Sorry, but I am not going to publish full amp schematic (no hard feelings). Will share some conclusions, solutions and experiences acquired during the building process. I sincerely hope that it will help others to focus mind and work in their own, right direction.

I was flipping through my documentation yesterday and found something you might be interested in. Rare Marshall 2201 JMP Lead & Bass 30W 2x12" Combo schematic.

Have fun ...

Rivera era Fender SS amps (Montreux, Stage Lead, Studio Lead). Nice clean and reverb.

@exztinct01

It is active circuit (OP Amp based) with optimized feedback network (gain and structure). The gain for each input is different to achieve optimal level and ratio of mixing signals at the output.

Best regards ...

@exztinct01

Letter "sigma" is summary sign, so that block represents the summing stage (mixer).

Best regards ...

A little bit about concept and technicalities ...

Specification :

Single channel amp
Speaker : Celestion 8"
Output power : 4W (switchable to 1W)
Front panel layout : Input, Single-coil/Humbucker voicing switch, Boost switch, Volume, Middle boost switch, Tone, Intensity, Effect On/Off switch, Delay, LED indicator, Main's power switch
Rear panel layout : Main's power input/Fuse holder, Speaker output, Speaker On/Off switch, Output power switch, Headphones output, Line output, AUX input
Cabinet dimensions : 450mm x 360mm x 230mm

At that moment I had Celestion Super 8 in possession. Cabinet is made of 15mm thick plywood, finger-jointed. I've chosen plywood over pine because I wanted a little tighter sound. By the way, I apply 7V, AC to a speaker for 12 hours in addition to loosen up it's cone.

The final goal was to produce a practice amp, as simple as possible, with all necessary features according to "my specs" and at the lowest cost, using simplified Howler's bulding blocks. Naturally, above a certain, defined criteria. "Amp has to take pedals well" condition, referring to preamps, boosters, TS derivates etc, is a must on. That automatically determined a part of the concept. There has to be a stage, in front of the volume control, that will "cope with problem". The rest of the layout is pretty much ordinary as you can see in the block diagram, except for the output stage.

"At the lowest cost" criteria determined use of a chipamp. Considering that and the output power, the reasonable choice was TDA2030A. Datasheet schematic was used only as a starting point. The stage is operating in a mixed mode feedback regime with implementation of a few nested feedback paths. Personally, I don't like to use chipamps in output stages and since the project exceeded expectations, I'll probably replace it with one of my own discrete designs. You can see the output stage in the second picture.

The last picture shows the amp's guts ...

@mckayprod

Thanks for the kind words. I totally agree with you considering the tone :tu: (a little to bright), but I wanted to present that strat tone "as Fendery as possible". It is a little exaggerated ("guilty as charged", tone pot was pretty high - around 3 o'clock) but I also wanted to show that solid-state tone is not necessarily "ice-picking" in it's clean or overdriven form. Just roll back the tone knob on the amp - problem solved without tweaking guitar tone controls.

The idea was, also, to produce an amp that sounds good both with single-coils and humbuckers. I think you'll agree that without decent amount of treble, with humbuckers, amp tends to sound a little dark. That's why I implemented single-coil/humbucker toggle switch and voiced the amp this way.

Best regards ...

I've just read the message again and saw the part "If you are interested ..."   xP  :loco

Sorry, didn't mean "interested in the terms of purchasing". I apologize to all forum members and visitors for that.
Just ment that I am willing to share some additional informations considering project if anyone is interested in technical terms.

Message "fixed", hope no harm done ...

Mangas

It has been quite a while since my last post. Meanwhile, "The Howler" project experienced a lot of iterations and reached its final stage (I'll talk about that some other time). Anyway, the new idea was born and materialized based on the same concept. I would like to share it with you.
Practice amp with switchable 1 to 4 Watts output power (yes, solid state amp with built-in power attenuator), AUX input for "backing track use", integrated 50 mW headphone amp with dummy load (not just plane disconnection of the speaker and attenuation of the output power level), emulated output for recording, built-in FX module (my design, PT2399 based (only one chip used), not the infamous Belton brick) ... And yet, I tried to make it as simple as possible (only plane volume and tone controls, middle boost and boost switches, single coil/humbucker switch ... And ... I named her "The Toy".

This is the result ...

https://youtu.be/j47IyNkgv2M

https://youtu.be/UsENW2NEOBI

Videos were recorded with shitty camera microphone, Fender Stratocaster straight into the amp, no effect pedals, just a little of my "PT2399 'verb" ...

The middle boost switch and the attenuator were not built in the prototype (I added them later), but I think you'll get the idea 

Cheers ...

Nicely done!  :tu:

The rest of the files ...

Finally, the time for uploading some preliminary sound samples has come  xP xP xP . The clean channel is almost finished. Only a little "polishing" is needed considering a choice of active components and capacitor types (ceramic (np0, silver mica), polyester, polypropylene). Thanks for your patience. All comments are welcome.

A little info on clips :

Fender_1.zip (Fender_Clean.mp3) - Fender Stratocaster, neck and middle position pickups, clean sound (volume on 5, treble on 8, bass on 6, reverb on 5, middle boost off). Had to cut off intro to fit the file into 512kB. Sorry.

Fender_2.zip (Fender_Attenuated.mp3) - Fender Stratocaster, neck position pickup, amp fully cranked, guitar volume pot rolled back (volume on 10, treble on 6, bass on 6, reverb on 3, middle boost on).

Gibson_1.zip (Gibson_Clean.mp3) - Gibson Les Paul Pro Deluxe, both pickups, clean sound (volume on 4, treble on 6, bass on 6, reverb on 5, middle boost off).

Gibson_2.zip (Gibson_On the verge.mp3) - Gibson Les Paul Pro Deluxe, neck pickup, on the verge of distortion (volume on 7, treble on 7, bass on 6, reverb on 5, middle boost on).

Next stop ... The boost channel

QuoteImpressive piece of Engineering.
I loved the "motherboard".
I always suggest everybody to get a piece of plywood or pine, mount there a Proto (or two) and screw solidly a piece of aluminum full of holes for jacks, pots and switches, but yours deserves a Nobel Prize.
Congratulations.

Thank you J M, for your too kind words. You're making me blush. 

QuoteI guess you must have full access to a well equipped factory or metalshop, that amp was not built in a log cabin in the woods.

I wish that was true. Believe it or not, 70% of the amp was assembled on the floor of my study because the desk is not big enough for all of the instruments, modules, wires and cables. That creative disorder of mine is driving my wife crazy.  :grr
I have a few pals - one is good with metal, another is good with wood ... All in all, they are a bunch of crazy enthusiasts (like myself) ready to "meet my demands" at reasonable fee. What can I say... I am fortunate to know a couple of guys like that.

QuoteBut hey that's what is good about other eyes looking at our work, there is often someone who has thought of something I may miss.

I couldn't agree more.

QuoteSomething does not sit right in my head with the first post pic, the bottom pic. The mains input board has the mains cable *Earth wire* terminated on a PCB. Then I assume a thin copper track back to another terminal and then finally a lead to the chassis bolt. I'm just wondering if this is safe practice? From memory this would not pass Austrailian standards but other countries will have differing rules. I personally would make a *Direct unbroken wire* to Chassis terminal from a mains cord. In fact when I can I make sure the Earth wire is the longest so that in a worst case situation where the cord is yanked from the chassis the Earth wire is the *Last one to break* thereby minimising the risk of shock to the user.

And I am very glad that the fellow forumers pay that much attention to my posts.

First off all I would like to say that what you see here is not a final product, but the prototype. Only the PCBs have their final form. I'm surprised nobody has mentioned somewhat bizzare chassis construction. Initially my intention was to build something like 1970's Fender Champ - a little practice amp with Volume, Bass and Treble controls. So I bought 8" Jensen speaker, built appropriate cab and ... found out that I have Accutronics type 8 reverb tank spare. And it begun ...
Reverb? ... Why not?
Footswitchable? ... Why not?
Normal / Boost ... Why not?
Footswitchable? ..........
And there I was ... A zillion ideas running through my head, a little neat cabinet with sweet sounding speaker and ... a lack of space in the cabinet. Finally, I managed to tuck all in at the cost of chassis specific shape and component disposition.
The final product will have bigger cabinet, 10" (probably 12") speaker, chassis mounted male IEC main's socket and detachable AC power cord. Main's wiring cable (two layers of PVC insulation) will be mechanically fastened at both ends (Main's PCB (the pic previously posted) and Main's socket) inside the chassis. So, there is no way to "yank the cord" from the main's PCB and break "The Earth wire". Beside the fuse, there are the earth isolation circuit (10 Ohm resistor, 100nF capacitor, two antiparallel diodes) and metal oxide varistor as additional safety components. All capacitors are class X2.

Pretty safe ... I'd say.
     

A little info on progress ...
Still working on the clean channel. I don't want it to sound "clinically clean", as the vast majority of solid state amps do, so it has to be tweaked very carefully. The sound tweaking is performed using my genuine 1965 Les Paul Pro Deluxe.



So far, everything slowly fits in its place. Sound is very opened and dynamic. The amp is starting to lose its clean tone when volume pot past 2 o'clock and cleans up well with the guitar's volume control (when cranked). But, there is a little "thing" that still bugs me and I am not completely satisfied with the result. On the verge of distortion, when light picking produces a clean tone and heavy picking produces a distorted tone, everything sounds cool (two and three strings riffs, full chords, single notes) except tones generated by extremely heavy picking high E and B strings in the high neck position. This is evident only when using a plectrum. Playing with fingers doesn't "show this phenomenon". It is not so evident and has nothing to do with sudden "transistor amp distortion", ghost notes, etc ... It just has no place in sound pattern by my criteria, period. I can easily get rid of it, but "standard ways" make sound less open and airy. So I had to modify some of the existing modules and build some new ones to solve the problem.



And "the battle" continues ...
I wish you all Merry Christmas (to those celebrating) and Happy New Year.   <3) <3) <3)

The Pre amp "test rig" is finished. All necessary modules (gain stages (op amp based and fully discrete), buffers, summers, clippers, ...) are assembled and tested. Everything is ready for the final tweaking (at last).

"The motherboard" :

   

Modules :



Some modules inserted into the board slots :

   

I know some of you think I'm moving too slow, but building a guitar amplifier from scratch (especially a solid state one) is very demanding "activity" and takes a lot of time, effort and patience to be properly done. I'm not trying to emulate anything here like ... "turning a transistor into a tube" (maybe this will happen someday ... during the full moon ... just kiddin'  ). I would be very happy if the final result turns out to be something that plain sounds good.