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

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ironman28
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by ironman28 »

Jay wrote:
ironman28 wrote:
Jay wrote:No Transformer changes? Seems odd since he has been saying not to run anything except 6L6s in these amps. I wonder what made him change his mind all of the sudden? 6550s/KT88s would just require changing a few resistors, and EL34s would require resistors and grounding pin 1 on the power tubes. If they are using stock iron to run EL34s or even KT88s, then you should be able to use KT77s with just a bias resistor change if you want a simple way to get some EL34 type tone.


Well he probably knows the actual ratings of the heater windings on the chinese iron. They might have also upgraded the specs on new production to allow EL34 heater currents. You can test the heater winding by loading it down to simulate the EL34 current to see if the voltage drops more than 10%. The real problem is the rise in core temprature under those conditions.
I added a small 2A filament xformer for $17 to my 50h to run the preamp tubes and use the stock winding for the PA tubes only.
With some 1k sg resistors I can run almost any power tube I want. Also DC elevated the heaters for the preamp tubes.
I'm not confident in the reliability of the stock pwr xformer under stress for long term. It would be nice if JC actually published the design specs.


I like the idea of the filament tranny. $17 isn't bad. How small is it? Shouldn't be too difficult to wire in. I had also contacted Heyboer to make some replacement style Transformers for both PT and OT for the 50H and 100H and had them designed around the SLO spec, but with a higher filament rating. I gave them the dimension of the core and the footprint of the endbells, and they said it could be done, even to make the Hi-Def OT like the SLO has. Prices were VERY reasonable, but I just have not had the time and resources to getting around to doing it.


The tranformer is a Hammond http://www.tubesandmore.com/products/P-T166L6
It is about the same physical size as the choke on the 50H. it is very easy to wire in as the 50h has a jumper that connects the filament traces in the PA to the preamp section. Remove the jumper and wire the new xformer to the preamp. The hardest part was drilling holes in the chassis to pass the leads through. I did have to extend the primary leads to reach the AC input. The only drawback is the amp cant be used with a 220 line input. I will post some pics later.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by marnold »

marnold wrote:Unfortunately there was some problem with the 20HV where it would keep cutting in and out, like the cord was bad and someone was constantly wiggling it.

I was hoping to trade my 20H (with JJs) towards the 22H, but I'm not sure that they're going to give me anything for it.


Just as a follow-up, I went back to that store yesterday. They are evidently getting out of being a Jet City dealer and sending all their stock back. That means that I can't get a 20HV from another store to check. The 22H is still available (at least until they get word to box up their stock too), but I've a feeling that they won't give me anything toward my 20H if they are dumping Jet City otherwise.

Too bad, because a) I really wanted to try a 20HV, and b) I really did want to shop locally.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by marnold »

Well, they offered me the 22H for $339 and I jumped at it. I took the blue baffle and replaced it with the metal one I had on my 20H. Now I'll have to learn some new settings for my delay pedal because it sounds WAY different through the effects loop than it does out front.

Once I'm sure this one is working fine, I'll try to sell the 20H on Craigslist or something.

I know I'm going to want to replace the tubes. As I understand it, I'd only need to get the bias checked if I got new power tubes, right? I can basically swap out the preamp tubes as I see fit, correct?
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Hipster Salad »

Alright guys I'm going to brag a bit here, and after my quick 15 minutes of fame I'll get back to my business. I'm officially a Jet City Artist now :D

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http://www.jetcityamplification.com/#!artists/c1x2s
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Jay »

:thu:

Congrats and GTFO at the same time. :lol:
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by marnold »

One thing that I've noticed with my JCA22H, when I first power on the amp (with it in standby), the bottom of the V3 preamp tube seems to glow brighter for a brief moment before warming up like the other ones do. I don't know if I've got a tube going bad or if it is "reflected" light from V1 and V2 warming up. On my JCA22H V1 and V2 have shields on them while my JCA20H did not.

I've got my original Chinese tubes from my JCA20H in case of emergencies. I guess I could swap one out and see what happens.

Edit: I can answer my own question. I swapped the tube out and the new one doesn't glow like that. Also the amp became remarkably less noisy--even though I didn't think it was terribly noisy to begin with. I was surprised. At first I thought I had screwed something up because the crunch channel was dead silent. I mean, it wasn't turned up THAT loud, but still. Simplest solutions are the best.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Tortuga »

marnold wrote:One thing that I've noticed with my JCA22H, when I first power on the amp (with it in standby), the bottom of the V3 preamp tube seems to glow brighter for a brief moment before warming up like the other ones do. I don't know if I've got a tube going bad or if it is "reflected" light from V1 and V2 warming up. On my JCA22H V1 and V2 have shields on them while my JCA20H did not.

I've got my original Chinese tubes from my JCA20H in case of emergencies. I guess I could swap one out and see what happens.

Edit: I can answer my own question. I swapped the tube out and the new one doesn't glow like that. Also the amp became remarkably less noisy--even though I didn't think it was terribly noisy to begin with. I was surprised. At first I thought I had screwed something up because the crunch channel was dead silent. I mean, it wasn't turned up THAT loud, but still. Simplest solutions are the best.


Glad you were able to clear it up. Welcome to the club!

Also, in answer to your earlier question, yes - Bias power tubes only (your EL84s on the 22H) - Pre's don't have adjustable bias and can be swapped as needed.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Tortuga »

sahlomonic wrote:Alright guys I'm going to brag a bit here, and after my quick 15 minutes of fame I'll get back to my business. I'm officially a Jet City Artist now :D

Image

http://www.jetcityamplification.com/#!C ... s/imagey3n
http://www.jetcityamplification.com/#!artists/c1x2s


Congrats! :rawk:
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by neilrocks25 »

A quick pedal demo with the jca2112rc

viewtopic.php?f=5&t=9928
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by neilrocks25 »

I just did the tone stack mod, to give it more of an aggressive Marshall midrange. I put a switch in to choose between a stock 47k resistor and the 33k I put in.
I like it a lot. I am really pleased with the outcome.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Tortuga »

neilrocks25 wrote:I just did the tone stack mod, to give it more of an aggressive Marshall midrange. I put a switch in to choose between a stock 47k resistor and the 33k I put in.
I like it a lot. I am really pleased with the outcome.


Awesome - glad to hear it had same effect on the 20 as my 50! I'd say that I enjoy this mod just about as much as the depth knob. Do you find it gives the amp a looser feel when using the 33k? How's it working with your pedal collection?

Got pics / clips?
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by neilrocks25 »

GRIMESPACE wrote:
neilrocks25 wrote:I just did the tone stack mod, to give it more of an aggressive Marshall midrange. I put a switch in to choose between a stock 47k resistor and the 33k I put in.
I like it a lot. I am really pleased with the outcome.


Awesome - glad to hear it had same effect on the 20 as my 50! I'd say that I enjoy this mod just about as much as the depth knob. Do you find it gives the amp a looser feel when using the 33k? How's it working with your pedal collection?

Got pics / clips?


i only gave it a quick test, as my son had to go to bed (its 11:31 PM now) but I liked it and it sounded very good with my SD-1.
I will do clips as soon as I have a free house and time.
I am leaving Japan in a matter of weeks, but i might see if I can mod my JCA for 240v as i am really enjoying it, and want to send it over later.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Jay »

neilrocks25 wrote:I just did the tone stack mod, to give it more of an aggressive Marshall midrange. I put a switch in to choose between a stock 47k resistor and the 33k I put in.
I like it a lot. I am really pleased with the outcome.


Did you notice if it smoothed out the gritty or "disjointed" high end of the 20? I'm trying to smooth out the highs on my 20H without totally castrating the amp, but I've been so busy that I haven't had a chance to get to it.

Also, if you want to convert it to 240v, you may need to replace the PT, unless the leads are on the PT already, but suspended inside the amp somewhere. :idk:
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by neilrocks25 »

Jay wrote:
neilrocks25 wrote:I just did the tone stack mod, to give it more of an aggressive Marshall midrange. I put a switch in to choose between a stock 47k resistor and the 33k I put in.
I like it a lot. I am really pleased with the outcome.


Did you notice if it smoothed out the gritty or "disjointed" high end of the 20? I'm trying to smooth out the highs on my 20H without totally castrating the amp, but I've been so busy that I haven't had a chance to get to it.

Also, if you want to convert it to 240v, you may need to replace the PT, unless the leads are on the PT already, but suspended inside the amp somewhere. :idk:


it boosted the mids, and gave a more midrange tone, but i only tried it quickly and didn't crank it. i found with a cap across the feedback resister helped smooth mine a little.

The leads are in there on the PT there are about 4 to 6 of them unplugged so i am guessing a universal PT (at least I hope). I will contact Jet city and see what they say.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Jay »

neilrocks25 wrote:
Jay wrote:
neilrocks25 wrote:I just did the tone stack mod, to give it more of an aggressive Marshall midrange. I put a switch in to choose between a stock 47k resistor and the 33k I put in.
I like it a lot. I am really pleased with the outcome.


Did you notice if it smoothed out the gritty or "disjointed" high end of the 20? I'm trying to smooth out the highs on my 20H without totally castrating the amp, but I've been so busy that I haven't had a chance to get to it.

Also, if you want to convert it to 240v, you may need to replace the PT, unless the leads are on the PT already, but suspended inside the amp somewhere. :idk:


it boosted the mids, and gave a more midrange tone, but i only tried it quickly and didn't crank it. i found with a cap across the feedback resister helped smooth mine a little.

The leads are in there on the PT there are about 4 to 6 of them unplugged so i am guessing a universal PT (at least I hope). I will contact Jet city and see what they say.


Sounds about right. The PT I removed from a 50H and the one in my 20H have two white leads, a black, brown, blue and red lead.

I put a 470p cap across the NFB and it did smooth out the tone, but I'd like a little more. :) I like aggressive tone, but not quite as gritty.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by neilrocks25 »

well after a week of playing the Tone stack mod sounds the tit's, I am loving it.
It really pushes the midrange and gets rid of some of the high end fizz.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Jay »

Nice. I'm going to have to give that a whirl. I'm fooling around with a few caps and resistors in the coupling networks to dial out some of the additional grit, but without neutering the tone/harmonics/etc. So far it's coming along well.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Tortuga »

Would love to hear what you think about that simple slope resistor change, Jay. It's really great to be able to select between that and stock, so you can go from a looser tone with a lot of 'feel' to it to a tighter, more focused tone.

Glad it's working for you, Neil. Hope it makes the move with you. It's good having you on the JCA team! :thu:
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Jay »

I'm going to order a few knick-nacks this weekend, so I'll definitely give it a go. I need to replenish my stock of good resistors and caps. Been using radio shack specials for fillers. :D
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by neilrocks25 »

GRIMESPACE wrote:Would love to hear what you think about that simple slope resistor change, Jay. It's really great to be able to select between that and stock, so you can go from a looser tone with a lot of 'feel' to it to a tighter, more focused tone.

Glad it's working for you, Neil. Hope it makes the move with you. It's good having you on the JCA team! :thu:


Yeah the selection switch makes a world of difference.
If I can't bring my amp I will get another second hand and mod that too :)
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by mean_charlie »

hello fellow jet city amplification fans hopefully somebody here might have a clue to whats going on with my amp. so i have a jca 5212rc and its freaking awesome although recently the reverb has quit working and it just buzzes the more reverb i add the louder the buzz alittle bit of the guitar will come through but its greatly diminished once i turn the reverb off with the foot switch the buzz stops and the guitars volume goes back to normal i have checked the reverb tank and its good and so are the rca cables connecting it and i have no idea where to go from there and taking it to the shop is not happening as i wont be able to splurge on something like that for some time so any help or suggestions are greatly appreciated thanks
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Motocooney »

Hey Dudes...

Jay,
I actually blew the OT on my JCA100, I'm getting an "Upgraded SLO Spec" OT from Heyboer.
Turns out, they're about 30 miles away from me. $150. Custom wind, drop in.

I would like to run el34Bs in this thing. Even though Ive been running the 33k slope for about a year now.
In fact, I had it on a switch with the stock slope for a while. Hmmm, good idea;)

To run EL34Bs, aside from the OT, re-bias and changing screen grid resistors from 470ohm to 1k, what else needs to be done. Is the stock PT stout enough to run these tubes?

Nice to see you guys moved the party to a better forum.
I kinda forgot about the Harmony Central thread. Even though I was obsessed with modding this thing last year!

Having my JCA down has me fucking with my other cheap-copy amp. Bugera 6262.
Turns out, it's fantastic with a little love under the hood. A few simple changes and the thing sings.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by neilrocks25 »

mean_charlie wrote:hello fellow jet city amplification fans hopefully somebody here might have a clue to whats going on with my amp. so i have a jca 5212rc and its freaking awesome although recently the reverb has quit working and it just buzzes the more reverb i add the louder the buzz alittle bit of the guitar will come through but its greatly diminished once i turn the reverb off with the foot switch the buzz stops and the guitars volume goes back to normal i have checked the reverb tank and its good and so are the rca cables connecting it and i have no idea where to go from there and taking it to the shop is not happening as i wont be able to splurge on something like that for some time so any help or suggestions are greatly appreciated thanks
mean_charlie

Is the reverb tube driven, like it is on the JCA2112rc? if so ty changing the reverb tube, if you have not already i would get replacement tubes for the whole thing as the stock ones are not so good.
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Gibson les paul Traditional, les Paul signature T, U.S strat, Japanese Strat , 1970s Greco Tele, Charvel So-Cal Pro Mod style 1, Fernandes TEJ-85, 70's Greco tele. Marshall JVM 205c (Dan Gower modded), JCM900 SL-X, some pedals, Yamaha THR10


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

Post by Jay »

Motocooney wrote:Hey Dudes...

Jay,
I actually blew the OT on my JCA100, I'm getting an "Upgraded SLO Spec" OT from Heyboer.
Turns out, they're about 30 miles away from me. $150. Custom wind, drop in.

I would like to run el34Bs in this thing. Even though Ive been running the 33k slope for about a year now.
In fact, I had it on a switch with the stock slope for a while. Hmmm, good idea;)

To run EL34Bs, aside from the OT, re-bias and changing screen grid resistors from 470ohm to 1k, what else needs to be done. Is the stock PT stout enough to run these tubes?

Nice to see you guys moved the party to a better forum.
I kinda forgot about the Harmony Central thread. Even though I was obsessed with modding this thing last year!

Having my JCA down has me fucking with my other cheap-copy amp. Bugera 6262.
Turns out, it's fantastic with a little love under the hood. A few simple changes and the thing sings.


Oh hey, man! Glad you came to join the party. Heyboer is 30 miles from you? That's awesome. If they can make the Transformers as a drop-in, no chassis modification needed, then that would be awesome. When I emailed them, it sounded like they could, but I never got around to doing it. Been a bit busy lately.

To run EL34s, you would need to ground pin 1 on the power tubes sockets for the suppressor grid. I do not know for sure if the PT can handle the extra current on the heaters. Some of the custom shop JCAs can use EL34s, but I have not heard if any upgrades were done to the windings in the PT or not. You may be able to get away with using KT77s, though. Since they are a tetrode, you would not need to do the pin 1 connection, and they draw a tiny bit less heater current than an EL34, so you might be fine with those. Half-6L6, half-EL34. JJ and Gold Lion make the KT77s. I used the JJs in a few different Mesas and my Splawns. Great tube.
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Re: JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

Post by Motocooney »

Well I already ordered the Ruby EL34b

Also I just noticed back a few pages that Grimespace post a video of mike soldano running different tubes in a JCA50. Unfortunately, my connection is too slow to watch it at the moment.

What's up with that video?

Well either way, it sounds doable.

So you got a JCA22h?
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