Turtlerock Forum

If a had a 48volt power pack, how would I limit the output to 44v?
Sorry for the simple question.

Hey Mick.


...erm. Why?

There are a bunch of ways to probably do it... and a bunch of ways probably not to do it, but it
all depends on the application. Is the power pack outputting ac or dc?

Well I just got hold of a couple of yamaha pm1000 modules and they are meant to run on 44v. Some of the components have a maximum voltage rating of 50, so im thinking 48 may be pushing my luck just a bit. Ive got an adapter that outputs 48vdc at .75A. Could I run a couple of modules of this? Whats the standard way of running to units from one source, in series or parallel?

is the adapter regulated or unregulated?? if it's regulated, 48V should be fine.

run multiple units in parallel. - running 2 in series with your 48V will only give you 24V per unit, and will give you huge problems with ground references if there's not strict transformer inputs and outputs for everything....

Thanks a bunch.

Mick E

There's two basic ways to do this, if you really want to. The first requires that you know the resistance of the channel strip power supply (connect a multimeter between V+ and 0V of the card). You then put a dropping resistor in series with of the V+ terminal to drop the voltage. To calculate the value of the resistor, you need to think V=IR. Say your card shows up as 20K resistance, and its designed to run on 44V. So 44(V) = I * 20,000 (R), or I = .22A current draw (220mA). You then want to calculate how to drop the voltage by 4V and again V=IR, so 4 (V) = .22 (I) X R, or R= 18.2 ohms. The power loss (W) through this resistor is W= I^2 * R = .22 * .22 * 18 = .87W, so in this example you'd need at least a 1W resistor (not the run of the mill 1/4 or 1/2W). You need to substitute in your actual figures, of course, to work out your R and W

The second is to create a regulated circuit using something like a LM317 adjustable voltage regulator. You could easily build such a beast using a JLM PowerStation PCB and a few components. This is the better engineered solution.

What about a zener diode?

Here is a 43V one from rs
http://australia.rs-online.com/web/sear ... &R=4854069

JLMs simple zener regulator is perfect for this job. Stuff as per instructions and use the trimpot. Adjust the trimpot for 44V output.

joe's kits make most of my DIY (especially power stuff) a piece of pie. And I love pie. I've built maybe 15 p/s of differing types, a couple of DI's, go betweens and the 99v pre, dingo etc. if it suits your application then I just go with his kits and don't think about it anymore.

M

just reduce the diameter of the throttle inlet, and you'll be rockin.











oops. wrong forum.

Cheers guys. I think im gonna go with the jlm kit.