Archive for the ‘Sources’ Category

XMOS USB Audio 2.0 Reference Design Jitter Measurement

Monday, January 9th, 2012

The XMOS demo board sold for $149 in digikey.  The firmware need to be loaded before the board can be used.  There is a digital out from the USB 2.0 demo board and thus it will be a easy interface from USB to FDA-1 optical input.  What you need to do is to get an optical cable to link up output of demo board and input of FDA-1 Toslink.  I have tested this mode and the sound is better than using Ti PCM2707 USB receiver with I2S output.


On board, there is a I2S connector and thus the clock jitter measurement is taken at the MCLK, BCLK, LRCLK locations.  The jitter at MCLK from 48k to 192k Fs is from 10 to 13 pico second respectively which are excellent.  In fact the MCLK is taken directly from the onboard crystal oscillator after the buffer logic IC.  For jitter at other clock like BCLK (Bit Clock) and LRCLK (Word Clock, Fs), they are as high as 800 pS or above.  For any DAC using the MCLK as the clocking reference (like FDA-1), the result should be very good.

Attached is the document of jitter measurement for reference:

Jitter measurement by Lecroy DDA-120

From all the measurement, the lowest jitter mode is to set the output of the USB 2.0 at 24 bit with 48k Fs.

With a more accurate period jitter machine Wavecrest DTS-2070C, the jitter at MCLK is measured at only 4.6ps.  See attached document:

Jitter measurement by Wavecrest DTS-2070C

Squeezebox Classic

Sunday, August 16th, 2009

This is the version 3 of Squeezebox (SB3) and I can get it about 1,500 HKD in Mongkok computer center, Hong Kong.

This network player must be used with a computer or a NAS (network attached storage).  I use both as I have a old Qnap TS-201 NAS.  This is really a pain to install the squeezecenter in the Qnap as there is no more support from Qnap.  Finally I get it done with the help of the link here.

The SB3 has both optical and SPDIF (RCA) out plus a two channel analogy output.  I do not use the analogy out put but only the digital input and my D1V3 or D1V33 DAC.  I have modified the SB3:

  1. Outbox 5V 1.5A linear regulator to replace the stock switch mode power adapter.
  2. Add 3.3V regulator for CPLD and HCU04 ICs which hopefully can improve the jitter of SPDIF signal.
  3. Sync one of the clock to CPLD (11.2896MHz) from outside DAC – D1V3 via a SMA coaxial cable.
  4. Finally I settle with a XO to replace outside clock due to flexibility of my DAC to receive different sampling frequency from 32kHz to 96kHz.

Ok, the sound!

I would say SB3 is very good relative to normal CD/DVD Player (I have Marantz DV7600 and Yamaha DVD S2300MKII) or low cost transport.  Compare to CD-PRO2, it lack the lower bass authority.  Other than lower frequency, I think the SB3 is very good in mid and high frequencies.  This is a real bargain if you use it to replace your CD transport!

Rubidium Atomic Clock FE-5680A

Wednesday, August 12th, 2009

If you are lucky, you may be able to get one of this used atomic frequency standard for about US$100 from ebay.  This is a programmable clock from 1Hz to 20MHz.  With the low phase noise of this clock, it is the best choice to create a super clock standard using FE-5680A.  The supply of this clock use 15Vdc and current about 2A.  After warm up for 10 minutes, the current will drop to about 0.75A.  Thus the continue power consumption is about 12W which is quite a lot and thus the metal body should be attached to a heat sink or metal chassis for cooling.

Currently I am using this Rubidium Frequency Standard at 10Mhz as the reference frequency for other equipment like frequency counter or AP-2522 etc…

There are two documents that I can find from internet which are very useful for using this super low noise clock.

FE 5680A modifications

FE-5680A pinout jap

If I have time, I shall put this super clock into a chassis with all the connectors and power supply all in one box…  It is something like a reference clock used in a studio to sync all the digital equipment.

PlayonHD – Eaget Media Player

Sunday, August 9th, 2009

Whether A.C. Ryan or Eaget brand, this HD Media player is very similar.  Eaget is the China brand while AC Ryan is selling outside China.  The player can house one max 2T hard disk and it can playback almost every video or audio format found!  My set is a Eaget which cost me about US$150.  The only difference between PlayonHD is the remote control and I have tested that the PlayonHD firmware is able to be used in the Eaget set.  But I think I need a Playon remote to control the Eaget set as the key on Eaget remote is nto function accordingly.

You can use this cheap player to replace your transport and put all music file into the internal hard disk.  There is high potential for media player to replace CD player or Transport.  At this moment, only small brand are making lots of this players but I believe the big name is going to sell some better design media player in near future.

It uses a Realtek chipset and everything is done by this chipset even the digital output signal is directly from the chipset!  Thus nothing much can be modified inside!

As a digital source, it sound really ok with such a low investment!  The only thing I don’t like is that you must connect it to a TV so that you can search in the hard disk folder to select and play your music!  It is really a product for Video only.


Monday, October 13th, 2008

This is a DAT machine – Digital Audio Tape made by TASCAM (TEAC).  There is both AD and DA conversion in this machine and also digital input and output (AES only).  The analogy has both balance XLR and non balance RCA sockets. Thus this machine can be used as a DA or AD converter.  That say it can be used as a A to D, A to A, D to A, and D to D converter.  Some people just use it as a DAC when the tape part is not working.

The good thing about this machine is that the CD can be recorded back to a DAT tape and then play back again.  But why record into a DAT?  I think the sound of the CD is improved to be more relax and musical.  I do not understand why but this is what I found out!

The digital filter is NPC SM5813APT, AD converter is AK5339-VP and most of the op-amp are Philips NE5532AN & IV 5238.  For power supply, all the E-cap are Panasonic Purism and signal path is also Panasoinc BP cap.

For sound, the best sound is from DAT Tape –> Digital Out –> Good external DAC like D1V3.  The analogy output from this machine is also very good and the sound is quite relax and clean.  If the machine is used as a DAC, the sound is not as good as the sound when DAT tape is played back.  The lower frequency seems to be attenuated when used as a stand alone DAC.  Guess it is due to the receiver jitter signal is not attenuated down enough.

I use some DDS-1 or DDS-2 tapes and the machine can take it without any problem.  Anyway, it is one of the best 16bit CD digital source that can be found from ebay for only $300 to $500 USD.  Take note on the drum hour when you want to buy one of this as the life is about 2000 hrs.  Of course I am not using it as like in a studio and I think it should last at least 4000 hrs with some minor signal drop out.