Why do preamp sections in DACs SUCK Abysmally compared to good preamps?
- Thread starter caesar
- Start date
My best guess is - the preamp provides buffering. Preamp sections in DACs are probably just something of an afterthought. If the design's really a preamp rather than a DAC it'd be termed 'a preamp with a DAC section'. Then the DAC section would be likely to suck...
Depends on the preamp, but I agree completely. Dynamics are what suffer the most it seems, and this has to do with power delivery. A preamp just does it better.
I don't see how the preamp section in my DAC (Berkeley Alpha DAC 2) fails to make music. I use it into my tube amp. I had a Spectral DMC-15/DMA 260 combo in my system for comparison (with in that case the DAC at flat output close to max), and it was in some ways a bit better, in other ones a bit less good, but there were no night-and-day differences by any means. It was pretty even. There were also no differences in dynamics, an area of reproduction that is very important to me.
This was before I got the external power supplies for my amp that were a substantial upgrade.
IMHO most of the time theoretically nothing to do with buffering in a technical sense - the output of most DACs can perfectly drive the IC cable and power amplifier. The preamplifier simply manipulates the signal, in some cases making it more realistic for some people.
I have just written in another thread about the DCS Vivaldi:
I have now played with several amplification systems using it, and although when used with solid state amplifiers I preferred it going through a tube preamplifier, when using powerful tube amplifiers I was not so sure any more - there is a freshness and immediacy in the direct mode that brings instruments directly in your room in the direct mode. But still a lot to learn about this great system
And sorry, no high-end product is perfectly neutral ...
I have just written in another thread about the DCS Vivaldi:
I have now played with several amplification systems using it, and although when used with solid state amplifiers I preferred it going through a tube preamplifier, when using powerful tube amplifiers I was not so sure any more - there is a freshness and immediacy in the direct mode that brings instruments directly in your room in the direct mode. But still a lot to learn about this great system
And sorry, no high-end product is perfectly neutral ...
Agreed - when I was talking about buffering I didn't mean it in that technical sense - that the output didn't have sufficient drive without voltage or current limiting. Rather I meant it in the sense that the output loading affected the perceived dynamics. Of course there are technical reasons for this too but not generally ones accepted by mainstream engineers.
Gentlemen, out of intellectual curiosity, I checked the reference systems of some of the more famous computer geeks in our hobby. ( using the term "geeks" respectfully, as leaders in the field who rule the digital world and make our lives better ). Computer audiophile uses constellation preamp and audio steam guys use pass and ayre. So even they seem to agree.
Handling analog and digital sources in the same box is rather problematic due to digital sources (most especially USB-sourced digital) often having noisy power supplies that wouldn't be seen dead in high-end analog source components. Few designers that I've seen take sufficient notice of EMC related issues. Berkeley Audio Design though is one of the minority who does.
I don't know if this has relevance to your point about output loading -- which is not entirely clear to me -- but the input of my tube power amps is very sensitive. The DAC needs to deliver much less current to them than when driving typical power amps. Perhaps that helps.
Hi Opus, I haven't a clue -- sorry! Grace Design is regarded as a company with "clean" circuit designs. It was my intent to use the m905 for monitoring, only, as I preferred it to both the BAT REX and Atma-Sphere MP-1 Mk. 3.2 (need to send this back to Ralph for a check-up) preamplifiers as well as a Cranesong Avocet that was loaned to me, but after listening to the m905 converter - I retired the Audio Note 4.1X Balanced DAC. The AN DAC was my sole converter for approximately 5 years.
Yes that helps a lot - the dynamics issue is about the output current demanded by the next component in the chain. Tube poweramps can have input impedances well over 100k and such impedances cause little or no degradation to perceived dynamics in my experience. They would need short and/or low capacitance ICs though to maintain the ease of drive.
Making a source work harder can change the music a lot. Spectral's input impedance is high, so the effect will happen with it.
Perhaps many sources, including DAC's don't sound right unless they're warmed up a little? It more likely has to do with current, and increasing it. Most devices struggle to deliver current as well as they should. The biggest problem is the approach to oversize things doesn't necessarily help at all. In fact some times the most helpful thing is a resistor in line (depending on where, and the value, speaking more about the circuit topology) but that's as counter intuitive to reasoning as most non-engineers will get.
Perhaps many sources, including DAC's don't sound right unless they're warmed up a little? It more likely has to do with current, and increasing it. Most devices struggle to deliver current as well as they should. The biggest problem is the approach to oversize things doesn't necessarily help at all. In fact some times the most helpful thing is a resistor in line (depending on where, and the value, speaking more about the circuit topology) but that's as counter intuitive to reasoning as most non-engineers will get.
If the DAC's got a typical opamp output stage (many have) then I'd expect that output stage to be sensitive to its PSU quality. Normally opamp PSUs are decoupled by electrolytic capacitors and the ESRs of those tend to dominate their impedances above 3kHz or so (unless they're specially low-ESR types). The ESR of a capacitor is fairly strongly a function of temperature - even holding a cap when my LCR meter's connected to it warms it up enough to see changes to its ESR. ESRs go down with increased temperature meaning cold caps don't function nearly as well as warm ones.
The AN DAC was a NOS R2R type? If so that's a very interesting datapoint and I'll see what I can learn about the m905's internals.
I've done experiments to increase the current load on things. It can give an effect I've heard in numerous high end items. In some cases it can make the image grow a lot. But it tends to reduce the higher frequencies perceived volume. This is true of my impression of Spectral to a degree, but not enough that it's very obvious. A combo of Spectral equipment can project large images, which isn't a bad thing. But it may chnage some factors with what sounds good to you. I wouldn't call it the final word in fidelity, but it's far from bad; a more accurate description is its just preferance. This can much more desirable than alternatives most of the market offers.
Few PSU's seem to deliver power as well as we'd like. The voltage is there, but current isn't always in phase with the music and it doesn't "catch up" it simply never happens. Sadly this isn't an easily measured thing, so everyone does their best with it. I have some methods that have proven pretty useful.
Few PSU's seem to deliver power as well as we'd like. The voltage is there, but current isn't always in phase with the music and it doesn't "catch up" it simply never happens. Sadly this isn't an easily measured thing, so everyone does their best with it. I have some methods that have proven pretty useful.
I'd expect it to make the sound more 'forward', reduce the soundstage depth but widen it. I agree that the HF volume sounds more 'recessed' the more noise that's coming alongside the signal - the subjective effect is reduced dynamics.
Not noise, more specifically current loading. But you're correct that depth isn't necessarily as obvious, but depth has a lot to do with speakers too.
SMPS supplies with fairly high carriers and residuals tend to cause the "etched" sound we know to be familiar. But many manufacturers using them have effectively reduced them down to very low levels. I get no trace of it, say, from an MSB DAC.
SMPS supplies with fairly high carriers and residuals tend to cause the "etched" sound we know to be familiar. But many manufacturers using them have effectively reduced them down to very low levels. I get no trace of it, say, from an MSB DAC.
Similar threads
Members online
- ccxxvm
- Moladiego
- HansW
- Rico25
- andromedaaudio
- cminer
- Acci
- Birdwatcher
- alwayslearning
- Protegimus
- Dierkx1
- Tangram
- 2fastdriving
- dminches
- Charlie B.
- rdg
- Ferris010
- Long Live Analog
- Azjya
- Another Johnson
- Oracle1974
- audioblazer
- Bill Hart
- hopkins
- BBSBR
- godofwealth
- Mike Lavigne
- bonzo75
- Johngp
- psbake
- Raidersfan
- Hessec
- Stbo
- Rt66indierock
- Bonesy Jonesy
- Toymanmark
- cjfrbw
- Chop
- kennyb123
- billse
- AVDizainas
- Kjetil
- ticktock
- trekpilot
- Channel1.0
- admin1959
- Emorante
- Klonk
- austinpop
- tsaett
 | Steve Williams Site Founder | Site Owner | Administrator |  | Ron Resnick Site Co-Owner | Administrator |  | Julian (The Fixer) Website Build | Marketing Managersing |