GUITAR AMP - a new design for an old standard

[GJB17]

Hi people. I have been designing, developing and building a few different Guitar Amps over the past few (many!) years.
This is my latest effort.
I would much appreciate any thoughts and/or critiques that you may have.
I have actually sold a few of these to mates and acquaintances... but am now at the point where I would like to retire from my retirement... if you know what I mean!?
I'm just getting to old for this stuff!
So if you, or anyone you know might be interested in picking up the chalice I would be glad to hear. Depending on their context there may need to be some "nominal costs" attached.

Anyways... enough of that... the technical stuff follows...
In its simplest from the unit mimics a "regular" guitar amp...
* Outputs up to 50 watts or so
* Has a standard FMV tone control stack
* Both gain and volume can be separately adjusted
* Standard HI / LO high-impedance Inputs
* Etc... etc.

Now for the good bits!...
* Is built in a much smaller and lighter case than a "regular" Amp - actually in a standard Hammond case... roughly 6 x 8 x 6 inches... and only a few kilos in weight! (No more lugging a huge Marshall Amp up the stairs!)
* IMPORTATLY... uses a (discrete) FET based preamp that mimics the characteristics of a triode valve preamp... e.g. the ubiquitous 12AX7. How this is done is somewhat technical. Google "Dimitri-Danyuk FET Triode Emulator" for a full description. His Paper on this was originally presented at an AES conference some years back.
* (In this version) Uses a high efficiency Class D amplifier (pre-built) module... but
* Can also be built with a TRANSFORMER coupled output stage that I have developed driven by power MOSFETS. While a little larger now also gives a nice power amp overdrive tone... and 100+ watts of output power.
* Using the preamp and power amp in combination can produce anything from clean "jazz" tones to all-out crunch!
* Has the standard HI / LO (unbalanced) input connection - on 1/4" TS connections... but...
* Also has a low-impedance BALANCED input connector - on 1/4" TRS connection which provides really nice tones on guitars using an acoustic pickup. This input has a separate Gain control (as shown)
* (Looking along the front panel) Has a "BOOST" switch that (in a simplified view) alters the characteristic of the preamp that produces a more "edgy" tone. This can also be controlled by a simple (pull to ground) Footswitch through the adjacent TS connector. Great for switching clean to edgy tone quickly and cleanly.
* (Next along the row) A simple Line Output Jack that can be easily connected to a Mixer, Bigger Amp, Foldback Amp, etc...
* Also has an "INSERT" TRS Jack that can be selected as PRE or POST EQ... if you prefer to use an (outboard) EQ in lieu of the standard FMV EQ... or any other devices... Foot Pedals even!

OK... enough words... will await your thoughts.
Some pics attached. The one of the inside was from a prior version and does not include the front panel I/O's or the purpose built PCB's that I have subsequently done.

Cheers,
Graham

 

[ruffrecords]

Very nice build. I especially like the quality of the legend on the front panel. How did you do that.

Cheers

Ian

 

[GJB17]

Very nice build. I especially like the quality of the legend on the front panel. How did you do that.

Cheers

Ian

Hi Ruff... I always read your posts...
Labels were done by Laser Engraving (by others).
I would much appreciate any thoughts or suggestions on the build.
As mentioned I am getting to old (and tired!) to do any quantities myself and am wondering who / where / how I might be able to get something organised... any suggestions

 

[ruffrecords]

Hi Ruff... I always read your posts...

Labels were done by Laser Engraving (by others).

Interesting. I have not found anyone over here who is prepared to do it on a surface with bends in it.

I would much appreciate any thoughts or suggestions on the build.
As mentioned I am getting to old (and tired!) to do any quantities myself and am wondering who / where / how I might be able to get something organised... any suggestions

I feel for you. Some aspects of getting old are great - doing as you please and not going to work - others are not so great like health problems and the general wearing out of the body. I provide PCBs for many of my projects and quite a few I have open sourced so that people can get their own boards made. I still get loads of project related correspondence and do the occasional special design for someone to build themselves. I also occasionally license PCB layouts that are not yet open sourced, but so far I have not cooperated with anyone with the view to making quantities of a design (actually I have a couple of times but nothing came of it). As I am sure you are aware, there some serious hurdles to overcome before a volume product can be sold on the open market and I have neither the time nor the inclination to leap over them myself. Bottom line is I think you need someone much younger than you/me to take on that role. How you find that person I do not know.

Cheers

Ian

 

[jerry990]

Sometimes all that matters for the client (or wife) is the outside and how pretty it is, this would definitely fool the non-knowledgeable person, just make sure it's functional and label the performance with parameters properly