Guitar Gear Forum

sahlomonic wrote:Not sure if anyone here is aware, but looks like the Earhart coming to full mass production

First prototype (official name yet to be determined, but I can confirm it will NOT be called the 'Earhart'):



Compared to my Earhart 50:





Likely coming out in the summer, and will most likely be LESS than the HDM.

I haven't seen schematics, but I've been talking with Doug about this for a few months (had to keep my lips sealed until he released the first photo!) and I can tell you it's the Earhart in mass produced form.

If you guys want to know what it's based on, it's laid out like the Cornford MK50HII, except the Jet City version only has 1 effects loop and not 2, and this one is only EL34 and not switchable to 6L6.

mbranford wrote:I have been waiting to post here until I can get the mods done that I have been planning for several years. I have the JCA2112RC, which is pretty much like the JCA20, except with a tube-buffered reverb unit. Of all the Jet City models, this one seems to be one of the least popular, at least for modding. I basically had to take the who combo apart to complete it, making me jealous of everyone else who has a head.

Here is the schematic:
https://drive.google.com/file/d/0B77889FOL1MnSUNTSXoxbDEzME1tQjVzaDhzYWU0UXJtelZB/view?usp=sharing

These are the mods that I completed:
156M Hammond Choke
Depth Pot
Effects loop

I will also change the tolex on the front baffle from blue to black in the next few days, add new piping in the perimeter of the cabinet and at the bottom of the front baffle.

I will not waste time on the choke and the depth mod, as these have been explained and document previously except where the choke comes into play with the B+ voltage on the effects loop.

I decided on a kit for simplicity: the Granger Kit seemed easy, and is adjustable via internal screws inside the jacks. Because I do not want to open the amp for a while once I completed the mod, this seemed like an obvious solution.
Here is the link for the Granger kit: http://grangeramp.com/ufxloop.php
I looked at a tutorial posted on the Metro Amp site (and also considered the Zero Loss effects loop, but it was more money and had an internally set level). The tutorial is the last post from dustplumb. http://forum.metroamp.com/viewtopic.php?f=7&t=32582
There are many other acceptable kits from other companies, including Iron Sounds, and also a tube buffered loop kit from London Power (a Canadian company).

Here is the upshot: the loop needs to go between the tone stack and the master volume. On both the JCA20H and the JCA2112RC, the best spot is at R14. I lifted the easiest end to work with, as I didn't take the board completely out, so I think that I ended up with the loop before R14 instead of after. If I had to do it again, I would take the resistor off the board completely, to get it out of the way, the re-solder the connection. I don't think this issue will affect the sound, but if it doesn't work, I will re-attempt it so the resistor is before the loop in the circuit.

Here is the holes drilled in the back panel of the chassis:
https://drive.google.com/file/d/0B77889FOL1MnT3JYbE13Q3hab1U/view?usp=sharing
Please ignore the extra hole. (I will have to fill it with Grimespaces favorite mod, the slope resistor switch)

Here is the loop installed in the back panel of the chassis:
https://drive.google.com/file/d/0B77889FOL1MnM19ucmVhaHV3NXM/view?usp=sharing
To the right is the depth mod.

Here is the choke where the loop draws from the B+ current:
https://drive.google.com/file/d/0B77889FOL1MncFE3N1J2NFVUX0E/view?usp=sharing
The loop is laid out extremely easy, and the directions are clear. It is a good thing that I was working on the choke anyway, as this saved me a step.

Here is the wires to the in and out of the effects loop board, where I soldered it on to the pad where I lifted R14:
https://drive.google.com/file/d/0B77889FOL1MnOTN1ZWl1dFRQVDA/view?usp=sharing
Again, I believe I placed the loop before R14. We will see how this goes....

Well it is late. I will bias the amp tomorrow if there isn't any issues and get it fired up. Hopefully I can finish the baffle and the piping as well.

GRIMESPACE wrote:Wanna buy a JCA50H? I might consider selling mine. It's modded, but in excellent condition - the mods I've done are great, and well documented here.

rsd wrote:Good luck with the mods. I'm interested in how it all works out for you. These are mods I'm looking to do to my JCA20h. That London Power site is mind blowing, I was trying to understand the tech articles....got very lost. His kits look pretty cool though, I'm just not sure how they'd work on my amp.

Shinigami75 wrote:Hi Folks,

How hard (and practical) is desoldering and resoldering caps and resistors for mod purposes without removing the PCB from the chassis?

Khrille wrote:

Shinigami75 wrote:Hi Folks,

How hard (and practical) is desoldering and resoldering caps and resistors for mod purposes without removing the PCB from the chassis?

It's pretty easy. But it's a good idea to have a soldering suction device.

Cheers

Dunlop wrote:Hello guys

Has anybody in here done choke mod on jca20h or jca22h? Does it have any (positive or negative) impact on sound? Or the only thing it does is less hiss/noises?
Is this upgrade worth of 30€?

sahlomonic wrote:I did the choke on my 20H as well. $15 part and about 15 minutes of work. However, I ended up with using a Hammond 156L, and from what I've read since the mod I probably should have went with the 156M. Just slightly different specs on the two.

Dunlop wrote:Thank you for responses

sahlomonic wrote:I did the choke on my 20H as well. $15 part and about 15 minutes of work. However, I ended up with using a Hammond 156L, and from what I've read since the mod I probably should have went with the 156M. Just slightly different specs on the two.

Did you noticed any change in tone?
I just dont need to waste 30€ if there is not difference

GRIMESPACE wrote:Wanna buy a JCA50H? I might consider selling mine. It's modded, but in excellent condition - the mods I've done are great, and well documented here.