Minimize current draw in Phase 90

[Jaicen_solo]

I'm looking to build a phase 90, and its going to be running on batteries. In a guitar. Without a battery box. 
Therefore, I don't want to be changing batteries too often.

Am I right in thinking that the current draw of a P90 built without an LED indicator is around 4-5mA??

Is there any way I can get this down by swapping out the op-amps for low current alternatives?

[Kesh]

are you using the schematic with tl062s?

because they are already low current devices.

maybe you can push the 10k ref voltage resistor a little higher.

[Jaicen_solo]

Actually, I haven't really looked at the schem for a while, but I thought they used 072's??
If I use 062's that should get the current draw under 1ma?? I would think, that would be fine.
Do the 062's work well in this schem??

[Kesh]

Don't know which you are using, but there are '62 schematics out there



VR2 trim looks a little different. maybe that is all that is required to change, or maybe that's just to narrow the trim range.

tonepad build reports are a great source of info for this kind of thing.

[Jaicen_solo]

Just resurrecting this thread to report that I built the Phase 90 from tonepad. Build went super smoothly, worked straight away using TL062's and J201's.
I had to drop the Zener down to 3v6, but it did work at 5v, just not as nicely. It is ticking, but that's nothing to do with the 062's, as it did with an 072 in the opamp. I'm sure it won't be a difficult fix either way.
Oh, I matched the Jfets using R.G Keen's tester. (Seriously, what would we do without R.G?? 15 years on and I still don't know his first name  ).
I got three sets of four from the 20 I picked up at SB. The ones I used measured between 0.25 ~ 0.27v. There's another set that matched between 0.10 ~ 0.12v which I may try tomorrow, just to see if they work. Of the 20, only two were really low (0.01v), and two were 0.30v, so pot luck would likely have got me a working phaser, but matching all 20 took me 5 minutes. It's a no-brainer.

Oh, and back on topic finally, I measured the current draw of the circuit using my DMM.

1.6mA at lowest speed, up to 1.98mV at max speed.

That'll do!!   

[R.G.]

This led me to thoughts about guitars without battery compartments.

That reminded me of electric toothbrushes, and how they work without cords. They sit on a plugged-in stand. That stand has a primary coil of a transformer in it and the "peg" that sticks into the toothbrush to hold it upright is the core of a loosely-coupled transformer with pickup coils in the body of the toothbrush. This two-part transformer, poorly coupled and lossy as it it, charges the batteries.

Guitars with onboard batteries could have a similar charger with the primary in a guitar stand, guitar case, anywhere it's physically in a modestly-well-located spot and radiate the power into the onboard batteries when it's not in your hands. A small plug for charging when it's impractical for cradle-charging would be not too bad.

Hmmm. Flat lithium-ion cellphone batteries. Just like I recently decided were not all that good in another thread. Oooops. 

[Jaicen_solo]

It's a great idea R.G, but wouldn't the inductive coil be a GIANT antennae for noise when the circuit is in use? I think it might be a complex solution for a problem that doesn't exist.