Adding a pre amp

[Summit]

There are difference between different DACs output and between different pre amps. Even with a Chord DAVE direct to HP he prefer the Wells Audio Headtrip Reference Headphone Amplifier.

 

https://audiobacon.net/2018/02/15/wells-audio-headtrip-reference-headphone-amplifier-15000-musical-indulgence/ 

[Summit]

The main task for an amplifier is to take a weak audio signal and boost it to generate a signal that is powerful enough to drive speakers or headphones. This is an oversimplification there the whole amplifying process is seen as one process, but the processes inside most DAC, amplifier and audio systems is more complex and also depend greatly on audio design.

 

A preamp can both be a preamplifier circuit within a device (like a DAC or integrated amp) or it can be dedicated external preamp. A preamplifier is an electronic circuits that converts a weak electrical signal into an output signal that’s is (hopefully) strong enough to be noise-tolerant and strong enough to be sent to a power amplifier.

 

An amplifier is NOT amplifying by adding to an already exciting signal as many seems to believe. In reality an amplifier generates a completely new output signal that is BASED on the input signal. To understand how an amp works one need to see the signals as two separate circuits, there the output circuit is generated by the amplifier's power supply. That means that the power supply and power circuit is of great importance then it comes to amplify a weak audio signal, no matter if the preamp is placed in an external or internal box.

 

Let go one step deeper, every transistor or tube pair can represents one amplifying stage of an amplifier. Most amplifier have several amplifying/boosting stages there the final output stage of the power amp is driving the speaker.

 

So then someone are saying that a bit of transparency is lost with every amplifying stage it can be true because every transistor or tube will add its own noise, but not because different gear is double amplifying an existing signal or because all the noise from the source automatically will be added to the new signal. A good preamp is acting like a purifier that smooths the signal, not by adding coloration, but by make a new signal from (hopefully) cleaner power. Extra IC between components are always degrading the signal thou and it’s true that what’s lost is lost and cannot be added back later by an amp.

 

If we take a Chord DAVE for example and examine the difference between using headphones direct out of DAVE DAC/pre too DAVE + dedicated headphone amp, the difference in loss of perceived transparency is probably bigger than with speakers there also a power amp is used in the system that will add its noise (the noise from the preamp is masked by the noise from the power amp).

 

If a SOTA DAC sounds better with or without a preamp depends not only on DAC and preamp but on the rest of the system, and on preference. IMO a really good dedicated preamplifier doesn’t add more noise and coloration than say a power amp, probable a lot less. A really good dedicated preamplifier normally have batter impedance matching, staging, bass, tonality and drive than most DAC. A few exceptions may exist. Unfortunately a really good dedicated preamplifier cost a lot and therefore maybe not always the best bang for the buck in many modern audio system that only have one digital source.  

 

As always, best to test in your own system and see if a standalone preamp gives superior SQ or not.

 

[Summit]

Some observations from Paul McGowan to feed the flame debate ;-)

 

 “My adamant stance against inserting a preamp between a high quality DAC like DirectStream and the power amplifier should be no surprise to readers of this blog. As well, my subsequent turn around embracing the exact opposite should lift no eyebrows either. But why would inserting an extra piece of gear in the signal path sound better than a more direct approach? How could this make sense? ....

 

... For a long time I found that DACs with no-loss digital volume controls sounded better, cleaner, livelier, directly into the power amplifier. Whenever I inserted a preamplifier it sounded different–but not better. That is until I tried a different preamp. My first revelation happened with the stunning Aesthetix Calypso preamplifier. Placed between the DAC and power amplifier, music took on a life and dimensionality that took all of 10 seconds to find it was better–not just different....

 

... I had written earlier that it’s likely I am asking the wrong question. How could adding more to the signal path make the system sound better, not worse? It turns out the logic is correct: it cannot. So why does sometimes adding a preamp between a DAC and power amp help the system sound better?

 

Because it’s helping the DAC not sound worse. And that bit of logic is key to answering the question....

 

... Imagine we have a DAC with an identical output circuit to that of a preamplifier. How would this respond driving a power amplifier directly? Theoretically as well as a preamp and, perhaps, better because we haven’t another component in the mix. But here’s something you may not have thought about.

 

DACs are significantly more sensitive to power supply changes and noises than preamps. When an output stage struggles to drive a complex load, it is the power supply feeding its output stage that sees these changes. If this occurs in a preamp, it has little effect. But that same situation, when applied to a DAC, has very different results indeed. Small changes in power supplies have big impacts on sound quality–especially jitter.”

 

https://forum.audiogon.com/discussions/is-no-preamp-really-better-that-a-good-preamp?page=3

 

“Our recommendation is to use the DAC directly into your power amplifier and bypass the preamplifier. “There’s no preamplifier like no preamplifier”. Certainly this is your choice but we believe the fewer pieces of equipment in the chain the better performance of the system.

 

And until I heard my former reference preamplifier that statement was (and is) true. And it drives me crazy. How in the world can adding something in the signal path, complete with wires, power supplies, components and more wires, improve the sound of music in honest ways? Sure, we could imagine some added this or some added that, could enhance the music in unnatural ways, but improve its purity? That stretches credibility. And yet…

 

There isn’t one among you that would disagree with these findings were you to also sit in the Music Room and make the same comparison. DirectStream or PWD straight into the amplifiers sounds better than through any preamplifier I had tried, including our own PCA-2 of old.  But it wasn’t always that way. Before the PerfectWave DAC series appeared, we hadn’t the advantage of their lossless volume controls. Older DACs with volume controls lost resolution with decreasing gain and using them with any good preamp was better. Once we had DACs without compromised controls, the addition of a preamp was not only unnecessary, it was worse.

 

That is, until I was shown what became, for several years, the reference preamp in the Music Room. A tube based device of extraordinary sound, that I have written of before. What magic inside this box of glowing fire bottles, wires, and metal bits wrings sound truer than no box at all? I haven’t any ideas.

 

I just know what I hear.”

 

https://www.psaudio.com/pauls-posts/lunch-served/

https://www.psaudio.com/pauls-posts/excited-or-confused/

http://www.audiophilia.com/reviews/2016/6/18/ps-audio-bhk-preamplifier

[Summit]

One more thing. An analogue VC turns down signal and noise while a digital VC only attenuates signal.

[Summit]

 

Properly true in most system, just like extra noise from a good preamp is masked by the noise from the power amp, mains power etc...

 

https://www.soundstageultra.com/index.php/features-menu/general-interest-interviews-menu/311-what-s-wrong-with-digital-volume-controls

[Summit]

44 minutes ago, pkane2001 said:

This part doesn't make sense to me... Does the input stage of a preamp present less of a load on the output of a DAC than the input stage of an amplifier? That's the only reason a DAC driving a preamp will work better than when driving an amp directly, according to this explanation.

 

I'm sure one can come up with some crazy designs (both, preamp and amp input stages), but this explanation isn't true of the majority of audio equipment. My power amp has 25KΩ input impedance while my DAC has 200Ω output impedance. Would adding a preamp here help to change the load that the DAC sees at the output? I seriously doubt it would make much of a difference on the DAC power supply, even if the preamp input is around 40KΩ.

 

Where it might make a difference (and something I'm still testing) is when low-impedance headphones are plugged in directly into the line output of a DAC. My HPs are around 300Ω with some large variations, so there is potentially a need for a headamp in the path. Testing one now that has input impedance of 25KΩ and a variable output impedance.

 

It’s Paul’s hypothesis not my

 

I posted my hypothesis yesterday – which is; it’s depends on DAC, preamp and the whole system and preference if a standalone preamp will sound better than an pre integrated in a DAC. I have a VC and preamp in my Aesthetix DAC, just so you know am not biased to what I own.

[Summit]

29 minutes ago, mansr said:

Paul McGowan says himself he doesn't know much about circuit design (that's what he employs engineers for). Why should we listen to him?

 

Some background: ‘There is no preamp like no preamp’

 

“PS Audio has a history of being against the inclusion of external preamplifiers in a system, with its classic, ‘There is no preamp like no preamp’ motto. In fact, in one of his posts from August 12, 2012, titled ‘The era of the preamp is over’, CEO Paul McGowan made the following statement: ‘We’re all interested in music and its reproduction and the preamplifier has been central to most of us for most of the music we enjoy. The day of the preamp is over and I want to explain how we got to where we are and why.’ Fortunately, unlike most of us, when McGowan learns something with his ears that contradicts what he previously thought was true, he admits it, he then tinkers and he acts.

 

In some recent email exchanges with McGowan, he told me about his transformation as follows: ‘When I wrote that article the facts were correct, I had never heard a preamp that bettered no preamp. It wasn’t until I spent time at Arnie Nudell’s [Founder Infinity Systems, Genesis] house my opinion changed. I told him my story and he laughed and suggested I simply hadn’t heard the right preamp and promptly put my conclusion to the test. Arnie had the Aesthetix Calypso preamplifier [all vacuum tube, front and back end] as well as the DirectStream DAC. It was a simple test and the results were conclusive. With THAT preamp in the system, the music came alive in a way I hadn’t expected nor had ever heard.’ McGowan went on to use one in his own system. He ended his email to me with, ‘I would change my August 12, 2012 statement to read more like this: “Most preamplifiers do more damage to a great DAC and should be avoided when possible”.’

 

Meanwhile, legendary and passionate designer Bascom H. King (BHK) (Infinity, Marantz, Constellation Audio and Audeze, too) had been tinkering/listening to and helping design amplifiers and preamplifiers for many years, and came to the conclusion that, as he told me in a recent email, ‘an active system preamplifier, especially a real good tube unit, did something that made things sound better.’ Then more recently, he too was introduced to the Aesthetix Calypso preamplifier by Arnie Nudell, and as he told me, ‘Well, the Calypso handily trounced my solid state unit’. So he too acquired one for his system.”

 

http://www.audiophilia.com/reviews/2016/6/18/ps-audio-bhk-preamplifier

[Summit]

Transparency and resolution is good and you cannot really have too much of it. The problem, as I see it, is all those high end manufacturer that sacrifices the true tonality and harmonic richness to get those artificial sounding over-analytical sounding gear that some people seems to believe are transparent and to have high resolution, whereas to me they sound fake and to sterile.

 

 

[Summit]

On 2018-03-07 at 11:14 AM, fas42 said:

 

Yes, you can never have too much transparency ... what happens, as already mentioned, as the ability of the rig to resolve more and more of the recording rises, is that one becomes aware of finer and finer shades of distortion added by the playback chain - and more effort has to be made to eliminate or attenuate these anomalies.

 

An analogy with performance cars is in order - the faster the car can go, the more refined the suspension and steering have to be, so that the driver is comfortable with its behaviour at all times. Engineering that is adequate for a family car can no longer cut it - the capabilities of the system always have to be in balance.

 

Yes that’s correct. If the sound gets too thin sounding the problem is not necessarily the very component you changed, it can be made by other gear in your audio system. But remember that the veil that mask transparency can be made of many different forms of noise, distortion, EMI, RFI etc. and far from all types of noise are harmonic or add noise in a “pleasing” way. Removing noise, EMI, RFI etc, in most cases, make the sound clearer, smoother, more dynamic and tonally richer. So the more transparency and resolution your audio system has the less noise it has and the better sound you will get.