Wishes Upcoming PSA DirectStream MKII

The issues for amp to speaker are similar to what you are saying. The best transfer of power happens when the amp output impedance and speaker input impedance are the same. The real problems come when either impedance changes with frequency. But other places in (most) audio systems don’t need to transfer power. If you aren’t worried about power transfer you can simply use a low output impedance and high input impedance (or vice versa). Power transfer isn’t efficient but distortion caused by varying impedances is minimized.

In consumer audio the most common connection is high impedance inputs and low impedance outputs. Because the input impedance of a preamp (or amp, etc.) is high there’s virtually no current (V = I x R, where V is approx 2V and R is big). With little current there’s no real power issues (W = V x I, or W = V x V / R, With V being about 2V and R is, say 50000). (Output impedance - Wikipedia)

The impedance related issues center around an impedance that varies with frequency. With a constant impedance on the outputs and the inputs the only thing that happens is that the level of the signal is slightly lowered because there’s effectively a voltage divider formed: e.g. if the output impedance is 100 Ohms the input impedance is 10000 then the voltage level is lowered by (100 + 10000)/10000 or 1%. This doesn’t matter at all in the grand scheme of things, (Voltage divider - Wikipedia)

When the output impedance varies from 100 to 200 over the frequency band and the input impedance is, say a constant 10000, then the voltage level seen by the preamp varies from 1% to 2%, not very much but possibly noticeable.

The DS has a constant output impedance over frequency so there’s no problem if that impedance is 1 ohm or 100 ohms.


That all makes sense. But it leaves me struggling – yet again – to come up with an explanation for why it wouldn’t be optimal to connect DACs to power amps without a pre-amp, providing that signal and gain levels are appropriate. Maybe impedance mis-matching has nothing to do with it.

In principle would there be anything wrong with putting an additional analog LPF circuit between the DS Sr and a power amp? I wonder if maybe the ultrasonic noise that gets through the net is the explanation for the parts of the sound I don’t like when running direct. Maybe my pre-amp is partly acting as a filter. Certainly by letting me run higher SNR levels from the DAC and attenuating both the S and the N the pre-amp is reducing the HF noise that is presented to the amp – in which case the Mk II’s configurable output level is going to be very very interesting.

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I struggle with the reality alone that running the DAC into a preamp does in fact sound better than into an amp directly. The why adds more to the struggle.

I appreciate your attempts to understand why.


I find that adding a preamp to the mix just adds the flavor of the preamp to the sound, like if you add a tube preamp, it add warmth and body to the sound, but you may lose a little clarity. Some people may like it and some may not, you just have to try it and see for yourself.

I don’t have an answer, but it’s true of other components beside the DS so I suspect it may not be a DS specific issue. If a part of it is ultrasonic DS related issue or a simple level matching problem then the Mk II and the TSS will both probably work better than the DS without a preamp.

Gain Staging.

Perhaps, but what specifically? The DAC and preamp both output line level.

With a preamp, there is another gain stage in between the DAC and the amp. That allows you to “hit the amp” differently, and you have a choice of where you run it, to taste. How hard you hit the Pre with the DAC, then how much preamplification is used to make up the gain.

And to me, the argument that a DAC should be run at a specific level and left there is negated by the fact that in the no-preamp method, the DAC level is changed constantly - it is effectively the system volume control. So don’t tell me I can’t change my DAC level, or that there is only one “proper” setting. If that were true or if one claims to believe that, one would never use a DAC without a preamp.

With only a DAC, that is the only way to adjust the volume - it is direct and there are no choices . Less is not more in this case, IMO.

This is another piece of this - DACs have a built-in analog output stage. That may be self-evident (the “A” in DAC) but it is easy to lose track of the fact that they are not purely digital devices. And that much of the way they sound is down to the Analog output stage. For example, many manufacturers’ DACs use an identical Sabre chip, but they can and do sound different.

So yes, no surprise that the improved OP stages on the DS2 or the TSS (where the analog stage is in a separate box) contribute to better sound coming out of the DAC. So it is more likely running that sound directly to an amp will sound better than a DAC with an earlier or lesser OP stage.

However it is STILL more likely IMO, that they will sound even better through a good preamp.

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Yes, but the amp is getting the same signal level for a given volume, with or without a preamp.

If the DACs volume control is as good as the preamp’s, why would it matter which component is driving the amp?

Of course, if the DAC’s volume control is lossy playing the system quietly may sound inferior to the DAC run full level into a preamp with the pre controlling the volume.

Because it is not about signal level, as much as it may be tempting to think of it in those terms. The quality - and qualities - of the sound of the analog output stage of a good dedicated analog device (preamp in this case) far exceed the quality of the analog output stage of most any DAC.

And isn’t that why many audiophiles prefer separates?

Yup - but there has always been a Less-is-more, Straight-wire-with-Gain, How can more Parts in between Possibly sound better? philosophy. It seems to make sense on paper, or suggest that more in the chain can Only Degrade Things.

Especially with wires. If wires can only at best pass a completely unadulterated signal, how can Yet Another component, AND yet another Pair of Wires Possibly sound better than less?

Short answer - Because they Can.:man_shrugging:t2:

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Sure, but this has nothing to do with gain staging. This is just choosing the component with better sound.

My previous digital source was an Ayon CD player with a built-in volume control and a tube output stage. Tonally I didn’t feel the need to add a preamp as it had plenty of bloom and analog like sound, although I suspect it would have sounded better with a preamp than without.
Although the Direct Stream DAC connected directly into my amplifier sounded better in many ways compared to the Ayon CD player, I was never completely satisfied with it until I added the BHK preamp to the mix. The BHK preamp took nothing away, but added plenty of goodness to the sound.


You seem to be trying to intellectually separate things that aren’t separate. You can put a gain stage in between two things and have the measurably identical output level as without the gain stage.

But with the gain stage, you can change both the level being input by the preceeding device (DAC) to it, which potentially changes the character of the DAC’s sound, and then in the gain stage (preamp) make up the gain to that identical matched level, introducing whatever the gain stage sonically brings to the party.

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Please let me know if there’s some way in which we’re “talking past one another”, but a recent example that comes to mind:

The “best” volume setting on the DS for Snowmass was, I think, 83. With Windom it was 100.

If you were a no-preamp adherent, you likely lost out in that bargain, unless your amps and volume were happy at a DS volume setting of 100.

For me, 83 on the DS meant that I would run my ARC pre at around 60 for most things. With DS at 100 (if, for the sake of this discussion, I was to care about a “best” DS volume setting) I then had to turn down my pre into the 40’s.

And while it is perhaps inarguable that there would be less measurable distortion going on at the same volume level in the room, I LIKE the sound that the ARC imparts at higher volume settings, and - it is often argued that the DS volume control is lossless.

But again - I refer to the paragraph 3 P’s back.

I’ll take another run at it.

There are all manner of speaker efficiencies, which require different levels of gain from the amp. Two people with the same amps but drastically different speaker efficiencies will require different input levels to their amp. Without a preamp they will definitely be running the DS’s volume control at different levels. (And in many cases no level is correct, either it can’t get loud enough or there is too much noise since it has to be run at too low of a level.)

With a preamp you can set gains best for your amp and speakers and then use the DS volume control for over all volume or you can set the DS’s volume control at your favorite position (which is probably different with different releases as badbeef noted) and use you preamp for system volume.

Never the less I’ve personally never heard a system that sounded better without a good preamp.


Beef and Ted expressed my thoughts in argumentation very well without me having to write a line :wink:

But I certainly also have no solution to the quest. Isn’t it all just like comparing preamps providing the same output level?

My preamp e.g (just to concentrate on that one thing) sounds much more dynamic and lively than any other I have heard so far, just because something happens between input and same output in impedance and level as probably many have. Just this is so obvious that you wouldn’t want to go back.

Switching to the direct DAC output then means a complete collapse of energy. It’s a comparison that needs no words, it’s just otherworldly.

I put the whole discussion in the category, why a phono amp with 200 parts can sound much better than one with 50 parts, both having the same technical output data.

Some phono stages have proper preamp level output, too. Still they sound worse if connected to a power amp than with a preamp inbetween. It’s not only a DAC matter.

As an extreme and even a passive example: do we really think a theoretically direct connection of components sounds better than a very well cable connected combination? I’m not so sure. I never saw someone preferring the power amp standing directly behind the speaker with just a 4 inch conductor bridge to the speaker against a sophisticated cable connected setup there.

I am referring to your comment:

“The quality - and qualities - of the sound of the analog output stage of a good dedicated analog device (preamp in this case) far exceed the quality of the analog output stage of most any DAC.”

Under your posited circumstances, using the better sounding output will result in better sound.

That is, the sound quality of respective output stages is a different variable than matching gain. No splitting of hairs here - a better sounding component sounds better. :slight_smile:

(Yes, of course, one can imagine hideously mis-matched components which sound bad working together, regardless of quality, but this not the circumstance of using a DSD with or without a good preamp.)