JCA22H and so it begins!

[Dmoney]

So a while ago this site was being mentioned by Toe-Knee (I believe)
http://www.jetcityamplificationstore.co.uk

I've decided that once I've got my current project out of the way, I'd like to take a close look at a JCA.

I've gone and ordered the JCA22H. Hopefully service from the  site will be decent and it'll get here soonish.
I'm going to see what the deal with it is, and then maybe try out some of the SLO mods in it. See how just how SLO it was get and maybe try a few more things along the way.

Anyone hear already have one? I haven't had a lower wattage amp like this kicking around for a bit. Tends to be 100watters in my front room more than anything else. I'm looking forward to it arriving.

[dave_mc]

no but i've got the 50 watt head and from what i hear the preamps are the same...

hard to complain at the prices they go for there and on thomann... that's what swung the deal for me :lol:

[Kiichi]

Just had a first look at that amp...man that seems interesting ,espcially at that price.

Really really interested on how it comes out with the mods.

[_tom_]

Interesting. Didn't realise they were so cheap. Now I'm very tempted to try the 22w one out! Thanks for the GAS :lol:

[Toe-Knee]

I'm still very tempted to get one of these and make it more SLO like just so I have an amp that i dont care about getting damaged/lost/stolen that I can leave at the practice place.

not that anything like that has happened there as it's actually pretty secure but I would only really want to leave a cheap amp there.

[Dmoney]

I found 20watts too quiet for even a practice for me. Should a bit neater at home though.
Hopefully it'll turn up. Not sure about how runs this online store. I have a lot of plans other than to SLOify it. I'm tempted to see if I can squeeze and extra tone stack in there and some other bits and bobs. I have a spare choke I can sling in it, and I can add bias test points. Those should be easy things to do first of all.

I'm still not keen on the aesthetics. I thing they could style them a bit better. The ultra low pricing probably puts people off. IF they are that cheap, they should just think about sticking better iron in it and going after some of Marshall's JCM900 or DSL market. A few upgrades couldn't make them MUCH more expensive?

[Toe-Knee]

I found 20watts too quiet for even a practice for me. Should a bit neater at home though.
Hopefully it'll turn up. Not sure about how runs this online store. I have a lot of plans other than to SLOify it. I'm tempted to see if I can squeeze and extra tone stack in there and some other bits and bobs. I have a spare choke I can sling in it, and I can add bias test points. Those should be easy things to do first of all.

I'm still not keen on the aesthetics. I thing they could style them a bit better. The ultra low pricing probably puts people off. IF they are that cheap, they should just think about sticking better iron in it and going after some of Marshall's JCM900 or DSL market. A few upgrades couldn't make them MUCH more expensive?

The volume is the thing that puts me off. Especially with the other guitarist using a MKIV.

I'll be interested in seeing what you do. From the gutshots i've seen the pcb layout is pretty spacious so will accomodate all kinds of mods.

The ones i saw (22h gutshots) too were loaded with Illinois polys and nichicon electros so it's not exactly bargain basement unbranded rubbish like in the 100h & hdm

[Dmoney]

The guts shots I've seen have those blue poly caps, and maybe some that look like Xicons. The filters looks like panasonic's especially the big on for the DC filaments.

I've been trying to think of some ideas. Dual EQ is high on the list if I can figure it out.

The volume would concern me. That old 20watt Avenger I built was fine at home, but in a practice it had to be cranked, so the power amp would be into saturation being driven by an already saturated preamp signal. It didn't sound good and it got really unstable.

[Toe-Knee]

The guts shots I've seen have those blue poly caps, and maybe some that look like Xicons. The filters looks like panasonic's especially the big on for the DC filaments.

I've been trying to think of some ideas. Dual EQ is high on the list if I can figure it out.

The volume would concern me. That old 20watt Avenger I built was fine at home, but in a practice it had to be cranked, so the power amp would be into saturation being driven by an already saturated preamp signal. It didn't sound good and it got really unstable.

The dual tonestack should be pretty simple. In fact if the 22h uses LDRs for switching i have a small pcb layout for adding in a second tonestack unobtrusively.

[Dmoney]

It's relays. I need to look into it. I'm not sure about the DC from the cathode follower being fed directly into the relay like those LDR's. Still, could always block the DC with a large cap. There are other options.

[Dmoney]

So... it's here already!

Luckily I'm off work so I was in to take it. The crunch channel is pretty crunchy. Maybe more so than my SLO. The Overdrive channel is pretty much what I expected. Doesn't have the most low end but I'm used to have a depth/resonance on my amps, so I just turned the bass up a bit. I did have the dial back the presence way more than I do playing at low volumes on the SLO. Granted this thing and the SLO are very different beasts.

It sounded really fizzy in the high end out of the box, but it is full of chinese valves. Also noticed that the power transformer was pretty warm after I got finished jamming on it. Looks ok inside.

[marauder]

I swapped a JJ into V1, and it sorted the fizz on my JCA20H.

[Dmoney]

I'll probably do that too. I have a few JJ's knocking about. I thought it would be the valves and not the circuit adding that fizz. I want to add a switch so I can change channels with the pedal. That seems like job number one.

[Dmoney]

First mod is done. I got tired of needing to use the footswitch with the fixed cable to change channels. My SLO footswitch wouldn't work with it.

So I've installed a front panel channel select which is disabled when a footswitch is plugged in at the back and I put a jack socket on the footswitch and cut off the fixed cable, so now I can use any guitar lead between the footswitch and the head. Pretty easy going.

[Dmoney]

Here we go!

I've been having some fun with this. It's more aggressive than a full blown 100watt head I think, but thats probably due to the nature of the EL84's I'm thinking. It is my first ever EL84 amp. It does do things a big amp won't do however, which is cool.

I did some mods! Looking at the big photo and going left to right...
Added the Depth/Resonance control and an extra orange drop as part of that circuit just at the top left of the PCB.
Added 10nf snubbing caps to the rectifier (4x little blue things) to share the rectification task equally between the diodes and reduce switching transients.
Added a Choke (its outside the chassis though).
Added some bias test resistors to easily measure cathode current draw.
Changed the jacks from PCB mounted plastic ones to the isolated switchcraft jacks (just because I had a bunch).
Rewired my front panel channel switch to the new jack.
Swapped the power supply caps for EE series Panasonics, just because I know they are awesome.
Added SLO100 style Clean/Crunch switch, a Bright/Normal switch and what is know as the 'SRV' mod (a mid scoop with a boost of the low and high end) to the "crunch" channel.
Added a bright cap switch to the "Overdrive" channel aka the Haynes mod.
Swapped a few gain pots and resistor values to SLO values.


It's sounding cool still!
Now that the Crunch channel can be knocked down the "Clean", the bleed from the Overdrive channel into that circuit is more noticeable. So I might do a bit of researching and see if i can locate a fix.

Pretty happy with my work on this. It's come out really well.