JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

[guitardave]

Ok, cool, thanks for that - I'll let you know how I get on, and how it sounds afterwards of course :-)

[Tortuga]

Pretty sure the chassis isn't labeled, but Sahl is right about V1 being next to input jack. Here's a shot of the circuit board showing tube locations. 12ax7s all on lower row, starting from low-right

[guitardave]

Took a while of staring at that photo to see the tube locations, but I got there in the end! Very helpful, thank you :-)

[Tortuga]

Cool

to the club!

[jb37804]

The Boss NS-2 Noise Suppressor (in an X pattern setup) and the Digitech Hardwire Delay DO NOT work in the JCA50H loop. They suck tone bigtime, sound like its under a pillow.

Also, The EBTech LLS-2 DOES NOT work to compensate. Save your money.

The TC Corona Chorus does work.

[lefty52]

Good evening all,
Today I purchased a used JCA20HV on Reverb and thought I ought to high tail it over here and start reading. From what I gather a new set of tubes is in order, other than that, the reviews and youtube videos have been very positive. I look forward to reading the past 30 pages and if you've got any advice, please pass it on.

[Tortuga]

Good evening all,
Today I purchased a used JCA20HV on Reverb and thought I ought to high tail it over here and start reading. From what I gather a new set of tubes is in order, other than that, the reviews and youtube videos have been very positive. I look forward to reading the past 30 pages and if you've got any advice, please pass it on.

Tubes and Bias, then report what you like / don't like.

I've put a pretty comprehensive list of the mods we've covered (here and other forums) on the first page of this thread. Definitely the place to start.

to the cool kids club!

[spadearcher]

[b]The Boss NS-2 Noise Suppressor (in an X pattern setup) and the Digitech Hardwire Delay DO NOT work in the JCA50H loop. They suck tone bigtime, sound like its under a pillow.

The Digitech Hardwire Delay (DL-8) works just fine in my JCA100H's loop. In fact that is why I bought it. It's been a while since last time I plugged it in, so I will give it a try just to make sure. I will try it in both channels I cannot remember if I did back in the day.

[starbelly]

Hi all,

Tomorrow I will be receiving my JCA22H! I'm pairing it with a Mesa Recto 2x12 loaded with V30s, and I intend to use the JCA22H as my workhorse metal-centric amp. I've been scouring the forums and have noticed a few things that people tend to do with their new 22s in order to improve the sound. Bearing in mind that I want to use this amp primarily for metal, I was wondering about the following:

Should I change the tubes?
I have a few JJ El84s and 12AX7s that i'm not using. Should I replace the respective tubes in V1 and V2? Would this tube swap lower the gain out of "metal range"? Is there anything else you would suggest tube-wise?

Should I do the depth mod?
I've read about many people reading about the depth mod, but I'm worried that the mod will make my tone sound boomier and looser overall. Any opinions on this? Additionally, could any of you point me to a literal step-by-step guide to performing the depth mod (including the specific parts to buy)? I have zero experience with this kind of thing, and all the wiring diagrams are just confusing to me (I'm a neuroscientist, I should have a handle on these things, haha).

Anything else you would suggest to get some quick tone improvements in?

Also, GRIMESPACE, I love your avatar!

Any feedback would be greatly appreciated!

[Meelocheck]

Hi all,

Tomorrow I will be receiving my JCA22H! I'm pairing it with a Mesa Recto 2x12 loaded with V30s, and I intend to use the JCA22H as my workhorse metal-centric amp. I've been scouring the forums and have noticed a few things that people tend to do with their new 22s in order to improve the sound. Bearing in mind that I want to use this amp primarily for metal, I was wondering about the following:

Should I change the tubes?
I have a few JJ El84s and 12AX7s that i'm not using. Should I replace the respective tubes in V1 and V2? Would this tube swap lower the gain out of "metal range"? Is there anything else you would suggest tube-wise?

Should I do the depth mod?
I've read about many people reading about the depth mod, but I'm worried that the mod will make my tone sound boomier and looser overall. Any opinions on this? Additionally, could any of you point me to a literal step-by-step guide to performing the depth mod (including the specific parts to buy)? I have zero experience with this kind of thing, and all the wiring diagrams are just confusing to me (I'm a neuroscientist, I should have a handle on these things, haha).

Anything else you would suggest to get some quick tone improvements in?

Also, GRIMESPACE, I love your avatar!

Any feedback would be greatly appreciated!

Welcome to the forum. And the tubes swap right off the bat isn't totally necessary but the Chinese tubes that come with tit sound a little thin and grainy. Some new tubes will make it sound a little more full IMO. And the depth mod is pretty easy and straight forward. I want to say there are some pics on the first page of this thread but I'm not sure. Basically all you are doing is cutting one wire and placing a potentiometer in the circuit. I didn't notice the sound becoming boomier or looser, but again, maybe more "full", or even "dynamic" would be a better description. Once you get the amp and crack it open it will be easier for you. The wire is fairly easy to locate and the mod is fairly simple. Cost for parts is like 8 bucks...The rest is just time on your part and it shouldn't take more than 30 minutes if you don't know what you are doing.

That being said. BE CAREFUL inside these amps. There is enough juice in there to stop your heart should it find a way to it...Don't give it a chance. Read up on how to discharge the caps inside the amp before you go poking around - again - it is fairly easy. Good luck and ask away...That's why we are here. Oh, and ROCK ON!

[Tortuga]

Hiya! to the board and to the best JCA thread on the 'net

Make sure you go through at least the first few postings on page 1 of this thread - I've combed through the entire 30 page history of this monster and cataloged links of most (if not all) the significant mods, as well as mods that are on other forums.

To add on to what Meelocheck said, tube upgrades in these amps are pretty much the standard step, along with setting the bias correctly. Nearly everyone I've come across agrees that this is the biggest positive change you can make to the JCA amps. Yes to the power tubes, yes to V1, and then V2 / V5 (Phase Inverter) will make the biggest difference. Most people seem to change all the tubes out (I did), because there's only V3 and V4 left, but if you're looking to save $20-30 on upgrades, that's the place to start.

Depth mod is actually a pot plus a cap (or two, depending on whether you install a DC blocker or not), and it's pretty easy to do. This is usually the first thing people do after tubes / bias.

As Meelo said, you gotta make sure you take the time to research and understand the high voltage dangers that can exist in these amps - even when the power is turned off. Knowing how to discharge filter caps is paramount to your being able to continue breathing, much less being a neuroscientist

Good luck! Make sure you report in on what you find and what you do.

...and, Puddy

[starbelly]

Awesome, thanks for your replies GRIMESPACE and Meelocheck!

As far as tubes go, I currently have 2 JJ EL84s, and 3 JJ ECC83s. I'm assuming I'll swap out the power tubes with the El84s (right?). However, I don't have enough ECC83s to swap out the entire preamp section. Which positions should I swap out with the ECC83s?

Is the depth knob a "passive" mod that you perform on this amp? I have seen people perform the depth mod, but also install a knob on the rear of the amp to control the level of depth. Is this always necessary, or can one simply just perform the depth mod so that it's always on?

One other question I forgot to ask previously was whether swapping tubes or performing the depth mod will negatively impact how the amp behaves when boosted with an OD pedal. I plan on doing that fairly regularly.

I'll definitely be careful when considering opening this amp up! I definitely feel that that will be the biggest bottleneck to tweaking the amp, haha.

[guitardave]

So, I opened up my JCA22H today and swapped out V1 and V2 for a pair of Tung Sol 12AX7's. Pain in the ass to get to these tubes, so I ended up removing the 4 screws on the underside of the head to take out the chassis, which made it all very easy.

Here's some photos I took at various points along the way - I thought they may be of use to other owners.

V1 is on the far right in these pictures.



Only tiny hands could get in here...



V1 and V2 have a protective metal case over them - twist to remove. They are spring loaded for ease. Here you can see V1 with case still on, and V2 with it removed.



V1 removed from its slot.



The old and the new...

[guitardave]

Hmmm images not appearing for me... Any ideas?...

[guitardave]

Here's a link to the photo album, you should be able to see them there.

http://www.photobox.co.uk/album/3383695776

[starbelly]

Nice, those images are helpful.

I just realized that among the JJ ECC83s that I have, one is balanced for the phase inverter. Unfortunately, I no longer know/can't tell specifically which tube this is. Will this pose a problem when swapping the tubes in my JCA22H?

[Thundarius]

First off Hi! I'm new to forums and I'm new to modding so bear with me.

I bought a JCA50H (blue rocker switch) from ebay, the seller had previously had a SLO and depth mods done. he also included a Red retrovalve in V1. I have since clipped C19 with positive results, making the gain more usable. I upgraded the PI to a sovtek 12ax7lps I believe the rest of the preamp and power tubes are stock

Okay, so I have some problems
**first let me claim responsibility for not biasing or upgrading my power tubes**
I turned on my amp today and played at my normal bedroom volume of about 0.25 I got the urge to take her to 1 as I sometimes do but while turning up the OD master volume, poof the amp is dead quite no noise from my cab. The tubes stayed glowing as normal as well as the illuminated rocker. It was very sudden with no pop or screech. I decided to check my power tubes because I knew they needed replaced for a while now. I found a few chips in the glass on one. It appears to be from the tube retainer. It seems like surface only abrasions but, I can't help but wounder if this could have caused my problem. I have read something about the HT fuse being in the OT so could the tube just triggered the fuse? My cables and cab are all fine. I play this amp daily in a stationary location. Aside from hum/buzz issues I have never had a problem with it. I also keep noticing that the retro valve occasionally flickers or gives a "florescent bulb slightly out of socket" look. it appears to be well seated, tube socket is clean, and has the retainer/shield on it. I heard this things are supposed to last forever could it somehow be faulty. It still works as far as I know but is it possible that it could have shorted out temporarily?

I have contacted Imbesi amp repair in CA(the tech the seller cited for the mod) with no follow up so I have no clue exactly what all has been changed. Can anyone comment about the work there and if it is to be trusted.

Thank you all for your time and patience

[Tortuga]

Hiya - welcome!

I'm not the most knowledgable, but there's plenty here that are. Let's start with some clarification...

Can you replace the retrovalve with a regular tube to see if that's the issue?

You've got two power tubes with retainers on them. Does one look light grey / otherwise different on the inside, as if it's lost vacuum? Do you have any other power tubes to try out?

If you run your guitar into the loop return (might want to use a boost / distortion pedal with the output vol/gain turned up), do you get sound?

[Thundarius]

I turned the amp on after letting it sit most of the day. I had no problems even when cranking up past the initial stopping point. I did notice a blue florescent glow in the power tubes. I read that glow is ok but it was not present before. the tubes and flash seem unchanged. The only thing I may have done differently second time around is switch my speaker cable from the secondary 8-ohm jack to the first. Not real sure if that was it or not just a possibility. I did read somewhere that the high voltage fuse resets after the amp cools down could explain it working again.

I'm sure I'll figure it out. I was planning on doing a slope resistor, Warren Haynes, and bright mods. I was going to wait until after the re-tube this gets me to it faster I guess. Anyone here use TAD 6l6GC-STR? based off of what I read it seems to fit my style as I play 90's inspired melodic death metal. but I'd like to know how the compare to the JJs. I guess while I'm off rambling about tubes, are Genalex Gold Lion tubes effective in this amp? I've heard great things about them as far as clean tones. But, the reviews are few and far between on for high gain settings.

I have another question . after skimming through the page I've seen a lot of people talk about raising the heater wires to reduce noise. Is the amount of noise reduction worth the time and risk(cutting traces)?

sorry for the book

[Thundarius]

I have found the problem! Dirty pre-amp tube socket. in case anyone else has a similar problem.

[Tortuga]

Wow - must have been seriously dirty. Great find! Great job!

[Tortuga]

I'm a huge fan of the depth mod and slope resistor (mine switches between stock & modded values). The clean switch is ok - just don't expect the world. It gives you a decent clean, but it seriously drops the volume from the regular crunch output.

A bunch of guys have done the SLO mod. I don't think there's been anybody that's been unhappy with that one. Right now, I'm debating selling my JCA ( ) - my new Marshall DSL is that good - but if I keep it, I'll probably be doing the SLO mod to see if it's a keeper for the higher-gain, more modern tone.

I did the heater mod, pretty much the same as shown earlier in the thread. I don't feel like I got a massive reduction, but it's a little better. If I had it to do over, I'd probably skip it. midnightlaundry talked up changing the rectifier diodes, and I'd like to give that a shot some time. Also, I think the best thing to do would be converting the preamp heaters to DC, but that's a pretty extensive change (likely an upgraded PT) if you don't want to resort to a secondary thing to plug in (I sure don't).

If you haven't done so, definitely change out power tubes, P1, P2, and P5 (probably best to do P3 and P4, since its only $20 more), and set bias correctly.

Good luck!

[Tortuga]

Oh yeah - forgot to add - make sure to check page 1 of this thread. I did a hell of a lot of work putting those reference links together (after spending way too much time reading this and the HC threads, along with combing for some others), and I'd sure like to know that someone is getting use out of them

[Thundarius]

Thanks man! actually I've been lurking around here for as long as I've owned the amp(7 months or so). It's my go to source for debugging. Great job man
I must have missed some stuff.
The socket wasn't extremely dirty, but I think it was a combination of seating, being dirty/tarnished and a lose fitting prong. I sprayed some contact cleaner in there refitted it a few times and so far it's good.
V1 is a red retro valve I like this especially after I clipped C19, V2 ElectroHarmonix V5 Sovtek LPS
I was waiting on the Power tubes mostly out of indecision.

I bought the amp with the SLO and depth mods added from Ebay on a whim
Mods I'm undertaking
Jays suggestions for Warren Haynes & bright on toggle
Slope resister mod as covered by CTN not sure if 33k is what i want yet I tried finding an update on weather or not you could use multiple switches or a rotary to select different values (IE 47k, 33k, 66k)

The UF5408s (rectifier diodes)seem to have gone out from Mouser. It's showing the UF5408-E3/54 at least that's what it's looking like to me But I wanted to do that in conjunction with a Mercury magnetic's Choke to combat noise(new tubes and bias too of course!!). Hopefully, making the heater wire mod unnecessary. They(Mercury Magnetics) use a 3 Henry Choke instead of the stock 10 Henry. I emailed Patrick at MM about it. He said that they found it to help with noise and tonal richness over the stock. I'll update with results & Pics when I do it. I have some other things I'm wrapping up financially, but hopefully soon.
Thanks again GRIMESPACE! Your hard work really has paved the way for me. I wouldn't have even considered modding it if it weren't for this lounge. I do better with gut pics then with Schematics which made some of Edge 11s confusing

[hackeiommi]

Hi guys! Greetings from Istanbul! I think i found a heaven here as a 40 years old Rock'n Roll and GASer pagan.

When i was looking for a good amp -and of course for a reasonable price, i bought a Jet City JCA50 from Thomann. I saw a couple of videos. Some much of them had influenc upon my decision. And later, a JC video brought me here. After a few messages under the "JCA50H with Mercury Magnetics PT and TungSol 6550s" video of Jay on YT, i registired. Especially for JC topics. I am glad to see this online lodge. 30 pages to read. Thanks to GRIMESPACE, GuitarBilly and Jay for this club, sharing and guiding.Now, so much pages to read and learn.

Live Long And Prosper!

_\\//

H