a cool idea that probably isnt very good.....

Brian Marshall · May 30, 2004, 12:04:45 AM

using a voltage regulator as an class A amplifier.

this probably wouldnt work, because it would probably over heat, but here it is.

usually the regulator pins are connected to V+, Vout, and Grnd, but if you connected the ground to the output of an opaamp, in theory the ground, would actually be a voltage reference, and would move arround. A voltage regulator in theory has low output impedance, but not sure how low in reality. Also not sure what units could take the current and heat that would be generated at 9 or 18 volts.

Anyone ever try anything like this?

Peter Snowberg · May 30, 2004, 12:12:34 AM

Very cool!

I've never tried anything like that or heard of a reglator being used as an "output stage" but I have seen them with opamps being used as a programmable current source. I can't wait to hear how it works!

Most regulators have a thermal shutoff so you should be safe there.

Take care,
-Peter

petemoore · May 30, 2004, 01:56:16 AM

And like Peter, I too am interested to see how that works.
I don't know if this is related, but introducing a frequency wave into a gain setting parameter always for some reason piqued my interest...if the R/C of a gain setting parameter could be caused to osdillate at whatever frequency the input sees, it might cause a neat effect??/its just a concept/theory I've been mulling for sometime now, however feasable or relevant it is... a compression effect, but at the speed of the incoming waveform...[probably wouldn't sound anything like a compressor]

Brian Marshall · May 30, 2004, 02:27:00 AM

Quote from: petemooreAnd like Peter, I too am interested to see how that works.
I don't know if this is related, but introducing a frequency wave into a gain setting parameter always for some reason piqued my interest...if the R/C of a gain setting parameter could be caused to osdillate at whatever frequency the input sees, it might cause a neat effect??/its just a concept/theory I've been mulling for sometime now, however feasable or relevant it is... a compression effect, but at the speed of the incoming waveform...[probably wouldn't sound anything like a compressor]

wouldnt that give you a ring mod, or tremello effect?

maybe i am misunderstanding you.

Peter Snowberg · May 30, 2004, 03:00:06 AM

I was thinking a tremello also.... or a ring mod depending on the frequency.

It would by like tremello that varies the cathode voltage or the screen or signal grid bias voltage.

Take care,
-Peter

punkaled · May 30, 2004, 08:23:59 AM

maybe i'm wrong, but wouldn't you just end up with the same signal you had from the op-amp, but with 9v worth of DC element (if you used a 9v regulator for example)
or did i miss something?

petemoore · May 30, 2004, 09:23:57 AM

But it almost certainly also infuse some 'other' tonal [atonal?] element...who knows exactly what, I was 'dreaming up a ripple or slight distortion to the wave, being there would probably be a very slight difference in the time constant or some other oddity that may cause an interesting [or unusable] distortion element.
Now..if one were to put a teeny amount of delay in the Gain 'sweep, this would most surely cause some kind of 'rippleing' or distortion of the wave form..
I think I mentioned this unorthodox [clazie?] concept before, never tested that I know of, I don't think anyone found it very intruiging...which is fine...my little whacky pet!!!

gez · May 30, 2004, 11:56:36 AM

I think I understand what you're saying. Interesting idea, but the level shift would limit headroom in one direction (depending on what type of regulator you use).

Would probably be better to just use a power amp if you needed more current, unless there's some sonic advantage to doing this? (keep us posted)

Ansil · May 30, 2004, 01:31:37 PM

http://www.blueguitar.org/new/articles/other/hi_v_ss.pdf

not exactly what you are talking about, but it is using the mosfet as a voltage regulator according to the article. couple this with a jfet and its supposed to sound tubish.. i haven't tried this circuit at high voltage yet, but i liked what i heard at 18v

anyway its slightly in tune with topic

Brian Marshall · May 30, 2004, 05:52:16 PM

Quote from: gezI think I understand what you're saying. Interesting idea, but the level shift would limit headroom in one direction (depending on what type of regulator you use).

Would probably be better to just use a power amp if you needed more current, unless there's some sonic advantage to doing this? (keep us posted)

Well obviously you would have to find one with a low voltage rating, high current rated, and low impedance.

I'm not sure if there are sonic advantages or not. It was just an idea to use something in a way it wasnt meant to be used..... I mean think about it most of the stuff we use to make dirt boxes like transistors, opamps, and diodes werent really designed with us in mind.

That said, I would imagine a regulator would be extreemly linear until you hit the rails.... that could be good or bad....

the other thing is that you could also use (for example) 2 regulators in a push pull amp, which would allow you to use much more of your voltage head room.

niftydog · May 30, 2004, 09:44:15 PM

I did a quick spice simulation in Protel... and you seem to have discovered a wide bandwidth voltage follower with DC offset. It's quite happy from 1hz through to 100Mhz... according to the simulation!

Set right, it hard clips the positive peaks, but soft clips the negative peaks.

The fun bit comes when you screw with the input voltage. It clips on the positive peaks, and you can set the amount of clip with a variable input DC voltage!

It also looks to me as if it linearises the sine wave, making the transistions from peak to trough straighter.

DISCLAIMER: This is all simulated results using Protel 99SE. In my experience, this has little to do with real world results! But it is often fairly indicative of what might actually happen.

I'd say it's worth a quick breadboard!

Let us know how you go, Brian!

gez · May 31, 2004, 04:12:46 AM

Quote from: niftydogSet right, it hard clips the positive peaks, but soft clips the negative peaks.

The fun bit comes when you screw with the input voltage. It clips on the positive peaks, and you can set the amount of clip with a variable input DC voltage!

O-VER-DRIVE!...O-VER-DRIVE!...

Well, perhaps it does have sonic advantages?!

Brian Marshall · May 31, 2004, 05:09:30 AM

im thinking more along the lines of power amp, but even more, now im thinking push pull.

News:

a cool idea that probably isnt very good.....

Ansil