Blackpool - Marshall on steroids

[sinner]

This is little something I was working on lately. It started as an all-doing combo amp that I was going to build for myself to take on jams with my buddies. Amp that could go from early marshall sounds up to modern high gain distortion

It started to grow big and there is no way I will fit this thing into bluesbreaker type combo enclosure so I'm thinking to build it as an head somewhere in future.

Here's description I've made for sloclone forums:

This is something I'm working on since quite a while.

It started as a project based on Marshall JTM45 with some twists I was going to build into 2x12 combo enclosure for my personal use. Idea was to have Bluesbreaker-alike appearance with few additional features taking this lil amp into more high gain territories

In time projects evolved into dual channel head idea, and I'm going to develop it in this direction.

What it is is basically cross between vintage Marshall SL topology with additional gain stage (stages) wired after the first one. If you look on the Cornford RK-100 schematic you will see similarities, yes - I took that idea from RK-100. Why? It's less 80's that way, that's the modern sound approach that I dig more. Brown sound is gay and so well-worn. I did this (panel) switchable - kind of my take on Marshall Vintage-Modern amp

I had half valve unused, so I have added spare triode to serve as a return stage for clean channel. I have nicked that from our beloved BE-100. I was also thinking and I'm quite sure I will go for it - to add diode clipping to the clean channel to make it switchable between clean and crunch

Switching between clean and OD channels will be done on relays, I want to add dedicated fx loops for each of the channels as well as presence and depth (thanks Jed for inspiration)

As you see the schematic is not quite done yet. I'm still on it. I was going to post it here with hope for community project AFTER I do my part and finish it up as I see it, but being between jobs (finishing old and started new one already) Time is a luxury. I will finish it up as soon as I can.

This is kind of learning process for me. Huge part of what I know I have learned here. I'm hoping you guys appreciate my little contribution and help me to improve it making great alternative to threadbare Marshall-alike hot rodes

I'm happy to draw Vox-alike tagboard layout when I (we) done with schematic. PCB's nor turrets are not my kind of thing

Any comments are welcome and appreciated

Right now I don't do much with this design, but I'm sure I will back to it at one point. Probably will do it less complicated - less = more, right? Or maby just for the hell of it more complicated? Will see

I will just leave it here, maybe you will find it useful for your own megaplex ideas

Have a fucking nice weekend

[IvIark]

Nice one buddy. Have you got the components list?

[sinner]

Ok, just realized that this is old version schematic, clean is now done differently. I cannot find updated version on THIS laptop, just add another v1a ra is series and set coupling cap to clean's channel tonestack between those two. Highier B+ for clean channel = greater headroom, more Ra for overdrive = less headroom, more drive. That's it

[sinner]

Nice one buddy. Have you got the components list?

Well... yes I may, but I was thinking about this as a kind of user development platform. I can list you the most popular values for all and any of the circuit blocks if you want

[Groovenut]

Nice job Sinner!

It looks good and should have a ton of gain on the lead channel. I personally dont like bright caps on master volume pots but if the amp isn't bright enough they might be needed. The C5 R11 treble peaker might be better relocated between Volume a and the switch so as to not have the two treble peakers in a row. Nice use of the AX84 style ganged gain pot. Makes the gain control much more useful (though anytime I have used dual gain pots I always wind up running the second one wide open). Do you think C38 will be necessary? I know of a few Engl designs that use that but their circuits are a bit on the buzzy side, so it helps there. Also is the C29R2 fixed resonance necessary if you have the two adjustable resonance pots?

Just my two cents. As is it looks pretty good just thought I would chime in

[sinner]

Thanks Groovenut

Yep, fixed resonance is a mistake on my side. Early version leftover

Dual ganged gain control is there to give you an ability to go higain as well as clean ccw. Also early version take when this was just a single channel amp. I may just stick fixed divider before 3 gain stage.

Bright cap on mv is just a something I've seen in dumble amps and I was curious to try. It's easy to clip it off

C38 anode bypass cap may be needed, but not necessarily where it is right now also it's better to actually set it from anode to ground instead of HT. Helps to fight off parasitic oscillation in the same way but without applying HT noise straight to the anode. Extra gain stage may need this depending on how we voice it

Whole fx loop probably will be charged to high voltage mosfet type. Save whole valve and won't serve as another voicing factor.

You right about treble peaker. The thing I want to do in the final version is to make a schematic with all possible mods and addition, just for a sake of having multi purpose platform. Most if not all mods and additions can be easly omitted but not easily added if/when needed

It's gonna be kind off like sloclone forum's Jed amp projects. Blend your own crap in it and build as you like

I'm learning how to program controllers since quite a while, so this going to be DA BIATCH when ill be done with it

[DrNomis]

Thanks Groovenut

Yep, fixed resonance is a mistake on my side. Early version leftover

Dual ganged gain control is there to give you an ability to go higain as well as clean ccw. Also early version take when this was just a single channel amp. I may just stick fixed divider before 3 gain stage.

Bright cap on mv is just a something I've seen in dumble amps and I was curious to try. It's easy to clip it off

C38 anode bypass cap may be needed, but not necessarily where it is right now also it's better to actually set it from anode to ground instead of HT. Helps to fight off parasitic oscillation in the same way but without applying HT noise straight to the anode. Extra gain stage may need this depending on how we voice it

Whole fx loop probably will be charged to high voltage mosfet type. Save whole valve and won't serve as another voicing factor.

You right about treble peaker. The thing I want to do in the final version is to make a schematic with all possible mods and addition, just for a sake of having multi purpose platform. Most if not all mods and additions can be easly omitted but not easily added if/when needed

It's gonna be kind off like sloclone forum's Jed amp projects. Blend your own crap in it and build as you like

I'm learning how to program controllers since quite a while, so this going to be DA BIATCH when ill be done with it

I noticed with that first schematic you posted that you've got resistors going from the cathodes of the power valves to the suppressor grids, in my amp head I'm using two 1 Ohm 5 Watt Ceramic Wirewound resistors to connect the cathodes and suppressor grids of the power valves to circuit ground, I'm rebuilding my amp head as a Sloclone 50, the previous design had a Triode/Pentode switch in the power amp so I could switch the power valve configuration from Triode to Pentode, this effectively drops the amps power output down to 25 Watts and also causes a slight change to the tone of the amp.....


One thing you could try doing is make the bright caps switchable.....

[sinner]

PA is not finished yet, nor the PSU. I don't think I will go with triode in this one, more likely some way of power scaling will be presented