Roon vs Separate PreAmp

Roon Software Discussion
43

A preamp has two functions - to provide input switching and to provide gain.

If you have no need to switch different inputs, i.e. only one source and you’re signal is already at line level, you need neither of the above.

What you need in this case is attenuation. Provided your source’s output impedance is compatible with your amplifier’s input impedance, volume control via Roon, or a passive volume control is all that’s required

A preamp doesn’t have magical “sound improving” properties. At best it can have noise and distortion levels sufficiently low compared to the power amp to not degrade the signal. It can never “improve” the signal.

This is basic electrical engineering.

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49

And yet again we sink to getting personal with each other!
A community reminder…
Remember to debate the subject and not the members and we might get somewhere constructive.

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55

With due respect, bipassing a preamp will work well with some DACs and some amplifiers. If it works in this particular case, that’s great, go for it. But a blanket statement that preamps are only about switching sources and gain does potentially do a disservice to full truth.

Preamps assure the impedance is likely to be a better match for the amp - there are plenty of components that have sufficient gain to be fed directly to an amp but which sound like crap until properly preamplified. It depends much on the input stages of the amp too, yes?

I’m much more in Graeme’s objectivist camp than the converse, but in this case it’s maybe too sweeping of a statement.

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56

I’m in agreement with @Graeme_Finlayson and @James_I

Let’s take a simple streamer such as the WiiM Pro. We can probably agree the built in DAC is rather weak but stick with me.

The line out via the RCAs can be 500mV, 800mV, 1V or 2V.

2V is enough to connect to a suitable power amp. Agree?

  • Yes
  • No

0 voters

But reading some reviews the built in DAC and output stage measures better if set to 500mV.

This is when a pre-amp is needed.
Agree?

  • Yes
  • No

0 voters

A good pre-amp should be a straight piece of wire in essence, with attenuation, and should not affect sound quality.
Agree?

  • Yes
  • No

0 voters

However, I preferred my pre-amp between my DAC and mono power amps as there was, to my ears a difference, even though subtle, it was smoother iirc.

Measurements can tell us one thing, but the proof is in the listening. We are all different and we have a different taste in what sounds better. That’s cool. Doesn’t make anyone wrong or right though.

Some of my tools I use for work are cheap rubbish, but they out perform my more expensive ones. My most expensive screwdriver is stronger but not as comfortable. Plenty of analogies to throw at you all.

Roon with DSP volume control or Roon to control a DAC volume does make sense in the right circumstances.
Agree?

  • Yes
  • No

0 voters

But you can do what you like and if it works and sounds good to you then good :+1:.

Now let’s go have a cup of tea and a biscuit.

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57

Sure, we can add to the list:

  • Impedance matching, as you pointed out
  • Tone control/EQ

In terms of impedance matching, let’s take a somewhat extreme example and say the output impedance of the DAC is 1kohm (which is rather high) and the input impedance of the power amp is 10kohm (which is rather low) - both assumed purely resistive. You lose about 10% of the signal due to the voltage divider, which is less than 1dB. Nothing to lose sleep about.

58

My streamer / DAC has a pre-amp functionality built-in, so the choice is clear, no pre-amp is needed.

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60

I think this guy understands amps and preamps pretty well:

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61

Here’s my experience for what it’s worth because it very much depends on your system and particularly your room. I’ve done a lot of room treatment and have spent an embarrassing amount on gear. I was feeding my Weiss DAC with a LUMIN (use Roon). I used the Weiss volume control and that fed my Anthem STR power amp. It sounded very good but I just wasn’t quite ha-pay with it. I added a secondhand Esoteric C-02 as the line stage and the difference was something I still can’t believe. People told me that a decent line stage would make a big difference but I was still shocked. I’m completely happy with my system now and have the bonus of a HT bypass.

One day someone will convince me I should upgrade my power cables or interconnects but that’s just snake oil… right?

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62

I used to think the best sounding analog device was the one I could leave out. This led me to try a transformer based passive preamp in front of my Manley Snapper tube amps.

It wasn’t a good match in my system. A bit of tube hiss was gone (had been using a VTL preamp), but the sound felt more compressed and the soundstage shrank considerably.

It may have been an impedance mismatch. The passive preamp used a series of taps off a transformer to send different fixed voltages by way of volume control. The line level input was sufficient to fully drive the power amps so the taps reduced voltage and increased current. The Snappers had switchable input impedance between 15k and 600 ohms, neither of which sounded as good as 15k with an active preamp.

I went back to an active tube preamp (Doge 8) and have been very happy with it.

It is worth bearing in mind when talking about electrical engineering that oscilloscopes still sell for a reason. Engineering has to use real world components. You can’t walk into a shop and buy an ideal capacitor or resistor. Components with similar specifications can have very different timbres in an audio circuit.

An orthodox signal processing view might regard all distortion as bad and a lower noise floor as always better than a higher noise floor. But audio is not necessarily best served by such absolutes. Our ears, in the midrange, can distinguish remarkably small variations in distortion. I suspect that such variations are responsible for different staging cues and that some distortion products (that don’t appear in nature) are destructive of the stereo illusion and soundstage.

While a new analog device can only increase total distortion, it can mask undesirable distortion products from equipment earlier in the chain by (for example) adding more musical second order harmonics or raising the noise floor above such products.Yes, total harmonic distortion (a term invented by semiconductor manufacturers) can increase, yet the music sounds better with increased soundstage.

I would suggest trying a preamp and comparing the sound with a direct connection to your power amps. Go with what you enjoy and sounds best to you, regardless of orthodoxy or iconoclasm.

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63

[Moderated]

Adding an active component is very likely to make a difference, possibly even pleasing, even if all it does is slightly increases volume. I got a gadget like that. Had gushing positive reviews from all the usual suspects. If you’re not paying attention to what it does, it’s quite a bit if difference! Or, you could turn the volume knob…

64

No, it’s not volume. It’s altogether different. It’s much more spacious, almost surround sound stereo imaging. I’ve listened to my system for many hours and I change the volume a lot, especially during long listening sessions. I don’t know the reason but I suspect it’s about a better match from the Esoteric to the Anthem versus the Weiss to Anthem or possibly the DSP volume isn’t as good, although I’m unsure how the Weiss does volume. I know when I use the MiniDSP in this system it just destroys the sound quality much to my annoyance as I wanted to integrate subs.

Anyway, if you’re a ‘digital all sounds the same’ type I can’t help you.

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65

I did qualify my response by stating that provided the output impedance of the source and the input impedance of the amplifier are compatible, then a preamp isn’t required in this case.

It wasn’t a totally blanket statement.

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[Moderatied]

This idea that an active preamp is always a bad thing is just not correct. The idea that if you like what an active preamp does to the sound quality of system means you like what distortion does to the sound quality is misguided [Moderated].

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67

PS Audio always has opinions where it comes to something they want to sell you!

In nearly all examples, he’s talking about tube preamps which add euphonic colouration, generally due to a disproportionate amount of 2nd order harmonic distortion compared to solid state devices.

@andybob the transformers used in the passive pre you mentioned could well have been the culprit here. Transformers “ring” due to magnetic hysteresis which adds significant harmonic distortion:

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68

Yes. My audio technician friend told me hysteresis could also sound like compression.

In any event, an active preamp sounded better for me.

I’m not brave enough to directly drive my power amps with my DAC and use software volume control. If, for some reason, the volume control failed and the power amps were completely unleashed on my speakers I think my apartment would resemble a small smoking crater.

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69

Exactly

Class A/B volume control = foot always on the break

But

Class D volume control = foot on the gas

70

What do you think is a “class A/B” or “class D” volume control"? Types of amplifier topology are not related to types of volume control.

AJ

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But reading some reviews the built in DAC and output stage measures better if set to 500mV.

This is when a pre-amp is needed.
Agree?

It is not clear IMO.

People seem very aware of the potential downsides of bit/resolution loss with DSP based volume controls, but this argument is long in the tooth and modern DSP based volume attenuation (including roon) is nearly “perfect”. Alternatively, there is no perfect analog volume control- analog volume has simply been a traditional “best practice” due to early DSP attenuation pitfalls that are in most cases are no longer relevant.

So in this specific case, I would guess- and I really am guessing- that the measured difference between 500mv and 2v falls outside of our hearing- or is so minute that it is only a consideration on paper. The solution of solving for this by adding another set of RCA cables, and routing the signal through an analog input switcher, gain stage and analog pot is not necessarily the best choice.

The analog preamplifier is nowhere near a perfect device but we often tend to think of it as one.

72

Entirely possible. It’s an active device, it could be doing all kinds of things to the signal. Although I would think that Weiss would do volume right.

Same bits to the same DAC will sound the same, regardless of Roon version, ethernet cables used, or phases of the moon. Change bits or DAC and it’s very likely to sound different. Not sure where this strawman came from…

It’s not a bad thing. But the only thing it can add to the signal is noise and/or distortion.

[Moderated]

73

If the straight wire with attenuation philosophy was all there was, we wouldn’t have come up with the term audiophile.

That it works for you should be enough of a criteria but you can never escape the fact that synergy is a thing and component A and component B are never going to be a guaranteed fit. It’s why you have to listen to things and it’s also one of the reasons why I currently own an integrated amp. :slight_smile:

Years ago when I was just buying things, not really having a clue. I bought a Lampi Amber 3 as my first big boy toy DAC and the user’s manual said the following: (a bit tongue in cheek)

The load presented by the preamp or amp or simply the next analog component that
the DAC sees, should be as high as possible. It is measured in kilo-Ohms and 47 Kilo
Ohms is a perfect ballpark value. More is VERY rarely seen. 20 K is next common
value, and it is great too. 20 K is kind of on a low side, but we can handle that. Lower
than 10k is bad news. But our Amber-3 DAC will handle 10 as well because we
configure the DAC with additional cathode follower, low impedance buffer stage.
Having said that - every properly designed amp or preamp keeps the load value above
40k. And if it doesn’t - we simply don’t choose such amp because it was not designed
with audiophiles in mind.

I had a Schiit Freya + preamp at the time, a fine pre especially at the price point. The input Impedance on the Freya was 10K ohms. What did I know to me my new DAC sounded great feeding the Cary 200.2 SE I had it plugged into.

Some time later I switched the Freya to a Pass X2.5 and was floored at to how much better it sounded. The input Impedance specs for it were: 66K balanced (XLR), 33K single-ended (RCA)

Was it all just to to specs, IDK, but it was my introduction to preamps and their significance.

If you’ve got a DAC feeding directly to an amp, it may or may not be a good match, probably a good idea to check what the vendor says would be optimal and start at the very least with having them be a good match.

Also, living and dying on the idea that $500 chi-fi all in one can have a great pre-amplification line out stage or be better than a quality active pre is a limiting position to take. Things can change a bit when you’re dealing with a DAC like a Weiss 502 which had a good built in volume control and still IMO couldn’t hold a candle to the difference in sound I got feeding it through a quality pre with great synergy.

Living an dying be one philosophy as always being best is a good way to miss out on a lot of enjoyment in what comes out of your transducers. :slight_smile:

There’s no real wrong or right in the hobby if you’re happy with what you’re hearing from your system but there’s no point in going out of your way with belligerence telling others that what they hear is not “technically” correct or physically impossible.

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