Impedance matching DAC to power amp

[DKT88]

I ordered an Aune X8 DAC and want to connect it directly to a NORD NC502MP stereo power amp with 47K input impedance. The Aune has a "preamp" output which I assume is just a potentiometer. I haven't found an output impedance spec the Aune. Could this be an issue? And if it is, how would I know?

 

[andreasmaaan]

Probably not. 47KOhm is quite high - the Aune would have to be a really strange design to get close to that. You should be fine IMO.

 

[daftcombo]

What is the minimum ratio to respect?
For example, the Topping D10 has an output impedance of 100 ohm. What would be the minimum input impedance for an amp?

 

[DKT88]

What is the minimum ratio to respect?
For example, the Topping D10 has an output impedance of 100 ohm. What would be the minimum input impedance for an amp?

I've seen a "rule of thumb" number for an active preamp/amp impedance ratio, typically 1:10. I've seen different higher ratios for passive preamp/amp but I don't understand why it would be different. Like to know the answer.

 

[solderdude]

For capacitor coupled outputs (tube pre-amps) it is best to have a >1:10 ratio, when the load R is too low the lower part of the frequency range may roll-off sooner than desirable.
For transformer coupled pre-amp outputs a certain range of load resistance is warranted.
For SS 1:10 will already be O.K.
For passive pre-amps the output impedance varies per volume setting.
In that case 1:10 (for the highest output R) will be O.K. otherwise the scale on the volpot (when present) won't be accurate.
For the ones with autotransformers in its path a specific range could be preferred.

the Aune X8 DAC will certainly not be above 100 Ohm so any load > 1kOhm will be fine.

 

[DKT88]

For capacitor coupled outputs (tube pre-amps) it is best to have a >1:10 ratio, when the load R is too low the lower part of the frequency range may roll-off sooner than desirable.
For transformer coupled pre-amp outputs a certain range of load resistance is warranted.
For SS 1:10 will already be O.K.
For passive pre-amps the output impedance varies per volume setting.
In that case 1:10 (for the highest output R) will be O.K. otherwise the scale on the volpot (when present) won't be accurate.
For the ones with autotransformers in its path a specific range could be preferred.

the Aune X8 DAC will certainly not be above 100 Ohm so any load > 1kOhm will be fine.

Thanks for the clear explanation.

 

[MZKM]

Yeah, I’he heard anywhere from 1:8 to 1:20, and even for the extreme of 1:20, that would mean anything less than 2kOhm is good.

 

[ThomasMac]

So...
If one was to pair a schiit freya + with a input impedance of 10k with the denaphrip ares 2 that has a output impedance of 2.4k...
..it'd prob be a bad match?
(feya + in tube gain, using balanced xlrs to dac)

 

[egellings]

Simply not an issue

 

[MakeMineVinyl]

What others have said. I would add that if you had an output which was simply the wiper of a potentiometer of, say 50k ohm, and attached it to an input impedance of 47k, the taper of the volume control would be altered. If it was a log taper before, it would have a more severe taper after.

 

[solderdude]

The taper would be changed more when the input impedance of the following section was lower impedance.
A common 'trick' to make a linear pot act more logarithmic-ish is to put a resistor of 1/10 the track value between wiper and ground.
Downside is the input resistance of the attenuator varies a LOT depending on the volpot position.

Most passive attenuators will be around 10k but there will always be some manufacturers that also sell higher values.

 

[egellings]

Maybe the pot's output should be buffered so that changes in the pot's setting do not act to change tone quality.