Amps

[kocher]

In case anyone is interested, they also suggest this, for an open but warm sound:

V1: 7025 WA
V2: 7025 S
V3-5: ECC83 WA

This combination costs around twice of the JJs that's why I postponed that for now

[Edge11]

Originally Posted by GRIMESPACE

Since Edge hasn't had a chance to reply (he's pretty busy with school these days, it appears), I took the liberty of putting something together, which is what I think he's talking about. I picked up ground off one of the resistors (pretty sure it was R49) near the input jack, which is where I put my switch. I'll try to get a gut shot of my hatchet job this weekend to post up. You can also run a wire to the back of the chassis and pick up ground off the speaker jacks.

Note - I haven't tried this actual wiring. I originally put in two switches so I could try them independently, and have since removed the cathode bypass. If this is right (Edge - please let me know), I'm probably going to rewire to this, based on his recommendation above.



Other particulars:
.001uf cap is ceramic, and may be labeled 1000pf (mine was).

From Edge:
"22uf is 50v or more.
the .001uf is 1kv (most common value)"

Correct. I use 3pdt switch so when the scoop mod is of it changes the value from 2 1ms to a 680k resistor, aka the normal sucker punch mod.

[clay189]

kocher, so your amp was set at aroiund 10ma from the factory. When i changed my tubes and rebiased I thought I was crazy seeing a 10ma reading. Nice to know I still have my sanity.

Originally Posted by kocher

Today I changed preamp tubes to JJs and biased the amp. I was pretty cold with something like 10mA. With a measured plate voltage of 468V I calculated a 70% value of 37mA and that's what I set to bias to.
I measured plate voltage with a DMM and used an adapter like this to read the bias:


Overall sound has improved quite a lot but still too much compression for my taste. Looking forward to use other tubes in the power section: 6L6GC-STR RCA-Style black-plate TAD PREMIUM Selected

That is a recommendation from the guys at Tube Amp Doctor for an open tone.

[Blakkwater]

Edge11...or anyone else...

Lately I've been trying to tweak the tone controls/depth/presence controls while playing on the overdrive channel, trying to get that bright/middy hot rodded JCM800 kinda sound, but I always find that the overdrive channel has far too much low/low-mid muscle to do the Marshall sound.

Is there a mod for a voicing switch or something similar that would be able to give the OD Channel a more Marshall flavour?

[Edge11]

Originally Posted by Blakkwater

Edge11...or anyone else...

Lately I've been trying to tweak the tone controls/depth/presence controls while playing on the overdrive channel, trying to get that bright/middy hot rodded JCM800 kinda sound, but I always find that the overdrive channel has far too much low/low-mid muscle to do the Marshall sound.

Is there a mod for a voicing switch or something similar that would be able to give the OD Channel a more Marshall flavour?

Change the slope resistor to 33k

[clay189]

Hey Edge, The depth mod kicks ass and for us beginner moders was simple and smooth so thanks for that. Now for my next rookie ? I am thinking of the Scoop mod but what does this exactly do does it bring the mids down even more than just rolling them back on the Eq. Forgive me if the ? is just plain stupid.

[isuck]

Hi looking for a little help with my sons jca22h. My twelve year old son has been playing the jca20 for about a year and his grades earned him an upgrade. Yesterday we got a 22h from an on line retailer. the crunch channel sounds great I think maybe a little fuller then the 20 sounded. The problem is the od channel. When he hits the switch it squeals like a pig in heat and the only thing that will control it is the preamp knob. I emailed jet city and there response all though fast was a little lacking in information. It said to check the tubes to make sure they are glowing. It also said that the amp was designed to plug and play so if a tube is bad you can just get the same kind and put it in. Being a total noob (or kook which ever you prefer) I have know idea where to start. I can only see 5 tubes through the grill and they all have some color some a little stronger then others but color. Any help that you may provide would be helpful. I am not totally mechanically challenged so I am willing to give this tube replacement a try just don't know where to start. By the way v1, v2 v3 etc. mean absolutely nothing to me. Thanks

[67mike]

Originally Posted by isuck

Hi looking for a little help with my sons jca22h. My twelve year old son has been playing the jca20 for about a year and his grades earned him an upgrade. Yesterday we got a 22h from an on line retailer. the crunch channel sounds great I think maybe a little fuller then the 20 sounded. The problem is the od channel. When he hits the switch it squeals like a pig in heat and the only thing that will control it is the preamp knob. I emailed jet city and there response all though fast was a little lacking in information. It said to check the tubes to make sure they are glowing. It also said that the amp was designed to plug and play so if a tube is bad you can just get the same kind and put it in. Being a total noob (or kook which ever you prefer) I have know idea where to start. I can only see 5 tubes through the grill and they all have some color some a little stronger then others but color. Any help that you may provide would be helpful. I am not totally mechanically challenged so I am willing to give this tube replacement a try just don't know where to start. By the way v1, v2 v3 etc. mean absolutely nothing to me. Thanks

V1 is the preamp tube nearest the input jack on the 22h.

I would suggest the following:

Buy 2 JJ EL84 tubes and 4 SOVTECK 12ax7wa tubes.

Unplug the amp and take the back panel off the amp. Then set the amp face down on a soft surface like a rug....remove the 4 screws on the bottom to free up the chasis....then slowly and carefully put the amp back on it's bottom and carefully remove the chassis from the cab....DO NOT touch anything under the chasis....simply slide it out and place it on the floor...this allow you to access the tubes. replace the 2 EL84 power tubes, then replace the 4 12ax7's in V1 to V4 with the sovtecks.

This should help out a lot.

[isuck]

Thank you for your help. Placing order has we speak. One other thing the metal housings on a few of the tubes do they screw of or just pull off

[isuck]

Will he notice much of a difference if I just put JJ's all the way around? thanks for your help.

[Blakkwater]

Originally Posted by Edge11

Change the slope resistor to 33k

Which # resistor is that on the PCB?

[GRIMESPACE]

Originally Posted by 67mike

V1 is the preamp tube nearest the input jack on the 22h.

I would suggest the following:

Buy 2 JJ EL84 tubes and 4 SOVTECK 12ax7wa tubes.

Unplug the amp and take the back panel off the amp. Then set the amp face down on a soft surface like a rug....remove the 4 screws on the bottom to free up the chasis....then slowly and carefully put the amp back on it's bottom and carefully remove the chassis from the cab....DO NOT touch anything under the chasis....simply slide it out and place it on the floor...this allow you to access the tubes. replace the 2 EL84 power tubes, then replace the 4 12ax7's in V1 to V4 with the sovtecks.

This should help out a lot.

While I'm not hands-on familiar with the 22h, I'm pretty sure it's just like my 50h. No need to pull chassis - remove the back, then using a long screwdriver, remove the screws for the front baffle and remove it. You may find that the back panel wants to fight you - it's not glued in, so just heave-ho. I have full access to all my tubes with the front panel off.

Originally Posted by isuck

Thank you for your help. Placing order has we speak. One other thing the metal housings on a few of the tubes do they screw of or just pull off

The metal housings can be pulled out by twisting them - they release sort of like a child-proof cap. I've been running my 50H without them, and don't notice any increase in noise, and I like the tube glow .

Originally Posted by isuck

Will he notice much of a difference if I just put JJ's all the way around? thanks for your help.

I'm running JJs from Eurotubes all the way around on my 50H, with the exception of the phase inverter (V5 - furthest from the input jack and closest to the power tubes), which is a specifically balanced 12ax7. I'm guessing that 67Mike has more experience with different tubes than I do, so you may take that into account. All I know is that replacing the tubes and setting the bias properly made a massive difference in every way. My best advice is to get in contact with one of the more popular tube vendors (Eurotubes, Tube Depot, Valve Queen, etc.) and see what they have to say - you can usually describe what it is you're looking for (more gain, less gain, more punch, etc.), and they'll steer you right.

[Edge11]

Originally Posted by Blakkwater

Which # resistor is that on the PCB?

r24 on the 50h Idk what # it is on the 100h.
the original value is 47k change it to 33k.

[isuck]

Thank you for the help. I am starting to get a better understanding. I have found that Eurotubes has a complete retube kit for the jca22h and I am going to give it a try.

[GRIMESPACE]

Originally Posted by isuck

Thank you for the help. I am starting to get a better understanding. I have found that Eurotubes has a complete retube kit for the jca22h and I am going to give it a try.

Good call - are you going to do the bias setting as well? This also makes a huge difference.

[isuck]

I am looking for someone in my area that can do it. Any Idea on what a decent price would be to have the bias done. One thing to remember is he is only 12 and this whole band thing seems to nickle and dime me every week. Does the Bias make that huge of a difference. Thanks

[67mike]

Originally Posted by isuck

I am looking for someone in my area that can do it. Any Idea on what a decent price would be to have the bias done. One thing to remember is he is only 12 and this whole band thing seems to nickle and dime me every week. Does the Bias make that huge of a difference. Thanks

I did not rebias my 22h when I swapped out the stock tubes.

According to the manufacturer, you do not need to rebias it with tube changes. I do believe the guys here (who tinker with that) that it made a difference for the better....so eventually if I am bored, I might do it...to be honest...it sounds so damn good right now...there is no need for me to do it.

I prefer the sovteck over jj 12ax7 tubes.....I like the JJ EL84 though...hence my suggestion.

[isuck]

thanks for the suggestion.

[Bumhucker]

What kinda boost pedals sound good with the 22h? Right now I'm using a bad monkey, but I'd kinda like something not as middy.

[GRIMESPACE]

Originally Posted by Bumhucker

What kinda boost pedals sound good with the 22h? Right now I'm using a bad monkey, but I'd kinda like something not as middy.

I'm loving my TC Electronics BLD (18v) on the crunch channel of my JCA50H.