is a fatter tone.

Another mod. lol

Cool man - what's the link? I'll put it up on the new reference list I put in post #3. Glad you're doing these one at a time, so we get solid debriefs for each

well i dunno if I really wanna do this latest one on the bypass cap. it's supposed to push the mids up and cut some of the bass. which is fine and all...but eventually i'm gonna wanna try it out with the slope resistor mod i already did and that on top of the modded slope resistor might be too much.

also the bypass cap is gonna be a PITA to uninstall. lol

So I've ordered the parts for the slope mod. I was just looking at your photo essay again CTN, is it possible to solder
the wire to the PCB as is,or do I need to take it out?

Ebtech Line Level Shifter experiment is a success!! Any BOSS pedal--run from head FX send to LLS +4 input, LLS -10 output to pedal input, pedal output to FX return. Works perfectly and sounds great, exactly as expected.

Jase01 wrote:So I've ordered the parts for the slope mod. I was just looking at your photo essay again CTN, is it possible to solder
the wire to the PCB as is,or do I need to take it out?

Cool, Jase - I just finished pounding crappy riffs on my 50h and am about to take if offline and start to work on that very mod. If you want to do it right, I think you'll be better off taking the board out so you can do a proper desolder job. Otherwise you can clip the resistor body and solder to the leads that would be sticking out. At best, that'd be cheating. At worst, you'll start blowing yer shit up

...and yes, pulling the board out is a pain in the ass. Maybe I'll take a few minutes to snap some pics while I'm doing it and post it here.

racerevlon wrote:Ebtech Line Level Shifter experiment is a success!! Any BOSS pedal--run from head FX send to LLS +4 input, LLS -10 output to pedal input, pedal output to FX return. Works perfectly and sounds great, exactly as expected.

Right on, racerevlon - that's encouraging news. What model amp do you have, so I can put some details up on the list? And what did you pay for that thing?

Thanks for the help GRIM, and thanks for posting the new links on pg.3, the channel switching thing is ridiculously
easy! I found some left over parts from some pedal builds and am going to do that one too! I'm going to put an LED on the front
panel too to show which channel is engaged like on the footswitch.

Jase01 wrote:So I've ordered the parts for the slope mod. I was just looking at your photo essay again CTN, is it possible to solder
the wire to the PCB as is,or do I need to take it out?

I did it without taking the board out. wiggling the existing resistor out is a pain in the arse though. For me the leads broke while trying to wiggle it out (this is after heating up the solder), and then i was left with a little nub that I had to grab with a pair of needlenose pliers to finally get it out.

probably easier to do the mod once you take the board out, but then taking the board out is also a pain in the arse. lol your call. do whatever you feel most comfortable with.