The DIY LPRO-101 ruibidioum clock generator. This box together with some additional electronics on a separate PCB will transform this LPRO unit into stand alone equipment. I’ve always wanted a good and affordable frequency standard for my home lab. Searching the eBay one might find quite a lot of solutions. The good thing is that nowadays we have plenty of options.
Category: Digital Page 1 of 3
So it was a pleasant weekend. Just a few folks gathered together to listen to some good music. Well not only. It’s always about listening to something in particular and test it against something else. In this case one of the guys had brought his beloved CD player – the Unico CD Primo by Unison Research.
Well I had to say that I was rather suspicious about this testing. The first thing is that this CD player has a really good looking tube output stage. Having noticed that it was clear that this fellow has nothing to do with the neutral and transparent sound. However I kept my thoughts to me and we all sat down and listened.
This one is an interesting article by AES, featuring considerations about the interface, jitter and other interesting topics.
In a correctly functioning digital audio system the only observable signal impairments should be attributable to band-limitation and an additive noise residue. Thus although the subjective sound quality of digital audio has received some criticism since the launch of the compact disk (CD) medium 10 years ago, there can be little doubt that the theoretical performance obtainable from the 16 bit linear PCM format sampled at 44.1 kHz is superb compared to any analog source available to the customer
Is the AES/EBU / SPDIF Digital Audio Interface Flawed? – >>>LINK<<<
Here is an interesting schematic diagram for USB DAC based on the famous PCM2706 chip by Texas Instruments.
The design incorporates opto isolators to reduce the high-frequency garbage and prevent it from entering the analog part of the DAC. Like most of the DIY minimalistic designs, this one uses passive low-pass analog stage at the output of the DAC chips. The current to voltage conversion is done passively (duh) thanks to R19 and R17. Those are subject to experimentation to obtain the optimum value. Too high the resistor value and you get increased THD. Too low means you get lower output level.
PCM2706 + 4 x TDA1543 – LINK
Here is a way to make an I2S output from your CD player. This one includes a reclock option inside the CD player.
This idea uses a standard cat5 network cable. I personally don’t like the idea of reclocking the I2S bus and then sending it over the cable. A way better solution would be to include a low clock source inside your DAC. This source could have two outputs. One used to make the reclocking and feed the DAC chips with clean clock. The other output could be sent out over the same cat5 cable (using the 4th pair inside the cable) to the transport. This would make the transport a slave to the DAC and will practically eliminate it as a source of any troubles.