Modded Jet City Amplifier vs Stock
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- เผยแพร่เมื่อ 7 ก.ย. 2024
- In this video I compare a modded Jet City JCA2212C I made for a client against a stock JCA22h. The crunch channel has been improved with a clean crunch mod plus 3 position bright cap switch being able to achieve VOX AC30 style cleans and Plexi crunches.
The overdrive channel has been modded with a Marshall style mode plus my original mode which has more gain and less compression.
Thanks for watching
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Wow I really like what you did with the crunch channel. So versatile
Thanks!!!
Loved the mods and also those riffs!
The channels bleeding, hmmm going to check that out! Thanks for the review. I also have a modded Jet City and it’s great!
It´s something very subtle. By fixing that I think the gain range is more usable on both channels
Chamo, you are the man!
I'm thinking about getting the head or the combo, and I'll do some mods for sure.
Yeah man, that amp is awesome if you want to mod it because the pcb is very robust. Mine has been getting surgeries since 2016 🤣. I am about to finish a new version of that prototype so stay tuned 👍
hola alber.. esperando videos tuyo.. hace full... soy Jorge , nos conocimos un dia.. haciendo un curro de AV en Madrid.. en un hotel.... saludos 🤟👍👍
Que pasa Jorge!! Muchas gracias tron. No habia visto tu comentario. Acabo de postear otro video. También por instagram @alverdura. Un abrazo
Wow great mods!! You've pulled tones out of this amp way more effectively than stock. My JCA100HDM has the Crunch / Lead bleed-over too. I'd love to know how you did that. Is the problem the opto-isolator, or vactrol switching? I'll rewatch the video.
Thanks man!!! I haven't seen the JCA100HDM but it should have the same switching system as the JCA20. It uses a DPDT relay for switching in this configuration: The signal goes to the first gain stage and then it splits un two paths, one goes to the crunch gain and the other to the overdrive gain pot and that is responsible for having both gain pots interacting. Each signal goes through their paths and then they meet at one of the circuits of the relay. The other circuit just mutes the overdrive path when the crunch channel is selected. So, what I did was to take out the relay from the pcb and connected it in this way:
After passing the first gain stage I took the signal to the second circuit of the relay so it send the signal to the gain pot isolating it from the other pot and the rest you can leave it the same.
Great makes sense, thank you! Btw the JCA100HDM is more rare now, but many put the mods on the more available JCA100 to make it an HDM. Which has a Depth control, 1W resistors...I forget what else. I love my JCA100HDM. Very well built and with the simple SLO mods it's incredible. This video, " Jet City JCA100HDM with "SLO" Mod
RubberDuck Tech ch.
My goal is just a great Marshall that pulls off the Plexi sound, but with versatility of more bottom end. These Jet City amps have good headroom. I like his 'Marshall' sound...you know the sound. You're mods are great. 🙂
@@alverduratonejunkiealveram1017
@paulj0557tonehead thanks man!! Yeah, it is definitely a great amp. I started doing mods to mine like 8 years ago and still try new things with it. The PCB has held up pretty well because its good quality. The only thing I complain (of the 20watt I have) is that the sound of the transformer changes a lot with volume. Al higher volumes the sound becomes a bit harsh in the midrange. That is something that you would expect in an amplifier of this price anyway.
Cool mods for sure
nightrain is the most used riff in amp modifications :D
@@Valerio_VDF yeah sorry, but it is so good 🤣
@@alverduratonejunkiealveram1017 I play it in all the video of my mods too :D haahah
@@Valerio_VDF LOL
Nice mods.
Thanks!!
Sounds really good
Thanks man!!!
Did they retain the 22n coupling caps?
You could go 10K on the third stage, change to voltage divider to 470K/470K and change the first cathode bypass cap to a smaller value...33K on the tonestack mid resistor and you are closer to some 2204 specs I guess.
However I think most of that is more or less attainable with a pre eq or boost from the outside.
I mean, too much bass interstage and you favor single coils, less and you point the uses to humbuckers...
I think a negative feedback mod like putting a 1M pot in series with the pressonance path would be a great mod. Kind of letting the amp breathe more if the user wants to. Do they still have it overdamped like the SLO?
By the way this preamp became the basis for the hot rod 25 which became the basis for the 2020 SLO preamp...I don't know if I like the kevin o'connor tube loop after the masters to be honest...fuck that. The original loop worked good enough if you used rack gear...The double cathode follower (not on the original SLO by the way, mike's first amp) is what configuration most people like...
Yeah I kept the 22n coupling caps, the rest of the signal path I changed it completely. I didn't follow any amp schematic in particular just tweaked it by ear. The 39k cold clipper doesn't do much in my opinion and I changed that cathode for a regular high gain one and kept the slope (tone stack resistor) as it was 47k. The presence I changed it using the cap connected to ground and added the standard depth/resonance control.
The fx loop in this amp is right after the master volume and I think is pretty ok but I have seen the schematics of the 100w version of this amp and the loop is between the tone stack and the master volumes and a guy I know that has it says that it sucks but I haven't try it personally
@@alverduratonejunkiealveram1017 It sucks if you use regular low headroom input pedals that you would normally use driven by a guitar pickup.
It sends 100+volts from a cathode follower and it's hot, but nothing a rack fx can't handle. As it is cathode follower output, impedance is about 600 ohms...so it pretty much doesn't care where it plugs into in that regard.
But as you drive hard you have the third stage doing clipping a-la diode the soldano way, the forth stage, low sensitivity easily driven and the cathode follower tube compressing and smoothing the sound. The regular SLO uses two of these arrangements (in actuallity two CF after the third stage) with the loop in between. So if you want to move the loop but not change the sound, you should leave them as they are (in the SLO amp, not the 22h).
Now, what exactly is the output impedance vs send level on the 22H? It depends on the master setting...so it needs another master to use correctly. That is a bummer to me and coloration after the preamp. Either you design the amp with it and compensate or you don't put it there. Some prefer it between the treble wiper and the master volume...
About the soldano loop there is a mod to bring down to a more manageable level with a 1K to ground at the voltage divider before the send cap but it needs a 22u cap to bring the level up in the cathode of the return stage...that changes the sound, yet again.
@@81giorikas i haven't mess with the fx loop yet because for me this one is fine. I use pedals in the loop, maybe a couple when I play live but that is it.
@@81giorikas I have the 100w and you're correct. Making it switchable from line to instrument level, and buffered will do a lot for it. I wasn't aware that placing it after the master might be desirable. I'll have to look into that before I do the mod....
I'm not sure what you mean by you split the impudence to fix the channel bleed. All I did was put a relay in the amplifier and ground the input of the opposite channel's gain pot so whenever you switch channels with the foot switch or the front panel switch, neither channel bleeds into the other anymore..
Yeah that's exactly haw is normally done but have you seen the schematic of soldanos?? If you haven't the signal goes to the first gain stage and then it splits in two directions, one goes to the crunch gain pot and the other to the overdrive gain pot. Further down there is a relay before the tone stack that works this way: When it's crunch one side is selecting the crunch path and the other is sending the overdrive path to ground. When it's on overdrive one side of the relay is selecting the overdrive path but the other side is open to nothing. So, on both channels both gain pots are affecting the signal. What I did was to use the second side of the realy in a way that receives the signal from the first gain stage and switch only to send it to the corresponding gain pot. Obviously with the sacrifice of not muting the other channel but I with it worth.
You don’t happen to have created a schematic for those mods by any chance?
No I didn't. But anyway the schematic is going to be the same except the way the relay is connected. I might have to make a video about this because a lot of people have asked me
Yes please! That would great if you could 🙏
@PhuketMyMac I have to open up my amp soon so when I do I'll show what I did in the amp and how that translates to the schematics
I have the same problem with the presence knob it's annoying. How did you fix it?
I changed a bunch of components but if I remember correctly the most important thing is the cap and the presence pot which I think I used a 5k instead of a 25k.
Sik mods.🤙
Thanks!!!!
What have you modified to get the better presence control ?
Swap the stock pot for a 5k and try different presence cap values. I changed a bunch of components but if you want to keep it simple just the pot, the presence cap and the feedback resistor
@@alverduratonejunkiealveram1017 thanks.