Marshall Silver Jubilee - Tagboard layout with mods

[Turret]

Since I have a lot of free time recently and I'm trying to learn as much about valve amps as I can. I decide to jump on tagboard (VOX style) layout for this amp. Mainly because is more advanced than other layouts I did before - Relay switching, odd tonestack, diode network clipping stage... Sounds like fun, large field to learn for noob

Even so I'm a noob, I decided to fuckaround little with the schematic, and I wonder what you guys think about it

Firstly I have added additional volume (preamp gain) control for clean channel as suggested by DrTube. It uses remaining half of relay.

Also, I decided to go with early JCM800 PA and PS - better filtering, Marshall went with poorer PS in Jubs and later JCM800's as far as I learned

I have changed stock pre PI master volume to PPIMV from Trainwreck Pages modified by Larry (metro forum member, great amp builder)

I have attached complete schematic, but without part values, and my layout. Component layout is almost finished, just few connections left

I'll be happy for any feedback, specially with constructive criticism. If you need the schemo and layout with component values now, let me know. I presumed it will be simpler to read that way

The chassis I had in mind doing my project files is the one from valvestorm.com - 69plexi with blank front panel - seems perfect for this

Cheers
torg

[RB]

Hello Torg

Beautiful - Very precise documentation.
Thank you so much for your generosity.

Regards
Randy

[Turret]

Thank you RB, you welcome, but don't heat up your iron yet

I'm not sure about my modifications, specially the PPIMV implementation. What I did is I simply dropped (ommited) old master volume. I set the signal from middle lug of treble pot straight to the PI input cap.

Do I have to change any circuit values doing this?

[Reeltarded]

1st VERY NICE!!

Don't delete the simple master. You will make the clean channel useless with just a PPIMV.

[xtian]

Yaw, beautiful work, mate! Adobe Illustrator?

[Turret]

@Reeltarded - so you suggest to go back to stock Master Volume setup?

@xtian - no mate, it's DIYLC v3 https://code.google.com/p/diy-layout-creator/ With just a little of creativity you can do everything with it.

[pablogt]

I tried a number of different master volume alternatives in that circuit, including traditional and PPIMV. The most transparent one was the bootstrapped MV (see schema). It also uses a tandem pot. For my taste, PPIMV generated a too "grainy" distortion (due to loosing NFB at lower volume levels) and the traditional loosed a lot of treble at lower settings

Pablo

[Reeltarded]

The channels both need local master and whatever other master setup you would choose or the clean channel will be the victim of the dirty channel when you start turning knobs.

I also dislike the PPIMV for loss of NFB at settings below 7 or so, but it can be nice as just a pad above 7-8.

Pablo is probably right about the bootstrapped master. I haven't used it. I normally use a CF master and the simple pre-PI together. (plus he's always right)

[pablogt]

[Turret]

Bootstrapped MV? Never heard about it before... Does it also affects the presence control?

I wanted to include the fixed deep circuity, as seen in Cornford amps, but I don't want to fuck around with the spec to much

What I'll do is, I'll make two more layouts and schematics

One with bootstrapped master and one stock

Should be ready for tomorrow

[Turret]

double post, I'm sorry

[xtian]

it's DIYLC v3 https://code.google.com/p/diy-layout-creator/

I love it! Will you post your source for the Silver Jub? And any others? Or maybe you know a good place to find such files for DIYLC?

Thanks!

[xtian]

-duplicate

[Turret]

Sure

Here's the Jub files zipped (schemo, and project data). Let me know what else you need/want

If you going to rework it and publish anywhere it would be nice of you if you leave specific comment with the name of my website

[xtian]

Thanks! I won't be messing with the Silver, but the 1987 plexi, or jtm45, or jcm800, those would actually be useful.

Actually, i would encourage you to start a "DIYLC files" thread in the Marshall Discussion forum here.