What impedance load does DAC want to see?

glynnw · 5718

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Offline glynnw

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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?
« Last Edit: April 20, 2015, 11:54:56 AM by glynnw »

PC, J River software, opticaRendu, Schitt Ygg DAC,Tortuga Pre, Torta Radu tube buffer, Linear Tube Audio ZOTL10, Spatial Audio X5w/pair of GR Research dual 12" open baffle servo subwoofers tamed by DSpeaker Dual-Core DSP , Audience AU24 SE  spkr cable, handmade silver interconnects,


Offline Paul Birkeland

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Reply #1 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)

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Gerry E.

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Reply #2 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/

Gerry     



Offline Paul Birkeland

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Reply #3 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.


Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline glynnw

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Reply #4 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.

PC, J River software, opticaRendu, Schitt Ygg DAC,Tortuga Pre, Torta Radu tube buffer, Linear Tube Audio ZOTL10, Spatial Audio X5w/pair of GR Research dual 12" open baffle servo subwoofers tamed by DSpeaker Dual-Core DSP , Audience AU24 SE  spkr cable, handmade silver interconnects,


Offline Doc B.

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Reply #5 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. 


Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline glynnw

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Reply #6 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.

PC, J River software, opticaRendu, Schitt Ygg DAC,Tortuga Pre, Torta Radu tube buffer, Linear Tube Audio ZOTL10, Spatial Audio X5w/pair of GR Research dual 12" open baffle servo subwoofers tamed by DSpeaker Dual-Core DSP , Audience AU24 SE  spkr cable, handmade silver interconnects,


Offline Paul Birkeland

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Reply #7 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)

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man