Jca20H Mod thread and owners club.

[drmrboy5150]

The Saturation Switch is basically a jose mod on a switch. A couple of 1N4747 zener diodes in parallel with a 1M resistor. I'm still playing with the resistor and diode values so I'll post a schematic when I get it right.

[Edge11]

The saturation switch is just a jose master. Also I posted up a bit of a picture instructional to doing the depth mod for the dogger, I'll post it up later.

[Edge11]

Originally Posted by pioneerprogress

just curious...I don't know jack about the "depth mod"...is it possible to make it switchable?
Also, now a proud owner...see sig

Just set the thing on zero and its out of the circuit.

[waswell]

Proud owner of a JCA2112RC.

I would like more clean and thought a 12AU7 in V1 and V3 might work. Maybe that's too drastic.

Any thoughts?

[ledvedder]

Originally Posted by thehephaistos

Hi JCA owners,

I tried a Fx loop schematic I found on this site http://www.blueguitar.org/new/schem/...od/fx_loop.gif.

It's not finished yet but I played it with a delay and my loop station and it sounds really good.
I'm not a wizard in electronics, so maybe it's not a good idea to use this schematic, but it worked for me...

Here is a picture of the thing.(the hole in the amp are from a iron sound Fx loop kit I have, but it was altering the sound in my opinion)
[ATTACH=CONFIG]328613[/ATTACH]

Can you provide some instructions for this mod? I'm not that great at reading schematics.

[Edge11]

Originally Posted by waswell

Proud owner of a JCA2112RC.

I would like more clean and thought a 12AU7 in V1 and V3 might work. Maybe that's too drastic.

Any thoughts?

Do the clean channel mod.

[waswell]

 

Originally Posted by mblooper45

Do the clean channel mod.

 

I would like to hear a sound sample of the clean mod before I drill into the chassis. Anybody have one?

[Edge11]

its on the first page of this thread mate.

[AHNUBISAKI]

Today I bought the Jetstream Iso cab from MF. Anyone got experience using this with the JCA20?

[jaha777]

Originally Posted by thehephaistos

Hi JCA owners,

I tried a Fx loop schematic I found on this site http://www.blueguitar.org/new/schem/...od/fx_loop.gif.

It's not finished yet but I played it with a delay and my loop station and it sounds really good.
I'm not a wizard in electronics, so maybe it's not a good idea to use this schematic, but it worked for me...

Here is a picture of the thing.(the hole in the amp are from a iron sound Fx loop kit I have, but it was altering the sound in my opinion)
[ATTACH=CONFIG]328613[/ATTACH]

Hi, did you try the loop with classics stomboxes? If yes, didn't you have a problem with too strong singnal going to the stomboxes?

[333]

Can the saturation switch be used without the be mod. erikm5150 posted a schem. mblooper45 do think i would use the pre tonestack detail? Or better off to use dues. crunch channel mod.

[waswell]

Originally Posted by mblooper45

its on the first page of this thread mate.

Don't know how I missed it.

Thanks for all your help and have a great day.

Sincerely,
Waswell

[thehephaistos]

Originally Posted by jaha777

Hi, did you try the loop with classics stomboxes? If yes, didn't you have a problem with too strong singnal going to the stomboxes?

Hi, I don't know what you mean by classic stomboxes? I have just tried with my delay pedal. The signal is quite strong, but the pots did the work OK to reduce it.

Ledveder, I can post a vero layout in the next days if you're interested.

[O'Rourke]

Originally Posted by SHinybulldozer

hey guys! i just got this amp (jca2112 version) and im very happy with the sound in general. however the gain can get way to saturated for my style of playing which is mostly heavy electric blues. first thing im doing with it is taking it apart of course to start re-voicing the gain structure a little bit. Thus i worked long and hard(5minutes *cough*) to create a very simple tool to calculate gains for me using various tubes, plate resistors, and cathode resistors. and decided to share, ive found it super useful already.
Here or Here.

you'll need the latest dotnet framework from microsoft for it work, get it here

heres a couple pics...




didnt mean to derail the topic, or if i broke rules XD

great fricken amp!!!

Links are down, could somebody upload this?

[SHinybulldozer]

Originally Posted by O'Rourke

Links are down, could somebody upload this?

it looks like they kicked it off the site >.> must be due to inactivity or something.

ill get it up really really quick. im redoing it really quickly so it doesnt require the latest dotnet installed (most people dont have, or have a clue on how to get).

Here is the link. just click download.

[jaha777]

Originally Posted by thehephaistos

Hi, I don't know what you mean by classic stomboxes? I have just tried with my delay pedal. The signal is quite strong, but the pots did the work OK to reduce it.

Ledveder, I can post a vero layout in the next days if you're interested.

Hi,

by classic stopboxes I meant guitar pedals like boss, ibanez, danelectro and many others are doing. Not rack mounted effect units that are designed to accept stronger input. I suupose dry signal from the send would be too strong for 9volt powered pedals. So my question is when you lower effects send level doesn't it make amp quiter? because I cant see anything that would boost the signal back to the level as it was before you lowered it by send level pot?

[SHinybulldozer]

Originally Posted by jaha777

Hi,

by classic stopboxes I meant guitar pedals like boss, ibanez, danelectro and many others are doing. Not rack mounted effect units that are designed to accept stronger input. I suupose dry signal from the send would be too strong for 9volt powered pedals. So my question is when you lower effects send level doesn't it make amp quiter? because I cant see anything that would boost the signal back to the level as it was before you lowered it by send level pot?

The return pot out in front will boost the signal back to the level you choose. looking at the values and considering the tube is a 12au7(looooooowww gain) it looks like you can boost the signal return by about 10 (gain around 10db). this means to you that everything sent into the return path is amplified roughly 10 times till cutoff. this should be enough to recover from any effect chain without amplifying noise to badly, unless its out of hand already XD.

I know what alot of people are thinking, GAIN!!!. no dont put a higher gain tube in there. a 12ax7 would give you about 25 gain (28db) which will most likely overdrive if the return signal is too high or the pot isnt cutting the signal enough.

[thehephaistos]

Originally Posted by SHinybulldozer

The return pot out in front will boost the signal back to the level you choose. looking at the values and considering the tube is a 12au7(looooooowww gain) it looks like you can boost the signal return by about 10 (gain around 10db). this means to you that everything sent into the return path is amplified roughly 10 times till cutoff. this should be enough to recover from any effect chain without amplifying noise to badly, unless its out of hand already XD.

I know what alot of people are thinking, GAIN!!!. no dont put a higher gain tube in there. a 12ax7 would give you about 25 gain (28db) which will most likely overdrive if the return signal is too high or the pot isnt cutting the signal enough.

I totally agree with you, actually, I didn't have an AU7 so I put an AT7 instead . The pots are quite hard to adjust, but yesterday I added a bypass and managed to have comparable signal between stock/Loop .

I played for a while today, the sound was good and my amp didn't burn

jaha777, OK so I only have classic stompboxes a cheap delay, a nano clone chorus and a holy grail. everything is OK with these in the loop.

I'll try to make a video this weekend.

[O'Rourke]

Originally Posted by SHinybulldozer

it looks like they kicked it off the site >.> must be due to inactivity or something.

ill get it up really really quick. im redoing it really quickly so it doesnt require the latest dotnet installed (most people dont have, or have a clue on how to get).

Here is the link. just click download.

Thanks man, cool program for sure!

[ledvedder]

 

Originally Posted by thehephaistos

Ledveder, I can post a vero layout in the next days if you're interested.

 

Yes, I'm very interested. Thanks!

[SHinybulldozer]

Originally Posted by thehephaistos

I totally agree with you, actually, I didn't have an AU7 so I put an AT7 instead . The pots are quite hard to adjust, but yesterday I added a bypass and managed to have comparable signal between stock/Loop .

I played for a while today, the sound was good and my amp didn't burn

jaha777, OK so I only have classic stompboxes a cheap delay, a nano clone chorus and a holy grail. everything is OK with these in the loop.

I'll try to make a video this weekend.

if by "hard" you mean very very touchy then its gonna be cuz of the gain of the tube. 12at7 are a high mu tube with a gain something like 60. just swapping it into the circuit will give you twice as much gain, around 24 (27db???) compared to the 10. also notice that the 12at7 would also be biased wrong, well not completely wrong... but really not very well ether. this may result in asymmetric clipping (alot of people like this but not in a effect loop) or premature clipping among other problems. since the tube isnt running at its "correct" operating point you really dont experience the flavor of the tube ether.

if you would like your 12at7 to have the same gain as a 12au7 you can get that by increasing the cathode resistor to 5.6k to 8.2k from 2.2k on the return half. this will drop the gain of the return down a little bit so its not as sensitive. imo id recommend the 12at7 compared to the 12au7, the fact is the 12au7 is operating very very close if not on the non linear region, but using a 12at7 as you are and dropping the return gain a tad to prevent overdrive (using boost pedals??) allows you to run in a more linear region. on the other hand if you keep the cathode resistor you can use the return as an extra gain stage.

but as with most things musical, whats right in theory is usually bad for the tone...

[drmrboy5150]

Yes, the Saturation Switch can be used without the BE mod. It is basically the jose master volume mod with a 1M resistor instead of a pot.

[butterguitar]

To mod or not to mod?

Ok guys, I have been thinking if I were to want to get any mods to this amp, what mods should I do?

I would love maybe just a little bit extra gain on tap, maybe a solo boost of some sort.
I also feel the bottom end can be tighened up a tad (just to my taste).

I haven't performed any mods to any tube amp, and I am curious on how it's done. Granted, I know how to check and set bias, and replace tubes, but that's about it on tube amps.

The only guy who I found that does mods for this amp is a guy named Jerry for FJAmods, anyone know if his mods are any good?

Or will I be much better off (like I think I will be) with just purchasing the Jet City afterburner boost and call it a day

[SHinybulldozer]

Originally Posted by butterguitar

To mod or not to mod?

Ok guys, I have been thinking if I were to want to get any mods to this amp, what mods should I do?

I would love maybe just a little bit extra gain on tap, maybe a solo boost of some sort.
I also feel the bottom end can be tighened up a tad (just to my taste).

I haven't performed any mods to any tube amp, and I am curious on how it's done. Granted, I know how to check and set bias, and replace tubes, but that's about it on tube amps.

The only guy who I found that does mods for this amp is a guy named Jerry for FJAmods, anyone know if his mods are any good?

Or will I be much better off (like I think I will be) with just purchasing the Jet City afterburner boost and call it a day

MOD THAT BAD BOY!!! Add a cathode select switch to the amp that can switch the cathode resistor from stock to a select resistor of your choice. however the easiest thing to do is simply taste and sample different tubes... simply messing with tubes can fix both of your problems, but it isnt as sexy as having a cool little switch on your amp.

[ledvedder]

Originally Posted by SHinybulldozer

MOD THAT BAD BOY!!! Add a cathode select switch to the amp that can switch the cathode resistor from stock to a select resistor of your choice.

What result would this give me?

Also, how is this mod performed?