Plugging the DAC into the power amp

[The Computer Audiophile]

Wow, I walk away from my computer for a bit and hell breaks loose. OK not that bad, but this one has the potential to turn good people away. CA is laid back and about maximizing the enjoyment of our wonderful hobby.

 

Dynobot - I'll give you the benefit of the doubt and chalk this exchange up to too much holiday fun and spirits. You've been a member of the site for a while now so I'm sure you know the established pattern of how CA operates. There is no room here for comments that polarize the readers and blatantly misrepresent what another has written.

 

 

 

 

 

[frankspain]

I am trying to connect my new 24/96 usb link bel canto with my computer (Vista OS) and to the 16-bit DAC Consonance using i-tunes, but it doesn't sound.

I have head this DAC under Vista with USB connector and I have not got any problems. I acquired the belcanto usb link in order to incrase the quality of music, but it seems ot work!

Could you somebody to help me to configure?

 

[cfmsp]

"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."

 

I do it (in my main rig) because it sounds better! I have no idea if 'audiophile' DACs (as opposed to the MH) might not sound as good - as you surmise. For as long as preamps have been made, people have been trying to do without them, so they are NOT without their negative impact, e.g. reduced resolution, and never mind the fact that TWO cables are required.

 

Pro audio units can not count on dedicated preamps in the chain, and are expected to function well with all manner of other devices connected to them - I'm not saying that all of them do.

 

'Hot rod' mode is decidedly NOT for everyone, and would be a PITA if I listened to anything other than my computers on a regular basis.

 

Who knows, maybe i'll switch back at some point - it's not like I sold my preamp.

 

clay

 

 

 

[ggking7]

Sounds like a Proton->amp connection is no problem, and that's great news. I'm considering a pair of the Outlaw 2200 monoblock amps, which do 300W into 4 ohms speakers like my Magnepan SMGa's. How loud would it be when the DAC's volume is set to 100%? Will that ruin the amp and/or speakers?

 

Socrates7, can you tell me why you said:

 

"a stand-alone pre (or integrated) will sound better, in most cases, than a DAC driving an amp"

 

[cfmsp]

"Sounds like a Proton->amp connection is no problem, and that's great news. I'm considering a pair of the Outlaw 2200 monoblock amps, which do 300W into 4 ohms speakers like my Magnepan SMGa's. How loud would it be when the DAC's volume is set to 100%? Will that ruin the amp and/or speakers?"

 

Perhaps others with better understanding of, e.g. (matching) voltage out vs. sensitivity, or power amp gain and/or wattage vis-a-vis speaker sensitivity, could elaborate.

 

I wouldn't assume yet that the Proton->amp connection is no problem (in your instance), as this could vary due to the aforementioned factors.

 

It might only be working out for me because at the moment I have somewhat underpowered speakers, i.e. mismatched sensitivities.

For that reason, in my instance, I'm still relatively near the top end of the volume controls when listening at the loudest volumes I listen at, and likely driving the amp harder than would allow for its best sound.

 

Dan (kana) and Barrows, and others, have a pretty good grasp of this I think.

 

...sooo many factors to consider in putting together a top notch audio system. sooo much time to listen to music, while doing so.

 

clay

 

 

 

 

 

 

 

 

 

[cfmsp]

 

"I think Clay needs more eggnog."

 

Yeah, maybe I over-did it ... not with eggnog, but with Charles Bronson like vigilanteeism (a la Death Wish).

 

 

clay

 

 

[ggking7]

Does anyone know why:

 

"a stand-alone pre (or integrated) will sound better, in most cases, than a DAC driving an amp"

 

[Purite Audio]

Does a preamp sound better,than a dac driving power amps directly ? Not sure that it does, some folk just like a bit of added colour.

Keith.

 

[Audio_ELF]

Keith (Coops) answered the question "Does a preamp sound better,than a dac driving power amps directly?" by saying "Not sure that it does, some folk just like a bit of added colour."

 

I think the true answer is a lot more complicated. There is often an issue of imedence matching and signal levels which are different between the output of a DAC and the input of a PowerAmp. A pre-amp can improve the signal by matching them.

 

So the answer depends on the DAC in question, what power amp you have, and what pre-amp you have.

 

Eloise

 

[Purite Audio]

Eloise Hi, you may be right, I really do not know enough about impedance matching , but dacs have such high output, I imagine that impedance matching was far more important when you are dealing with a tiny signal from a cartridge/phono stage.

Keith.

 

[cfmsp]

GG,

 

Since Scot uttered it, perhaps he should back it up.

 

I'm not convinced that it's true.

 

I"m also not convinced that preamps are in use becuase they improve the sound, but rather, becuase they are much more convenient.

 

OTOH, preamps should remove some of the guesswork from matching (the interactions between) amps and source components. Some manufacturers (I'm thinking audiophile here, NOT pro audio) might have come to rely on this 'service' being provided by a preamp and thereby created devices that don't match well without a preamp.

 

Indeed, the best thing one can say about any preamp is that it doesn't make a sound.

 

If the holy grail of amplifier is the proverbial 'straight wire with gain', then the equivalent for preamps would be 'straight wire with attenuation'.

 

Note the directly 'opposite' actions above.

 

Nelson Pass, among others, have noted the (rise of) high gain and high output voltages of components these days, and reckons that we're throwing away much of this 'expensive' gain (via the volume control), and thereby using preamps well outside of their 'sweet spot', WRT volume attenuation.

 

Said another way - the higher gain of components (presumably) costs more, then you need an even more expensive preamp (due to higher quality volume attenuator) to address the higher gain. This is due to the need for the volume attenuator to function with very low noise (or other degradation) even with significant attenuation - IOW, the task becomes more difficult, the greater the attenuation.

 

I can't find the article, but Nelson has lowered the gain (over the years) in his FirstWatt (don't know about Pass Labs) gear in response to this.

 

I say this to point to a reason that preamps might be more likely required than in the past, as well as to say that proper matching between components is definitely required, preamp or NOT, give that most preamps also provide gain.

 

FWIW, Nelson's First Watt B2 preamp is an active buffer, with NO gain. This helps deal with poor impedance matching between devices, yet another aspect of the 'matching' between source components and amplifiers.

 

A buffer such as this ameliorates situations, as Barrows described, in which some DAC output stages are not capable, in his view, of 'driving' amplifiers directly. Perhaps he will chime in here with the precise characteristics DACs might be lacking, other than output impedance.

 

hope this helps,

clay

 

 

 

[The Computer Audiophile]

Hi Clay - Thanks for the info and references to Nelson's work. Very interesting and reiterates that there is so much more to each audio equation (system setup) than meets the eye.

 

[cfmsp]

 

Chris,

 

This speaks to the value of the volume control (and presumably other preamp-like characteristics) being included in the Alpha DAC.

 

I wish I could find the article, perhaps it's just a quote buried in one of Srajean's many reviews of Nelson's products, I'll look for it again.

 

Clay

 

 

 

[aljordan]

The following design paper on the B1 talks a bit about impedance matching and throwing signal away.

 

http://passdiy.com/pdf/B1%20Buffer%20Preamp.pdf

 

Alan

 

[barrows]

DACs do not have an output driver stage that is the equal of a really good preamp. Because of a weak output stage, many DACS will not sound as good running direct into amps, regardless of how well their volume control is implemented. If a given DAC has an output stage, and volume control that is as good as a given preamp, then the system will perform better with the DAC run direct into the amps, as the additional gain stages and connections to and from the preamp can only add distortion and noise.

There is no simple answer to this question, as the answer will depend on the entire system, including interconnects (and their length), DAC, amplifier, and preamp. Gain is almost never an issue though (as noted by Clay), as most systems have more than enough gain to drive the amplifier to well beyond full output. My preamp has 10 dB of gain, and even playing very loud, with low average level recordings (like Reference Recordings) my volume control never goes higher than -5 dB.

 

[Purite Audio]

A decent preamp will not magically recover a poor signal , so buy a decent dac!

Keith.

 

[cfmsp]

"Gain is almost never an issue though..."

 

Lest it go unsaid, gain is more of an issue WITHOUT a preamp - too much gain requires much more attenuation, and thereby creating much greater concern as to blowing out tweeters, etc., in the event that a totally unattenuated signal leaves the DAC.

 

 

"Because of a weak output stage..."

 

Barrows, what characteristics (or lack thereof) define a weak output stage? Is this something that interested observers can glean from specs or measurements, or is listening the only way to tell?

 

thanks, and also thanks to Alan for the link to the B1 info.

 

clay

 

 

[cfmsp]

"A decent preamp will not magically recover a poor signal , so buy a decent dac!"

 

Agreed. Preamps can hide problems with a DAC, or even magical sound, however.

 

clay

 

 

 

[barrows]

As an example. The PS Audio Perfect Wave DAC was designed specifically to be able to perform well when run directly into amplifiers. Great care was placed into the design of the analog output stage: with +/- 30 volt power supply rails, a discrete FET/Bipolar circuit design and high current power supplies. While the numbers (volts) and specifications required to drive most amplifiers to full output do not seem that demanding at first glance, listening tests performed on low level output stages have shown that output stages designed to meet the minimum requirements generally sound thin, and lacking in body and dynamics. Very good sounding preamps often have output stages capable of swinging up to ten times the number of volts typically required of them, and preamps designed to this kind of standard (with lots of headroom) usually sound better than ones designed to a lesser standard.

"Overbuilt" power supplies, and output stages running on higher voltage rails are common in high end preamps, but they are not so common in high end DACs. So these are some of reasons that I suspect running DACs direct into amplifiers may not always be the best solution. Of course, there is a negative factor of using a preamp: additional circuitry and interconnect cables are always going to introduce their own compromises-for a digital only system, the best solution would be to run a DAC with a very well designed output stage and volume control direct to the amp(s). But I would not expect the typical DAC output stage, of a couple of IC opamps, running on 15 volt rails, off of a minimal power supply (low current capability), to sound as good as a very good high end preamp.

 

[cfmsp]

 

 

Thanks Barrows,

 

Much appreciated,

clay

 

 

[ggking7]

"This speaks to the value of the volume control (and presumably other preamp-like characteristics) being included in the Alpha DAC."

 

Even better is the Proton with its digitally-controlled analog volume control.

 

[Hi-Fidelity-4-All]

I recently pulled my Monarchy M24 DAC/preamp out of my computer chain and put it back in my main setup. I replaced it with a Monarchy DIP (to convert optical to coaxial because my soundcard has only optical out and the DAC input is coaxial) going into the DAC (no volume control on DAC), with the expectation of controlling volume through my media software player JRiver Media Center.

 

It works fine, although the gain is not quite what I had with the preamp, i.e. the volume will not go as high, but that is acceptable in this second system.

 

I do have some hum that wasn't there previously. I will pay around with cables and checking what else may be plugged into the outlets in the room and any room's on the same house circuit to ensure no appliances are generating the interference.

 

I obviously can't compare sound because they are two different DACs of a different class.

 

Are the comments to this point applicable or is my control of volume through the software player introducing anything different. (or am I missing something?)

 

Thanks!

 

[hifitubes]

Depending on your OS, there are a certain number of options in J. river for volume control; given the changes made starting with Vista. I think it is System, Apllication, and Internal. I would use Internal set to 100%. Jriver has a quality volume control as discussed here.

 

This is a good thread. I have been for days been contemplating what to do with my new Eastern Electric DAC. I plan on using the tube output stage into a Mini-Torii. I do viinyl, redbook, and high resolution losses from the PC.

 

A couple of points about digital RIAA. In the long run it is cheaper, well can be..... I don't need a preamp now, and there are a slew of high quality mic preamps which would cost many thousands of dollars when the specs and parts are found in "audiophile" phono stages. I use a JFET based AEA TRP...it's incredible for the price.

 

There is plenty of documentation on digital RIAA at Channel D's site, and high resolution archiving of out of print material ,rare records, OR poorly mastered material (think about crappy converters given the fact that in 2010 we are still dealing with jitter) can give VERY positive results; the midrange is enhanced/more accurate with digital RIAA curve. It is a little geeky, but more practical than you might first think.

 

If you find the right mic preamp for flat gain and good a nice converter, theoretically, you can fully represent/recreate input at output. I don't see how it is any different from running through an analog stage, it is still just another device in the signal path.

 

I'm going to stick with the sans preamp setup and no remote. Feels right. EE DAC has 3v output; switchable true tube stage or SS opamps (user changeable).

 

hifi

 

[Nicholas.Bedworth]

Well, you've probably got a few seconds to shut things down Depending on the source material, with any luck you'd only be driving the amp to 100% output, which, one hopes, it is capable of doing for some time.

 

With the Lavry DA 11 set to 46, that's 8 dBu, 5.6 V P-P, 2V rms, using Reference Recording source, my present mono blocks are just starting to clip when driving low sensitivity speakers. If one cranked up the Lavry to 56, its maximum, the output is 10 dBu more (unbalanced operation). BTW the 56 represents 1 dBu steps from -31 dBu to 24 dBu when operated in balanced XLR mod.

 

Can an amp survive 10 dB beyond clipping? Depends. But the designer is sure to have not only an opinion, but various dramatic experiences (exploding capacitors, fried output transformers, and, in general, the smell of smoke) to relate. Regarding the survival of speakers, depends...

 

Note that some powered speakers as well as components can be driven to full-scale with 0.5 V RMS. This is apparently to appease the louder, louder, loudest crowd, which tends to dominate the popular music scene right now.