Marshall JCM1H or JTM1H schematics

Tube or solid-state, this section goes to eleven!
User avatar
mavrim
Breadboard Brother
Information
Posts: 75
Joined: 07 Feb 2015, 01:16
Has thanked: 5 times
Been thanked: 25 times

Post by mavrim »

Here is a link to a sound clip of the 1/4 watt plexi circuit that I mentioned a few posts back. Not the best playing, but gets the tone across.

https://youtu.be/n0iN08inhps

User avatar
mavrim
Breadboard Brother
Information
Posts: 75
Joined: 07 Feb 2015, 01:16
Has thanked: 5 times
Been thanked: 25 times

Post by mavrim »

Matec wrote:As for the clipping with diodes and LED, well, just do not know how you could do. :hmmm:

Cheers

MATEC
Your JCM 1 Watt schematic had some strange parts/connections. There were diodes/leds connected on the tone board that look to be used for distortion after the second stage if I recall. I also remember seeing a diode and resistor going from ground plug on ac cord to ground and that looked to be useless? So far the best bet is to follow your HTM 1 schematic. Please keep us posted on this amp design and also any others from the marshall line.

User avatar
Matec
Information
Posts: 32
Joined: 28 Feb 2014, 11:04
Has thanked: 5 times
Been thanked: 17 times

Post by Matec »

mavrim.

I use Multisim 11 program to draw diagrams. As it is also a simulator, probably there is no compatibility between formats, .ms11, and .dsn.

I heard the sound of the video and thought it was good. Has less gain than the HTM1, but it is interesting. I await their new mounts.

Created nothing in JCM1 schema that was not on the board, do not know if you know the amp, but it is so. Also what do you think useless in the amp ground connections are in many Marshalls of a season. There's nothing strange about it.

If you want more information about the process of getting the scheme, read this topic:
http://ampgarage.com/forum/viewtopic.ph ... e8d5354535

Cheers

Matec

User avatar
cassoulet
Information
Posts: 16
Joined: 20 Feb 2014, 18:07
Has thanked: 4 times
Been thanked: 5 times

Post by cassoulet »

Hi Matec,

I am interested in your JCM1 schematic dated august 2014. Since then, have you been able to find the missing values for components on the external PCB? That is C101, C105, C106, C107, C108, R102, R106, R107, R108.

Many thanks for your work.

Cheers. :thumbsup

User avatar
mavrim
Breadboard Brother
Information
Posts: 75
Joined: 07 Feb 2015, 01:16
Has thanked: 5 times
Been thanked: 25 times

Post by mavrim »

I just purchased a Wangs VT-1H all tube amp for $155. Notice the push pull output transformer with 10K ohm impedance to each plate. Sounds like the correct transformer for the 1 watt marshalls!
WANGS_VT-1H_PCB_01.JPG

User avatar
Matec
Information
Posts: 32
Joined: 28 Feb 2014, 11:04
Has thanked: 5 times
Been thanked: 17 times

Post by Matec »

Hello cassoulet.

Yes I provide are values of the components of the tone board. No problem.

Here are:
C101 = 10uF / 100V
C105 = 470pF / 100v
C106 = 22nF / 100V
C107 = 1nF / 100v
C108 = 47pF / 100v
R102 = 1,8k 1%
R106 = 470k 1%
R107 = 470k 1%
R108 = 1M 1%

And yes, now looks exactly what it is: A blend of a JCM800 with JCM25XX, and in a very elegant way ...

Enjoy. Good assemblies.


mavrin

Thank you!



Matec

User avatar
mavrim
Breadboard Brother
Information
Posts: 75
Joined: 07 Feb 2015, 01:16
Has thanked: 5 times
Been thanked: 25 times

Post by mavrim »

mavrin

Thank you!
Ok, you got even! Mavrim, not mavrin

User avatar
Matec
Information
Posts: 32
Joined: 28 Feb 2014, 11:04
Has thanked: 5 times
Been thanked: 17 times

Post by Matec »

mavrim wrote:
Mavrim, not mavrin

Bingo!

:oops:

User avatar
cassoulet
Information
Posts: 16
Joined: 20 Feb 2014, 18:07
Has thanked: 4 times
Been thanked: 5 times

Post by cassoulet »

Hey Matec,

Many thanks for providing these missing values for JCM1! :thumbsup

I still have a couple of questions.

Has anything else changed since august when you published this JCM1 schematic? Any error that should be corrected? For example, is the tonestack the same as on your original drawing?

Also, can you confirm that the 3 diodes in the Jubilee part are normal 1N4007 and that the two LEDs are normal red leds? 3mm leds with a voltage drop of about 1.5V?

Again, thank you for this excellent work. :D :D

User avatar
Matec
Information
Posts: 32
Joined: 28 Feb 2014, 11:04
Has thanked: 5 times
Been thanked: 17 times

Post by Matec »

I have no doubt about the scheme (99% sure).

The scheme has been set up by others, and if there was any difference was due to the components used.

Being a amplified low power, people find that any component works, and leaves the same sound.
Purists do not want to put the MOSFET ...

1N4007 diodes, and red LEDs, 3mm.

Cheers

Matec

User avatar
cassoulet
Information
Posts: 16
Joined: 20 Feb 2014, 18:07
Has thanked: 4 times
Been thanked: 5 times

Post by cassoulet »

Thank you Matec.

Here is a schematic that I have just drawn in an attempt to clarify the Boost-On and Boost-Off modes of the JCM1. They are functional, equivalent circuits of the two modes provided with mechanical switches.
I don't know if they are correct.

Thanks again. :thumbsup
Attachments
JCM1-BoostOff-On.png

User avatar
Matec
Information
Posts: 32
Joined: 28 Feb 2014, 11:04
Has thanked: 5 times
Been thanked: 17 times

Post by Matec »

Yes! That's right!

User avatar
thereminator
Information
Posts: 20
Joined: 04 Oct 2010, 19:28
Has thanked: 6 times
Been thanked: 4 times

Post by thereminator »

Here you have a good output transformer

http://www.ampmaker.com/store/4W-push-p ... ormer.html
Image
In theory, there is no difference between theory and practice. But, in practice, there is.

User avatar
mavrim
Breadboard Brother
Information
Posts: 75
Joined: 07 Feb 2015, 01:16
Has thanked: 5 times
Been thanked: 25 times

Post by mavrim »

Matec,

How does the JTM/HTM amp sound? Just wondering if I should build it as your final schematic, or use the cascaded preamp from the mahaffay plexi amp. I love the overdrive I get with 2 tubes and single ended output. What kind if gain does this amp have? Looking for kiss, Aerosmith and AC/DC tone.

User avatar
Matec
Information
Posts: 32
Joined: 28 Feb 2014, 11:04
Has thanked: 5 times
Been thanked: 17 times

Post by Matec »

Hello mavrim

Currently I maintain that the JTM1 and HTM1 are with the same scheme, after some tests I decided that JTM1 is more versatile. The biggest difference between them is the complete tonestack, the HTM1.
It is a more amplifier to the AC-DC (my opinion).Especially with humbukers.

Mahaffay is good, with the JTM1 you would have a little more sound and a little more headroom. Of course, Overdrive.

(Best with boxes with four 12-inch speakers) :)

Cheers

User avatar
mavrim
Breadboard Brother
Information
Posts: 75
Joined: 07 Feb 2015, 01:16
Has thanked: 5 times
Been thanked: 25 times

Post by mavrim »

Thank you Matec!



Can you tell me if the JTM-1 can get this sound? It is one 12AX7 and one 12AU7

User avatar
Matec
Information
Posts: 32
Joined: 28 Feb 2014, 11:04
Has thanked: 5 times
Been thanked: 17 times

Post by Matec »

Hello mavrim

I think the sound of JTM1 is a little different from the sound of that video.

The JTM1 has more treble, more bass and less mid range. It is an amplifier with enough brightness. With the tone controls you can change some of this, but it is a feature of the amp.

Cheers.

User avatar
mavrim
Breadboard Brother
Information
Posts: 75
Joined: 07 Feb 2015, 01:16
Has thanked: 5 times
Been thanked: 25 times

Post by mavrim »

You could remove the presence feedback that connects from the 16 ohm output that feeds back. Or add a control to limit the presence.

User avatar
Matec
Information
Posts: 32
Joined: 28 Feb 2014, 11:04
Has thanked: 5 times
Been thanked: 17 times

Post by Matec »

What?

There is no "presence feedback" in this circuit. There is only negative FB.

The NFB helps to balance the circuit response. Without it, things get worse.

In this circuit, the preamp is brilliant, as all Marshall should be.

Cheers

User avatar
mavrim
Breadboard Brother
Information
Posts: 75
Joined: 07 Feb 2015, 01:16
Has thanked: 5 times
Been thanked: 25 times

Post by mavrim »

Oh, I thought that was presence. On another plexi 6V6 schematic it said presence. On the wangs circuit and firefly, they don't use negative feedback. What benefits does this offer?

Post Reply