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

[Drainbamage]

Hey guys new to the fourm and just got a Jca 20h for a 150$! Bought it to mod it because the amp is set up perfectly to do so. So stoked! I actually dont really like Soldanos crunch that much. Was thinking maybe just droping the V1 220k plate restitor to 100k. Clipping the 3rd gain stage cathode bypass cap and a 1k or something resistor. And last reducing negitive feedback. Trying to even out the gain between all the stages. Maybe if im not feeling lazy upgrade all the componets on the board aswell. It be inexpessive so why not.

Im also interested in the schematic of the Jca 20HV. Cant find it. Thanks guys!

[justinjag77]

You guys really need to put up before and after mods clips

[käsebrot]

I can't recommend the Electro Harmonix 12AX7. I really hate this tubes as the Sovteks (except the 12AX7LPS which is the same as the new Mullard). Very harsh and trebly sounding.

As for the Tubestore: I don't give anything about the reviews there and their "mystery Preferred Series" which is just a chinese 7025S Mullard Style (the same tube as the new Silver Pin Genalex and the Ruby 12AX7AC7HG).

JJs are dark sounding, sometimes even a little bit "muffled" compared to the Chinese ones. But selected ones sound really good and they are very well made, thick glass and pins!

I mostly prefer a mix of JJ and chinese 12AX7 in the preamp. All selected to low microphonics and low noise.


I've got a schematic of the 20HV, but I don't know, if that's ok for Jet City, if I post it here. So you might ask them yourself. The 20HV also has a 100k plate at V1a.

[Drainbamage]

Kas I understand. Perhaps you could just telling me the differences if you dont mind? I think that wouldnt be a problem with jet city. Or in a Pm would be cool. I really thought the HV sounded really bad honestly and im hoping its much different than what im thinking of doing. Thanks!

Oh by the way the jj ecc803 is completly differnent sounding than the short plate ecc83.

[shep]

seems like some if not all of the jet city amps are discontinued?

[Tortuga]

Where are you seeing that?

[shep]

well ive noticed alot of places online arent selling some of the models new anymore

[shep]

also, on amazon the 22h doesnt even come up only the 2212c.

[shep]

i've noticed this for about a month now. i believe most of them are being discontinued. dont mean to spread rumors or anything. i was just commenting in the whole 22hv schematic rights thing. google jca22h and go to shopping and tell me what you see

[Elessar [Sly]]

My JCA22H is up for sale in the UK. Thought I'd stick it up here. Seems more relevant than the UK Spam thread.

[shep]

they dont look discontinued from the looks of their facebook. maybe they are coming out with newer models? or back ordered?

[Drainbamage]

So I just got my jaca 20h yesterday and its exactly how I rememberd them. Buzzy and fizzy. The master has to be on at least 8 it helps but it still lacks in the tone department. Im thinking the PI cathode and tail resistor values also need to be changed. By the way this thing had Holland rx4 el84s in it when I bought it! Man how cool is that. I also tubed it with 165 amperexs and 161 mullards and you know what this amp still sounds bad!

[käsebrot]

So, if the amp is not modded, if the tubes are in good condition, and - very important - if the bias setting is right and it still sounds really bad and fizzy, then the amp is not ok.
I've also had one, bought new from the shop and even with good tubes and bias, it sounded really bad. So I returned it. Maybe this was caused by a bad output transformer, don't know.

If you don't like the sound with good tubes (and I mean new tubes in a good condition, f.e. JJs), then you should better buy another amp. You won't get a whole other sound by reducing the first plate resistor and swap out the cathode bypass on V3 (which isn't done on the HV - fyi there is a 1,8k bypassed with 25u - which I really don't like - but also some other changes in comparison to the normal 20H).

The JJ ECC803S is good in the PI. On V1, if you want to smooth out the sound a little. It has deeper bottom and crispier highs in comparison to the ECC83S, a little smoother sound overall. But also tends to be more microphonic, so if you would try one in V1, then go for the goldpin ones. They are factory selected before the goldplating (which is pretty useless, only spreads the contacts in the tube sockets more then silver pins because the goldplating makes them larger... and can cause a chemical reaction during years there, if your tube sockets have no gold contacts).

[Drainbamage]

The amp is fine. Tone is so subjective and im pretty picky anyways. I knew Soldano crunch wasnt my thing before purchesing. I wanted something cheep I could tinker with. The circuit board is set up for a lot of possabilitys. Laney el84 amps never sounded fizzy and I think it has a lot to do with the 1k5 cathode/47k tail resistors and I might try that. The buzz im thinking is in the first stage. Rolling down the guitars volumeleads me to think this.

Thinking
100k V1 Grid
Removing 3rd gain stage cathode cap/1k resistor
PI 1k5 cathode/47k tail
100k negative feedback 8 ohm tap.

I think that should round out the gain.

"(which isn't done on the HV - fyi there is a 1,8k bypassed with 25u)" Did I read that correct, there is a cathode cap on the 3rd stage?

[shep]

well, käsebrot, my jca5012c has a noticeably louder hum/buzz than my jca2212c as you said that they do. different tubes didnt help with the hum. i'll be elevating the heaters soon. but sh%^! i love the mix of the crunch channel with the overdrive. unlike the jca22's overdrive. its so nice having two gain knobs to play with. i love cranking the crunch drive and cutting back just a bit on the overdrive drive for leads. and just cutting back a lot on the crunch drive for chords and things.

[shep]

drainbamage, the buzz is probably the heaters my friend.

i'm going to be elevating the heaters in both my jca50 and jca22

also, putting a 100k plate-resistor on v1 will cause the amp to be between crunch and clean. In my own taste, i'd rather it be one or the other. the 100k in v1 works well on the 22, 50, and 100 because of the other gain stages. on the 22 it pretty much ruined the crunch channel for me. probably makes it cleaner on the 50 and 100. by no means do i wanna keep you from doing it. just giving my 2 cents.

[ovid9]

Just got a JCA100 modded to SLO100 specs. Has the depth mod, and two switches on the front too. A Heyboer OT too. The price was ridiculous, I couldn't pass it up.

Literally just got it today and have spent no more than 20 minutes messing with it mostly to see if it worked. Even so, at relatively low volumes, I can hear some awesome rock crunch.

Can't wait to really wind it up and get things roaring.

[shep]

lol sweet

[shep]

I took out the stock Chinese pre's and swapped in some JJ's. I have a buttload of JJ's, and have no idea how old they are, or what state of wear they are at. I still have a GE 5751 in V1.

This amp is so aggressive that a milder tube suits it better. There's no shortage of EQ on this amp. They work good, and the shorter plates of the JJ are more stable in a combo. It sounds just fine.

put jj's in my 5012c and it sounded good. in my 22 it lost some of its life maybe because of the 100k on v1.

[Drainbamage]

also, putting a 100k plate-resistor on v1 will cause the amp to be between crunch and clean. In my own taste, i'd rather it be one or the other. the 100k in v1 works well on the 22, 50, and 100 because of the other gain stages. on the 22 it pretty much ruined the crunch channel for me. probably makes it cleaner on the 50 and 100. by no means do i wanna keep you from doing it. just giving my 2 cents.

Really between crunch and clean? I mean the jca 20 has alot more preamp gain than a jcm 800. And I concider the 800 crunch to have plenty. Id also like to be able to roll the vol down for clean. I wonder what the volts are on the preamp tubes?

[Drainbamage]

put jj's in my 5012c and it sounded good. in my 22 it lost some of its life maybe because of the 100k on v1.

The 5012c has the 20h and 22 crunch channel right? And not the Lucky 13s normal channel? Im guessing you like lots of gain.

[shep]

the difference between the 22 and the 50/100 is the 50/100 crunch channel and the overdrive channel are running at the same time in channel 2. so both gain knobs work. in the 22 its just one or the other. the crunch is not running into the overdrive channel in channel two.

[shep]

the difference between the jca20 and jca22 is you only have the crunch channel. not the overdrive. with the 100k, it still gets distorted when dimed. i just didnt like the way it sounded. just wasnt quiet there gain wise when it was dimed. it brought the overdrive channel to life though. it may do just what your looking for. being able to clean up with the guitar volume.

[käsebrot]

- also on the 22H, the crunch gain will effect the overdrive gain. Try to set crunch gain at 0 when playing in the overdrive channel and then crank crunch gain to full, you will notice the difference. So the crunch is also running in the od channel. But not as much as on the larger ones - the 22H has the better tracing

- 100k plate on v1 will tame gain in both the channels

- there are more tweaks on the 20hv than this - some same ones which Soldano does on the "vintage crunch channel mod" which was offered by Ampfactory and you can see in this documentary from toneking (youtube user), I figured it out, but will not recommend this mod, as the od channel sounds really bad then...

- 1k cathode without bypass on v3 sounds more raw and natural in od channel (I think, 1,2k is even enough), but will ruin the crunch channel sound

- 1,5k cathode you can try on v1, gives a tad more gain and makes the sound a little darker and adds fizz, which you might filter then by some tweaks. I won't do that on v2 (2nd and 3rd gainstage od), this will be way too much.


And sorry guys, it's my opinion - if you don't like the sound with new (!) tubes in good (!) condition (no probably crappy NOS tubes, which are running out of specs), then buy another amp!

The mods make the amp even better - but won't change the overall basic sound!

[shep]

i didnt think that the 22 also does that .. the schemes show differently than the 50 and 100 for the channel switching. oh well. in fact, i remember running the crunch in to the overdrive myself and it was much different. also, i just checked it. and thats not how it works in the 22.