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RE: PLLXO question related to LDR

Posted by Satie on February 26, 2012 at 16:41:23:
Do you have any other source other than your DAC coming into the tube buffer?

The way to get a PLLXO and an LDR to work in tandem with minimal problems is to put the LDR in front of the buffer as a load to the DAC, and use the buffer's likely high input impedance as load for the LDR, also works well for TVCs (the ones based on Stevens and Billington's TX102 are excellent). The buffer's output impedance is ok for any load the PLLXO creates so long as it remains over 10Kohms, beyond that, the higher the better.

I would imagine the HP will end up being just one cap and a potentiometer (to control treble/bass relative volume) if you are doing 1st order, and the LP will be 10k or more resistor and cap - unless you are using an active for that purpose. In the latter case you would not need the pot on the HP and you will probably be ok on the combined input impedances as most actives have something around 20k, so combined you will have something like 10k ohms for the load the buffer sees.
If you end up having a problem, then just add a second parallel buffer for the bass after the LDR/volume control/pre, you can use a simple Y connector for it.

BTW, in Neo's calc, I would replace the fixed R-HP with a 20k pot (carbon or wirewound, linear - not log).