Marshall all in one 3 channel preamp sim with pcb layout

[ubaid88]

Hi,

Let me intoduce you Marshall all in one 3 ch preamp sim.

You may have seen Marshall Jcm800 fet sim. Now this is our project called Marshall Multi-Channel preamp with clean, crunch and Lead channel.

Clean will simulate 1959SLP.
Crunch will simulate as Jcm800.
Lead will simulate Jcm 900 SLX.

This is designed by Israel Luna(Anti-Idiot). He has discussed this with you previously. You use switch to between channels. This circuit 2 fet mu-amp gain stage which don't require biasing.


And pcb is design by me with pots mounted on pcb.


Here ready to tranfer pcb layout.
http://www.2shared.com/file/8851495/22a9fc22/marshall.html

Please comment.

Any question you got please ask from Israel.

[ItZaLLgOOd]

Nice work!  Is it verified? I'm in the process of deciding on a preamp for a simple chipamp practice amp.  Looks like this very versatile.

[aziltz]

Aren't those actually SRPP's? (or is it SSRP?) instead of Mu-Amps?  I thought the subtle difference in the two snippets was the resistors between the FETs, ie R4, R8...

[ubaid88]

Nice work!  Is it verified? I'm in the process of deciding on a preamp for a simple chipamp practice amp.  Looks like this very versatile.

No it is just paperwork now.
wait 1-2day. I am completing this and you will have the result with sound clips and pics or even a video.

[anti-idiot]

Nice work!  Is it verified? I'm in the process of deciding on a preamp for a simple chipamp practice amp.  Looks like this very versatile.

I designed this (well, i adapted 4 amps -jtm100 1959slp, jcm800 2203, jcm900 2100 slx and jvm410h) to work at >18v. it will depend on the fets (i recommend you to use low gain, as the marshall sound consist of low gain stages in cascade) and the voltage you use.

the target is to have the cleanest sound in the first mode. the second stage will add some gain, and the third will add more. the order of the stages is not a typo: in order to use the 3rd mode, you need to activate the 2nd (3rd mode is some kind of "solo boost").

i hope you enjoy it.

[Taylor]

The PCB looks a lot larger than it needs to be, is there a reason for that?

[ubaid88]

The PCB looks a lot larger than it needs to be, is there a reason for that?

because you have seen component layout.

You must see ready to transfer layout at 100% size for actual size.

But even if actual size looks bigger to you it is because you can mount and solder potentiometer directly on pcb instead of wiring externally .
It save you space and over crossing of wires which will future save you from squealing and other unwanted noises.

I must add one important thing that use any N channel low gain jfet like 2n5484/5/6, mpf102, 2n5457 or any one with similar pinout.I recommend 2n5484 or mpf102. Unlike j201s these fets are more easily available.Don't use j201. Or it will sound like a hell.

[jacobyjd]

The PCB looks a lot larger than it needs to be, is there a reason for that?

because you have seen component layout.

You must see ready to transfer layout at 100% size for actual size.

But even if actual size looks bigger to you it is because you can mount and solder potentiometer directly on pcb instead of wiring externally .
It save you space and over crossing of wires which will future save you from squealing and other unwanted noises.

I think Taylor's point is that the layout could be significant reduced in size, simply by minimizing unused board space.

[ubaid88]

The PCB looks a lot larger than it needs to be, is there a reason for that?

because you have seen component layout.

You must see ready to transfer layout at 100% size for actual size.

But even if actual size looks bigger to you it is because you can mount and solder potentiometer directly on pcb instead of wiring externally .
It save you space and over crossing of wires which will future save you from squealing and other unwanted noises.

I think Taylor's point is that the layout could be significant reduced in size, simply by minimizing unused board space.

I will try to do it. But not now. If anyone else is interested to design pcb for this then you are more than welcome.

[ubaid88]

Aren't those actually SRPP's? (or is it SSRP?) instead of Mu-Amps?  I thought the subtle difference in the two snippets was the resistors between the FETs, ie R4, R8...

yeah U got it right these are actually SRPP. They are kind of improved of mu-amp.

[bamera]

Thanks for sharing this project. I can´t wait to hear clips.

[dschwartz]

Interesting design!
as stated above, this must be used with fets like MPF102 or similars, with j201, this will go crazy with gain.. Other option is to adjust the voltage dividers between each stage to control gain.
Consider these recomendations for a more professional result:
- Tonestack: scale down the tonestack by a factor of 10, or add a buffer after the volume pot. as it is now, there is too  much output impedance..
- Treble: As it is, this will sound trebly as hell...put a LPF (or two) near the output to tame harshiness and step up the bottom end..SRPP will have enough volume to spare.
- add diode protection for reverse polarity
- 100uf feels like not enough for me..try 220uF or 2X100uF + 100 Ohms resistors,  like dr boogie
- probably the switches will pop, since there is ~1/2 V+ at the fet gate, i´d at least add a series resistor with the gats to avoid damaging the fets when switching. Nicer solution is to add a coupling cap before each fet gate that is conected to a switch.
- Idea: add a switchable diode clipping after the last stage to emulate older JCM900´s diode clipping,it may sound good, who knows? try 2 diodes per side if you´re using more than 12 volts
-Breadboard it first, then update schem and PCB
- PCB design presented is not very efficient, with a better use of space. With more patience , the layout can be half big..


regards!

[ubaid88]

Interesting design!
as stated above, this must be used with fets like MPF102 or similars, with j201, this will go crazy with gain.. Other option is to adjust the voltage dividers between each stage to control gain.
Consider these recomendations for a more professional result:
- Tonestack: scale down the tonestack by a factor of 10, or add a buffer after the volume pot. as it is now, there is too  much output impedance..
- Treble: As it is, this will sound trebly as hell...put a LPF (or two) near the output to tame harshiness and step up the bottom end..SRPP will have enough volume to spare.
- add diode protection for reverse polarity
- 100uf feels like not enough for me..try 220uF or 2X100uF + 100 Ohms resistors,  like dr boogie
- probably the switches will pop, since there is ~1/2 V+ at the fet gate, i´d at least add a series resistor with the gats to avoid damaging the fets when switching. Nicer solution is to add a coupling cap before each fet gate that is conected to a switch.
- Idea: add a switchable diode clipping after the last stage to emulate older JCM900´s diode clipping,it may sound good, who knows? try 2 diodes per side if you´re using more than 12 volts
-Breadboard it first, then update schem and PCB
- PCB design presented is not very efficient, with a better use of space. With more patience , the layout can be half big..


regards!

Thanks you for your suggestions, Daniel. This will be benefit this project.

[anti-idiot]

Interesting design!
as stated above, this must be used with fets like MPF102 or similars, with j201, this will go crazy with gain.. Other option is to adjust the voltage dividers between each stage to control gain.
Consider these recomendations for a more professional result:
- Tonestack: scale down the tonestack by a factor of 10, or add a buffer after the volume pot. as it is now, there is too  much output impedance..
- Treble: As it is, this will sound trebly as hell...put a LPF (or two) near the output to tame harshiness and step up the bottom end..SRPP will have enough volume to spare.
- add diode protection for reverse polarity
- 100uf feels like not enough for me..try 220uF or 2X100uF + 100 Ohms resistors,  like dr boogie
- probably the switches will pop, since there is ~1/2 V+ at the fet gate, i´d at least add a series resistor with the gats to avoid damaging the fets when switching. Nicer solution is to add a coupling cap before each fet gate that is conected to a switch.
- Idea: add a switchable diode clipping after the last stage to emulate older JCM900´s diode clipping,it may sound good, who knows? try 2 diodes per side if you´re using more than 12 volts
-Breadboard it first, then update schem and PCB
- PCB design presented is not very efficient, with a better use of space. With more patience , the layout can be half big..

regards!

Hi Daniel.
-My suggestion always was to use MPF120 and/or 18v.
-About the tonestack, it could be scalled down or use a buffer (simple source follower with 10k)
-I'm 100% with you about the caps, resistor and diode protection (i didn't consider this, since i was thinking of using an AC adaptor)
-The "bypassing stages" is taken from the JVM410, and i think there will be no pop.

About the diode thing, i'm not quite sure. that will reduce the gain and give compression. The reason why i choose the SL-X (super lead extended) instead of the High Gain Master Volume was because:

1. The SL-X was a full-tube circuit (except for the channel switching IC). No diode clipping like the dual reverb or the High Gain Master Volume.

2. The SL-X added another stage, which was a pretty common mod during the 80s (e.g. Levi & Caswell and the famous AFD amp, the SIR #36/39)

3. The SL-X was the the Marshall version of the Dual Rectifier topology.

I did modify some values, since the SL-X concentrated most of the gain in the preamp, while the previous models were 50/50 between pre and poweramp. The SL-X and the JCM800 2203 were based on typical mods (the 2203 was based on the one-wire-mod) and marshall f****d up big. It's a monster amp, and it's still missunderstood.

Back to the emu, I dont know if it needs a LPF as it is, buy maybe a 330n cap between the 4th stage and the tonestack.

And of course, always, ALWAYS breadboard before even thinking of making a PCB. The PCB is not mine, is u4ubaid's. The rest is mine (and Marshall's).


http://www.diystompboxes.com/smfforum/index.php?topic=79572.0

[dschwartz]

Interesting design!
as stated above, this must be used with fets like MPF102 or similars, with j201, this will go crazy with gain.. Other option is to adjust the voltage dividers between each stage to control gain.
Consider these recomendations for a more professional result:
- Tonestack: scale down the tonestack by a factor of 10, or add a buffer after the volume pot. as it is now, there is too  much output impedance..
- Treble: As it is, this will sound trebly as hell...put a LPF (or two) near the output to tame harshiness and step up the bottom end..SRPP will have enough volume to spare.
- add diode protection for reverse polarity
- 100uf feels like not enough for me..try 220uF or 2X100uF + 100 Ohms resistors,  like dr boogie
- probably the switches will pop, since there is ~1/2 V+ at the fet gate, i´d at least add a series resistor with the gats to avoid damaging the fets when switching. Nicer solution is to add a coupling cap before each fet gate that is conected to a switch.
- Idea: add a switchable diode clipping after the last stage to emulate older JCM900´s diode clipping,it may sound good, who knows? try 2 diodes per side if you´re using more than 12 volts
-Breadboard it first, then update schem and PCB
- PCB design presented is not very efficient, with a better use of space. With more patience , the layout can be half big..

regards!

Hi Daniel.
-My suggestion always was to use MPF120 and/or 18v.
-About the tonestack, it could be scalled down or use a buffer (simple source follower with 10k)
-I'm 100% with you about the caps, resistor and diode protection (i didn't consider this, since i was thinking of using an AC adaptor)
-The "bypassing stages" is taken from the JVM410, and i think there will be no pop.

About the diode thing, i'm not quite sure. that will reduce the gain and give compression. The reason why i choose the SL-X (super lead extended) instead of the High Gain Master Volume was because:

1. The SL-X was a full-tube circuit (except for the channel switching IC). No diode clipping like the dual reverb or the High Gain Master Volume.

2. The SL-X added another stage, which was a pretty common mod during the 80s (e.g. Levi & Caswell and the famous AFD amp, the SIR #36/39)

3. The SL-X was the the Marshall version of the Dual Rectifier topology.

I did modify some values, since the SL-X concentrated most of the gain in the preamp, while the previous models were 50/50 between pre and poweramp. The SL-X and the JCM800 2203 were based on typical mods (the 2203 was based on the one-wire-mod) and marshall f****d up big. It's a monster amp, and it's still missunderstood.

Back to the emu, I dont know if it needs a LPF as it is, buy maybe a 330n cap between the 4th stage and the tonestack.

And of course, always, ALWAYS breadboard before even thinking of making a PCB. The PCB is not mine, is u4ubaid's. The rest is mine (and Marshall's).


http://www.diystompboxes.com/smfforum/index.php?topic=79572.0

it may be no pop, but my gess is there will be..i don´t know, sometimes i´m wrong:P

about the clipping diodes..i just think it would make a nice easy feature to approximate to the older JCM900.. they were crappy..but many people love them! If you use various diodes in series to ground, you will not loose too much volume....

[ubaid88]

pcblayout updated.

Component layout(200% of the orignal size.)


Ready to Transfer Layout

http://www.2shared.com/file/8963476/3d6e1e8/pcblayout.html

[rroza]

Any updates in regard to this one??  Did anyone build it and verify it?  Are there any sound bytes??

Robb

[anti-idiot]

The PCB has some small issues which may lead you to oscillation (too many wires crossing over).

The LED should be a tricolor LED, not 2 LEDs (That way you'll have green, orange and red indicators).

[meffcio]

Any samples?