Hey, that's got a sound!  Very nice if a little bright for my taste...rolling off the tone on the guitar should fix that, or a humbucker box of some kind.  Good playing, too.

Just stumbled onto this british SS amp today.  Not sure what chip he uses for the final (TDAxxx, I think, can't confirm) but somewhere on the site he references TL072 opamps.  Quite a thoughtful design, IMO.  Anyone on the forum ever see or play through one?

http://award-session.com/index.html

Good reading on this site for design philosophy, etc.

That's a great video!  I had no idea the rework guys could do stuff like that.  It CAN be done!  I think I'll get a few different sizes of tips and some of that liquid flux and start doing more surface-mount work.

I'm just not very familiar with MOSFETs so I guess I'll learn some things, which is the point.  As I recall, these consoles were sold at the lower end of broadcast market, so I expect simple, durable, but not outstanding performance.  Maybe 20w of clean audio?  This should be fun!

MOSFETS!  Not what I had hoped for, but I want to find 40vac somewhere and try this thing out.  The chip has 16 pins for sure, so who knows what that is.  I may not dig too far into documenting this, but if it works, I'll use it.  Thanks, Enzo.

Aaaand, the photographer fails!  The chip is marked MA700, CP415, with a stylized, vertical SU or US on the left.  Means nothing to me; its a 16-pin IC so I assume its a quad opamp.

Let's try again with more light on the opamp...

I hope my pic attaches correctly, or I'm gonna look dumber than usual!  This is a monitor amplifier module from an old Howe Audio broadcast console we scrapped back in the '90s.  Couldn't be simpler, operationally, with balanced input (line level, probably), gain adjust, speaker out (not much power judging by the connector) and 40vac power input.  I think I'll play around with it, but documentation is nonexistent and I'd like to roughly figure out a schematic.  I can trace the wires, but can anyone identify the opamp or power transistors from the case markings?  Thanks in advance.

Got it.  Back to the search engine(s).  Thanks.

I guess I have another reason for wanting a lower power amp circuit.  What if I have a particular speaker that I like, but it can't handle 100w?  And, what if I'd like to monkey around with discrete components rather than a chip?  So, let's say I cut the power supply in half, giving Elliott's 100w arrangement 25w into 4 ohms.  And, my single 25w speaker is 8 ohms, so the power out is further reduced to (60%?) 15w.  I think that moves the project in the right direction, but how much can you reduce supply voltage before the circuit refuses to function at all?  If scaling a circuit is just a matter of applying fixed rules-of-thumb, I'm in.  Background:  I played through a Vox AC-15 with the Celestion greenback the other day.  Wow.  Wouldn't want to risk blowing one of those in an amp that will likely never see a stage.

Not sure where this topic fits in the forum, but I haven't seen it addressed.  I wonder what static discharge precautions the experienced builders and techs are using in this field.  I notice all the semiconductors I buy come in ESD packaging, and my previous job in an ISO 9001 factory setting had all workers in conductive smocks with shoe straps, wrist straps, controlled humidity, the whole deal.  They told us even passive components could be fried or weakened by ESD.  So, to prevent that kind of damage in my own shop, I use a grounded soldering iron and a wrist strap attached to the ground screw on the mains outlet.  Pretty minimal, but better than nothing.  I'd hate to toast a fancy opamp.  Thoughts?

This guy is a hoot.  Add a decent preamp to this (and maybe a zobel network) and I bet it'll work well for a low-power application.  Discrete components, easily adjustable sensitivity.  For some reason I can't copy & paste a link to this exact page, but go to http://www.sm0vpo.com/, then to the "Projects" tab then the "AF/Amps circuits". then "4-w AF amp".  Sadly, he doesn't have a board to sell us but the artwork is there.  Thanks, Harry!

Good points.  I guess I was hoping to avoid using a different transformer than the 20v I already have.  The way Rod built that project, you end up with a pretty compact amp, lightweight and with lots of room in a cabinet for reverb tanks and other small onboard effects.  Half power equals 3db less...words to live by!

I'm using the Velleman kit.  I originally used it as a quick-n-dirty guitar amp for my daughter, who got a strat copy for Christmas.  I built it into an old RCA hi-fi speaker with an on-off switch and a 9v battery.  As I remember, it sounded better on those single-coil pickups than it does with my humbuckers.  I think the battery power supply lacks enough current to give the chip all the headroom we are looking for, or at least that's the theory I'm working from now.

I'm going to build the Rod Elliott P27 circuit and experiment with the diode "soft-clipping" system http://sound.westhost.com/project27.htm.

I've been looking at the TDA datasheet and would like to try to reduce the gain of that chip...better to do that than to pad the input?  If we can drive the amp into clipping with just a guitar pickup straight in, why use a preamp (other than for eq control, pickup loading impedance)?  I think that's done by varying R1/R2, but I'll try to figure it out and post.

I am nobody's amp designer, so I'm drawn to existing amps that I can tweak into my own devious plans.  First question:  I've been looking at Rod Elliot's P27 amp, and the power amp seems pretty well-respected on this forum.  I'd like to build a lower-power version, so what's the simplest/best way to accomplish that?  If I reduce the supply voltage from +/- 35v to something like +/- 20v, would the amp still operate, but at lower power (and less stress on the transistors, less heat...)?  I don't mean to be too specific about the design; I understand this is a pretty straightforward (representative?) topology.  Does this approach work with SS power amps generally, or am I missing something important?  Second question:  how do I calculate some of the changes that would follow from this?  How much power change could I expect from a given voltage change?  How much less heatsink can I get away with?  Would different transistors be needed and how do I spec them?  Thanks for any help anyone can offer, and I'll be searching the forum to see if anyone else has looked into this.