Selasa, 13 Desember 2011

Battle of the old NOS legend? Part 1

I don't want to miss writing in December :), there are some design things in the pipeline, but first my current DAC adventures. I have managed myself  a piece of equally legendary AD1865-N-K DAC. It is one of 'a must have' DAC chip, I'm always a fan of multi-bit DAC, next in my list is the expensive PCM1704, may Allah The Great permits.

Me not buying ready made PCB for the AD1865 :), not challenging and not fun enough :),  so the usual PCB layout-ing took some time, and to my surprise, this time designing is a breeze compared to TDA1541 board!. The AD pins are very layout friendly. I use both NOS schematic with 74HC04 hex inverter and the other with 74HC02 NOR, why?. Well, blessing in disguise really.

First I made CS8414 - 74HC04 - AD1865 pcb. After powering up the damn thing just gives noise, all effort to resolve failed, check and rechecking everything, tried other connections etc...very frustrating.

So then come the other schematic, now instead of 74HC04 I use 74HC02. I always think less is better. Using the 04 you use only 1 logic, while with 02 you use all 4 logic's.

The 04 however has 1 data line for both left and right channel, i.m.o. not so elegant, both AD1865 inputs are continuously bombarded with digital data, while in the OFF state, I can be wrong of course :). One way to try is to slit apart data trace with a cutter, and listen to your DAC, it still managed to get through!.

The 02 in contrary have 2 separate data lines for each channel. Mind you though, both NOS digital glue with 04 and 02 introduce data phase shifts between channels and clock (SCK from CS8414), with 02 comes worst. I know this from DIYaudio and by simulating the digital input-output data stream. But the shifts are small, and people says this is similar with moving your head 8mm during listening :), or is it?

This can be fun to check, because TDA1541A NOS with CS8414 data stream is exactly in phase! Ok, here are the plan, I use mediocre power supply (ex. Pioneer LD player), measure all 3 DAC boards : the original hardwired TDA1541A DAC, AD1865 with 74HC04 and AD1865 with 74HC02, all analog stage are my favorite single ended -DC coupled 2SK170 jfet, All board will use the same CS8414 about that?..

How about the HC02 board?, still no luck bringing it alive!, must be the DAC...even a Vout mod from Iout did not help..

Frankly, I have listened to all of them :), I got my AD1865 replacement (many thanks Doc!....) , the AD1865-HC02 is still using Voltage output. This is preliminary listening though, I'll let them for a couple of weeks playing...

Here are the pics, AD1865 PCB's are CNC'ed, I tried as far as possible using same brand and same values component.

From bottom left : the 'Red' shoebox power supply, TDA1541A DAC, AD1865 with 74HC04 and SEJfet out, AD1865 with 74HC02 and Vout, note the coupling capacitors.

Now, back to listening he he he...

Jumat, 04 November 2011

TDA1541A Balanced DAC, part 2

I'm listening now to Andrea Bocelli's Amore album, right now Estate's is playing, using balanced TDA1541A-S1 DAC and it's direct heated triode output... the sound makes you really enjoying the Andrea's emotion... man... I have to write this instance..:). There were few moments like this when you're deep in to music you're listening, really caresses my ears and you forget about analyzing music, let alone measuring he he..I lost my measuring urge :). I'm just going to enjoy it before this DAC moving to it's new home.
Damned!!.....that voice of  Christina Aguilera...what a talent!..what a waste in her pop music!...and just past midnight here, the volume knob barely at 9 ...Somos Novios......., my ears were tickled nicely here :)

It's have been almost 2 weeks since I have boxed up brother Y's balanced DAC and fired it up. Before that I use his DAC - Jfet - LME49720 opamp board and the little DHT bugger in my DAC box with the famous Salas shunt regulator.

I should mention that a few weeks back we have had a very nice blind test session. I for sure have participated, bringing this balanced DAC. The result? well a mixed bag really. I've heard 2 to 4 very beautiful sounded DAC there. A matter of taste though, only 1 of my favorite made it to final. The winner is a humble AD1955 DAC..congratulation ! here is the pic of my box with brother Y's boards.

There are the 4 Salas regs, at center the TDA1541A-S1, the DC coupled single ended Jfets, next to it is the balance-single ended opamp converter (with bit of gain) that going to ..yup, a pair of direct heated triode :). a very nice sounded ones those little buggers !, I did not believe my ears when listened to them the first time. I've made both anode & cathode follower/CF, the above is CF. Heater cathodes were battery powered. Why DHT output? I'm quite bored actually doing another 9 pin tube things, maybe octal tubes will be nice but I'm daunted with so many choices and what if the sound is not right...

Now in new box, not as large as mine, standard thin steel box, but modified with 8mm thick aluminium face plate and 2mm rear plate

Anti clockwise from top left : 2 EI trannies for digital supplies, 1st 2x Salas board, DAC board, 2nd 2x Salas , SE Jfet's, opamp with LM317-337regs for supply up to +/- 17VDC, DHT DC heater (modified Tom Ronan's supply), DHT board with supply, analog transformer (both high voltage, 2x 10V for heater and 18V for opamps). At center are cap banks for opamps.

This project to me is the most difficult and challenging, but worth the effort. This is my many "first-time" experiences with balance topology, first with I2S splitter, first  balance- SE opamp, all including Salas board were custom designed and CNC'ed, and yes, first time DHT and I highly recommends you guys overcoming that famous DHT hum with DC heater!. very frustrating and yet rewarding ..completely gone? nope, but I remembered 'complaining' friend's DIY DHT I have experienced it coming with that "low' hum is admirable!.

Thanks for reading....thanks to brother Y for the challenge, may the emotion be with you!

now on : Solamente Una Vez (oh my...Stevie Wonder just great with Andrea..), Sony CDP950 digital out, TDA1541A-S1 balanced DAC-DHT tube out, Aikido pre amp, Aleph J clone tweak nr.xx, Scanspeak Elan

Senin, 26 September 2011

A new DIY audio adventure, TDA1541A Balanced DAC, Part 1

With no design thing comes to my mind lately, why not sharing my on going venture into another TDA1541A DAC topology with you?. After finishing and more or less settled with my hardwired single TDA1541A DAC, a good friend have listened to it during a listening session at a friend place, he's blessed with a old pair match of TDA1541A S1 or what we called single crown. Pair match? yup that's right, each TDA1541 chip I've listened sounds different to each other, some subtle within one production batch, others like night and day :).

My friend 'brother Y' was impressed with the sound of his S1 chips sitting  in my hardwired DAC and rightfully asked a balanced topology, I couldn't agree more. Balanced topology requires pair match of everything, from DAC chip down to Jfet and opamp output stage down to single resistor & capacitor in the signal line. After long study at (as always, thank you guys..) I've found  the way how to do balance DAC using I2S splitter, yup, there is one good man behind this, Pedja Rogic, kudo's to you sir!.

The digital data from CD transport is first entering the receiver CS8414, which gives I2S data out, this data then go into splitter which feed 2 TDA1541A, one chip received Left data, the other Right data. Now the splitter does something else, it split the audio data into + data and inverts the other half of data into -data. So one dac chip will output L+ and L- analog out, the other R+ and R-, clever isn't?

From there I will have 2 pairs of (now) my favorite discrete 2SK170BL's single ended current to voltage converter I/V as in my hardwired DAC. From the JFET's the the L+/L- and R+/R- signal are fed to balance - single ended converter op amp :(...but this is the easiest & speediest way. After op amp you can do tube out, just what I did, later on that... :)

Meanwhile, I did got busy making that double sided PCB which since the start of layout I've incorporated possibility for paralel and balance configuration. Not a world class digital PCB I admit, but it works wonderful. I got also many valuable advices from the NOS TDA1541 man himself : Thorsten Loesch, thank you T.., and this means the layout is evolving :).

Well, quite an introduction to this challenging DIY project, now (finally) some pictures, I've made my PCB's using my (DIY) mini CNC machine that I've made back in 2004, told you that I'm a hardcore DIY guy :)

CNC ing is very nice if you do only limited quantity, and when you experimenting (read: playing :)) but take bit of time of tracing & converting ECAD data to usable GCode for machining, but what we get is nice clean process without chemicals and of course nice copper area for power and digital ground plane...

The long awaited parts were finally complete, specially the hard to find old Philip chip for I2S splitter, the  famous Toshiba 2SK170-V for the 4 Salas regs, and the most important, a pair of dual matched 2SK170-BL, quad match were simply not available anymore. Got 1 quad match in my MC phono pre though he he..hope to share this as well soon.

Here is how the DAC and splitter board looks like

Top of pcb, the splitter with 3 red cerafines and the left channel DAC, bottom pcb are for the CS8414 and the right channel TDA1541A, notice detachable risers for ground return and power supplies.

And does these things worked? You bet!..perfectly by the way :)... here are early measurement using TDA1541 non A and John B's single ended Jfet, tested here the L+ and L- signals, the usual 500Hz/0dB

Green is the L+ signal, red the L-, they are exactly,  well..within the limitation of our beloved VisualAnalyzer of course :), have you got one installed yet?
You see, the whole balanced thing comes to to this, you add 2 exact but opposite phase signal, summing will get rid of all even harmonics (what????...said a nice tube guy over there...:;D..), what left are the odd harmonics...and in total lower distortion figure.....why oh why???...said another tube guy....:(...

That yellow curve is full of even harmonic and it IS being removed. This cleaned signal then enters the op amp to be made single ended again, want to add flavour? you can, I'll add tube out just to add a pinch of 2nd harmonic. My brother Y will have options of  DAC outputs to choose, SE JFET, Balanced JFET, SE opamp out, or .....SE Direct Heated Triode tube out

stay tuned & have fun

Sabtu, 13 Agustus 2011

TDA1541A DAC, Part 2, " measurements "

Now I have finished my DAC, also have done many tweaks (and still continuing...) It's time to do some "measurement", why the "...."? well because it is not very serious measurement, I have no mega hertz oscilloscope, no proper signal generator, but anyway there are plenty soundcard based software, and here is my favorite : Visual Analyser 2011, it is free and in my opinion, a must for DIY audio.

Why measuring ?, I think it is a proper step to at least measuring the frequency response of our DIY audio projects. We audiophile likes to have low distortion and flat freq response and how do you know that without measuring? no way, maybe possible with a very trained ears and a reference audio gears. Me for sure likes to see  what happened with my music signal, starting by putting simple sinus, square and pink-noise signals.

How do we start? first we must have test signals, some test CD are available, and you can make your own if you're lazy like me ;), I have my signals made with Audacity, loop recorded with EAC then burned to CD. The Pro's among us must be laughing when they see the 16 bit/ 44.1kHz digital sinusoidal waves, at 10kHz the signals looks like a triangle wave, at 20kHz even worst :). So I limit the signal up to 1kHz, a proper sinusoidal and square form still very good recognizable. With this frequency we can at least compare distortion and harmonics of our DIY gears, no more and no less.

I have 3 gears to test, my new DAC, my old tubed Sony CDP950 player and battery powered bit stream Sony DiscMan. I had a 8xTDA1543 DAC at home, listened to it, too bad have not measure it. Here is the setup when measuring CDP950.

It is very important to have any software like Visual Analyser calibrated  correctly or you'll get garbage results. Be careful with your measurement voltages, it can easily destroy your sound card. A simple voltage divider (variable resistor) or a full blown measurement jig like mine (SW Jig II) is a must. Measure the signal with your multimeter before connecting to soundcard.

What else? after calibration I measured the sound-card it self, I connected my laptop headphone out back to line input. I measure all signals including the 'silence' track to see the noise floor of my sound-card. Here are they, signal is my favorite 500Hz/0dB

the 'Silence' track :
 500Hz/0dB :
I know, I should have set the X axis to Log scale..hey...I'm just a beginner remember? What do we see here? the noise floor is below -114dB, and the 500Hz gives quite a lot of low magnitude harmonic spikes that will come back when you measure other gears. Ok, now my old CDP950, silence track and 500Hz see? that 500Hz thing looks way different than the sound card, notice the high (and nice sounded) even harmonics...well, it sounds muddier than my DAC alright, but veery nice..not enough for me now haha,  I want transparent and nice sound here, so the CDP needs tweaking for sure. How about the noise? well, it is just below -108dB, no worries for this AC heated tubed out CDP. If I have log X axis you can see the 50Hz and 100Hz peaks there quite high. And now my new DAC with very low noise Salas shunt regulator (big thank Salas...)

Now the noise? way below my CDP950, maybe a lot cleaner than the sound-card, and noise floor bit above at -114dB. And the 500Hz is way cleaner than CDP950, bet this that gave me better transparency :).

And how the discman measure? This is interesting, TDA1541 on my CDP and DAC are both multibit non oversampling, while the discman has 1bit deltasigma and battery powered, here is the 500Hz, forgot to measure the silence here, but you can see here as well, close to sound card noise floor. So battery does very good job indeed.

And this Philips Bitstream DAC measure very well, very transparent, much less harmonic spikes and in reality sounds smooth but have less soul in the music.Attack and decay in the music seems constrained, high is relaxed but bit feels synthetic / canny..I still prefer my NOS multibit TDA1541 here ;). I did try to measure the interesting square 1kHz signal, but its for next time :), thanks for reading and get this wonderful Visual Analyser right away. (below 1kHz square on sound-card). Happy measuring...

Selasa, 12 Juli 2011

Finally, my own TDA1541 DAC, part 1

After months of reading and mostly 'arm chair DIY' (just sitting, browsing and thinking...) finally I came up with NOS (non oversampling) schematic that combines what available on the Net, adjusted and combined them to my best knowledge.

There are great guys out there sharing their thought on this 'ancient' but highly regarded chip, the TDA1541A. Let's see, these gentlemen are Thorsten Loesch, John (aka ECDesign) , Pedja Rogic, Lesha, Pavouk, etc. and one Japanese guy whose name I can't read. Thank you gentlemen. Please read here on where I've got a handful of these jewels.

After having a schematic next headaches were PCB layout, at least I made my self 'difficult' by trying to learn about digital PCB layout which is to my understanding different than analog one. There are so many do's and dont's here up from PCB track level to component soldering pads and I think that ground return paths were most challenging.

To cut the crap ;), I've decided to use perforated board, good, thru-hole one and believe it or not, it is a complete hardwired DAC. Why? just quick and dirty way to check pcb layout and whether 'my' schematic runs or ruined. So here it is, receiver chip is CS8414, power supply is (or was) from my busted Panasonic Super VHS player.

Output stage is single ended JFET (2SK170) as per John schematic, still using output capacitor here to block DC offset voltage. I did have to add LM337 voltage regulator for -15V. Put in my favorite 500Hz/0dB Denon test CD, a nice 0.74Vrms was read ..yihaaa...!. It's alive and kickin..., now tested with some music..with my SOHA and my Samsung, what a powerful kick and what a wonderful NOS sound..and then..that details, tons of them. I know, what I will tell you next is cliche, I heard details never heard before..

Well, enough with first impression, I know from experience, it can sound better. My new DAC already making my NOS, tubed out Sony CDP sounding behind a curtain. Audio DIYer like me are always know that your best sound today may not be anymore after hearing better one.

After some tweaking I decided to get rid of all the output capacitors, changed some parts with better ones, and I've settled with this Shoebox DAC for a week or two and tried paralleling 2 DAC on top of each other. I liked single DAC better though. Friends coming listening to it likes what they heard..I did too..removing the C out really makes a difference.

I still have a plan on power supply, a very good one that is : Salas shunt regulators. Here they are, I used 4 of them, 1 feeding the 5V of CS8414, 3 feeding the hungry TDA1541A. The Shoebox is replaced by MDF board :), the sound? even better transparency and immediateness..but it can and must be better yet again..sigh..I have to get wider staging..

Now I can sit back and relax, enjoying another tweaks on my Sony CDP, it needed too..:), my Aleph J clone also needs power capacitor change..until then. I must thank many friends here, prof ATP for regulator boards, pak Richard for his generosity with his 2SK170-BL's, Mr. Bowo for  his IRF's and more, last but not least to Mr. Doctor for the DAC chips and of course my DIY audio friends. Thanks for reading.

in the Audio pipeline :
'measuring' DAC, Sony CDP950 NOS/Tubed and Sony Discman..