Why are all of the Craig Anderton circuits 18V?

[Tibbon]

Why is it that Craig Anderton's projects book uses 18VDC as the power supply for all of his circuits? I was thinking of building one or two of them, but power pedalboard power supplies are either 9/12VDC (Pedal Power, Brick, etc...)

Also, how are most of these when they are built? Are they worth anything more than the experience that you gain from building them?

[Ethan Winer]

Originally Posted by Tibbon

Why is it that Craig Anderton's projects book uses 18VDC as the power supply for all of his circuits?

The higher the power supply voltage, the more headroom you have. But there's an upper limit imposed by the parts such as op-amps. For this reason +/- 15 to 18 VDC is very common.

--Ethan

[Brightbird]

Pedal Power can be run at 18v if you use two outputs and a special cable (Voodoolab sells them).

[Tibbon]

Originally Posted by Ethan Winer

The higher the power supply voltage, the more headroom you have. But there's an upper limit imposed by the parts such as op-amps. For this reason +/- 15 to 18 VDC is very common.

--Ethan

Ok then, maybe a better queston.. why aren't MORE units running at somewhere between 15-18VDC if it would be of an advantage?

[Jim Williams]

Craig's concept is for this stuff to run on either a power supply or a pair of 9 volt batteries in series to extend headroom as some opamps don't work well using a single 9 volt battery. Since opamps are bipolar in design, they don't really run on a single 9 or 18 volt supply. A circuit that splits the 18 or 9 volts is used so the opamp is really seeing + and - 4.5 or 9 volts. Some opamps won't work at + - 4.5 volts so it's a single 18 volt supply that's internally split.

One disadvantage of this is the power supply noise rejection of the opamp is reduced, they are best to operate at a bipolar + - 15 volt supply.

Jim Williams
Audio Upgrades

[JohnRoberts]

Originally Posted by Tibbon

Ok then, maybe a better queston.. why aren't MORE units running at somewhere between 15-18VDC if it would be of an advantage?

The headroom benefit of pushing +/- 15V up to +/- 18V is only 1 1/2 dB, but you've increased the heat from power dissipation 20% and pushed the devices closer to their process technology limit. The typical IC substrate breaks down somewhere above, but not that much above 36V.

I typically run ICs at +/- 15V and if I want more headroom I use active balanced outputs that give you +6 dB of signal swing.

I used to run my internal audio paths on +4 dBu consoles at -2 dBu to line up internal path headroom with output driver clipping.

Regarding the OP, I suspect Craig might have figured that a) 9V batteries don't stay 9V that long, and b) 18V is better than 9V. But perhaps somebody should ask him. I'm sure he's around somewhere on the WWW.

JR

[Wavebourn]

Originally Posted by Tibbon

Ok then, maybe a better queston.. why aren't MORE units running at somewhere between 15-18VDC if it would be of an advantage?

I run GU-50 at 750 volts.

[Jim Williams]

Originally Posted by Wavebourn

I run GU-50 at 750 volts.

Beats me, I run the Basson 120 head at 475 volts, still enough to kill though.

It will fill an auditorium with sound very well.

I once heard this: "it's not how many volts you have, it's how you use them".

Jim Williams
Audio Upgrades

[paully]

Originally Posted by JohnRoberts

... But perhaps somebody should ask him. I'm sure he's around somewhere on the WWW...

>>>>>>>>>>>>>>>>>>>

http://acapella.harmony-central.com/...splay.php?f=50

And yes, he does read and contribute to posts.

Paul

[Wavebourn]

Originally Posted by Jim Williams

Beats me, I run the Basson 120 head at 475 volts, still enough to kill though.

It will fill an auditorium with sound very well.

I once heard this: "it's not how many volts you have, it's how you use them".

Here is one more prototype on stapples...

http://wavebourn.com/images/audio/gu50amp-8.gif

This time I am hidding output toobs inside of a transformers' compartment.

How I use them, I use them to amplify live concerts. It is great as well for a studio monitoring. Also, I use such tube amps in my home cinema theatre.

[Wavebourn]

This one I run on 375 volts only.
2x25W, but still enough to fill auditorium up to 800 seats. 6L6 tubes (2 in parallel) work in relaxed mode: low distortions, sweet sound, long life. Regulated screen grid supply (SS regulator), regulated filament DC, so it is clean and dead quiet.