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

[midnightlaundry]

Yeah, they we not matched!

I put in new JJ's, which were matched within 1 ma.

But this amp just has a lot of AC ripple that really comes out with the volume up.

[marnold]

New here with new JCA 2212. Question to all who have played one:

RE: the drive tones of the amp, (either channel) is there an inherent harsh/fizzy sizzle to the high end similar to a solid state distortion/or a software based amp model with cab IR bypassed?

I thought that my original JCA20H was a bit fizzy. When I replaced the tubes with JJs, that went away. The difference was somewhat subtle, but noticeable.

I have not noticed the fizziness so much on my new JCA22H.

[Tortuga]

New here with new JCA 2212. Question to all who have played one:

RE: the drive tones of the amp, (either channel) is there an inherent harsh/fizzy sizzle to the high end similar to a solid state distortion/or a software based amp model with cab IR bypassed?

I thought that my original JCA20H was a bit fizzy. When I replaced the tubes with JJs, that went away. The difference was somewhat subtle, but noticeable.

I have not noticed the fizziness so much on my new JCA22H.

Glepko - what's the latest?

[Promit]

Since somebody brought it up -- the Jet City amps, like mainly amps, will safely drain their own caps when you turn the power switch OFF while leaving the standby switch ON. I've checked the high voltage traces with a meter after doing their and they're clear. I do recommend checking the voltages before touching anything no matter how you choose to drain the caps.

As far as fizziness -- better tubes, don't over-scoop the mids, and the fizz will be dramatically reduced as you progressively open up the master volume.

[Tortuga]

Since somebody brought it up -- the Jet City amps, like mainly amps, will safely drain their own caps when you turn the power switch OFF while leaving the standby switch ON. I've checked the high voltage traces with a meter after doing their and they're clear. I do recommend checking the voltages before touching anything no matter how you choose to drain the caps.

As far as fizziness -- better tubes, don't over-scoop the mids, and the fizz will be dramatically reduced as you progressively open up the master volume.

I've noticed the self-discharge effect as well, and verified that there are drain resistors in place - at least on my JCA50H. However, I still do connect the tool I use to discharge the caps and leave it in place while I'm doing work in the chassis. You said it, but I'm going to repeat - no one should ever assume that they are safe to work inside the chassis by simply turning the amp off and expecting the caps to discharge themselves, and stay discharged.

[midnightlaundry]

New here with new JCA 2212. Question to all who have played one:

RE: the drive tones of the amp, (either channel) is there an inherent harsh/fizzy sizzle to the high end similar to a solid state distortion/or a software based amp model with cab IR bypassed?

I thought that my original JCA20H was a bit fizzy. When I replaced the tubes with JJs, that went away. The difference was somewhat subtle, but noticeable.

I have not noticed the fizziness so much on my new JCA22H.

I changed the rectifier diodes to UF5408's. That went a long way in cutting the buzzy fizz in the background.

[Tortuga]

New here with new JCA 2212. Question to all who have played one:

RE: the drive tones of the amp, (either channel) is there an inherent harsh/fizzy sizzle to the high end similar to a solid state distortion/or a software based amp model with cab IR bypassed?

I thought that my original JCA20H was a bit fizzy. When I replaced the tubes with JJs, that went away. The difference was somewhat subtle, but noticeable.

I have not noticed the fizziness so much on my new JCA22H.

I changed the rectifier diodes to 1N5408's. That went a long way in cutting the buzzy fizz in the background.

I've got quite a bit of hum / buzz going on with my amp. I was thinking that some of it would be caused by my not having the metal tube covers on. Does that make a big difference? If not, do you think it'd be worth changing out my diodes?

[midnightlaundry]

New here with new JCA 2212. Question to all who have played one:

RE: the drive tones of the amp, (either channel) is there an inherent harsh/fizzy sizzle to the high end similar to a solid state distortion/or a software based amp model with cab IR bypassed?

I thought that my original JCA20H was a bit fizzy. When I replaced the tubes with JJs, that went away. The difference was somewhat subtle, but notceable.

I have not noticed the fizziness so much on my new JCA22H.

I changed the rectifier diodes to UF5408's. That went a long way in cutting the buzzy fizz in the background.

I've got quite a bit of hum / buzz going on with my amp. I was thinking that some of it would be caused by my not having the metal tube covers on. Does that make a big difference? If not, do you think it'd be worth changing out my diodes?

UF5408's are rated at 1000 volts and are beefy as fuck. What they will do is a better job of converting AC to DC. In other words, there will be less switching noise thats amplified throughout the whole amp which can be attributed to as buzz and hash noise.

See, diodes only conduct electricity 1 way, so when AC current flips, the diode will clamp, preventing current flow in the other direction. This switching can be heard in the audio. In some amps, this switching contributes to the amp sound in highend content. But I think the JCA's have enough highend, so adding the diodes will purify the tone a bit, allowing you to add more tone control.

If you don't like it, you can always change it back. Diodes are cheap.

I'll post pics tomorrow.

[Tortuga]

New here with new JCA 2212. Question to all who have played one:

RE: the drive tones of the amp, (either channel) is there an inherent harsh/fizzy sizzle to the high end similar to a solid state distortion/or a software based amp model with cab IR bypassed?

I thought that my original JCA20H was a bit fizzy. When I replaced the tubes with JJs, that went away. The difference was somewhat subtle, but notceable.

I have not noticed the fizziness so much on my new JCA22H.

I changed the rectifier diodes to 1N5408's. That went a long way in cutting the buzzy fizz in the background.

I've got quite a bit of hum / buzz going on with my amp. I was thinking that some of it would be caused by my not having the metal tube covers on. Does that make a big difference? If not, do you think it'd be worth changing out my diodes?

1N5408's are rated at 1000 volts and are beefy as fuck. What they will do is a better job of converting AC to DC. In other words, there will be less switching noise thats amplified throughout the whole amp which can be attributed to as buzz and hash noise.

See, diodes only conduct electricity 1 way, so when AC current flips, the diode will clamp, preventing current flow in the other direction. This switching can be heard in the audio. In some amps, this switching contributes to the amp sound in highend content. But I think the JCA's have enough highend, so adding the diodes will purify the tone a bit, allowing you to add more tone control.

If you don't like it, you can always change it back. Diodes are cheap.

I'll post pics tomorrow.

I knew about diodes from my short-lived electronics education (clear back in the 80's ) and how they can be setup as a rectifier. I didn't realize that the current passing then stopping would actually make noise in the circuit, but that makes total sense the way you put it. Thanks for that! I'll definitely put in on my short-list of things to do next with the amp. Would love to see the pics of what yours looks like.

[midnightlaundry]

Dude, I knew these were UF5408's Ultra Fast recovery diodes. I just forgot the real part number. The ARE UF5408's..

I went with 225P tone and coupling caps, an external bias pot that I use with an Eurotubes Pro Ine Bias Probe, and the UF5408's. I might go with some Silver Micas over the stock ceramics latter on.

Here's some pics. Dig my clumsy burn marks..

[flowmastergfunk]

Hey group! I have been the proud owner of a JCA20H for a couple of years now. I have stalked the old HC forum over the last year, checking out mods, reading feedback and plotting my "attack" to mod this amp, but just finally found a link to this forum yesterday. Compared to the 60 some-odd pages of the other form, this thread looks less intimidating, and I feel I will have more intimate feedback and discussion here. I would like to shed a little light on how I found my JCA, what I look for in an amp, the tone I feed into and where I stand.

I have a '79 anniversary strat. Swamp ash body, lil'59 in the neck, old school hot rail in the middle, Screamin' Demon in the bridge. It is a hot little number, but it has a good deal of versatility. I have had this guitar since I was in high school, but when I bought it, it had hotrails in all 3 slots.

My first amp that I fell in love with (and swore I would never sell) was a 69 bassman silver face. That was when I developed my "start clean, add dirt" mentality. I had two different cabs I played it with. Started with a 2x12 Peavey Scorpion cab (which I miss) and a Carvin 2x12 Legacy cab with v30's (which I miss). Maybe it's in the name, but I loved the jazzy cleans and bass response through that head with either cab. I still hold the Scorpions in high regards.

Down the line, playing with a louder band, I did the unthinkable. I needed moar loud

I had also had a Peavey Vintage 30 as a practice amp in my early years, and LOVED the overdrive.
So I figured, if I got a Vintage 50 410. Much louder, had my fun, but never got the bass response that I wanted out of it. Ended up taking the amp out of the combo, sealed the 410...little better. Tried playing though a 1x15cab that I put a Jensen neo speaker in it. Better, but still wasn't what I was looking for. I was not about to spend a small fortune experimenting and buying four speakers at a time, so I figured it was best to put the combo back together, sell it, and find something new.

I got the call off craigslist offering a partial trade with the JCA20h. I had never heard of them, and thought it was some kind of joke...but dude told me...you gotta hear it. Then he started talking about a CAE Line Driver that he wanted to include in the trade...and again...I really didn't think I was interested. So he brought them both over, and started playing through the 1x15. Fell in love.
I didn't understand why he wanted to get rid of it, and he told me he didn't haha. The Peavey was just more fitting to what he was doing at the time (moar loud, moar twang). The deal was done.

Cab wise, I went back and forth between the 1x15 and a vertical Tubeworks 2x12 that had an open back eminence in the top, closed back with a JBL in the bottom. Again, the time came to sell one or the other, so I kept the Tubeworks, due to my love for the JBL. The JBL was a 8 ohm woofer that I had removed from a decrepit-spare Century L-100. I had a nice set (stolen) that I had for years, and I knew darn well how good the bass response was in those monitors!

My quest for low end continued, but I knew there was more to be had. It would just take time, research, experimentation and a bit of money

The next obvious step was tubes. I have a set of Mullard 12ax7/ecc83's that have landed in v1 and v3, a 12ax7EH in v2, and a sweet set of Sovtek el84/6bq5. Much mo' betta. Night and day difference. Fuller, warmer, more clean headroom, and it still wailed it I wanted to dime the gain.

Not too long after, I decided to ditch the 2x12 and pick up a solid 1x12 cab locally. Put the JBL in the 1x12, found more warmth. More punch.

A few days ago, I saw another early model on craigslist (metal toggles), and picked it up for $120 and a ts-808 clone. I won't be able to live without the 808 for too long, but couldn't pass on the deal!

I am a beyond confident in my soldering skills, but have not been brave enough to "test" random, word of mouth schematics on line. I plan on doing the depth mod myself, but didn't want to dive into the "clean" mod without being able to hear a real world example of how it sounded. I know a fair deal of electrical theory, but I am not a guru. I can't look at a cap value and say, " oh yeah! Put that right there and it will bring out _____ frequency"

In my last stretch research, I saw a "Verellen" mod out of the corner of my eye. I had just met Ben Verellen last month when his band, Helms Alee, was playing here with Russian Circles. That man KNOWS tone! Turns out, he did a full clean mod that was available directly through the Jet City website years ago! I have been in touch with him this week, and plan on sending him one of the amps to work his magic. I know I could do the work myself, but I am more than happy to pay for his wizardry and mojo. He is a great guy, and I am happy to give him my support. The check I am going to send him for my JC overhaul is a STEAL, since a $2500 bill for a Meatsmoke head is a litttttle out of my range these days haha.

I am excited to have a modded amp to sit next to a bone stock amp for a side by side tasted test! After the comparison, the next question....do I have an A/B rig for a full clean full dirty setup, or do I replicate the modded amp and run twins in stereo, and rely strictly on my dirt pedals

Sorry for the lengthy intro, but happy to be part of the group! I am only on page 6 of this thread, but I should be caught up soon. Here is a picture of my current rig for good measure. Cheers!
Greg

[Tortuga]

@midnightlaundry - great pics, and much appreciated! Really like that you covered the external bias adjust as well. I'm wanting to do that, along with putting in a set of external bias test points. I take it that all the orange caps seen on the board are the ones you replaced. Did they make a huge difference? Any chance of a list of cap ID #s, and did you alter any of the values?

@flowmastergfunk - welcome! Standard response for getting the most from your JCA: tubes and bias first, then assess what you're looking for before digging into mods. I really liked the results from the depth control and making a switchable slope resistor in the tone stack. I did the clean mod on my JCA50H, but was really surprised at how drastic a volume drop I get when I turn it on. I'm having to compensate by cranking the crunch channel master - gawd help my ears if I kick the clean switch back off without bringing the channel master back down first. I'm not certain what that means for you, since you've got a single channel amp, but I'm guessing it's not going to be something that you can expect to flip on and off without a corresponding change in master volume, and I'd think your max volume with the clean switch engaged would be quite low. Not a huge mod to try out - just be somewhat cautious with your expectations.

[glepko]

Here are more impressions after a few more hours with the 2212, with lots of playing/tweaking/playing. Then more playing/tweaking/playing. A day of rest followed by more playing/tweaking/playing:

RE the fizzle: The primary frequencies of nuisance for me are between 3-4k. A judicial cut with EQ in the loop reduces the fizz. However - opening up the volume does the same thing, much to my surprise. The low end grows into too much when letting the master section work - that's a good thing. Very pleasant surprise with that. Gorgeous with mid gain on crunch right through ripping high gain on overdrive channel.

Now then, that solution, as fun as it may be, is not right for me. I can't bear being in the same room with it at those volume levels. I have never played with that much volume - not in practicing, not in performing. My compromise is a multi-effects in the loop with the send level decreased. It's not perfect, but it does help.

I've noticed as the amp heats up, the fizzle increases. A hum comes and goes with heat as well. Reminds me of a problematic old Dual Showman head I owned for too long.

I'm considering a set of EL844's and curious on anyone's experience with them? Do they sound similar and is there an appreciable decrease in output? This amp is seriously too loud when operating at settings which sound best to me for the tone I want to use.

[midnightlaundry]

I used the stock values. I replaced all coupling, and cathode bypass caps (.022uf-1uf) with 225P's. I got them from Mouser.

http://www.mouser.com/Search/ProductDet ... 5P22394XD3

http://www.mouser.com/Search/ProductDet ... 5P10591YD3

The 1uf caps are huge, but I soldered them on top and bottom. Same with the .022's, so no worries. Go over your amp and reflow and add more solder to your connections, especially on the tube sockets top and bottom as these amps seem to be light on the solder. It will be more reliable.

Polyester caps are arguably less harsh and more complex in the mids because polyester isn't the perfect dielectric, so there's color to the sound whereas a 715P/716P is more sterile and hifi. I built an amp where I used 716P's, and then switched to 6PS caps which are Polyesters just like 225P's, and the difference was noticeable. There was a difference in the JCA in that the cracks seem to be more filled in if that makes sense.

[atrox]

I apologize for not reading this entire thread. I had a JCA100 for a while and i loved it. FX loop pissed me off though.

Does the 22H have the same FX loop or is it instrument level?

[ironman28]

RE the fizzle: The primary frequencies of nuisance for me are between 3-4k. A judicial cut with EQ in the loop reduces the fizz. However - opening up the volume does the same thing, much to my surprise. The low end grows into too much when letting the master section work - that's a good thing. Very pleasant surprise with that. Gorgeous with mid gain on crunch right through ripping high gain on overdrive channel.

There is an known problem with master volume controls that connect the wiper of the master volume pot to the input of the PA section. This is common on all the JCA amps. The master volume, in combination with the PA input capacitor,becomes a high pass filter at low settings on the master. This gives a thin, fizzy sound with the master set below 3-4. You open up the master and the low end jumps up. The fix is easy, one 100k resistor in series with the MV wiper restores the low end below 3-4 on the master. I find this far more effective than the standard "depth" mod to restore lows and it only takes one resistor.

[ironman28]

I apologize for not reading this entire thread. I had a JCA100 for a while and i loved it. FX loop pissed me off though.

Does the 22H have the same FX loop or is it instrument level?

The 22 schematic shows a post master FX loop with lower levels. Not quite "instrument level" or -20dbv. But that's a lot lower than the +4dBu loop on the JCA50/100. The problem is there are no adjustments to match the loop to your FX.

[Tortuga]

RE the fizzle: The primary frequencies of nuisance for me are between 3-4k. A judicial cut with EQ in the loop reduces the fizz. However - opening up the volume does the same thing, much to my surprise. The low end grows into too much when letting the master section work - that's a good thing. Very pleasant surprise with that. Gorgeous with mid gain on crunch right through ripping high gain on overdrive channel.

There is an known problem with master volume controls that connect the wiper of the master volume pot to the input of the PA section. This is common on all the JCA amps. The master volume becomes a high pass filter at low settings on the master. This gives a thin, fizzy sound with the master set below 3-4. You open up the master and the low end jumps up. The fix is easy, one 100k resistor in series with the MV wiper restores the low end below 3-4 on the master. I find this far more effective than the standard "depth" mod to restore lows and it only takes one resistor.

Whoa - any potential drawbacks to this mod? Will it reduce the max volume potential of the amp if it's cranked? Should this be done to both masters (on the dual channel amps)?

[glepko]

There is an known problem with master volume controls that connect the wiper of the master volume pot to the input of the PA section. This is common on all the JCA amps. The master volume becomes a high pass filter at low settings on the master. This gives a thin, fizzy sound with the master set below 3-4. You open up the master and the low end jumps up. The fix is easy, one 100k resistor in series with the MV wiper restores the low end below 3-4 on the master. I find this far more effective than the standard "depth" mod to restore lows and it only takes one resistor.

ironman - Thank you very much for this reply. This is perfect, and exactly what I am looking for. I know it's accurate advice as the effect of turning up became very apparent at between 4-5 for me, and from 5-6 is perfect.

I was considering the depth mod, but nope. I can handle this one with parts on hand even. Cool

[ironman28]

RE the fizzle: The primary frequencies of nuisance for me are between 3-4k. A judicial cut with EQ in the loop reduces the fizz. However - opening up the volume does the same thing, much to my surprise. The low end grows into too much when letting the master section work - that's a good thing. Very pleasant surprise with that. Gorgeous with mid gain on crunch right through ripping high gain on overdrive channel.

There is an known problem with master volume controls that connect the wiper of the master volume pot to the input of the PA section. This is common on all the JCA amps. The master volume becomes a high pass filter at low settings on the master. This gives a thin, fizzy sound with the master set below 3-4. You open up the master and the low end jumps up. The fix is easy, one 100k resistor in series with the MV wiper restores the low end below 3-4 on the master. I find this far more effective than the standard "depth" mod to restore lows and it only takes one resistor.

Whoa - any potential drawbacks to this mod? Will it reduce the max volume potential of the amp if it's cranked? Should this be done to both masters (on the dual channel amps)?

With a 1M master and a 100k series resistance you lose 10% of the signal at full volume but by that time your power amp is well into clipping. Its all relative anyway like knobs that go to 11. if you need that extra 10% to push you over the cliff then you probably don't set your master to 2. JCA amps only go to 9 anyways If you have a 500k master try a 47k. I have used as high as 220k on some amps. If you routinely run the master above 5 this mod will not be noticeable. You only need to install one resistor at the PA input in series with the input cap for dual masters.

[glepko]

Happen to have a quick link to schematic, or a photo handy? What is the PA input? So many pages of comments in threads I can' remember where the good schematics for the 2212 are

[Tortuga]

RE the fizzle: The primary frequencies of nuisance for me are between 3-4k. A judicial cut with EQ in the loop reduces the fizz. However - opening up the volume does the same thing, much to my surprise. The low end grows into too much when letting the master section work - that's a good thing. Very pleasant surprise with that. Gorgeous with mid gain on crunch right through ripping high gain on overdrive channel.

There is an known problem with master volume controls that connect the wiper of the master volume pot to the input of the PA section. This is common on all the JCA amps. The master volume becomes a high pass filter at low settings on the master. This gives a thin, fizzy sound with the master set below 3-4. You open up the master and the low end jumps up. The fix is easy, one 100k resistor in series with the MV wiper restores the low end below 3-4 on the master. I find this far more effective than the standard "depth" mod to restore lows and it only takes one resistor.

Whoa - any potential drawbacks to this mod? Will it reduce the max volume potential of the amp if it's cranked? Should this be done to both masters (on the dual channel amps)?

With a 1M master and a 100k series resistance you lose 10% of the signal at full volume but by that time your power amp is well into clipping. Its all relative anyway like knobs that go to 11. if you need that extra 10% to push you over the cliff then you probably don't set your master to 2. JCA amps only go to 9 anyways If you have a 500k master try a 47k. I have used as high as 220k on some amps. If you routinely run the master above 5 this mod will not be noticeable. You only need to install one resistor at the PA input in series with the input cap for dual masters.

This is really cool. Definitely on my list of things to try next time I open the chassis.

[Tortuga]

Happen to have a quick link to schematic, or a photo handy? What is the PA input? So many pages of comments in threads I can' remember where the good schematics for the 2212 are

Just made a new documentation thread for the 22H / 2212, including the schematics I have. http://www.guitarampboard.com/forum/viewtopic.php?f=53&t=12372 They're not great, but it's a start...

Also, for anyone reading this, I've been trying to keep the important threads noted on the first 3 posts of this thread (page 1). I'll be adding the 22H stuff momentarily.

[thesockmonster]

Figured I'd check with you lot before going nuts. Just took in a new JCA5012c....loving it, although the crunch channel died on on day two. No sound, no output. Multiple guitars, multiple cables - OD channel is just fine. Any ideas? Thought about tubes, but I'm not sure on the layout for the preamp.

[ironman28]

Figured I'd check with you lot before going nuts. Just took in a new JCA5012c....loving it, although the crunch channel died on on day two. No sound, no output. Multiple guitars, multiple cables - OD channel is just fine. Any ideas? Thought about tubes, but I'm not sure on the layout for the preamp.

Based on the JCA50 schematic:


First half of V1 used by Crunch and OD
2nd half of V1 used by Crunch only
V2 used for OD only
V3 and V4 are common to Crunch and OD

V1 is closest to the input jack. Try replacing that first.