What impedance load does DAC want to see?

[glynnw]

My preamp has variable input impedence between, I believe, 1K ohms and 99K ohms.  What would be an ideal setting to match to my Bottlehead DAC?

[Paul Birkeland]

That's an unusual feature for a preamp.  I can't think of a good reason not to leave it at 99K for any source.  (The DAC would like to see 4.7K or more)

[Gerry E.]

I noticed that the OP has a Tortuga Audio LDR-based attenuator which does indeed have adjustable input impedance between 1k - 99k ohms.  Here's a link to Tortuga Audio's very detailed page about this feature:

http://www.tortugaaudio.com/ldr-passive-preamps-with-adjustable-impedance/

Gerry     

[Paul Birkeland]

Ah, yes, the LDR is a passive level control, not exactly a preamp.

Just as an example, if you set it to 1K input impedance, you would need a Crack just to drive the passive.

[glynnw]

Thanks for the input.  So far most people say they hear no difference when changing the impedance on the Tortuga so I'll just play with a few of the higher settings to be safe.

[Doc B.]

No one has directly answered your question.

PB gave what I thought was a pretty direct answer of 4.7K minimum and 99K as a good choice. 

[glynnw]

FYI, I found no discernible difference between 20K going up to 99K. The owner of Tortuga concurs that this feature (adjustable input impedance) really delivers no great benefit for the majority of users.

[Paul Birkeland]

FYI, I found no discernible difference between 20K going up to 99K. The owner of Tortuga concurs that this feature (adjustable input impedance) really delivers no great benefit for the majority of users.

With a Reduction+Integration, I bet the difference would be pretty audible.  (But not for many other sources, as mentioned)