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Bottlehead Finished Products => Legacy Products => Bottlehead DAC => Topic started by: glynnw on April 19, 2015, 06:52:25 PM

Title: What impedance load does DAC want to see?
Post by: glynnw on April 19, 2015, 06:52:25 PM
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?
Title: Re: What impedence load does DAC want to see?
Post by: Paul Birkeland on April 19, 2015, 07:12:05 PM
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)
Title: Re: What impedence load does DAC want to see?
Post by: Gerry E. on April 20, 2015, 08:59:18 AM
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/ (http://www.tortugaaudio.com/ldr-passive-preamps-with-adjustable-impedance/)

Gerry     
Title: Re: What impedence load does DAC want to see?
Post by: Paul Birkeland on April 20, 2015, 11:31:56 AM
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.

Title: Re: What impedance load does DAC want to see?
Post by: glynnw on April 20, 2015, 11:53:45 AM
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.
Title: Re: What impedance load does DAC want to see?
Post by: Doc B. on April 21, 2015, 05:35:14 AM
Quote
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. 

Title: Re: What impedance load does DAC want to see?
Post by: glynnw on April 22, 2015, 04:50:09 AM
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.
Title: Re: What impedance load does DAC want to see?
Post by: Paul Birkeland on April 23, 2015, 05:58:28 PM
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)