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Richard Murdey

diyAudio Member

About Me

  • About rjm
    Biography
    Canadian citizen, Japanese resident.
    Location
    Kyoto
    Interests
    Audio Circuitry
    Occupation
    Research Scientist
    Country
    Japan
    Real Name
    Richard Murdey
  • Signature
    RJM Audio (phonoclone.com / G+)

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General Information
  • Last Activity: Today 09:31 AM
  • Join Date: 2nd May 2004

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View rjm's BlogRecent Entries
Latest Blog Entry

Posted 14th January 2015 at 12:29 PM by rjm Comments 0
Have I just been living under a rock or why the hell haven't I heard about this before now!?

http://www.njr.com/MUSES/index.html

Posted 14th January 2015 at 07:07 AM by rjm Comments 9
Posted in Uncategorized
The shift of the center of gravity of the high end from component, rack systems to portable continues. Exhibit A

I've also noticed that over the last couple of years the basic blueprint for a portable headphone amplifier as defined by the Sony PHA-1 has now been taken up by all of the major Japanese audio companies.

Sony PHA-1, PHA-2, PHA-3
Denon DA-10
Onkyo DAC-HA200 and TEAC HA-P50 (variants of the same basic unit)
JVC SU-AX7 (report) (seems to be mostly Kenwood DNA)
Audio Technica AT-PHA100
and Fostex hp-p1

For all the above you are looking at a battery powered, slim-cased DAC + headphone amp typically with some sort of guard around the controls. They all feature a good variety of analog and digital inputs, offer switchable gains, and are priced over a range from $200 to nearly $1000.

You are looking at the convenience of having the DAC built in, the small size, and the rechargeable lithium battery. Its...

Posted 14th October 2014 at 01:55 PM by rjm Comments 0
Posted in Uncategorized
Eye candy.

My fourth. Each one comes packaged the same, with a serial number and individual calibration sheet.

This little guy is no. 2096, .39/.40 mV. Signed off by Mr. Nemoto (根本さん、ご苦労様!)

Posted 3rd October 2014 at 01:40 AM by rjm Comments 0
What we are looking at here is the Fast Fourrier Transform (FFT) of the line output from my b-board buffer recorded at 24 bit, 96 kHz by an Onkyo SE-200PCI sound card. Upstream from the b-board is the Phonoclone 3 MC phono stage, connected to a Denon DL-103. The tonearm is Denon DA-307, and the deck is a Denon DP-2000.

Four recordings, taken 1) with music playing, 2) with the tonearm raised 3) with the phonoclone powered off and 4) with the b-board and all upstream components powered off.

True 24/96 data was obtained, measurements out to 48 kHz are possible, with -130 dB noise floor. (I was using Digionsound 6 to do the recording as Audacity truncates 24 bit recordings to 16 bit in Windows due to licensing issues. The FFT was generated in Audacity however.)

The soundcard's line input may have an impressive-looking low noise floor, but it's still useless for measuring line level audio devices like the b-board because the noise of the preamp/ADC...

Posted 23rd August 2014 at 12:33 PM by rjm Comments 1
I suppose everyone has at one point or another adjusted the volume sliders in Windows. The ones that go from 0-100, and you are never quite sure what whether its a boost, or an attenuation, or what.

Some years ago I measured the outputs and inputs using a fixed amplitude .wav file created in audacity and played back through the Onkyo SE-200PCI. I've taken another look at the worksheet I made and I've noticed that the volume settings correspond to very logical, even steps, namely:

100 0 dB
90 -1 dB
80 -2 dB
70 -3 dB
60 -4.5 dB
50 -6 dB
40 -8 dB
30 -10 dB
20 -14 dB
10 -20 dB

or for the mathematically inclined: 20*log(volume/100)

This scale is the same for both the output master volume and the line input, so its probably maintained throughout the operating system.

So now you know.
Recent Comments
Yes, I wasn't meaning...
Posted 15th January 2015 at 11:50 PM by abraxalito abraxalito is offline
I don't think you get...
Posted 15th January 2015 at 11:23 PM by rjm rjm is online now
Having the trafo improves...
Posted 15th January 2015 at 03:34 PM by abraxalito abraxalito is offline
Oh, I imagined MOSFETs...
Posted 15th January 2015 at 06:34 AM by rjm rjm is online now
I guess mine are parafeed,...
Posted 15th January 2015 at 02:01 AM by abraxalito abraxalito is offline
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