Complete 100 watt guitar amplifier in1590b stomp Box

[rring]

right... you can also change the gain setting on the final amp such that a couple of back to back silicon diode pairs will be in the correct range. Maybe I am full of it..but never liked the sound of LED's clipping.

[dschwartz]

right... you can also change the gain setting on the final amp such that a couple of back to back silicon diode pairs will be in the correct range. Maybe I am full of it..but never liked the sound of LED's clipping.

Well the function will not be high gain clipping, but limiting instead..
I would combine leds with a resistor and Si diode in series ( like dynatouch clipping stage)
This way, the signal is reduced if higher than the led Vf, and clipped if higher than led+ Si Vf.
Then you'll have a nice transition between clean, compressed and clipped

[dschwartz]

Or...a cmos inverter stage with V supply of 7 volts..in my opinion they sound very like tube power amps

[rring]

yes makes sense... the  limiting will be clipping so it will  end up acting like an overdrive of a sort...so don't like LEDs so much... Love the inverter idea. The beef stew 4049 overdrive concept with a limited supply...that would probably work great...need to look and see if there is a soic 8 or sot23 type dual or single inverter package that will work(not much room).

[Transmogrifox]

Also consider that @24v 4ohms, in btl mode the max power is about 60W @1% thd.  At 100W the thd is 10%...

I think this kind of thing is pretty much an expectation of even most commercial amps...especially when this Class D chip is what you will find in many amps claiming 100W output.

For home stereo stuff I use a Class D amp rated to 250 Watts, but rarely push it past 50W peak output power (if that).  In fact, my power supplies won't give much more than 120 Watts, but I rigged them up with huge capacitor banks to handle transients at more than 100W -- based on a typical audio signal at even 40 Hz could do more than 300 W short term.  Since it's built up as an "all-in-one" with no external inputs, I have coordinated the output limiting of the USB audio device on the raspberry pi with the total preamp gain so that it's all clean and the PSU can keep up when my volume knob is cranked and the Rpi output is limiting.  As-is if it's cranked it's too loud to listen comfortably anywhere in the house.

The point is the unit sounds really good at normal listening levels even though the rated capacity would be insane for it's intended use.

That said, a "100 Watt" guitar amp will blow you out of your bedroom and keep your guitar in the mix in most moderate sized venues without having to max it out.

My conclusion is this thing is just about perfect for a general purpose guitar amp.  Nice work!

As an aside, from a psychoacoustics point of view I believe it has come to be understood that an SPL increase of 10 dB will be perceived as being twice as loud.

This means it takes 10x the power to sound twice as loud, so a 100W amp cranked is perceived as only 4x as loud as when the power output is 1W.  On a good audio taper pot, the drive from 50W to 100W is in the last ~1/8 turn of the volume pot.  Another way to think of it is 1/2 way up is only about 10W output.  This gives some understanding for why the little Zvex 1W tube amp really cranks when plugged into a 4x12 stack.

Of course, speaker efficiency plays a big role in perceived loudness.

[rring]

Yes you pretty much nailed it. I just said it was 100 watts for hype! We all know its BS To your point I am generally using a 2 10" cabinet with celestion 30 watt speakers. They are very efficient (cheap also). In tandem with the amp its just plain loud and pushing it to the max starts to sound like an exploding garbage can. Its more than sufficient for club/bar setting. I do like the idea of the inverter stage as a limiter and perhaps over-drive...need to make room for a new knob! Perhaps I can use a few inverters and drive the power amp differentially for cheap thrills.

[dschwartz]

Rring, did you put big caps at the power​ rails?

[rring]

yes they are 220uf low ESR types and they are right next to the two sets of supply pins on the power amp IC.

[dschwartz]

Try putting a 2200uF for extra power

[Transmogrifox]

Mine uses 4700uF but that's just because I got free samples.

Energy in a certain amount of discharge = 1/2 C(V1^2 - V2^2)

Energy = Power * Time

[rring]

well I added a blue led clipper for the hell of it! Works really well...starts to clip at about 2.4 volts...which is just about perfect




Here is a little video recorded on my phone at full volume...you can't tell but it was painfully loud..My phone was overloading so it actually sounds much better in person.. but you will get the idea...it actually sounds good as it overdrives...go figure...you can see the LED's driven to conduction and flash

https://youtu.be/2YG01f64nNw

[printer2]

Heck, you could get a light dependent resistor and almost have a compressor. Just kidding, glad it turned out. I may have to add it to my amp, if I ever get to building it.

[graemestrat]

That sounded pretty nice, RRING. Good job!

[R.G.]

It occurred to me upon reflection that what we really need are 100Wrms SPEAKERS in a 1590.

I still have very clear memories of carrying a 4x12 up stairs to a gig.

In many ways, it would make sense to have the power amps always inside the speakers, and only put a preamp on the pedalboard.

Or to never go more than one speaker per box, with its own amplifier in it.

[rring]

Yes true...most the burden of schlepping equipment is the big cabinets...and I have had requests for small light amplifiers from other players but you still have to lug around the cabinets. Should look into the lightest speakers you can get in 12" and 10"(maybe 8") and come up with a really rugged but light weight structure for the cabinet...such that you actually end up with a loud, nice sounding lightweight rig in totality. If you could make a significant reduction in weight(and to some extent size)...it would have great value to journeymen musicians.

[robthequiet]

... or a diy crane that climbs stairs and fetches food ...

A music shop sales guy tried to sell me an Ibanez amp on the basis that it contained a Tube-Screamer.

Now I can go back and tell him that my Tube-Screamer contains an amp. Brilliant!

[dschwartz]

I always wandered  about small "tuned" cabs like bass reflex and stuff..
Once i heard a small bose box with very small speakers but it had an amazing bass response for the size

[rring]

Not to beat a dead horse with this thread...but here is a sound clip of me playing Jazz in a small club using the amp at 70% of max