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12w Marshall

Started by Tassieviking, July 22, 2022, 01:39:40 PM

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Tassieviking

I started to looking into building a 12 watt Marshall by mixing all the 12watt Preamp circuits I found, and also mixing the 12 watt and a 30 watt amp circuit in Marshall amps so I could make any one of the 12 watt amps with 12 to 30 watts output on the same PCB. You just had to pick the right components to make the version you wanted.
Some 12 watt amps had a Bias pot and some did not. Mk1 preamp has diode clipping and the later ones dont, etc.

I got derailed when my dad got sick, traveled from Tassie to northern NSW (Australia) and spent 4 weeks with him. Had to go back to Tassie for medical reasons and be with my family for a week, then back as dad passed away as soon as I left, stayed 5 weeks then back home for Doctor visit and now I am going back up to pack what I want to keep and sell the rest, sell houses, cars,  etc.
I am going to sort all my stuff nice and neat when I get a chance because its hell trying to go through your parents stuff when they are both gone and everything is all over the place.

Anyway, this is as far as I got on a 12 watt amp before the wheels fell off.
I was going to post the KiCad files  of the PCB when I finished and still might when or if I get back to it. I put a jumper on the board if reverb is not wanted, and a place for effects to be inserted which can be bridged if not wanted.
I made the PCB so TO3 transistors had to be wired in or TO247 can be used on PCB.


There are no stupid questions.
There are only stupid mistakes.


joecool85

Great work!  I split the topic though and made this it's own so it can be an easy resource for others later.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

Tassieviking

I have finally gotten back home a week ago and had some time to  work on this PCB, I can't guarantee it's correct but I will order some PCB's for myself later this year to test.

I decided to squeeze in a 9V regulator for pedals as its a smaller amp and is good for practice and learning on, and it cant hurt to be able to run a pedal or two from the amp.

I have made the Gerber files for JLCPCB to make the boards, but feel free to use the project any way you want.
I am going to use the KiCad schematic to make a pedal eventually as well, without the reverb circuit (unless I can get the correct mini spring pan).
There are no stupid questions.
There are only stupid mistakes.

Tassieviking

If you want to see the pictures larger, right click on the small picture and select open in new window, this makes the picture really large.
There are no stupid questions.
There are only stupid mistakes.

joecool85

If I could like this more than once, I would!  Please share results when you get a chance to build it.  I'd love to hear it play too!
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

Tassieviking

Slowly making progress, I got some PCB's made so I can test make some.
I ordered the PCB's from JLCPCB and picked the cheapest shipping, I have too many other things going on so I was in no hurry to start.
They got to me faster then I thought so now I have to get some components I don't have on hand.

I also found a circuit for the 12 watt Bass amp so I modded the PCB so that can be build as well as all the other 12 watt Marshall circuits I found.You cannot view this attachment.

I made a PCB for a front panel as well, I always wanted to try that out.

I also got some Sound Lab L4 Bass pre-amp PCB's made for an experiment, I don't know if they will work or not but I added one  LM13700 chip instead of a CA3080 and a CA3094 as original. I am to lazy to breadboard the whole pre-amp to try it out because it is so bloody big.
 
There are no stupid questions.
There are only stupid mistakes.

joecool85

Quote from: Tassieviking on November 10, 2022, 04:38:11 AMSlowly making progress, I got some PCB's made so I can test make some.
I ordered the PCB's from JLCPCB and picked the cheapest shipping, I have too many other things going on so I was in no hurry to start.
They got to me faster then I thought so now I have to get some components I don't have on hand.

I also found a circuit for the 12 watt Bass amp so I modded the PCB so that can be build as well as all the other 12 watt Marshall circuits I found.You cannot view this attachment.

I made a PCB for a front panel as well, I always wanted to try that out.

I also got some Sound Lab L4 Bass pre-amp PCB's made for an experiment, I don't know if they will work or not but I added one  LM13700 chip instead of a CA3080 and a CA3094 as original. I am to lazy to breadboard the whole pre-amp to try it out because it is so bloody big.
 

Awesome! Stoked to see this come together!
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

phatt

Brilliant work TassieV,
Can I ask how much this has cost you so far?
Of course one would still have to add the cost of a Chassis and a Cab for a complete build.
Phil.

Tassieviking

I'm not sure how much this one cost.
10 off 12 watt PCB's  US$ 11.40
10 off 12 W front facia PCB's US$ 18.60
5 off Lab Series L4 PCB's US$ 8.00
Shipping cost US$ 23.10

I have most of the components, but I had to order some pots and transistors for them.
I also bought a toroidal transformer for the Marshall 12 watt, 30V CT 50VA.


There are no stupid questions.
There are only stupid mistakes.

joecool85

Quote from: Tassieviking on November 12, 2022, 09:30:27 AMI'm not sure how much this one cost.
10 off 12 watt PCB's  US$ 11.40
10 off 12 W front facia PCB's US$ 18.60
5 off Lab Series L4 PCB's US$ 8.00
Shipping cost US$ 23.10

I have most of the components, but I had to order some pots and transistors for them.
I also bought a toroidal transformer for the Marshall 12 watt, 30V CT 50VA.




+1 for the toroidal!
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

Tassieviking

#11
The 50VA Toroidal I had ordered lasted 1 minute before the primary went O/C, I went to a local shop and grabbed a 20VA 30V CT transformer yesterday and tried again, all seems good so far.
I tried it with the 12 watt reverb circuit and mostly ok, when I tap the box I get reverb noise even with reverb pot on zero, possibly feedback through the final OP amp ?
Anyway, it sounded good through a Celestion V-type 70watt speaker I had on hand.
I built this one using 2N3904, 2N3906, TIP142 and TIP147 transistors in the power amp.
I borrowed the reverb from a Marshall G15RCD someone gave me earlier in the year, not the correct reverb tank but close enough for trying out.
At least it worked first time so I'm happy.
Now I just have to get some ply and make a cab for it, and a speaker and reverb tank.
I am also making a 12watt Bass version at the moment so I will have to see how that goes, I might have to modify it as I think the Bass version has some HP filters that are a bit too high for my liking.
I might make the cabs slightly larger then original because the original Bass cab was open back the same size as the lead cabs.
I might make the bass cab a lot deeper but the same front size as the lead and reverb cabs I am going to make for these.
Here is the Gerber file I sent to JLCPCB to make the PCB's, and the latest revision of the BOM.
I have noticed one fault with the BOM already, C24 on the 30W Bass 5503 list should be 220nF and not 22nF.
The schematic is a combination of all the 12watt schematics I found, and the power amp section is a mix of all the 12 and 30 watt schematics I found.
Just use the right combination of components and it should be ok.
There are no stupid questions.
There are only stupid mistakes.

guzzis3

Hi,

If you had to order extra PCBs that you want to sell I'd be very happy to buy them from you. I am in Brisbane,

This is my first post to this forum. I was pointed to this thread by a person on the marshall forum. I've been building electronic stuff since I was a kid but while I have built quite a few valve guitar amps I've not built a SS one.

I have the complication that I had 2 strokes in 2020 and am now part blind. The part of my brain that processes the written word was also damaged so I can barely read. I don't mention this looking for sympathy. I just need to explain sometimes I can't read things and sometimes it takes me a long time to get to things, so your patience is much appreciated.

I have a 8008 marshall power amp, 80w a side into 4 ohms. I could build a stereo preamp and run it into that or build a stereo amp including output stage. Have you determined if the 5005 etc develop their distortion in the preamp, power section or both ?

I realise you haven't finished your design, and there may be problems, but starting even with a flawed PCB is probably easier than laying it out on tag strips or breadboard.

Thank you for reading.

Dino Boreanaz

Hey guzzis3, I'm glad you made it over here!  Lots of amazing, knowledgeable, and helpful people here.  Enjoy!

Tassieviking

G'day guzzis3, welcome to the forum.
I often drop in on the Marshall forum as well.
I don't own a Marshall, but one day....
I can't afford one on a disability pension.
I sent you a PM for your mailing information.
Well se what happens next time I go into town.
There are no stupid questions.
There are only stupid mistakes.