Dual Outputs for WAD Pre 3

[david]

Hi All,
What is the best way to use two outputs from the Pre 3?

I remember the Pre 2 simply had two paralleled outputs and that worked fine, but the balanced output form of the Pre 3 gives other options.

My use for the second output will be driving a second amp which will power some speakers in the kitchen end of the kitchen diner, the main system being set up in the dining end of the room.

Also, what value resistors should I use to dim leds to a reasonable brightness?
Thanks
David

[pre65]

My Pre3 has two pairs of output phonos in parallel.

[John Caswell]

Hi David,
As you have said, you can wire the pre outputs in various ways. So assuming that you use them as unbalanced outputs, you can have several phono sockets in parallel and send the signals as and where you wish because the output impedance is about 10R (very low - nice). The only thing you need to note is that each destination ideally should be high impedance, at least 50K or higher, and that if you use unbalanced outputs you cannot use balanced simultaneously and vice versa.
Dimming LEDs. I usually run them a about 10mA ie with 10V available a 1K resistor is fine, but because LEDs are now very efficient you will probably have to raise the value somewhat. As they don't give the value in the manual I suggest that you look at what you have and initially double its value and go from there. Different coloured LEDs may require different values.

John

[david]

Hi John,
Thanks for the reply re leds. However, I'm still not convinced I should simply parallel the outputs of my Pre 3. On the one hand I'm paralleling a 10k solid state input with 100k at the 300b pp end. On the other hand I'm paralleling whatever is at the front end of my solid state amp with the carefully chosen Shinkohs on the front end of my 300bpp.

Intuition says I would be better off using the unused half of the balanced output not connected to the current output phonos, maintaining purity and accepting I will be out of phase at the other end of the room (which doesn't matter as that's only for back ground listening)
David

[bob orbell]

I suggest a cheap trany in the kitchen and do your listening in the main room, my save a lot of problems. Take note of what John say's, what he dose not know about WAD WD isn't worth knowing. BOB

[John Caswell]

Hi David,
Not quite sure what you are worrying about here, although I guess that you are concerned about one input feeding into another but paralleling the 10K i/p input imp with the 100K one will make no difference to either as they are both being driven from a very low impedance. I seem to remember that the o/put impedance of the whole of the PreIII optx is 10R so driven from half it will be down to approx 5R, negligible!
If you are concerned about DC on your very expensive Shinkohs then don't be because there is none on the PreIII output and most likely none on the input circuits. If you wish to drive each from half of the output transformer then do so, they will, as you say, be out of phase but that doesn't matter as they are in different rooms but they will also have a common earth which you might find worrying, on the other hand you might not!

John