Guitar Gear Forum

Dunlop wrote:I would like to do a simple line out from preamp, so I can send the signal to the another poweramp or for recording purposes.
Has anybody did that? I have 20h, so without a loop.

The effects loop I installed from Granger Amplification can be used as a line out. It was pretty easy to install. $70 plus shipping, I felt was a good deal. Then you will also have an effects loop.

You'd still have to put a load on the speaker out. I'd say a load box would be a better way to go.

GRIMESPACE wrote:You'd still have to put a load on the speaker out. I'd say a load box would be a better way to go.

Yup, but it is pretty simple to do dummy load with couple of resistors and heatsink. But you need a lot of money for great load box with line out (cheap resistive load boxes are pretty shitty IMO, reactive loadboxes are in the other league but sadly also in price range)

You can get a Weber Minimass pretty cheap ($132 new). It'll do 50 watt (more than enough for your 20w head), and user Riffraff has one for sale in the classifieds. Look for his threads - he's gotten some damn good sounds from his.

You can still route the output of the send through the recording interface and back into the amp, because the effects loop can be set as a line level source. The audio can be recorded and monitored. Then it can be digitally processed, using effects and modeling software. You get real tube sound, but the flexibility of digital recording.

Just a quick update: Got to play my JCA50 head with my band for the first time last night. All I took was my Boss GE-7 in the effects loop to bump the low end a tad.
This thing sounded killer! No mods, just an EQ pedal and it sat perfectly in the mix with my other guitarists Marshall TSL.

Anyways, just thought I'd report back that after playing this amp at band volume (where it likes to be played) I have no desire to do any mods as it sounds amazing just how it is. The cleans were clean and the gain has a nice thick saturated, but clear tone. Such a great sounding and playing amp!

GRIMESPACE wrote:

atrox wrote:also.. anyone with a 50 or 100, i highly recommend trying the Sovtek 6l6wxt+'s. They really tightened up the low end made that amp scream.

I've heard that from more than one place - might have been you and Billy a while back. I'm still using the set of JJs I picked up when I first got the amp, so I don't really have any basis of comparison. Might just have to check into the wxt+'s when I change them out.

I just loaded a set of Mesa Boogie 6L6's (Cleverly disguised Ruby's!) in the Power Amp section, and the difference was immediate from the stock tubes
Also loaded a Mullard 12AX7 in the OD gain socket (V2), a Tung Sol in the Crunch gain socket (V1), Mesa Boogie 12AX7's in the tone and FX stack (V3-V4) <<Not sure what they actually are?>>
and a Sovtek LPS (balanced triode) in the Phase inverter (V5)
Running this through a 2x12 loaded with Eminence Lynch Super-V's... It now actually approaches my friend's 2011 SLO on the OD channel!

Nproctor wrote:I'm a new owner of the JCA100hdm. I love the amp but want to fool around with some preamp tubes. I have done a bunch of research online and I cannot find a confirmation on the tube positions when looking at the front of the amp. Does anyone know for sure? I assume it's L-R V1 V2 V3 Then I'm not sure if it's the tube for the loop or Phase inverter or cathode follower.... And does anyone know what roles V1 V2 and V3 have? I.e.: clean, overdrive, etc.??? I'm totally lost!

I have the same amp (2011 HDM) and was talking to Doug White recently and have this information.

Preamp tube positions Left to right (from the front)
V1 = Crunch Gain
V2 = OD Gain
V3 = Tone Controls
V4 = FX Loop
V5 = Phase Inverter

My most awesome combo to date:
V1 = Tung Sol
V2 = Mullard
V3 = Mesa Boogie / Tung Sol
V4 = Mesa Boogie / Tung Sol
V5 = Sovtek LPS (Balanced Triode)

For the Power Amp section (6L6 tubes)
I recommend either TAD, Ruby or Mesa Boogie Red

Hope this helps!

sefloval wrote:"And does anyone know what roles V1 V2 and V3 have? I.e.: clean, overdrive, etc.???"

I want to know this too! I can't find exact documentation on this anywhere.
I'm thinking of trying either a 12AU7 or a 5751 in V1 to try and tame the beast a little. I put a 5751 in V3 position which helped a little.
V1 starts to the far right when you're in the back of the amp replacing tubes.

Nope, its from the front
Left to right V1 | V2 |V3 | V4 | V5

V1 = Crunch Gain
V2 = OD gain
V3 = Tone Stack
V4 = Effects Loop
V5 = Phase Inverter

Hi Folks,

Sorry for the question (non relevent to Jet City amps...) but I'm about to get an old Carvin Quad X preamp delivered and I was wondering how I could tame the 4th channel...it has 11 gain stages!!!!!!

Yep, 5 1/2 tubes out of 9 are dedicated to the 4th (Sustain) channel only.... Will using 5751 tubes instead of 12ax7 be a wise move? Returbing it is gonna cost me a kidney

Cheers

Shinigami75 wrote:Hi Folks,

Sorry for the question (non relevent to Jet City amps...) but I'm about to get an old Carvin Quad X preamp delivered and I was wondering how I could tame the 4th channel...it has 11 gain stages!!!!!!

Yep, 5 1/2 tubes out of 9 are dedicated to the 4th (Sustain) channel only.... Will using 5751 tubes instead of 12ax7 be a wise move? Returbing it is gonna cost me a kidney

Cheers

Pretty sure I'm not going to be of much assistance. You'd be much better off posting this question as a new thread in the general forum - you'll get much more traffic that way. Lots of knowledgeable guys there that can help!

Theoretically, would it be possible to convert jca20h to 2x el34 amp?
I know I would need new output transformer and new tube sockets, but other than that what would be needed? Is it possible?

Hey everyone
I've bought jca50h yeasterday and I'm realy happy) Finaly my setup is stereo
I want to change tubes but first i want to ask you guys about your opinion.

My curent rig: fender tele (sd blackwinter), engl blackmore (jj 6l6), DL412pro v30. Od808 for boost and couple effects in fx loop. Tone is bright, and sharp, realy punchy.
For Jet City I've got 1960a but I thinking about 212 from DL with creambacks. I think that I'm serching for rounded and little darker tone to fill Engl sound.

first, I will do slo mod and depth mod
second, I will change power tubes, so I could put almost new GT6L6R for cheap option or buy new JJ. Maybe something else??
then i will try new preamp tubes. And it will be greate if you could recomend me something. I was thinking about electro harmonix 12ax7 or JJ ecc803 (low noise)for v1 and v2 and 12at7 for v5 rest eec83 JJ

so, What tubes are you recomending? what tubes have you used?

Hi,

Please take a few minutes to check out the references section I put in the first three postings of this thread (page 1). There's a lot of information about various mods, loop-compatible effects, etc.

Standard recommendation before performing ANY component changes / mods with these amps is to replace power tubes, and at least V1, V2, and V5 with good quality tubes. That's most of 'em - replacing V3 & V4 isn't going to make a huge difference, but it doesn't hurt to replace them, either. I was pretty happy with the set of JJs I bought, but everyone seems to have their particular favs.

Next up is getting the bias set properly. If you know what you're doing (ie: know how to discharge caps and work safely inside the chassis), you just need a bias probe and multimeter. I got mine from Eurotubes and was happy - again, lots of other options out there to choose from.

After that, the depth mod has always brought happiness to most people, especially if playing at low / bedroom volume levels.

My next recommendation is to check out the slope resistor mod, particually if you're looking for a bit more 'give' to the feel / Marshall-type flavor.

SLO mod has been pretty popular with the folks that have done it. It's one of the more involved mods, as there are a large(r) number of component changes that have to be done, including a few of the pots. I have yet to do this to mine.

Good luck

Thank you !

of couse I've read all posts in this topic realy, realy helpfull but I decide to join this forum and get some opinion.

So my friend will do all the mods and set the bias. I know how to do this but, he will also check whole amp, and channging tubes and biasing. It easier this way

I play only on OD channel and realy lowd. I will make depth mode for shure. I will check this slope resistor mode, but maybe after slo mod. This is most common mode for a reason. From yt samples i heard great improvement of tone. I will tell you mine fellings in future!

so i decided that put jj eec803 for v1 and v2 , beacouse that will reduce amp noise also it give warmer sound, I will buy JJ eec83 for v3 and v4 , one 12at7 for v5. So if eec803 will not work well in this position(v1 and v2) I will try eec83 in diffrent combination.

I could buy used but great condition GT6L6R for 1/4 of the price. I think that it is worth the risk. What do You think?

cheers!

best mods are tube replacement in V1 and PI
I have a JJECC83s and an sovtek 12ax7LPS there
actually the stock chinese are good in V2,V3,V4, they have a lot of gain and are bright tubes
for the mods, depth mod is mandatory, the SLO mod is also nice but it will gives the amp even more gain...
slope resistor is very easy to do and can be made swichable: i have a 66K slope on a switch, great for taming the excess of low-mids this amp has and it gives the amp a more "fenderish" tone
another nice mod is to remove the bypass cap of V3a (can be made switchable too): clean/crunch channel will stay clean, OD channel gain will be more usable.
in my amp I have now a classical 470K/470p with 500K gain pot, I have replaced the coupling cap of V2a (0.002uF) to tame lowmids and I have now a 220K/220K divider between V2a and V2b, with 33K cathode resistor to warm up that stage - less gain and buzz but OD channel is more usable, sounds more rock oriented. for ultrametal sounds, i boost the OD channel with a pedal.

My JCA22H Custom arrives friday. Looking forward to checking it out with the factory mods that have been done.

From Jet City:
Updated voicing by Martin Kidd in the UK. The updated Crunch channel has less gain than its predecessor and the Overdrive has even more gain. The result is an entirely new voice with greater range and touch-sensitivity. Further tone shaping is possible via a bright switch and mid-boost / low fat switch.

The simple feature set is rounded-out with a pedal-friendly effects loop and front-panel channel switch

Really hoping the effects loop is actually good with pedals. It'll be a deal breaker if not.

Can't wait to hear what you think, Jer. Hope it's a good one!

GRIMESPACE wrote:Can't wait to hear what you think, Jer. Hope it's a good one!

This. I have done a small handful of mods to mine and I have def tapped into a Marshally type tone on the crunch channel. The OD channel has been tamed slightly by a couple mods so it doesn't have that frying pan sizzle and the treble knob is more usable. My speakers are complete ass but I can record at lower volumes and get decent tones. Curious to know what they did under the hood and what changes it has made to the sound. Keep us posted.

Will do. Makes me a bit nervous that the lead channel has MOAR gain! I guess I may need to look for some lower gain preamp tubes. It says it'll be here tomorrow and is on schedule.

JerEvil wrote:My JCA22H Custom arrives friday. Looking forward to checking it out with the factory mods that have been done.

From Jet City:
Updated voicing by Martin Kidd in the UK. The updated Crunch channel has less gain than its predecessor and the Overdrive has even more gain. The result is an entirely new voice with greater range and touch-sensitivity. Further tone shaping is possible via a bright switch and mid-boost / low fat switch.

The simple feature set is rounded-out with a pedal-friendly effects loop and front-panel channel switch

Really hoping the effects loop is actually good with pedals. It'll be a deal breaker if not.

Yeah I'm glad you bought this and can tell us about how good that loop is. I'm like 90% certain I will be getting this for the kids.

M.Mike LX-R wrote:I'm like 90% certain I will be getting this for the kids.

You may find that daddy likey too. Through decent speakers mine is a fire breather even though the low end still needs some tightening up. I can only imagine the newer one will be a nasty little fire breather as well. I wanna see what changes they made and if there is anything there I can use in my quest for tonal bliss.

I'm gonna try to bring my modded 50 to the Ampfest next month for you to check out, Mike

Awesome Steve! That would be cool I've been curious about the JCA line for years.

And Meelo, I predict daddy will likey too which is the ulterior reason for going this route. It'd be really cool to have a solid auxiliary rig.

Hi everyone,

I have both a JCA20H and a JCA2212, and I love them both! I am overloaded with information from this page--I'm amazed at all the different mods you guys have done! I thought I would ask your collective opinion about reducing/revoicing the gain on the 20H's OD channel. I love the tone of the crunch of the first channel--is there a way to make the OD channel sound closer in tone to the 1st while keeping a slightly higher gain? Hopefully that makes sense...and happy to hear any responses, thanks!