Turntable Power Supply

My turntable (Acoustic Signature Challenger) came with a 12V ac synchronous motor and outboard power supply.  The power supply unit produced a smooth sine wave (in fact : two waves some 90 degrees apart) as confirmed using an oscilloscope.  Opening the unit revealed that the timing is by RC circuit and switching in/out different combination of R and/or C to change the frequency to either 50Hz or 66.7Hz (for 33.33rpm or 45rpm platter speeds).  Fine tuning of the frequency is by trimming the variable resistors (one trimmer for each speed). Disappointed that the timing circuit wasn't quartz/crystal locked that I expected (RC timing circuits are not known  for its accuracy or stability), I decided to build one myself.   Searching for sine wave generators led me to DDS (Direct Digital Synthesis) and without having to build one from scratch using a PIC and programming in the codes, I just purchase one from eBay for about USD45.  This DDS can output sine, square, triangular waveform up to 2V peak to peak from a few Hz up to 2MHz with 0.01Hz resolution - offering more than what I required.  I thought, with 20MHz crystal clock, outputting just 50Hz (a division of some 400,000 times) - its frequency would be highly accurate and stable.

Next step would be to amplify this signal (of about 1V AC sinewave) to the required 12VAC.  I just followed this idea : TTPSU  and built a class B power amp (5W) using TL072 Op Amp and BD911/912 power transistors, with +/- 18V supply.  Connect everything up and put into a plastic box, we have a complete turntable power supply for 12VAC synchronous motor.  The 2nd 90 degree out out phase waveform was created using a 4.7uF capacitor (no-polarity).  Later, I may add an op amp 'integrator' to derive the cosine wave (90deg) and another set of power amp as an alternative to the capacitor solution.  Sine waveform checked with oscilloscope - very fine, distortion not checked.  Tested with the motor it works on first try.  And with the motor driving the platter, the speed of 33.33rpm was achieved when the frequency is set at 48.90Hz (due to pulley /platter diameter combination and manufacturing tolerances).  Satisfaction? You bet.

Hufiduino software update and new display

Hifiduino updated the software codes to version B09c, fixing some bugs and now my DAC can be controlled by a Apple remote control (only the volume & muting though).  The LCD displays a fresh look as shown in the photo below.  Uploading the program code is easy - via USB and using Arduino's own software and you can easily edit the codes to display the 'welcome screen' (when powered on) of your choice - for eg. your own name , etc.

When in use, the sampling rate (SR) is displayed to the last digit and is not 'rounded' to 100s, so you get figures like 44105 or 44095 (below) when playing 44.1kHz, which is acceptable considering it is only an error of 5Hz.  What I meant is you won't get exactly 44100, 88200, 96000 or 192000 on the display unless you change the software code to round off to the nearest 100.  Using different sources will result in slightly different figures but we don't know the actual absolute figure because there are many sources of error from the sources (cd player or Musiland) clocks error, Arduino clock error, the Buffalo clock error.  If all else remain constant, it can tell the relative clock rate of different sources (faster or slower by comparison only - not the true absolute clock rate). Sonically, the most important thing is the stability of the clocks - frequency drift (with time/temperature) and jitter. Unless we use a master word clock to synchronise all the clocks in the chain, or better still use atomic clock, maybe next time .........

Musiland Monitor 01USD

I use Foobar2000 (a free Windows digital audio player) to playback high resolution digital audio files purchased or downloaded from the web.  Foobar can be user customised and plays most digital audio files well up to 24bit 192kHz rate.  Initially I connect the PC directly to the DAC via SPDIF, after configuring the output to SPDIF but I wasn't sure if the PC alters the sampling rate or not.  I got a good value, China made, Musiland Monitor 01USD (instead of the more well known and expensive M2tech Hiface) to do the job of outputting SPDIF.  Using its own drivers and connecting to the PC(notebook) via USB cable it can output SPDIF in its original sample rate and bit depth - exactly what I wanted.  Connected to the Buffalo II DAC with "Hifiduino" display confirms that, showing 192038 when playing 192kHz HD audio files.  Tried with files of resolution 88.1kHz and 96kHz with no problems.

With the Apple ipod dock Onkyo ND-S1, the digital output connecting directly to the Buffalo II dac, the sampling rate was always 44.1 k, the same as when connected to my TEAC cd player.

Hifiduino

Got me an Arduino UNO board and started doing its basic programming tutorials and got an LCD display panel to toy with.  Great to have these tools and dedicated people to learn from.  I always wanted to know the actual sample rate of digital music that is fed into the DAC so I searched for solutions on the web and found this : Low cost SPDIF digital monitor.  I then stumbled upon Hifiduino who provided the answers and more - it controls the settings of the Buffalo II DAC too.  So, I set out to build the DAC display as described in Hifiduino following each steps carefully and cut and paste the software codes (with minor modifications to the codes and some emails to the code writer) - bingo it works!  Now, I not only have a good sounding DAC but also a well featured one too.

Twisted Pear Audio - Buffalo II DAC

For about a year now I have used the Buffalo II DAC for my digital music playback and I must say its my best DAC to date.  The initial lead was from the information that big name DAC makers are using the 32 bit ESS9018 chip from Sabre and it sounds good but expensive.  I found that they made 'evaluation kits' and people buy these kits to make DACs of audiophile grade.  Then the DIY Buffalo II (now Buffalo III) from Twisted Pear Audio crops up as the most economical solution to a DAC using ESS9018 chip. The rush and very low volume supply couldn't meet demand for months but I managed to buy one last year and the rest is history.

Sony Open Reel Tape Deck - TC766-2

My restored Sony Open Reel Tape Deck, besides cleaning, polishing and oiling, the rubber pinch rollers were machine ground by specialists.  The old transistors in the preamp circuits were replaced with new ones and this significantly reduced the transistor noise (hiss) to an inaudible level.  Without tapes to really test out the machine, I purchased a few from eBay sellers, choosing only 7-1/2 ips (inch per second) tapes.  Sounds wonderfully analogue - frequency response was acceptable and the recording is as good as the equipment and technology could reach back then.  As the unit can go up to 15ips it would be good to lay hands on such a recording (hard to find) - as the Tape Project  tapes are definitely out of reach for me.....