
JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
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- Eddy Current
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Can somebody please reference the picture below and tell me which tube is which? Specifically the preamp tubes. I've read that replacing PI with a 12AU7 makes a nice difference and I have one of those tubes but I have no idea which preamp tube is Pl.


- Tortuga
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
I can't see the input jack, but I'm guessing it's the one on the right in that photo - V1 is usually the one closest to the input jack. (one closest to power tubes is likely the Phase Inverter, or V3)
Co-founder of the Jet Setters 2.0 (Jet ★ City Lounge Redux)
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- benjamin801
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
One of the JCA experts or GAB amp builders/modders may be by shortly with a definitive answer, but in 95% of amps, V1 is the preamp tube closest to the input jack, and the PI the one closest to the power tubes, for reasons of simple topography. I would be shocked if the preamp tube right behind the two EL84 sockets was not the phase inverter. 

"If there was only a way that I couldn't even any less than I already can't then I'd gladly not, but I think I've entered some quantum paradox, dark matter levels of can't evening where the total absolute value of not evenness exceeds all ability to explain the can'ting." - MR RUBATO
- Eddy Current
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
I just Googled the circuit board layout
and found photos that do indeed agree with what you guys are saying. V3 which is also PI is the one that's between the el38s. And the one right behind the input jack is V1. Thanks for the info, looking forward to switching some tubes out, powering it up and hearing what it sounds like.



- Eddy Current
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Ta-dah! New grill and knobs, JJ EL84s and an EH 12AU7 in PI and I put blue LEDs in but the installation sucks so I have to redo it. I thought it sounded good before but the tube swap really brought it to life. Volume near max, gain about 3 and my Strat with Fat 50s is wondrous. I really heart this amp. I'm glad they're so cheap on GC used because I might get another one. Or two.
That isn't a crappy paint job on the grill, just oddball outside lighting.

That isn't a crappy paint job on the grill, just oddball outside lighting.

Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
So I am definitely looking to do/get some mods done to my amp or sell it. I know lots of guys offer a clean channel mod and this guy needs it desperately. Overall the amp sounds killer but no true clean tone is driving me nuts. Also, just watched this vid:
[video]https://www.youtube.com/watch?v=bQKbZCR_WqE[/video]
Here are the component changes. How hard do you think this would be (From YouTube comments):
"Here ya go bro... All of the components below will replace the stock resistors and caps. For example, R36 - 470k means that you will replace the stock resistor in that location “R36” with a 470k resistor"
Depth Mod - You’ll need a 500k potentiometer and a .0047u capacitor for this mod. You’ll cut the FB wire and place this in line.
Choke – R52 - Hammond 156M
C2 - .047uf
C5-.0022uf AKA 2200pf
C6-1n AKA 1000pf
C7-220pf
R1 - 47k
R5 - 470k
R9-500k
R10-700k
R18 - 220k
R24 - 33k
R26 - 33k - More Bite
R32 - 10k - Tighter Overall Tone
R36 - 470k
[video]https://www.youtube.com/watch?v=bQKbZCR_WqE[/video]
Here are the component changes. How hard do you think this would be (From YouTube comments):
"Here ya go bro... All of the components below will replace the stock resistors and caps. For example, R36 - 470k means that you will replace the stock resistor in that location “R36” with a 470k resistor"
Depth Mod - You’ll need a 500k potentiometer and a .0047u capacitor for this mod. You’ll cut the FB wire and place this in line.
Choke – R52 - Hammond 156M
C2 - .047uf
C5-.0022uf AKA 2200pf
C6-1n AKA 1000pf
C7-220pf
R1 - 47k
R5 - 470k
R9-500k
R10-700k
R18 - 220k
R24 - 33k
R26 - 33k - More Bite
R32 - 10k - Tighter Overall Tone
R36 - 470k
_____________________________________________________
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I have some gear and junk...
Like Coffee? Like Pedals and amps? Like General Jackassery???
Check out "Dunky's N' Demos at:
https://dunkysndemos.com
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- Meelocheck
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
I'm pretty sure I made a bunch of those changes as well. I ended up reverting a lot of those changes back to factory. Some of them just didn't sound good at all. I was too lazy and didn't keep track of anything I did, for the most part. I do know the depth mod is a huge must. Bias that thing too. I also snipped one leg of C6 and put it on a switch I added to the front of the amp. There's also a mod where you jump a resistor with a small cap - to get rid of some of the sizzle on the OD channel. Fuck if I can remember what I was doing 15 minutes ago. I changed the slope resistor (r26) but have no clue to what. I do know I did some stuff with r5 and r9, trying different values, and ended up settling back to factory. Again, some of the changes should sound good in theory but don't translate well audibly. Dunno. Your mileage and all that jazz.
Guitars: Early 90's Ibanez EX Series, Late 80's B.C. Rich Mockingbird, Fairly new Epiphone LP Custom
Amp: JCA22H with 4x12 Ibanez Cab
No pedals or any real skills...
Amp: JCA22H with 4x12 Ibanez Cab
No pedals or any real skills...
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Hey folks had a chance to open up the volume today on my 50H. Here are a cpl clips, phone recording so...
https://youtu.be/bdeFSlM5GW0
https://youtu.be/YmUQvT80fdE
https://youtu.be/bdeFSlM5GW0
https://youtu.be/YmUQvT80fdE
- Tortuga
- Crystal Lettucer
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- Joined: Sat Jan 19, 2013 11:29 am
- Location: Slow and steady, bruh
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Heya, Jimmy - sounds pretty cool. Extra style points for rockin' the pointy headstock 80's carvin 
If you use the [video] [/video] tags around the youtube link, it'll show better... here's the embedded ones for ya
[video]https://youtu.be/bdeFSlM5GW0[/video]
[video]https://youtu.be/YmUQvT80fdE[/video]

If you use the [video] [/video] tags around the youtube link, it'll show better... here's the embedded ones for ya

[video]https://youtu.be/bdeFSlM5GW0[/video]
[video]https://youtu.be/YmUQvT80fdE[/video]
Co-founder of the Jet Setters 2.0 (Jet ★ City Lounge Redux)
Gear
DIY
Gear
- CEOwLP (Sig T), Carvin DC135, Westone Spectrum SX (guitar) & GT (bass), Squier strat
- '66 Bassman, '61 Magnatone, Mark III, 1960AX, homebrew 2x12 (C90 / EVM12L Thiele), HX Stomp, JCA50H
- PLX GABion, SD-1, TS9, Crybaby, MXR108, Algal clone, Carbon Copy deluxe
DIY
- New workshop - Teh GRIMESHOP™!
- Bassman overhaul - G-MAN
- Home studio - GRIMESPACE Sound Lab!
Ostinato Rubato wrote:"That's the second boomery bro on this forum I've helped seduce to the greenside."
"Slow and steady gets to **** again eventually"
- Tortuga
- Crystal Lettucer
- Posts: 17174
- Joined: Sat Jan 19, 2013 11:29 am
- Location: Slow and steady, bruh
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Co-founder of the Jet Setters 2.0 (Jet ★ City Lounge Redux)
Gear
DIY
Gear
- CEOwLP (Sig T), Carvin DC135, Westone Spectrum SX (guitar) & GT (bass), Squier strat
- '66 Bassman, '61 Magnatone, Mark III, 1960AX, homebrew 2x12 (C90 / EVM12L Thiele), HX Stomp, JCA50H
- PLX GABion, SD-1, TS9, Crybaby, MXR108, Algal clone, Carbon Copy deluxe
DIY
- New workshop - Teh GRIMESHOP™!
- Bassman overhaul - G-MAN
- Home studio - GRIMESPACE Sound Lab!
Ostinato Rubato wrote:"That's the second boomery bro on this forum I've helped seduce to the greenside."
"Slow and steady gets to **** again eventually"
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- Joined: Sun Jun 28, 2015 6:22 pm
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Cool I'll use that next time. Yeah I'm an old 80s rocker so I love those old Carvins. Thanks !
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Sweet DC135, man!
- Eddy Current
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
I finally got my blue LEDs sorted out. This little amp kicks ass.




Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Hello!
This is my first post here.
I recently bought myself a JCA22H. It doesn't cost much and seems to have quite a good reputation as a platform for modding so I thought I'll give it a try.
The first thing I will do is to convert the crunch channel to a 2204 according to the info from stump. I'll also add a switch to bypass the first tube which will be the same as the lo input on a 2204. The switch is wired as a true bypass switch in pedals.
EDIT: The slope resistor (R26) will, of course, be changed to 33k even if it's not shown in the schematic above.
This is my first post here.
I recently bought myself a JCA22H. It doesn't cost much and seems to have quite a good reputation as a platform for modding so I thought I'll give it a try.
The first thing I will do is to convert the crunch channel to a 2204 according to the info from stump. I'll also add a switch to bypass the first tube which will be the same as the lo input on a 2204. The switch is wired as a true bypass switch in pedals.
EDIT: The slope resistor (R26) will, of course, be changed to 33k even if it's not shown in the schematic above.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
My JCA 100h is on the fritz AGAIN! I took it to my amp tech about 9 months ago for the same intermittent volume cutting problem. Why is this happening? I'm playing at band volume and suddenly in the middle of a song I disappear, then come back. What's going on in my amp? Plus my my power light went off years ago, but that's not really a problem for me.
I'm thinking about ditching the JCA and saving up for a used soldano avenger to replace it. And while that's clearly the preferable answer I don't have any money and that purchase would be a year or more off, and that's if anything catastrophic didn't happen first. I'd really rather not have to deal with that and just have a working JCA 100h which I was just fine with.
I'm thinking about ditching the JCA and saving up for a used soldano avenger to replace it. And while that's clearly the preferable answer I don't have any money and that purchase would be a year or more off, and that's if anything catastrophic didn't happen first. I'd really rather not have to deal with that and just have a working JCA 100h which I was just fine with.
- Meelocheck
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- Joined: Wed Mar 27, 2013 9:05 am
- Location: Norfolk, VA.
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
JerEvil wrote:So I am definitely looking to do/get some mods done to my amp or sell it. I know lots of guys offer a clean channel mod and this guy needs it desperately. Overall the amp sounds killer but no true clean tone is driving me nuts. Also, just watched this vid:
[video]https://www.youtube.com/watch?v=bQKbZCR_WqE[/video]
Here are the component changes. How hard do you think this would be (From YouTube comments):
"Here ya go bro... All of the components below will replace the stock resistors and caps. For example, R36 - 470k means that you will replace the stock resistor in that location “R36” with a 470k resistor"
Depth Mod - You’ll need a 500k potentiometer and a .0047u capacitor for this mod. You’ll cut the FB wire and place this in line.
Choke – R52 - Hammond 156M
C2 - .047uf
C5-.0022uf AKA 2200pf
C6-1n AKA 1000pf
C7-220pf
R1 - 47k
R5 - 470k
R9-500k
R10-700k
R18 - 220k
R24 - 33k
R26 - 33k - More Bite
R32 - 10k - Tighter Overall Tone
R36 - 470k
Ok, so this clip sounds fucking angry and awesome. Soooo. I am going back in. I already made a list and checked it twice. Shopping for components is easy as there is an awesome supplier local. Will see if I can score a used Tech 21, maybe. Mine right now is just a little looser and flubbier...This should tighten it up for sure. If I can get closer to THAT tone tho...Sheeeeiiiit...
beje, someone with more knowledge than I will hopefully be along soon enough to help you out. Also, don't forget tubes and bias. And always be careful poking around in there. Make sure you know what you are doing before sticking your hands near deadly voltages. And welcome to the forum.
Guitars: Early 90's Ibanez EX Series, Late 80's B.C. Rich Mockingbird, Fairly new Epiphone LP Custom
Amp: JCA22H with 4x12 Ibanez Cab
No pedals or any real skills...
Amp: JCA22H with 4x12 Ibanez Cab
No pedals or any real skills...
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
beje, someone with more knowledge than I will hopefully be along soon enough to help you out.
I'm ok, I just thought I would share what I'm about to do.


And welcome to the forum
Thanks Meelocheck.

Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Hey Guys
I just registered here ..Was browsing this thread and I see that some of you are really into those Jet city's . Here are a couple pics of one of the few I did mod recently ..Don't be scared ! I know there is almost nothing original left :-)
This one is the same exact circuit as the CAE 3+ SE preamp's Channels 2 and 3 . Using the same brands of components too . I also posted a pic of the headshell with the Copper shielded I added . I didn't see it mentionned here but it is very important for this particular amp for cutting some particular hum noises
FYI I'm the guys who mods those preamps to Suhr's specs for over a decade now in EU
Cheers
Bruno


I just registered here ..Was browsing this thread and I see that some of you are really into those Jet city's . Here are a couple pics of one of the few I did mod recently ..Don't be scared ! I know there is almost nothing original left :-)
This one is the same exact circuit as the CAE 3+ SE preamp's Channels 2 and 3 . Using the same brands of components too . I also posted a pic of the headshell with the Copper shielded I added . I didn't see it mentionned here but it is very important for this particular amp for cutting some particular hum noises
FYI I'm the guys who mods those preamps to Suhr's specs for over a decade now in EU
Cheers
Bruno


Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Sorry bumping this post but where did you get that Custom 22 Schematic ? Something looks weird to me .001 coupling cap with the same cap to ground just behind after 3rd gain stage of OD channel ?
Thx
Bruno
Thx
Bruno
capota wrote:I don't think that anyone has the Custom 22 Schematics))
who can help me to tame down the gain on the Lead channel?? I've Already changed the R6 from 220k to 110k (switchable) and changed the Slope resister (R26) from 47K to 33k (Marshall feel, also switchable). I want to make it a bit more Marshall flavor.
Also cut the C6 but it made it too much of a dark amp. What value for the C6 (Bright cap) do you guys recommend??
Thank You!!!
Here it is after the mods
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Seems to me I saw it posted somewhere in the 38 pages here, but, I'd like to know if there is a consolidation of all the mods for the JCA 20H or 50H? I've got a power amp constructed and considering this preamp as possibility.
Great job here,
silverfox.
Great job here,
silverfox.
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Hi @Bruno, it was sent to my by the owner of Jet City (Doug White), because I was one of the first to buy this amp (bought on November 2015) and had a little problem with the connections, so, in order to fix it, I needed the schematic with values.
I Have both the Pre and Power schematic.
I Have both the Pre and Power schematic.
- Tortuga
- Crystal Lettucer
- Posts: 17174
- Joined: Sat Jan 19, 2013 11:29 am
- Location: Slow and steady, bruh
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

silverfox - see page 1, 3rd post for my consolidated reference list. Most everything is linked there.
Co-founder of the Jet Setters 2.0 (Jet ★ City Lounge Redux)
Gear
DIY
Gear
- CEOwLP (Sig T), Carvin DC135, Westone Spectrum SX (guitar) & GT (bass), Squier strat
- '66 Bassman, '61 Magnatone, Mark III, 1960AX, homebrew 2x12 (C90 / EVM12L Thiele), HX Stomp, JCA50H
- PLX GABion, SD-1, TS9, Crybaby, MXR108, Algal clone, Carbon Copy deluxe
DIY
- New workshop - Teh GRIMESHOP™!
- Bassman overhaul - G-MAN
- Home studio - GRIMESPACE Sound Lab!
Ostinato Rubato wrote:"That's the second boomery bro on this forum I've helped seduce to the greenside."
"Slow and steady gets to **** again eventually"
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
capota wrote:Hi @Bruno, it was sent to my by the owner of Jet City (Doug White), because I was one of the first to buy this amp (bought on November 2015) and had a little problem with the connections, so, in order to fix it, I needed the schematic with values.
I Have both the Pre and Power schematic.
Hello
ok though there could be a mistake printed there ..There is a big one on the JCA22H service manual where the power tubes and preamp tubes heaters supplies are inverted
When you have a chance can you check C11 and see if it really is a .001 ?
Thanks
Bruno
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
Hi Guys, WOW this thread is immortal !!
Been a few years since I've been here, did the SLO mod on my 100HDM using Jay's specs back then and have been mega happy since.
Everytime I start to think about getting a new amp, I crank her up and when I hear that huge roar, I realise there is no way I'm parting with that, even these days with all the Friedman frenzy.
One thing though I would love to get from the amp ( rather than a pedal ) is to get a nice early breakup in the crunch channel, like some Hendrix type sounds.
At the mo it sounds only ok, but the breakup sounds 'wrong' , difficult to describe, its more of a 'hard' edge to it. My cheap assed Joyo American Sound pedal actually does a better job at it, and cleans up to a better clean too, however that means more stomping when switching to OD, which is something I don't want. I just want guitar, lead and amp.
I've Tung Sols in V1-V4 and a JJ in V5, would putting something like a Mullard in V1 bring me closer to what I'm after ?
Murph
Been a few years since I've been here, did the SLO mod on my 100HDM using Jay's specs back then and have been mega happy since.
Everytime I start to think about getting a new amp, I crank her up and when I hear that huge roar, I realise there is no way I'm parting with that, even these days with all the Friedman frenzy.
One thing though I would love to get from the amp ( rather than a pedal ) is to get a nice early breakup in the crunch channel, like some Hendrix type sounds.
At the mo it sounds only ok, but the breakup sounds 'wrong' , difficult to describe, its more of a 'hard' edge to it. My cheap assed Joyo American Sound pedal actually does a better job at it, and cleans up to a better clean too, however that means more stomping when switching to OD, which is something I don't want. I just want guitar, lead and amp.
I've Tung Sols in V1-V4 and a JJ in V5, would putting something like a Mullard in V1 bring me closer to what I'm after ?
Murph
Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!
So here's a funny thing... Since getting the 1x12 w/K-100, the cleans are pretty great on the Custom 22 but the OD sounds are more "meh". Not a biggie as I want to use it as a pedal platform.
_____________________________________________________
I have some gear and junk...
Like Coffee? Like Pedals and amps? Like General Jackassery???
Check out "Dunky's N' Demos at:
https://dunkysndemos.com
https://www.youtube.com/c/JeremyVarao
I have some gear and junk...
Like Coffee? Like Pedals and amps? Like General Jackassery???
Check out "Dunky's N' Demos at:
https://dunkysndemos.com
https://www.youtube.com/c/JeremyVarao