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Plugging the DAC into the power amp


ggking7
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I remember there was a thread on this somewhat recently. I've got the Wavelength Proton USB DAC (excellent!) and I'd like to buy a pair of Outlaw 2200 monoblock amps and plug directly in. The only thing that worries me is the DAC's volume accidentally getting set to 100% by some misguided application, or accidentally by me. 100% would surely destroy my ears and/or amp and/or speakers if it's the only volume control in the entire chain, right?

 

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This subject came up a little while ago and the opinions went both ways. Personally I won't use the Proton connected directly to my amps. The volume control works great, but when your OS hangs up or something goes wrong you can be stuck at the current volume level until the issue is corrected. It's not the fault of the Proton rather the computers its connected to. During my review period with the Proton I could never get comfortable when it was connected directly to the amps. I just couldn't do it.

 

It's a great design to have software control of an analog volume control, but it has its limits. FOr headphones and listening through a preamp it's wonderful.

 

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I can see what you mean, but I can only offer that -- in 9 months of running my Proton -- I've not had this problem.

 

But right, I think you'd have to be of the habit to turn your computer on and then check the volume before tuning on your amps. For what it's worth, I think that's what I'd do if I was running from my preamp as well. That is: preamp on, volume down, and then amp on.

 

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Every preamp adds something and every software removes something when using the volume control.

 

Its just another trade off in the unperfect world of audio.

 

Get a Goldpoint passive volume pot, it adds nothing what so ever. At least nothing worth measuring. But then there are always those people who try to call themselves purists who will see causes of un-pure signals in anything.

 

 

 

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"Every preamp adds something and every software removes something when using the volume control."

 

Software controlled analog volume controls that attentuate the signal in the DAC avoid both of these.

 

FWIW, passive devices (esp. passive preamps, etc.) are also not immune from making their own contributions, and are pretty well known for taking away from the signal, the most common examples are rolloff at frequency extremes and 'sucking the life' out of the music.

 

YMMV,

clay

 

PS, I use both of my DACs direct to power amp these days with nary a worry, and nary a problem. Given that only one pair of cables are required in this scenario, I finally broke down and bought an expensive interconnect - spending more than $1000 for a pair of balanced XLRs - the improvement was more significant than anything else I've purchased at it's price.

 

 

 

 

 

 

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"PS, I use both of my DACs direct to power amp these days with nary a worry, and nary a problem."

 

And a nary holiday season to you!

 

"FWIW, passive devices (esp. passive preamps, etc.) are also not immune from making their own contributions, and are pretty well known for taking away from the signal, the most common examples are rolloff at frequency extremes and 'sucking the life' out of the music."

 

Exactly!

 

I would point out that in some (many? most?) cases, what people take to be "sucking the life out of the music" is in fact removal of distortion. One example is big bass. Another is exaggerated treble. One listener's distortion is another's rolloff at the frequency extremes. But, as the broken record keeps saying, to each their own.

 

The person I live with, who keeps claiming some kind of legal status regarding me, tells me that at music school, when somebody wanted to feel better about their performing, they sang or played in the dorm or classroom building rest room. All those smooth hard surfaces in the relatively small volume provided wonderful reverberation and emphasized some of the overtones. Instant improvement. Accurate? Nope. But they liked it.

 

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I would suggest that there is almost always no free lunch when it comes to volume controls.

Volume control in the digital domain will reduce resolution-but properly implemented, and assuming the DAC has a strong, low impedance, output stage, a digital volume control will do the least damage to the signal, versus a passive attenuator, or most analog preamps.

A passive attenuator has many problems, any passive attenuator is a directly in the signal path-in every case this will introduce noise/distortion, and will lower output impedance, which can result in frequency response problems at lower volume levels.

An active preamp, with no gain, but an active output stage (line driver, or output buffer) will still have the additional noise/distortion of the attenuator, and will have a little additional noise/distortion from the active devices in its output, but it should not have output impedance issues, so will not have frequency response issues of a purely passive device.

A traditional preamp, with gain, all over things being equal, will have a little more noise/distortion than the no gain active preamp.

The question really has to be-which one of these solutions will do the least damage to the signal, in my system. This will depend on a lot of factors including the input impedance of your amplifier(s), how long of an interconnect runs to your amplifier(s), how strong the output stage of your DAC is, what is the word lengths of the files you are playing (in the case of digital volume controls), etc. It is important to understand that few DACs feature an output stage that is the equal of a good high end preamp, and these DACs may not capably drive the input stage of an amplifier.

 

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The question is how much of the damage is imagined vs. real?

 

People claim they can hear all sorts of things, which in some cases is well beyond the capabilities of human hearing. I suggest that some Golden eared Audiophiles offer their services to SETI, because surely their hearing is so keen they will hear off into distant galaxies.

 

The thing is, EVERYTHING makes a difference in audio. Change a wire, change a power cord, re-connect some IC's and disturb the settled wire, all these things make a difference. There is a point well above the threshold that listening for a difference takes away from the enjoyment of the music. Simply put, if John Doe can hear a difference between brand X preamp, no preamp, and a digital volume control to the point where its un-listenable then John Doe simply does not enjoy music in the first place. Its kinda like having a good meal on your plate but obsessing about the fork so much that you don't enjoy the meal.

 

 

 

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"I would suggest that there is almost always no free lunch when it comes to volume controls."

 

Ain't that the truth.

 

Because of the impedances involved (usually a high input impedance at the receive end), the various interconnects in a home audio system are limited by the effective capacitance of the interconnect cable and connectors. The inductance and the resistance don't matter much. (The low impedance speaker connections are a different situation.)

 

The driving stage has to charge up and discharge this capacitance. This affects not only the frequency response in the treble, but also the time domain response, aka slew rate. In the latter, the slew rate limits are determined by the available current from the driving stage. From freshman physics, I= c dv/dt. In the case of a high output impedance "passive preamp", you just can't get very much current with such a large resistance in series with the driving stage's output.

 

In addition, an amplifier stage that is configured as a form of opamp, as most amplifier stages with loop feedback are, depends on a certain driving impedance to balance out common mode distortion effects.

 

Preamps always add noise, to some degree. Depending on a lot of factors, they may or may not add significant overall system distortion. In combination with the amplifier, they can even lower the overall system distortion, at least for some parts of the spectrum and some conditions! (The reasons for that are left to the reader to discover.)

 

Keep in mind that these are not just engineering babel, but also characteristics that can be heard. This is partially the reason why what really counts is the overall system performance.

 

Whether these matter to you is a different question. If something works for you and you like the sound, that should be the only requirement.

 

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DAC-driven amps are great -- aside from my occasional odd desire to play vinyl.

 

And while yes, many can and do drive the amp well, I've never found one that sounds as good (or is as flexible or as convenient) as a good preamp. Dunno what to say about that.

 

But if I had a computer-only system, sure, why not?

 

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"Who uses a "Software controlled ANALOG volume"??????"

 

Anybody who uses a Wavelength Audio Proton.

 

And, now that I think of it, anybody who uses a "full-sized" iPod, at least up to Gen 5.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

 

So in your mind a iPod makes for a better Preamp than say an Audio Research of a Accuphase....

 

LOL!!!

 

 

 

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"So in your mind a iPod makes for a better Preamp than say an Audio Research of a Accuphase....

 

LOL!!!"

 

uh no, that's not what he said, he simply answered your question.

 

That you would put those words in his mouth for a cheap laugh IN YOUR MIND says a LOT about you, and nothing about the topic of the thread.

 

 

clay

 

 

 

 

 

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The subject was about volume controls, which is best....analog or digital.

 

Supposedly Wavelength and iPod have superior volume capabilities because of their digital/analog nature.

 

So apparently these products can attenuate volume better than all others...ie Pass Labs, Audio Research, Accuphase and the like...

 

If you make a statement then stand by it....don't back paddle, just admit you were wrong instead.

 

 

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"So apparently these products can attenuate volume better than all others...ie Pass Labs, Audio Research, Accuphase and the like..."

 

You jumped to that conclusion. Let me repeat, you asked a question, which CG answered. You're the only one responsible for the lame conclusions that resulted IN YOUR MIND.

 

 

"If you make a statement then stand by it....don't back paddle, just admit you were wrong instead."

 

Well, since you're the only one here who is wrong, let's see if you man up and follow your own directives.

 

 

Specifically what was said:

 

In response to Barrows' comment...

"Every preamp adds something and every software removes something when using the volume control."

 

I said:

"Software controlled analog volume controls that attenuate the signal in the DAC avoid both of these."

 

What that means is that software controlled analog volume controls (in DACs) avoid preamps adding something and also avoids software-based (volume controls) removing something (form the signal).

 

No one said that an iPod is better than an ARC, nor even inferred that.

 

 

 

Dyno, this is NOT the Assylum. We don't need the type of attitudes that proliferate there here on CA, specifically the straw man arguments where someone misrepresents what others say to create an argument where none should exist.

 

 

 

clay

 

 

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The flexibility point is tough to argue with.

 

But, if someone were to take the general concept used in the Ayre KX-R preamp and apply that to the I/V stage of a DAC box (to distinguish it from a DAC chip) you could potentially have a DAC with an output that would sound as good as the best preamps out there.

 

Then, if you had a phono stage that did the same along with a power amplifier with multiple switched inputs...

 

 

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"But, if someone were to take the general concept used in the Ayre KX-R preamp and apply that to the I/V stage of a DAC box (to distinguish it from a DAC chip) you could potentially have a DAC with an output that would sound as good as the best preamps out there.

 

Then, if you had a phono stage that did the same along with a power amplifier with multiple switched inputs..."

 

Oh yeah, I want that. And all for $5k or less, if you please!!!

 

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"On a ULN-2, you connect it at the analog inputs, just as when you're recording LPs via the ADCs."

 

Blasphemer! Burn him, he's a witch!!!

 

Sorry, there is something inherently wrong with doing A>D and back again on a perfectly good analog signal. Get's me all medieval. I won't do it and you can't make me!!!

 

More seriously, why would you record your LPs to digital, anyway? I know, some folks are into that, but honestly, WTF? If you wanted it in digital, buy it in digital. The average audiophile Joe, even with all the "best" fancy audiophile gear, isn't going to make analog recordings of LPs sound better than a 24/96 or 24/192 digital studio master -- so why bother? Of course, this is easy to say because if it's available at all, chances are its available on CD. If it's too old to be available on CD (or, available anymore, say), then chances are, the LP is not in any condition to be worth the trouble to record it ....

 

But yes, you're quite right. Any good A-D/D-A converter can do this, my philosophical horror notwithstanding.

 

But my point stands -- while yes, it's way more expensive, a stand-alone pre (or integrated) will sound better, in most cases, than a DAC driving an amp -- this is what it was designed to do! And be easier (and less philosophically horrifying to boot) to work with as chances are it'll have enough inputs to handle all your legacy crap -- SACD player, turntable and DAC, and not just one of the above.

 

So, yes, it's cool and kinda geeky to do it, but unless it's for a backup or a mini-rig/headphone setup, I don't really feel the pull.

 

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