# DSD Output Impedance has two values?

Hello,

I am looking to changing an interconnect and looking for the component with the highest output impedance.

My Pre has an output impedance of 100 ohm, the DSD has, according to the manual, an output impedance of 100/200 ohm.

Hmm, does this have to do with the 2 output levels? Attenuator IN 200 ohm, Attenuator OUT 100 ohm?

Thank you

TD

The input impedance of the next device is usually on the order of 47k to 100k so those differences in the sourceâ€™s output impedance are inconsequential in almost any system.

The differences in the specâ€™ed output impedance are when measuring the single ended vs measuring the balanced outputs. I.e. the output impedance is the same from either signal line to ground.

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The input impedance of the next device is usually on the order of 47k to 100k so those differences in the sourceâ€™s output impedance are inconsequential in almost any system.

``````                       ahhhhh... What?   I'm sorry, I do not understand the 47-100K as
compared to Ohms...and why it wouldn't matter. Im not an
engineer Jim.
``````

The differences in the specâ€™ed output impedance are when measuring the single ended vs measuring the balanced outputs. I.e. the output impedance is the same from either signal line to ground.

``````        Ok, so you are saying the different numbers are simply for testing
purposes and the actual out impedance is the same? And what is that
number, 100 or 200 ?

Just to explain why I am asking so that you may be able to dumb it down
for me. I am getting new ICs one 1/2 meter and one 1 meter, but only one
at a time so I asked the maker which should I worry about first, source to
pre or pre to amp, and he said, "which ever has the highest output
impedance would be more important. My pre has an output impedance of
100 ohm.
``````

T

The input impedance of most preamps or amps are approx. 47k Ohms to 100k Ohms, a big number. The output impedance of most audio sources is a small number of ohms. Thereâ€™s no practical difference between a typical active preamp output and the DSâ€™s output. If possible the best thing with a single new cable is to try both and see which you like best. E.g. buy the one meter and try it in both placesâ€¦

I was just trying to explain that the specs for output impedance donâ€™t have anything to do with the 20 dB attenuator, but instead are whatâ€™s expected for balanced vs. unbalanced: Each side of the balanced output is identical and has the same output impedance to ground. One of those sides is in parallel with the unbalanced connector so the unbalanced output impedance is the same as one of the two sides of the balanced output. Donâ€™t worry about it in your circumstance.

Much better

Thank you,

TD

Hi @tedsmith, please can you clarify something for me. 30 years ago (so itâ€™s all a bit vague) we were tought at collage that Power Amps have an incompatible input impedance for source components, due to amplifier gain I think, so that main purpose of a pre-amp was to match impedance of the source to the Power Amp.

My question is: in the modern world of hifi, does that still stand? I.e. in theory you shouldnâ€™t connect the dsd straight to a PA but always use a preamp in between. Is this why some people that dont use a preamp experience hiss due to impedance miss-matches?

To have the best power transfer you want to match the source impedance with the destination impedance. We donâ€™t care about transferring power to the power amp so most consumer audio equipment define the signal in terms of voltage and have a high input impedance and most consumer audio devices have a low output impedance. A few companies like Krell have done the opposite for some systems, they define the signal with current and have a high output impedance and a lower input impedance. There are a very few consumer audio companies that have a link that matches impedances (which could, in theory, make for a quieter link.)

Put another way consumer audio equipment is almost always impedance mismatched and the worst of the noise related to connections can be suppressed with proper use of balanced connections. The fact than unbalanced connections work so well most of the time indicates that high input impedances arenâ€™t the biggest culprit in system noise.

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Thanks Ted, So presumably the point my tutor was making matters if you were perhaps setting amps for a stadium concert with their high output, but the relatively low gains for peopleâ€™s homes itâ€™s not important, which is why you can connect a domestic source component with a volume control straight to a domestic power amp.

I assembled the buffers using symmetrical OPA1632 amplifiers. I connected them to DS

DAC output. It is possible that with a preamplifier this would not change much, but in my system with active loudspeakers controlled directly from the DS DAC, even with the best Van den Hul The Platinum Hybrid cables, these buffers improve the sound in every respect.
This system has an additional advantage, by changing the value of resistors you can set any gain. I used it to compensate for the attenuator - on Tedâ€™s advice I started listening with the attenuator on, I confirm, SQ is better.

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Well done!