Guitar Amplifier Design

[stevenj]

I am studying electrical engineering and I have also been a guitar player most of my life.  It's now time for my senior project and I want to design a guitar amplifier.  This design/build/test cycle will go from this September till next March where I then should have a working build and a report backing it.  There are so many options as far as discrete, chip, etc...  Basically, I'm looking for a few different designs to base mine off of.  Any suggestions for a low watt (<50) design?

[teemuk]

What kind of features should it have?

Sounds kinda like a project where I'd really would choose just something quite simple and easy; building the thing may not be a problem nor overly time consuming but documenting the project in proper extent - if I understand correctly - is where these things fall down to and you may find yourself seriously struggling if you try to chew a too big piece at once.

Google for a few schematics and evaluate. What pops in my mind are designs like the Vox Pathfinder, the low power solid-state Marshall JCM800's (eg. Lead 12) or perhaps some of the MG series amps, basically anything in the sub 50W range that doesn't have DSP or anything too fancy in the features department.

[joecool85]

Easy to build but also useful amps are the old (1980's/early 90s) Dean Markley series like my K-20X that I won't stop talking about.

Schematics are available here: http://deanmarkley.com/Info/LegacyAmps/Docs.shtml

I would suggest regardless of what you go with to pick one primarily using "chip" power amp circuits and opamps (TL072 etc) in the preamp.  This will keep your design simple, inexpensive and also relevant in today's industry.

[stevenj]

As far as features go I'm going pretty basic.  Gain pot in the preamp, bass, mid, treble pots, and a master.  I had originally considered chip-based or op-amp based but I thought that it may not leave me quite as much design flexibility or creativity.  What are your thoughts?  I've been reading through Kyttala's recently posted PDF on solid-state guitar amplifiers and I find it quite enjoyable but also very overwhelming with possibilities.

[J M Fahey]

From the above discussion I suggest you build the Lead 12 preamp which is exactly what you wish and sounds very good, plus a 15 to 50Wchipamp.
The power amp is noy the place to become creative, from 1W to 1000 they are different sizes of big Power Op Amps, conceptually the same.
You generate your almost-ready sound from the preamp, and the faithfully boost it to speaker levels.
What I suggest can be built in a reasonable time (as was said above, not only the actual "soldering" time but layout, PCB design, chassis construction, etc. , plus debugging :grounding, hum, hiss, maybe even radio interference)

[stevenj]

Alright, you guys are definitely swaying me more towards chipamps.  I'm reading Teemu's coverage of chipamps.  Do you recommend any other resources to learn more about different variations of chipamps and design struggles that sometimes render them inferior to discrete?

[stevenj]

Also, to add to the previous post.  Are there any chipamp schematics that you know of that have some annotations that mark key voltages so I can get a better idea of what simulation I should try to create.

[joecool85]

Alright, you guys are definitely swaying me more towards chipamps.  I'm reading Teemu's coverage of chipamps.  Do you recommend any other resources to learn more about different variations of chipamps and design struggles that sometimes render them inferior to discrete?

I can't think of any literature off the top of my head, but searching and reading on this forum always provides a wealth of knowledge.

[phatt]

I Can't see why the need but; http://www.national.com/ds/LM/LM3886.pdf.
Basic circuit only but should be enough to get a sim happening. :tu:

Schematic,, page 7.
Phil.

[J M Fahey]

Agree, there's not much to simulate.
It's a *big* op amp, able to supply 5 or 10 Amperes into the load instead of 5 to 20 milli Amperes, and stand +/-28V to +/-45V rails instead of +/-15 to 18V , but its behavior, clipping, frequency response, etc. is exactly the same.
If you need to simulate anyway, I *guess* that you can specify any generic op amp, but editing its parameters or properties into chipamp datasheet values, similar to what I suggested.
Of course the *best* simulation is not run on the PC but on the table, surrounded by a cloud of solder fumes, he he.

[joecool85]

Of course the *best* simulation is not run on the PC but on the table, surrounded by a cloud of solder fumes, he he.

Exactly.  It's time to get the lead out and build it.