[CButterworth]

Following from my posts on choice of DAC's, I am thinking of buying an ART Di/O which can be modified at some later stage.

Apparently, the output voltage of the ART DI/O is 7V which is considerably higher than the output from my CD-player, which I think is at the milivolt level.  I am already using 33K resistors to attenuate the input signal, and using a 50K pot to shunt excess signal to ground.

How on earth do I calculate the required resistors to reduce 7V to a line-level voltage, or do I really need to as the AKSA can accept an active preamp?

I suppose that I can connect all items EXCEPT the AKSA and measure voltage levels across the outputs, to attempt to get an idea of what different resistor combos would do.

Any advice would be most welcomed.

Charlie

[Occam]

Charlie,

I don't see as you really have much of anything to do to accomodate a stock ART DI/O in your system.  If I interperate you correctly, you've a passive attenuator with a fixed 33K series element and a 50K variable shunt element.
A typical CD player has a 1-2V rms output. If the DI/O puts out 7volts rms, you're really only talking about a signal that is around twice as 'loud' [less if the dio is specified as peak-to-peak] Leave things as they are, and remember to lower the volume.... but if you don't, it shouldn't be disasterous, just annoying.
Typically, the first thing one does after you upgrade the powersupply on the DIO and IO connectors is change the integrated circuit and at that point changing the output voltage is a simple change of feedback resistors.
As you're planning on modding the DIO, don't bother with it until you do the mods. That is how I initially slotted in a DIO until it was modded, turn the volume down.

If you have an active linestage, one that provides gain prior to the attenuation, only then would[EDIT:COULD] the 7v output of the DIO be problematic.

As far as calculating resistive voltage dividers -
http://sound.westhost.com/vda.htm

[Lost81]

I have used an ART DIO with my TLP N and AKSA Ns before and after the DIO was modded.

The only difference is that the volume dial has to be turned lower for the 7V (stock DIO) output.


-Lost81

[BobM]

You can always construct a voltage divider circuit on the outputs of the DI/O or on the inputs of the preamp (or in the interconnect between the two). I would strongly suggest using high quiality resistors here, metal films at least.

Here's the values I used in my DI/O to reduce it from 7 to 2 volts:
series resistor: 3.4 kohm
ground resistor: 1.37 kohm

Here's a link to a calculator that can give you other values:
http://www.raltron.com/cust/tools/voltage_divider.asp

First time I put together the voltage divider I screwed it up. I put the ground resistor before the series resistor in error - the signal was diminished a little but not enough. The resistor to ground should be connected AFTER the larger series resistor based on the directional flow of the signal.

So if the voltage divider is inside the DI/O the ground resistor should be from the center pin on the output jack to ground. If it's in the interconnect source side RCA it should be from the hot wire (not the center pin on the RCA jack) to ground. If it's inside the interconnect destination RCA then it should be from the center pin on the RCA jack (not the hot wire) to ground.

Enjoy,
Bob