Lm833 chip substitution

[~arph]

Yes, it is.. this one is supposed to be even around 17V pp

http://i81.photobucket.com/albums/j207/merlinblencowe/Glass%20Blower/GlassBlowerSchematicII.jpg

[Paul Marossy]

Yes, it is.. this one is supposed to be even around 17V pp

http://i81.photobucket.com/albums/j207/merlinblencowe/Glass%20Blower/GlassBlowerSchematicII.jpg

How would you get an output of 17 PTP with a 9V power supply?

[~arph]

It has to do with the transistor bootstrapping arrangement:

http://www.valvewizard.co.uk/glassblower.html

I haven't tried to fully understand this particular circuit but here is an idea: With a charge pump you can produce a -9 rail from a +9 supply. So you have a range of 18 volts from a single battery. So I'm not surprised there are other methods to acquire higher then supply voltages, it's the amount of available current that drops proportionally I guess (ohms law)

Btw, I think Merlin can explain this as he is posting in this thread as well 

[Paul Marossy]

OK, maybe with a charge pump, but I don't see how a 17V PTP output would happen in your typical 9V unipolar power supply. That is what the typical distortion pedal is built around.

[~arph]

The typical 9V powered pedal would indeed not exceed 9V pp. (even less usually as not all opamps are rail to rail)

The example was just to show that indeed it is possible to get a higher voltage output from a pedal then the voltage it is supplied with.
The particular arrangement in the glassblower lets the supply rails of the opamp ride on the signal output, so you have a theoretical swing of 9V in both ways.

[Paul Marossy]

The typical 9V powered pedal would indeed not exceed 9V pp. (even less usually as not all opamps are rail to rail)

The example was just to show that indeed it is possible to get a higher voltage output from a pedal then the voltage it is supplied with.
The particular arrangement in the glassblower lets the supply rails of the opamp ride on the signal output, so you have a theoretical swing of 9V in both ways.

Yeah, that all makes sense. What I was really getting at earlier is that I didn't see how you could get a higher output from a pedal than it was powered with, even if you have opamps that could literally go from rail to rail. In AC power, I know you can double, triple, etc. the voltage with diodes, but with DC that ain't how it works....

[merlinb]

What I was really getting at earlier is that I didn't see how you could get a higher output from a pedal than it was powered with

Actually you can, if you're sneaky. That's exactly what the Glass Blower does. 9Vdc supply, 12Vpp out (more with a rail-to-rail opamp).

[Goodrat]

I've been reading some things today and I am going to give the LM4562 a try.
Great specs and works down to a lower voltage.