Guitar Gear Forum

käsebrot wrote:

GRIMESPACE wrote: because I'd be after less gain - I barely run the preamp gain above 4 (usually closer to 3) on the OD channel as it is.

Easiest way to get more dynamic response and less gain in both channels is to lower R46 to 150k (at JCA50H).
If this is not enough gain for the crunch channel then - just raise C23 up to 470pF. If you want an even cleaner Crunch, lower C23 to 220pF or even 180pF.

Everything else is just trial and error, mess with the coupling caps to get more clarity - f.e. the one between 1. and 2. gainstage - there is no need for 22nF, try 4,7nF or 6,8nF.

Oh and I'm sorry that I can't recommend any good supplier for all the caps, resistors and other parts - because I'm in Europe and don't know the dealers in the US.

GRIMESPACE wrote:

Jase01 wrote:Grimespace, just wondering, do you use your Bad Monkey and 250 as boosts with your JCA?

No - I have them on a pedalboard with some other effects for my Church rig, being played through my Fender Pro Reverb. They're really great in that configuration. Only thing my JCA needs is a 'clean' pedal to reduce the amount of gain that the thing has

I've tried the pedals out with the amp on different settings, and the only place I found them to be of much use was when I switch on the clean mod, but it's nowhere near as good as my Fender. I'm still determined to put in a boost switch on the amp (MV limiter, or whatever you want to call it - see my discussions earlier in this thread) at some point, but it's just to jump / reduce overall volume - not affect the gain, which as I say is way to dam much as it is. And, that's me with my SG hammering out various things from rock, hard rock, early metal, 80's thrash, and everything I've got in between with the OD gain running between just under 3 to 4 on the dial. I don't know how the world got such a need for higher gain, but they can have everything from 5 to max on my amp if they need it

sahlomonic wrote:*Assuming I performed the SLO mod correctly and with the correct parts*, yes - that is exactly what my experience is. I normally had the OD gain at 6 when it was stock, and after the mod, was comfortable with it at 5, but I could turn it down to 3 or even 2 and was still enough to have a healthy palm mute. Also, with the OD gain dimed it did not fizz, flub out, or overly compress like it would on a stock JCA100H. I don't think it made the amp have any more gain, it just has more gain at lower settings and more usable throughout the sweep. I didn't mess with the Normal channel at all so I can't comment on if that changed or not. Again, this is assuming the mod was done correctly.

Honestly, when mine was stock, I found the OD gain at 3 to have identical characteristics to the Normal gain maxed.

Hmmmm... as much as I want to tame gain, this still piques my interest. I have noticed that the amp does tend to turn into a big, unusable, muddy mess when I get up to the upper-end of what I'll dial for gain - I wonder if it'd be worth all that work to do the mod and see how it'd do for me...

Kevin Brush wrote:Hi Grime, I took some pics of the HDM this morning. The transformers and choke look to be the same as the JCA100H. The first pic of the guts is the half power switch and the depth mod pot. The half power switch has a black and red wire that go into the board at J13 and another set at J14. I took a picture of J13, J14 is under a cluster of wired to the left of it. Let me know if you would like any other pics.

Holy moley - this totally made my day!!! Thanks so much, Kevin! Do you mind if I take your pics and put them into a separate 100HDM documentation thread like we've done for some the other models and I'll index it at the beginning of this thread?

I haven't had a chance to look at the pics much (yet), but might come back to ask for a few more. Thanks again!

Jay wrote:

kissmyace wrote:I play in a more classic rock type band. One supplier would be good, and always budget conscious !!! lol

thanks !!!

Alrighty. Let me see what I can come up with.

+1 on the classic rock thing! We need mods to help shore up the lower-gain usefulness of this amp!!! And no, I don't want to just relegate myself to using the normal channel for regular playing - that's reserved for cleaner stuff - need moderate gain capabilities throughout the entire sweep of the OD gain dial.

Jay - how's the quest for a 50 head going? We need to get a donation hat going 'round? I'm starting to put together a small personal fund for some transformers later this year...

jhall wrote:Too bad that my JCA 20 RC112 Sounds like warm wet doodoo. I tried to like for ever and through a ton of speakers and with different tubes. But alas even with the Bitmo mods it is a dog. I'm wondering if it's that I'm a moms basement kind of guy and can't grasp that an amp mixed into a proper recording
may actually NOT be the best bedroom sound. I wish I could like this amp but it eludes me and my feeble dialing in ability.

Welcome! Never heard too much positive about the bitmo mods. Actually, I haven't heard much about them in ages - is that company still out there making this mod? Have you checked out any of Edge11's mods for the 20 platform? (see the index on page one of this thread). Can you give us some indication (examples would be helpful) of what you're really wanting to achieve?

käsebrot wrote:I am actually messing a lot with one of my 22H - but it will take a bit more time until I'm happy with the sound.

This will be very different from how it sounds in stock. Fatter and tighter, more direct and brutal sounding - more "Roarrrr" - and yes it's possible with this little amp! : )

I will write down my mods here when I've finished.

kissmyace wrote:my band is a Christian band with a classic rock influence. I play mostly electric (LP, sometimes Tele). The 22 is good for the places we play. I have a Bad Monkey, Cool Cat Fuzz & Cool Cat Transparent OD on the board with EQ, delay & gate in loop. I'm looking for that clean drive and the od channel not to be so over the top gain

käsebrot wrote:I have always recommended 180k/120k for R46/R19.

Soldano Hot Rod + is 220k/100k, SLO is 220k/220k.

The 150k/150k is also not a bad one - very modern. And if you really want less gain and more dynamic response 150k at R46 is ok - but that's just a matter of personal taste. : )

Jay wrote:Well, I have in my possesion a JCA 50H! Woohoo! buuuut......it's my buddies amp that won't turn on. Boo. At any rate, I'm going to have it for a while, fix the problem and do the SLO mod to it for him. I'll try to get some pics of the mod stuff for anyone that cares.

kissmyace wrote:Where'd everyone go ????

BleedingWhiskey wrote:I'm not sure if this has been asked in this thread (I'm sure it was in the HCAF thread, but I dare not tread those waters), but here goes...

How do I fix the pilot light issue on my 100h head amp? About a year ago, it stopped turning on with the amp. It sometimes flickers on since then, but it never stays on very long. I'm thinking the bulb is not the issue, so I'm guessing it's a socket or wiring issue. I know this is a typical issue on earlier JCA amps (mine was built within the first 6 months after the start of the 100h production), so I figured their was a typical repair procedure. How do I fix this?

Promit wrote:Hey guys, I just wanted to mention that the Vox Tonelab LE works great in the loop. It's totally transparent, too. (I'm looking at you Digitech...)

GRIMESPACE wrote:

kissmyace wrote:Where'd everyone go ????

I'm still here. Jay's definitely still here. Others too. It's just been on the down-low lurk mode lately :0

You posted about getting your parts back at the end of April for the SLO mod (?) - how you doing with that?

BleedingWhiskey wrote:I'm not sure if this has been asked in this thread (I'm sure it was in the HCAF thread, but I dare not tread those waters), but here goes...

How do I fix the pilot light issue on my 100h head amp? About a year ago, it stopped turning on with the amp. It sometimes flickers on since then, but it never stays on very long. I'm thinking the bulb is not the issue, so I'm guessing it's a socket or wiring issue. I know this is a typical issue on earlier JCA amps (mine was built within the first 6 months after the start of the 100h production), so I figured their was a typical repair procedure. How do I fix this?

I'm assuming you have the older style head - toggles with a separate LED (not a bulb) - not two rocker switches, one that has an integrated light. Did you contact JCA about it? I've seen plenty of postings about this old issue, and JCA has always done a great job getting replacement parts to the owner right away.