FET Audio | Hi-End Audio & Electronics DIY Electronics & Repair

October 8, 2009

F5 – Amplifier

Filed under: Pass Amplifiers — Spencer @ 9:18 pm

The is my new project in Oct 2009.  Making use of my original F4 casing and power supply, I can complete the two sets in about a week.   One set is using IRFP240/9240 mosfets and another set is using Toshiba 2SK1529/2SJ200 mosfets.  I only adjust the bias to about 1.2A which give about 20W at 8 ohm load.  Also I do not get the super low distortion that Nelson Pass got in his measurement. According to Nelson Pass, the distortion can be trimmed using a source resistor at the input jfets but I am too lazy to do that as I am very happy with the sound!

The sonic signature is very much similar to F4 but with a bit better control on bass.  I do not hear much difference between IRF and Toshiba F5 but the distortion of Toshiba set is almost double of that of the IRF set.

Here are some pictures of the IRF F5 and some measurements that I have.

F5 FFT IRF at 1W 8 ohm

F5 FFT IRF at 20W 8 ohm

F5 IRF distortion vs input level

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September 11, 2009

D1V3 + Squeezebox Classic (SB3)

Filed under: DAC — Spencer @ 1:00 am

This is a modification of SB3 clock to sync to D1V3 on board super clock 11.2896MHz XO.

  1. Major improvement on D1V3 is to use a clean super clock for SM5842AP.
  2. Major problem is to connect the D1V3 super clock back to SB3.  Thus SB3 internal modifications are needed.  SMA coaxial cable is connected to pin 9 of HCU04 IC and ground.
  3. A separate 3.3V AMS1117 regulator is used for the CPLD and HCU04 ICs.  Sanyo OS-con and film cap are used for supply bypass.
  4. A linear 5V 1.5A regulator is used to replace the original switching adapter.

With this modification, the SB3 will not be able to play back other sampling frequencies file other than 44.1kHz!  Thus it is only good for CD playback now.

Some measurements:

SB3 SPDIF digital out FFT @ 1kHz

SB3 SPDIF digital out FFT @ 18kHz

D1V3 and SB3 FFT @ 1kHz (D1V3 analogy output)

D1V3 and SB3 FFT @ 18kHz (D1V3 analogy output)

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August 16, 2009

Squeezebox Classic

Filed under: Sources — Spencer @ 8:52 am

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.

http://forums.slimdevices.com/showpost.php?p=302757&postcount=332

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!

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August 12, 2009

Rubidium Atomic Clock FE-5680A

Filed under: Sources — Spencer @ 10:15 pm

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.

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August 9, 2009

PlayonHD – Eaget Media Player

Filed under: Sources — Spencer @ 4:18 pm

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.

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