Does a DAC need a pre-amp

[GUTB]

3 hours ago, pkane2001 said:

 

Once again you are confusing price with quality. When you know of no other way to judge quality, then price is your only criteria. But please don't assume that everyone is like you.

 

 

I didn’t mention price. A Goldmund is better than a NuPrime. 

[pkane2001]

28 minutes ago, GUTB said:

 

I didn’t mention price. A Goldmund is better than a NuPrime. 

 

Progress!

 

[Ralf11]

no, you didn't explicitly state prices; instead, you listed a set of high-priced vs. low-priced items thereby implicitly invoking price

[Speed Racer]

7 minutes ago, Ralf11 said:

no, you didn't explicitly state prices; instead, you listed a set of high-priced vs. low-priced items thereby implicitly invoking price

 

He could have been implicitly invoking quality which, by the way, is often more expensive. In other words, your making an assumption that cannot be proven. 

[Ralf11]

you're

 

I agree often but not always.  Sometimes it is just an error of misplaced precision

[gmgraves]

3 hours ago, Speed Racer said:

 

That is not accurate. I said (complete quote):

 

"My experience is that a quality active preamp sounds better than no preamp or a passive preamp."

 

You came back with:

 

"You are misinterpreting what you have experienced*." 

 

An then you went on with this:

 

"Every active stage adds distortion."

 

So you did not "merely state" that active preamps add distortion. You said I was misinterpreting what I have experienced. Since my interpretation said that "a quality active preamp sounds better than no preamp or a passive preamp", you must be saying that is not the case. That a quality active preamp does NOT sound better than no preamp or a passive preamp.

 

Own up to what you write......

 

Since my statement: "You are misinterpreting what you have experienced." seems to be what's stuck in your craw, let me apologize for a poor choice of words. What I meant by that is just because you find that an active preamp sounds better than a passive one (or no preamp) doesn't mean that an active preamp doesn't add noise and distortion that a passive unit does not add and I read your remarks as denying that statement and confusing SQ with a basic fact of electronics circuitry. Obviously I was wrong, and we were just posting at cross-purposes.  

Now can we get by this? Don't we have better things to discuss than to make verbal mountains out of molehills? I have apologized for the poor choice of words and my misunderstanding. Now, what else do I have to do to get off this particular merry-go-round without causing you ill feelings; which is the last thing I want? 

[bobbmd]

i have an AQ DFR connected to my iPad air 2 out to a vintage Pioneer Elite c-90 preamp and m-90 poweramp both circa 1987/88 and stream TIDAL Deezer Qobuz Spotify Pandora alone or through A+3/ROON w/iPENG from Apple airport extreme wifi and everything wonderful even <=325 kbps stuff and ROON's internet RADIO sound like HiFi

[gmgraves]

23 hours ago, bobbmd said:

i have an AQ DFR connected to my iPad air 2 out to a vintage Pioneer Elite c-90 preamp and m-90 poweramp both circa 1987/88 and stream TIDAL Deezer Qobuz Spotify Pandora alone or through A+3/ROON w/iPENG from Apple airport extreme wifi and everything wonderful even <=325 kbps stuff and ROON's internet RADIO sound like HiFi

All MP3 "sounds like Hi-Fi" in that it all has full frequency response and low distortion (I assume you are talking about MP3 since you mention 325 kbps). Where this falls down is the so-called compression artifacts. At low bit-rates, 128 kbps or less, the artifacts are easy to hear even on a car radio when the car is traveling at 70 mph, and at less than 64 kbps, MP3, is, to me, unlistenable. These artifacts manifest themselves as a nasty modulation noise which appears to "ride" upon the waveform. At 128 kbps, the artifacts are less audible on speakers but are still, quite audible (and annoying) on headphones. At 192 kbps, the artifacts are essentially inaudible on speakers (at least they are to me) but occasionally I can still hear them on headphones (where they sound like a rush of noise when dynamics go from soft to loud very quickly, or when listening to a solo acoustic classical guitar or a harpsichord). At 192 kbps (the rate at which WCRB in Boston feeds it's Internet radio channel and thus their live Boston Symphony Concerts) and higher, MP3 becomes, essentially transparent.  

[4est]

On 12/3/2017 at 3:23 PM, gmgraves said:

 

We still seem to be talking at cross purposes. We are certainly talking about two different things. You are talking about overall sound quality (which is, subjectively speaking, an opinion, that, as I have indicated, I share), and I was talking about adding distortion to the chain by introducing more active components to that chain, which is indisputable. 

Actually, this sorta is disputable unless we are talking about theoretically perfect circuits. If the active pre sounds better than the passive, it could simply be a mis balance or excessive loading which may actually measure worse in circuit than using an active stage. Not you perhaps, but some seem to think there is very little difference between amps and pre amps. That indicates to me that whatever distortion is present in active circuits is fairly benign and it wouldn't take much mis match to be worse.

[gmgraves]

7 hours ago, 4est said:

Actually, this sorta is disputable unless we are talking about theoretically perfect circuits. If the active pre sounds better than the passive, it could simply be a mis balance or excessive loading which may actually measure worse in circuit than using an active stage. Not you perhaps, but some seem to think there is very little difference between amps and pre amps. That indicates to me that whatever distortion is present in active circuits is fairly benign and it wouldn't take much mis match to be worse.

What you say is certainly correct, the truth is, that traditional forms of amplifier distortion (and that includes pre-amps) simply are not that audible - as distortion that is. But the amounts and kinds of distortion does alter the sound of the amp circuit, and I've never heard a system that didn't benefit sonically from the simplification of said circuit. Remove a preamp from between a tape deck (for instance) and the power amp, and the tape will invariably sound better than it did through the preamp. It is impossible to amplify an audio signal with either tubes or transistors without adding noise and some distortion. It's possible to minimize the amount of noise and distortion, of course, with the proper components and good design practices, but there is still no such thing as a straight wire with gain, after all.

[4est]

4 hours ago, gmgraves said:

What you say is certainly correct, the truth is, that traditional forms of amplifier distortion (and that includes pre-amps) simply are not that audible - as distortion that is. But the amounts and kinds of distortion does alter the sound of the amp circuit, and I've never heard a system that didn't benefit sonically from the simplification of said circuit. Remove a preamp from between a tape deck (for instance) and the power amp, and the tape will invariably sound better than it did through the preamp. It is impossible to amplify an audio signal with either tubes or transistors without adding noise and some distortion. It's possible to minimize the amount of noise and distortion, of course, with the proper components and good design practices, but there is still no such thing as a straight wire with gain, after all.

Well of course there is no such thing as straight wire with gain. There is also no such thing as transmission without losses. In your example using a SP 11, there is nearly a whopping 40db of gain. Of course one can hear that. For this exercise, even a simple unity buffer might have a positive aural effect. All I mean by this is I feel that you are over simplifying. If everything is just right, then yes, likely a pre only adds distortion. IME, things are seldom just right.

[gmgraves]

8 hours ago, 4est said:

Well of course there is no such thing as straight wire with gain. There is also no such thing as transmission without losses. In your example using a SP 11, there is nearly a whopping 40db of gain. Of course one can hear that. For this exercise, even a simple unity buffer might have a positive aural effect. All I mean by this is I feel that you are over simplifying. If everything is just right, then yes, likely a pre only adds distortion. IME, things are seldom just right.

I'm not oversimplifying in the least. All active stages do change the sound of the audio chain of which they're a part (heck, to hear some people tell it, a half-meter or so of coaxial interconnect between a CD player and a pre-amp, for instance, changes the sound, but that's another discussion). Whether or not the net result of the insertion change of a preamp is sonically positive or negative is not the issue here. That's a subjective issue, and on that front, i am in complete agreement that in many (perhaps even most) cases, an active preamp sounds better than just a passive preamp or simply a passive volume control between source and amplifier. The only time that one can actually hear "damage" done by an active preamp circuit is when the source component has it's own buffered variable output (few components have this, but most tape and digital recorders do, which is why I used one as an example) and the preamp is bypassed. One doesn't need a DBT to hear this either, the difference in clarity and overall musicality is astonishing if one hasn't experienced it before! 

[Ralf11]

and Benchmark cautions that putting a pre-amp after their DAC3 will raise the noise floor; tho one may not be able to hear the distortion...

 

OTOH, some distortion may be euphonic (e.g. tubey goodness)

[sandyk]

George

 I agree with 4est.

A good Preamp can  have distortion that is not accurately measurable without using special techniques.

Once you get close to 4 Zeroes in the distortion figures you need to use measuring techniques similar to those suggested by Douglas Self. A good Preamp will also be able to drive today's more recent SS amplifiers with input impedances around 10K ohms far better than any Passive Preamp, even when they use VERY short connecting leads to reduce HF rolloff.

Many people will also tell you that a very wideband Preamp sounds better .

My own DC  coupled Class A Preamp has distortion figures of very close to 4 Zeroes, and can even drive a terminated 75 ohm line without problems. It has a gain of only 3.2 times, so that excessive attenuation is not normally needed.

 

 According to a U.S. friend who also built one, it is :  

 

Quote

Freq. Response Flat 10hz to 500khz; falls off 2db at 1.6mghz. (my generator goes up to 3mghz).
Output w 50ohm load= 12volts rms= 2.9 watts
Output w 100 ohm load= 12 volts rms= 1.45 watts

 

He didn't measure S/N as "there is none to be heard with my CD player connected & the gain wide open."

 

P.S.

 Have you read any of the Amplifier design books by Douglas Self ?

[gmgraves]

1 hour ago, Ralf11 said:

and Benchmark cautions that putting a pre-amp after their DAC3 will raise the noise floor; tho one may not be able to hear the distortion...

 

OTOH, some distortion may be euphonic (e.g. tubey goodness)

 

Both of your comments are absolutely correct!

[gmgraves]

28 minutes ago, sandyk said:

George

 I agree with 4est.

A good Preamp can  have distortion that is not accurately measurable without using special techniques.

Once you get close to 4 Zeroes in the distortion figures you need to use measuring techniques similar to those suggested by Douglas Self. A good Preamp will also be able to drive today's more recent SS amplifiers with input impedances around 10K ohms far better than any Passive Preamp, even when they use VERY short connecting leads to reduce HF rolloff.

Many people will also tell you that a very wideband Preamp sounds better .

My own DC  coupled Class A Preamp has distortion figures of very close to 4 Zeroes, and can even drive a terminated 75 ohm line without problems. It has a gain of only 3.2 times, so that excessive attenuation is not normally needed.

 

 According to a U.S. friend who also built one, it is :  

 

 

He didn't measure S/N as "there is none to be heard with my CD player connected & the gain wide open."

 

P.S.

 Have you read any of the Amplifier design books by Douglas Self ?

 

I think that I said, essentially, the same thing:

 

"...i am in complete agreement that in many (perhaps even most) cases, an active preamp sounds better than just a passive preamp or simply a passive volume control between source and amplifier. "

 

I have several amplifier design books including one by Doug Self. I also have several design cookbooks by Walt Jung including his famous Op-Amp cook-book. 

[sandyk]

2 minutes ago, gmgraves said:

have several amplifier design books including one by Doug Self

 George

 Is it "Audio Power Amplifier Design Handbook 5th ed - D. Self" ?

 

Alex

[gmgraves]

3 hours ago, sandyk said:

 George

 Is it "Audio Power Amplifier Design Handbook 5th ed - D. Self" ?

 

Alex

 

3 hours ago, sandyk said:

 George

 Is it "Audio Power Amplifier Design Handbook 5th ed - D. Self" ?

 

Alex

I think so. My technical books are in storage so I don't have access to them immediately. That title seems familiar, though.

[GUTB]

Here are some statements made by Stereophile in some category A recommended preamps:

 

"intense surprises that I'm sure can't be measured. Record after record, I found that the Reference 6 greatly increased my understanding of very familiar recordings."

 

"singers beamed from the soundstage with a matter-of-fact, lifelike presence that I'd never heard from my system...the Rex II captured . . . their most softly whispered asides. It was spooky-palpable."

 

Boulder 2110 "[it] produced image intensity, physicality, and solidity that were unprecedented in my experience. First take: a giant Wow."

 

Stereophile are industry shills and thirsty lapdogs of advertiser money? How about Part Time Audiophile:

 

"I also borrowed a Christine from Merrill, just to see what an additional $9,000 would buy. The Christine was jaw-dropping, with more bandwidth, superior speed, greater detail and a wider and deeper sound stage. It definitely earns its price difference. But when I switched back to the Cara, I didn’t feel like I’d stepped too far down the ladder. The family resemblance was remarkable."

[bunno77]

This is a stereophile review of a dcs Debussy. Obviously a great dac but their cheaper offering and he states there to be not much difference so really you could go without a 30k preamp. Pretty impressive 

 

 

 

The differences in sound between the Debussy into a preamplifier and the Debussy directly driving a power amplifier will depend on the preamp's transparency, dynamic capabilities, and overall quality. Sending signals directly to my Musical Fidelity Titan amp from the Debussy or through my reference preamp, a darTZeel NHB-18NS, I heard minimal differences. Given the darTZeel's price of $29,500, that's what you should expect.
Read more at https://www.stereophile.com/content/dcs-debussy-da-processor-page-2#vLyhuJGoSdRgEuMv.99

 

Using my own dac as a pre has been pretty similar to this

[esldude]

So what is the difference in the analog output stage of a DAC/pre and an analog pre-amp.  What can the analog pre be doing that is improving the DAC directly feeding the power amp?

[sandyk]

59 minutes ago, esldude said:

So what is the difference in the analog output stage of a DAC/pre and an analog pre-amp.

 

 Basically, it's usually Current Output capabilities, and more often than  not, a discrete output stage using higher supply voltage rails with the Preamp. Your average DAC would be lucky to have  + and -15V supply rails using a generic opamp for their output, sometimes even using a Dual opamp, and most likely also using 100 ohms series output resistors,(or higher)  as many I.C.s don't like driving capacitive loads of >100pF as with some Interconnect designs. 

Some better DACs MAY also use an output Buffer I.C. which makes them less sensitive to Interconnect vagaries.

 Many discrete Preamps have > + and - 20V supply rails and a markedly more sophisticated PSU, most likely not SMPS as with many DACs either. Neither do they usually need to share power supplies with a Digital area either.

With my own DIY Class A Preamp, you will see it is of a dual mono construction with separate sophisticated PSUs for each channel, and it is fed low voltage A.C. by 2 separate external transformers. This Dual Mono type construction also results in a considerable improvement in channel separation, especially in the HF area.

(Click twice on the image for a much larger image.)

[esldude]

5 hours ago, sandyk said:

 

 Basically, it's usually Current Output capabilities, and more often than  not, a discrete output stage using higher supply voltage rails with the Preamp. Your average DAC would be lucky to have  + and -15V supply rails using a generic opamp for their output, sometimes even using a Dual opamp, and most likely also using 100 ohms series output resistors,(or higher)  as many I.C.s don't like driving capacitive loads of >100pF as with some Interconnect designs. 

Some better DACs MAY also use an output Buffer I.C. which makes them less sensitive to Interconnect vagaries.

 Many discrete Preamps have > + and - 20V supply rails and a markedly more sophisticated PSU, most likely not SMPS as with many DACs either. Neither do they usually need to share power supplies with a Digital area either.

With my own DIY Class A Preamp, you will see it is of a dual mono construction with separate sophisticated PSUs for each channel, and it is fed low voltage A.C. by 2 separate external transformers. This Dual Mono type construction also results in a considerable improvement in channel separation, especially in the HF area.

(Click twice on the image for a much larger image.)

Yes your preamp is an exemplary example.  Many, many expensive preamps now use the same op-amps as the DAC/pre units.  Many good op amps can output far more than the needed current with no difficulty.  The best they can do is buffer the DAC if needed.  Many modern DAC/pre's don't benefit from the buffering.  There of course are some that do benefit from buffering, but you don't need to cross $1k prices to get models that don't benefit.  The outputs of the better DACs indicate they have been well designed to prevent PS issues from corrupting the output.  Otherwise all any analog pre could do is pass that corruption along.  

[sandyk]

6 minutes ago, esldude said:

Many, many expensive preamps now use the same op-amps as the DAC/pre units.

 Hi Dennis

 You will see in the photo that there is only 1 OPA134PA opamp per Channel PCB. This is only for DC offset correction as this Preamp is Direct Coupled.  The Class A Bias is adjusted for approx. 100mA in each channel, hence it's power output capabilities of :

Output w 50ohm load= 12volts rms= 2.9 watts
Output w 100 ohm load= 12 volts rms= 1.45 watts

Several other people have constructed my design , some for use as a Headphone Amplifier where the only real difference is the output resistor value., which is chosen to match the headphones used.

 100 ohms is used in the Preamp version, and has been found by several constructors to be ideal with most 1M long Interconnects.

Alex

 

 Attached is a photo of a C.S.I.R.O friend from Brisbane's H.A , where he managed to squeeze in 2 small transformers as well.

[4est]

8 hours ago, esldude said:

So what is the difference in the analog output stage of a DAC/pre and an analog pre-amp.  What can the analog pre be doing that is improving the DAC directly feeding the power amp?

Maybe a bespoke pre amp just performs better or that more care was taken with the pre. It has been said that one of the issues is that analog engineers are not always the best digital engineers and vice versa.