Jet City Modifications

Thinking about trying to mod one of these, I’ve seen a few different things people are doing to them so wondering where to start? This would be my first try at modding something so a little guidance would be appreciated! I’m grabbing the 50 watter but sounds like they are the same as the 22

Paging psychodave...

I have a JCA100 original version and have done plenty to it. I will say the best thing was replacing all the tubes and a good bias. Now from there replacing all the signal caps was a giant leap in tone. I added bright switches to both channels and the scoop mod to channel 1. You can tweak from there, they are very easy to work on and schematics are available...

The original 2 channel 22watt has DC heaters and of course EL84's, otherwise the same as the original 2 ch. 50watt. Lots of different, slightly tweaked versions have been released since.

I had outstanding results with my original 22H doing the SLO mods that are all over the net.
One thing that you don't see mentioned though, is changes to the power supply. Have a look at an SLO schematic and try to get your filtering and voltages in the same ballpark. Helps a lot on top of the other changes.
My modded amp turned out so well in fact, I dumped my '93 SLO.
I know, I know - crazy talk .... but head to head, up to medium "playing with a drummer" volume, I liked my modded Jet city better. At ear-shattering volume it was no contest. SLO all the way. But I don't play stadiums any more

The Jet city amps are well made and have a fairly robust PCB, making mods very easy to do. The transformers are surprisingly good for the price. There is a TON of info and schematics for these amps on the net.
Good luck with the mods!

i'm curious are you tinkering, or doing a specific mod...i've seen a few on the YT that sound pretty good..

also...

Is there a difference in the blue face heads, and the black face heads? i'm not very familiar with them, though im aware the Soldano "designed" one generation of the amp. my reason is there are two near me on CL. one is blue ($225) and the other is black ($300).

to clarify, i'm looking at the jca20's

MrDowntown":a7echq0n said:

i'm curious are you tinkering, or doing a specific mod...i've seen a few on the YT that sound pretty good..

also...

Is there a difference in the blue face heads, and the black face heads? i'm not very familiar with them, though im aware the Soldano "designed" one generation of the amp. my reason is there are two near me on CL. one is blue ($225) and the other is black ($300).

to clarify, i'm looking at the jca20's

Click to expand...

I did a complete re-working of the amp to SLO values ( or as close as I could get ). The component value changes in the pre-amp are straight forward, but I had to experiment with the power supply. The filtering is easy enough, but because its an EL84 amp, the B+ is just under 400v. I had to tinker to get the pre-amp voltages as high as possible without exceeding 200v on the cathode folower.

If I had a choice, I would buy the first version Blue face "333" amp, especially at a discount.

Just to be clear, my amp is a 2 channel JCA22H. There is also a single channel JCA20. The 22H is the one you need for the SLO mods. From what I can gather from internet sleuthing, the single channel 20H lends itself more towards a Friedman BE type mod, which I have not done.
I believe Psycodave's is a single channel version, and his sounds killer, but not sure exactly what was done to his.
There are also YT vids of "BE" modded single channel amps that sound great too.

Reading is critical which I fail at a lot .... the two Amps I mentioned, one is the jca20, the other is the 22.