Guitar Gear Forum

I got my replacement EL84s for my JCA 20 from Valve Queen. She's always very helpful and ships fast.

KwakaZX10R wrote:\

Re: removing cap 7, as the amp is under warranty I will hold off for now. Thanks for the advice though Drainbamage, I will certainly remember this, especially if re-biasing voids the warranty anyway!



Cheers lads

All you gotta do is lift one leg off the circuit board. If any warranty work is needed solder it back in. No one would even know.

I actually had to remove that cap in my heavily modded jca20h. I brightend up the stage before it and that cap made my amp unstable.

Greetings fellas,
Just joined the forum

I'm Chris , happy owner of a JCA22h and the 24s cab

here are few pics of my pimped head







recently I did the depth mod which is fantastic!

I'm looking for the clean mod but can't find it

Welcome!

Will try to dig up the mod in a bit (gotta get to work)

Probably need to clean up the front reference page - I'm guessing the HC links are getting stale...

GRIMESPACE wrote:Welcome!

Will try to dig up the mod in a bit (gotta get to work)

Probably need to clean up the front reference page - I'm guessing the HC links are getting stale...

thank you for welcoming me

if you find it please let me know

I'm also interested in the choke-mod but I can't find a hammond 156m in my country (Greece) and having it shipped from overseas is pretty expensive.
are there any alternative chokes that I can use instead?
I guess any 3Henries/400Volts choke is suitable for the mod?

thanx

For Soldano clean, just put a 39k parallel to crunch gain pot.

Hi again,

I guess my previous post was not read or taken into consideration... The Zoom G3 does NOT work well in the JCA100H loop (produces nasty clipping), as opposed to that said in the second post of this thread. Please edit!

I was planning on using the G3 in the loop due to the great delays and reverbs it provides, but had to replace it with a Hardwire DL-8 Delay and a Hardwire RV-7 Reverb, both of which work perfect in the loop of the JCA100H

käsebrot wrote:For Soldano clean, just put a 39k parallel to crunch gain pot.

thanx
I have few 20KΩhms and a couple of 18KΩhms . I'm going to conect 1 of each in series (for 38K) and then parallel to the pot

spadearcher wrote:Hi again,

I guess my previous post was not read or taken into consideration... The Zoom G3 does NOT work well in the JCA100H loop (produces nasty clipping), as opposed to that said in the second post of this thread. Please edit!

I was planning on using the G3 in the loop due to the great delays and reverbs it provides, but had to replace it with a Hardwire DL-8 Delay and a Hardwire RV-7 Reverb, both of which work perfect in the loop of the JCA100H

thankfully the G3 works great in the 22h loop.

Hi everyone,

This is my first post. I own a Jet City 22h and I absolutely love it. However recently after a gig the Crunch master volume pot got broken off in transit. I've done a bunch of guitar repairs and can solder pretty well, but I'm new to modding/repairing amps. Could anyone let me know how easy it is to replace the pots on this amp?

Just joined this morning, been reading this thread since last January when I impulse bought a MF SDOTD JCA5012C. I had been eyeing the heads for a while and couldn't resist the post Christmas $350 50 watt combos.
It had the obvious preamp hum the 5012C appears to be plagued with, but it's a fun amp to play. Thought the stock Jet City Eminence was a little thin sounding, ended up swapping in a G12T-75 as well as putting one in the extension cab I use under the combo. Not usually a beloved speaker, but the pair vertically stacked sounds great.
I played with the notorious Soldano loop between the gain stack and the tone stack and can confirm the Zoom G3 does not play well with line level. Recently I tried the loop again and discovered the DigiTech iStomp sounds great there running delays/reverbs! The modulation/other stuff didn't work well, but delay/reverb algos are perfect. The other discovery was that with the iStomp bypassed, the amp sounds a heck of a lot nicer. I had seen some mention of people putting buffers in a Soldano loop to clean up fizziness and that seems to work for this loop too. I leave the DigiTech in the loop now all the time, it's a bargain line level buffer for $40.
Now the sad part, the amp popped a fuse a week and a half ago. I pulled the power tubes and powered it up with another fuse, but it blew as well. I called Jet City and Doug asked if I could pull it out of the cab and send it to Hovercraft Amps in Portland for a warranty fix. I mentioned the loud preamp hum, and he asked them to do the heater trace mod while it was there. Glad I was still under warranty and the service has been great, I hope to have it back soon to see how much hum is removed by the mod. Here's a pic, the depth control was a nice surprise that wasn't on the MF pics when I ordered it!

I recently purchased a JCA2212C and I've been excited to start modding it. However, as I quickly realized, I have no idea what I'm doing! I'm pretty decent with a soldering iron, but I am a beginner when it comes to modding amps. I have been devouring all of the information I can find online about these amps. I saw a recommendation on a different forum to lift one leg of C6, R9, and C20. That seemed like a simple enough (not to mention, reversible) thing for me to handle so I tried it. Lifting a leg of C6 made a HUGE improvement in the overall sound, removing that annoying "ice pick" sound. I can now use the treble and presence knobs instead of keeping them all the way down.

I don't actually know what lifting a leg of R9 and C20 did. I can't really tell a difference for better or worse there. Could you shed some light on what effect these have?

Also, while removing C6 made the OD channel much less bright, the Crunch channel is still overly bright. Is there a bright cap for that channel that I can lift a leg on to achieve similar results for that channel?

VanquileX wrote:Hi everyone,

This is my first post. I own a Jet City 22h and I absolutely love it. However recently after a gig the Crunch master volume pot got broken off in transit. I've done a bunch of guitar repairs and can solder pretty well, but I'm new to modding/repairing amps. Could anyone let me know how easy it is to replace the pots on this amp?

It can be challenging removing 3 legs of the pot at the same time. If you're able to get the board out of the chassis, I would just clip all 3 legs and de-solder individually. For a replacement pot, you will need a 16mm vertical PCB mount pot, but offhand I'm unsure of what ohms you would need for yours.

C6 is the bright cap, you can remove it - but also can bridge it or use other values between 220p and 1n, just try it out.

C20 is the fizz cap, I wouldn't remove it unless you want to hear oscillating high fizz. You can try some lower values than 270p, the lower it goes the more high end fizz you will have, especially in the OD Channel (the 20H and 20HV without the OD have 120p in this place).

Removing R9 will reduce bass and make the amp less ballsy/wooly. Therefore I prefer to change the gain pots to 500k (and adjust the resistors and caps there) and if necessary reduce the first two coupling caps, maybe also the 2nd cathode bypass cap.

Kasebrot, I didn't see your response until just now.

Thanks for the help! I put C20 and R9 back in the circuit and prefer it that way...which makes sense, after receiving your information. I pulled a leg from C6 and C7 (which seems to be the bright cap for the "Crunch Channel") and I'm loving the tone this way. I can actually use the treble and presence controls now without that awful "ice pick" high end.

As for the other suggestions you made, could you give me the actual numbers on the PCB? I'm still learning the lingo, so I need the "For Dummies" version. I appreciate your patience with me!

I took an old demo from a band I used to be in and re-recorded my guitar parts with the JCA2212c. See the description for details. I'm not super happy with the tone, because it sounded MUCH better in the room, but oh well. Here it is!

https://soundcloud.com/briggsaudioprodu ... oostedboth

I also threw this clip together today to showcase some of the tones to be had from the Roadhouse Pickups "Tele Specials." Nothing special about the playing, but hopefully you'll enjoy the tones. Mic'ed up the speaker inside the combo for this clip.

https://dl-web.dropbox.com/get/Public/R ... oUUFWW55CA

Pickups: http://www.roadhousepickups.com/pickups ... s-for-tele

BWB2632 wrote:I took an old demo from a band I used to be in and re-recorded my guitar parts with the JCA2212c. See the description for details. I'm not super happy with the tone, because it sounded MUCH better in the room, but oh well. Here it is!

https://soundcloud.com/briggsaudioprodu ... oostedboth

what was your recording set up? i think that sounds pretty effing good dude

shep wrote:

BWB2632 wrote:I took an old demo from a band I used to be in and re-recorded my guitar parts with the JCA2212c. See the description for details. I'm not super happy with the tone, because it sounded MUCH better in the room, but oh well. Here it is!

https://soundcloud.com/briggsaudioprodu ... oostedboth

what was your recording set up? i think that sounds pretty effing good dude

Thanks man! This was the set up:
Hohner HR-1000>JCA2212c>B52 AT4X12>Audix i5>Focusrite Saffire Pro 40>Studio One 2 Pro. The boosted tracks were boosted with an Electro Harmonix East River Drive.

By the way, the gain on the JCA2212c was at 1.5


For a frame of reference, here's a video I made when I had my old 2 channel Dual Rectifier. In this case, I used three microphones and spent more time tweaking the tone. Having said that, I still think the JCA2212c turned out better...Only thing is that I lost all of the files with the orchestral samples, so they are in the Dual rec clips but not the JCA clips. Oh well.

https://www.youtube.com/watch?v=tfG16S2 ... RoFfjASf2g

Awesome clips! Sounds great. I love my 22H...Gonna look into lifting a leg on that cap to tame that fizz/ice pick sound a bit.

what was your mic placement?

shep wrote:what was your mic placement?

Very slightly off center, on axis, about 3"-4" off the grill. I typically dual mic with one 45 degrees off axis halfway between the center and the edge (pointed toward the center) but I just did the one yesterday.

Has anyone put a Metro Loop in one if these amps?

Odd question, but anyone know where a replacement power transformer could be had for a JCA50 on the cheap? A friend just blew his, and he's hard up at the moment and without an amp. Thought I could do him a solid, grab a PT, and have it repaired for him.

It would seem that there are problems with the trannies in the JCA50 amps, as this is probably the 4th or 5th time I've seen this issue happen, and only on this particular model of that series.

Having said that, I believe Jay here spec'd and priced a set of OT and PT trannies from Heyboer for something like $350 if I remember right, so you can figure one of them to be about half.

EDIT: Heyboer trannies are for an intended upgrade. Stock replacement, definitely contact Doug at JCA.

I'd check with Doug at JCA for the replacement transformer, if all you're looking to do is replace it. Upgrades, like what Jay was looking into, are really more for handling other power tubes (ie: EL34s,KTs,etc) or tone mods. Good luck!