THE STORY

Zero can be considered a further  developement of our kusunoky style DAC "Minimo". Minimo impressed  us a lot expecially  with its clear, life-quick sound.

But of course every  DIYer can't  ignore the "DIYer's bug voice"  always saying "Can you do better?".....   ;)) so we soon started to experiment around another DAC unit. The idea was to:
 

• stay fatithful to the "16bit - 0 oversampling philiosphy"
• increase the output driving capabilities using an output stage.
• increase noise/distortion performance

The usual quick investigation in Internet clearly suggested that a very nice DAC to experiment was TDA 1541. This DAC distortion is among the lowest in the 16bit category. Thorsten in his site also said that one advantage of this component is the very peculiar "timbre", very sweet and detailed: That's what we're looking for.

Minimo had a lot of "impact" but there were something missing in the higher part of the spectrum, and -in general- the soud had too forwardness expecially in some live recordings.

very had lot of improvement in the  that the sinvestigatedd eDIYerand  our previuos 16 bit DAC based on a parallel of four TDA 1453 has so many merilistened for  several month to the 1bit dac on the Cd pro, we realized it was time for a big change, and to take a step in the undiscovered (for us)  realm od DACs.

At the beginnig  the idea was to stay faithful to 1 bit technology, anf if possible (money matters) ,  improving it with a 24 bit /96khz DAC.  This apperared a nice choice,  coinsidering that one bit DACs are very cheap.

One of the nicest - in our opinion was- Perugini's Crystal DAC.

We also take a look on pluribit DACs, projects based on PM63 appeared one of the best solutions but the cost soon discouraged us.

We were in the middle of "evaluating suppliers" phase for Perugini's DAC, when looking in a newsgroup in Audioasylum we read a post   about no oversampling, no digital filtering 16 bit DACs, following the *very* worth-a-reding Kusunoki article:

http://www.sakurasystems.com/reviews/a2.kusunoki.html

Expecially One Opinion in Tweaks Asylum make us think: ".... After all if Audio Note is working from long time around 16 bit DACs there must be a reason!...."

So just to spend time in order to get more "cash" for the "big project", we decide to build a Kusunoky style DAC too, one of the simplest 16 bits DAC..

The Original project can be found in many places on the internet, ad firstly apperared on MJ magazine during late 1996 (!).

This project uses a CS4812 to recostruct bistream from a SPIDIF input. Besides has a built in de-emphasis filter, used to play old CDs. Of course this de-empahsis in nowadays not very useful.

The main part of the DAC is build around the very cheap TDA1534, often used in TV sets, and very easy to find as spare part . Four of these chips are put in parallel to increase output level & S/N dinamics.

This DAC as plenty of things to "stole", most notably in the power supply part. See also the great idea of using a TL431  as shunt regulator to obtain supply voltages, avoiding those noisy LMXXX chips.

Another 16bit DAC project called  "TNT Convertus"  appeared recently in TNT-audio magazine, using the same chips.
This is a slightly simplified Kusunoky stile DAC, mainly in power supply  and besides has an output filter to suppress the sampling frequency.

The DAC we've built is maily based on this version, but -you guess-  we've simplified the shematic further  because a I2S bus  is already available on CD pro unit, so we don't need even the CS4812 chip and is power supply!!!!.

So at the end this the circuit we've build.

Simple isn'it?. A little experimental board is enough to build it !. Looking at this bunch of components on a bread board it was very natural to call this DAC "MINIMO"

Anyway, if you've the chance to build Minimo a little etched boad is better. Here is the experimental board we're using:

As you can see you need a lot of wire bridges. We suggest to build them using silver-teflon wire.
 
 

Minimo  need only a variable power supply to drive the for  TDAs 1543.

We've put some  slight modifications in the schematics provided in TNT site:

• we've increased the rated power of the MS transistor using a IRF 540
• we've improved a bit the stability of the output voltage using a zener diode to fix the source bias.

Here are some ideas to adapt the performance of Minimo to you listening pleasure:

• Remember that TDA1543 are rated 5V (!) So increase slowly  the voltage of the PS starting from 6V, try to reach 8V, listening carefully to the sound. You'll see that band response and dinamics improves trough the way. Suggested voltage can be around 8-8,5V. We've a good 8,3V. Best is to use a scope and a CD test record setting the voltage to minimize distortion.

We use the quick & dirty way: I adjusted  a bit the voltage keeping an eye to the VTM not to reach the Abso. Max Rating voltage while Andrea was listening.... any better idea?.... ;)
• You can use a battery-powered PS.
• You can take away one or two couples of 680pf in the output stage if you fell the need for more highs
• You can put a switch to bypass the 1mH inductors + resitors. doing so you'll have an output stage very close to the original kusunoki project. We prefer this situation now.

Listening Impressions

We put a switch to compare "Minimo"  to the build-in DAC of the CD pro unit. At the beginning we fell very unconfortable with the sound. It was something really new!.
We had several sessions  in Andrea's listening room. The chain we used is this:

• CD Motor: CD Pro philips unit
• DA Unit:    Built in Cd pro DAC & Minimo
• Preamp: Euridice with 6c45P
• Power Amp: Mono-Triodino III (2a3+6sn7) see the details in my homepage
• Speakers:  Side Vivace (side horn with PM2A)
• Signal cables: DIY silver-teflon Cables
• Power cables: Megahertz "silver-Tef" cable

These are (in my poor english) the impression we had:

• "Quick": The sense of quickness this DAC has in hard to belive. Bass are far powerful and fast compared to our previous dac. Listning to those sudden noises you can find in some live recordings you'll find that there 's a lot of improvements in the "impulse response": all seems more natural and uncompressed.
• "Rough"  The one bit DAC that comes with the CD pro unit has a  very "golden"  and "all notes are similar" sound. I mean that the highs and basses are all nice &  extended but with a very close-one-another character (maybe this is an effect of digital filtering). With this DAC, expecially in the bass section the different "character" of each instruments appears, with all his "roughness" and "spikes", no filter to reduce the dinamics.
• "What's that": CD after CD you'll find -expecially in live sessions- that "there is life out there". A lot  of new details will come out.
• Highs Modulation:  This is a  dark side  (for my oscilloscope?) . .  Having no digital filtering, means that the highs suffer from modulations from the sampling frequency (22kz) thus changing the "color" of the tones in the higher section (18-20khz) This  could be seen using a CD with a 19-20kz tone and a scope.  Could be a problem if you can ear  20Kz freqs and around... this not my case even if I'm in my 30ies, ..  ;)

 

Rating pro and cons we could say that the main  "minus" of this DAC is the sense of "aggresivness".
In the groups they say it's greatly due to the "sound" of TDA1543, after all a  low cost component.
In such judment we agree with Mr Thorsten (couldn't we??).

We're enjoing the sound of this  DAC from Oct. 2000 and we could say that  the sound is very pleasant and could bear face to face comparison with some  high-end DACs, for a 1/1000 of the expense. Remember that all this costed us about 30 euros!

Seems impossible this bunch of components sounded so good.
Needless to say we leave completely behind the idea of oversamplig and 1 bits DACs.

That's all folks, Listen and ENJOY!
 

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