Yamaha PM2000 direct out help/question

[mkiijam]

IC 10 seems to be the best place to pull the direct out, but I have a couple of questions / issues that I need some help with.

1. I've whipped up a little THAT 1646 circuit, but then realized that I need (according to the THAT applications engineer) need to allow for maximum current draw against a short to ground which is 80mA. This is a 32 channel desk, and there is NO-WAY I wanna put that extra load on the Yamaha PSU. Now, maybe realistically the added circuits would never see that kind of current draw?

2. So then what about just adding another cap (470uf-ish?) and a transformer directly to the output of IC 10? Would the cap and TRX interact with the PAN control in some weird way?

3. Nothing's free in waterworld. How do I know how much extra current is pulled from IC 10 to drive a transformer? Just as simple as DCR and RMS of IC 10's output?

Thanks guys. I love this place!

 

[mkiijam]

I guess I'll just wire it up and see what happens.

 

[Ike Zimbel]

Unless you can see a situation where you are shorting all 32 outputs to ground (I can't), I wouldn't worry about the THAT 80ma spec. You will probably be fine. I mixed on PM-2000's for years and I don't ever recall the PW-2000 power supplies being even remotely overstressed, ever. That said, I don't think the 1646 can run on +/-24v so you will need to step those voltages down to something more like +/-18v or less.

 

[mkiijam]

I don't think the 1646 can run on +/-24v so you will need to step those voltages down to something more like +/-18v or less.

Right. a couple of LM79 / 78L18's was my idea for that.

Any thoughts on just tapping the transformer in AC direct?

 

[Ike Zimbel]

Forgot to mention that I did a similar job on an Yamaha M-1516, adding THAT-1646's to create direct outs. I took the source for the Direct Outs off of the Insert Return jacks. Why? Several reasons:
1) It allows you to insert an external processor (eg; Eq, Comp) before the direct out (IOW "to tape").
2) It allows you to use an external Pre-amp "to tape" if you decide you don't want to use the Yamaha pre on a particular source.
3) It gives you a direct balanced path* to your converters, should you need it. It basically turns the existing row of Insert Send/Return jacks into a patch-bay.
*I can't recall if the Insert Return path is balanced or quasi-balanced, but the 1646 has +6dB of gain in it, so just using the Tip as source should give you unity gain.