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65.31.171.38
Since all the other stuff pre Cd was in the one quarter to one half volt output range, and CD came along with it's way too high in comparison 2 volts output..
Why has no one offered a one half volt DAC?
Then some of us who also use LP and such might want it JUST FOR THE LOWER OUTPUT.. Let alone decent sound it might offer.
So Question is: Is there anyactual reason the output has to be 2 volts os more?
Why is ther no lower one half volt output DAC???
Follow Ups:
Ack dAck uses an output level of 1V (0.7 VRMS), in part to complement analog systems. A more complete discussion can be found on their FAQ page:
http://ack-industries.com/faq.html#q6
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A very valid question.
The increased SNR is not the only thing you need to look at, as some inmates suggest.
The typical signal level after the volume control is much lower then 0,5V.
If you consider that many people run > > 24db minimum attenuation on their systems to cope with pretty much the same or larger fixed added gain by the typical amplifier, 2V must be considered much too high.
Even 0.5V @ 24db amp gain @ 89db/W SPL speaker sensivity would be much too high, for the typical listening level out there.
You'd e.g. end up at 15W on a 4R 89/dbW SPL speaker if you'd feed 0,5V without attenuating it even further. That would be too much.
All this gets worse if you run an even more sensitive speaker.
In the real world DACs even amplify their output voltage to get to 2V. These 2V will be attenuated with your volumecontrol next. And finally your amp amplifies this - at this point - much more lossy signal again.
Pretty much nonsense all this "up'n down".
All that should be nicely engineered. It's not even difficult.
One way to cope with the subject is in fact to lower the DAC output voltage for most of the systems out there.
The best solution though would be to do some engineering once you start building your system.
The biggest problem in the majority of cases is IMO the typically much too high amplifier gain. Typically you'll find 26db > 30db gain factors out there.
The DAC output voltage should be kept as high as possible (native DAC output voltage without amplification) for best SNR. The gain of your amp would have to be chosen accordingly. It just doesn't make any sense to attenuate a signal first to get it amplified at the next stage again.
Example:
@2V Udacout @89db/w SPL speaker + 4R speaker impedance and 89db listening level we would need
Uampout=SQRT(P*R)=SQRT(1W*4R)=2V
Ampgain=20log(Uampout/Udacout)=20log(2V/2V)=0db
Intersting result! You'd get along with a unity gain amp. You'd need no voltage amplification - you just need the current.
To add some headroom 6 to 12db gain for that amp would probably be more than sufficiant.
But again. All this needs some math and some more knowledge about how your device manufacturers handle the signals. If your DAC manufacturer
amplilfies the native DAC output voltage, you might want to skip that stage first. And than you lower the amp gain accordingly.
0,5V can be right on one system on another it might be the wrong value.
Though from what I've seen on the majority of system I can say that 2V
is a too high value.
The main problem is that the vast majority of devices out there just let you control the levels by a volume control stage. That must be considered highly inefficient. What we really need are amplifiers with variable gain stages.
Enjoy.
--------------------------------------------------------------------------------------------
::: Squeezebox Touch Toolbox 3.0 and more ::: by soundcheck
"What we really need are amplifiers with variable gain stages."
Yup.
I know there's been a few done but I have no idea how well. I vaguely recall PS audio had products with what they called a "gain cell" or something like that but I've never heard one.
As far as I know the "standard" for home audio has always been 1V for line-level interconnects so I was surprised when CD players were 2V. Marketing in action I suppose. IT'S NEW, IMPROVED, 6dB more fun right out of the box!
There's a lot to be said for deliberately mis-matching impedances from a design and compatibility standpoint but I've been toying with the idea of building a chain focused on preserving as much signal energy as possible all the way through. Probably won't make much difference but might be a fun thing to tinker with.
Rick
I had one of PS Audio's preamps with Gain-cell, it sounded great although not exactly neutral. It was a tad on the warm side. I have another pre by a different company that uses a similar technology at its on the warm side too. But are/were great and sound very musical.
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
It wouldn't be a problem if CDs were made properly, which would set the average RMS level at about -18 dBfs for the loud portions of a track. Then the extra voltage output would only be used for headroom purposes.
Most pop and rock recordings made today are nearly 10 dB louder, and some even approach being square waves. This done by a process that includes multiple stages of compression, limiting, filtering and sometimes even deliberate clipping. One gets one's music at "communications quality" which would be appropriate if it were voice going into an AM or SSB radio transmitter. But then, I've never considered most of this stuff to be what I call "music" anyhow.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
"Most pop and rock recordings made today are nearly 10 dB louder, and some even approach being square waves."
Fortunately I have scant interest in that genera. Unfortunately it has now largely ruined classical streaming radio with both MPR and KWAX compressing their signal all to pieces but in MPR's case still clipping on announcer voice peaks. To add insult to injury ABC (the Oz one) has reduced their data rate from 128K to 64K as the default and has very limited access to the old stream. Tried it the other day and it's worse than a good AM transmitter was in the 50's.
You know, in our callow youth we would joke about how the old folks would pine for the 'good old days'. Damn it, now I sound just the same! But it's too true and them thar good ol days were only a few years ago.
By the way, my old plate modulator had a lot better fidelity then most of today's stations...
Rick
I listen to classical music from Czech Radio over the Internet. This comes at 48000/16, FLAC encoded. Quality is good, there is no compression. The only problem that I have with this service is the occasional drop out which is probably related to how clocking and buffering is done. (This is a touchy issue due to the huge amount of buffering required to deal with network latency.) This usually happens no more than once every few hours.
The music is broadcast at a relatively low level, so there is never any problem with distortion. Unfortunately, they broadcast the announcements im Czech at a volume roughly equivalent to fortissimo in the music. Unfortunately, the excessive volume doesn't make up for my lack of linguistic expertise, but the web site usually provides the needed information.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
....?
Sheesh.......
Oz
Don't worry about avoiding temptation. As you grow older, it will avoid you.
- Winston Churchill
Funny
Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
The results are all I care about. If I worried about dickheads like you, I would not have them set up the way I do.
As it is, i am NOT worried about dickheads like you, so I use a tubed preamp just for it tubyness factor into my main preamp. Not YOUR problem.
Oh sorry in your opinion it is your problem. You must stay up nights worrying about it.
I'm actually quite interested in this use of dual pre-amps - can you provide a link to further discussion of this, or give a brief explanation of how it is implemented?
I would be interested in using the phono stage of my Wrightsound WLA20 into the NAD326BEE - so far, I've tried it directly into the amp stage, but also using the tape out/in connections.
Piping a phono stage into a line level preamp is no different than had the phono board been in the line stage. The very best separates operate that way.
What Liz does is daisy-chain multiple line stages and throw away most of the unnecessary gain. As for me, I go in the diametric opposite direction - I eliminate redundant gain stages where possible. My digital sources drive the power amps directly. A (single) preamp is used only when the equalization and gain is required by a phono source.
Originally I bought a set of Brystons... preamp BP-26 and amp B4B-SST2 to replace my old Adcom preamp and Forte'4a amp.
I had too much gain on my digital with the Brystons so I wondered what I could do to attenuate the output. I still had my Adcom, so I stuck it over at the amp end of the 7 meter preamp to ammp wires to see if attenuating the signal there would be 'OK" (this is where Ozzy decided to start in on the two preamps shit BTW) anyway I was not fully pleased with the setup, and still wanted a buffer for the digital anyway.I had a problem with my digital stuff and wanted to try a tube buffer.
So I bought a cheap ($150) tube buffer, but it did not do much for me.
I happened to see a great deal on a VAC Standard preamp on the gon, (($1,500 for an upgraded VAC Standard ($4,000 plus a grand for the factory mods)) so i jumped on it.
The VAC does exactly what i want to the digital signal as a glorified tube buffer, plus I can now leave my main preamp volume at a good position (unity gain) and for digital, use the VAC volume control.
Wonderful.I also have another preamp laying around I want to keep. An Audio Research SP-15 two chassis preamp with a great three tube phono section.
So have that going to my Bryston preamp also, and just use it sometimes, to just keep it in good shape (better than in a closet)Anyway the output of any amp into another is no problem electrically.
Soundwise as Ozzy states, it may be idiotic if it degrades the sound. However for my needs what i now use and how i use them works out just fine for me.
The Adcom when it was in the chain certainly did degrade the sound.
The VAC is perfect at want I want from it, and really my digital is exquisite at this time with no interest on my part to change any of it soon.----
You can use the regular output, or the tape out if you want to avoid the volume control.
For the Vac, having the Bryston at unity gain, and using the VAC to fine tune volume works best.
For the Audio Research Sp-15, using the gain set at -24db, and volume at maximum, using the bryston volume to fine tune the volumeworks best for that pair.And for Ozzy, i guess his repeated 'rubbing it in' crap is just his way of reminding me he thinks of me all the time, I guess some call that love.
Edits: 05/17/12
Thank you very much, Elizabeth, for your very complete answer, and thanks to E-Stat for your helpful comment.
This may provide a way to use the excellent tube phono stage of the WrightSound, while still retaining some of the benefits of the NAD's preamp section.
Dickhead? Are the gloves coming off? I don't remember ever calling you a name...
If you ever hear the "right" preamp in your system, you will realize you only need ONE.
I just think it's funny to call you out and see you spin like a top.
Good job!
Don't worry about avoiding temptation. As you grow older, it will avoid you.
- Winston Churchill
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Dynobots Audio
Music is the Bridge between Heaven and Earth - 音楽は天国と地球のかけ橋
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As others have already pointed out, there are digital components with less than a 2VRMS output level.I don't know that there is any solid technical reason for the nearly standard 2V output leveI. I don't see noise as being the driving issue. Even a 0.5 volt level would be about 100x the amplitude of a high output moving-magnet phono cartridge. In addition, you begin to incur increased distortion as the output signal amplification is raised.
One of the system level issues is that there is usually too much total gain between the input to an active linestage and the output of an power amp. This fact is why Nelson Pass created his B1 buffer. It seems to me that CD's 2V output level is probably one of the worst choices. It is simultaneously too high, given the excess gain of most systems, and a little too low to universally eliminate the linestage.
_
Ken Newton
Edits: 05/16/12 05/16/12 05/16/12 05/16/12
My Muse model 2 dac has a 1 V output that I prefer. I think 1 V is as low as you can go before noise would become an issue during the quiet passages. I've never had an issue with volume between my cd and phono source.
In the case of a DAC, I don't see how 0.5V would offer sonic advantages over 2V as a rule?
"Knowledge is knowing that a tomato is a fruit. Wisdom is knowing not to put it in a fruit salad"
"In the case of a DAC, I don't see how 0.5V would offer sonic advantages over 2V as a rule?"
12 dB more signal, probably the same amount of noise, so 12 dB better signal to noise ratio.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
If the DAC put out 0.5V instead of 2V, the signal to noise would be 6dB WORSE than with the higher voltage all else being equal, not 12dB better.
0.5V is 25% of 2V, which corresponds to -6dB
Unless there is something I am missing?
"Knowledge is knowing that a tomato is a fruit. Wisdom is knowing not to put it in a fruit salad"
dB is a power ratio, not a voltage ratio. 1/4 the voltage is 1/16 the power.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
If a DAC is designed with a low 0.5 volt max output level, there would be issues with noise, because it is difficult to keep noise levels low relative to a low-level signal.
The Audio Alchemy DDE v3.0 that I used for more than 10-years had five different outputs. It could be set for full-scale output voltages of 3.6, 1.14, 0.36, 0.11 and 0.04 using internal jumpers. I still own it but when its corresponding DDS Pro transport bit the dust I replaced it with Stello components by April Music.
The DDE v3.0 is a very nice DAC with HDCD decoding capability. It also has a digital volume control, which I always left disengaged and it has an absolute polarity switch, too. You might be able to find a used one on eBay or Audiogon.
Best regards,
John Elison
you've got too many gain stages.
As for me, I really like the 4V output of my CDP since I get better sound sans line stage. Only attenuators are needed.
"you've got too many gain stages."
This usually happens when you daisy chain two preamps together......
Oz
Don't worry about avoiding temptation. As you grow older, it will avoid you.
- Winston Churchill
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LOL yourself.....
Don't worry about avoiding temptation. As you grow older, it will avoid you.
- Winston Churchill
.
Some DACs have adjustable outputs either via internal jumpers or switches or via volume controls. If the standard is 2V and you make one fixed much lower than that then you really limit your potential customers since their systems are set up for the higher output.
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Seems to me it was designed to be 2-volts out to match all the other line level sources. 0.5 volts would seem to necessitate a reduction in output voltage as most transistor circuits require a minimum voltage of around 0.7 volts to operate the transistor junctions.
Therefore, phono stages should have enough flexibility to also attain the nominal output level, even though that voltage is mostly attenuated in the line-level stage.
It is easy to design a lower output voltage (we're talking about a AC signal, not a DC one) - if you needed to use a diode in the signal path, you would use AC to send the AC Zero into the linear part of the curve and then have the ausio signal ride on that. So any voltage right down to zero is easy.
However, most circuits have noise that does not change - and in a good DAC, you want to maintain -120dB from the peak - which means it has to be darn quiet and dropping the signal out by 6dB doesn't help!
"Knowledge is knowing that a tomato is a fruit. Wisdom is knowing not to put it in a fruit salad"
I recall 2 volts being part of the original Red Book CD spec also.
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All audio transistor circuits are biased well above the point where the the junction is forward biased or there would be severe distortion.
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