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rjm rjm is offline

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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  • Wiki Comments: 0
  • Recent Wiki Activity: rjm has no recent wiki activity
General Information
  • Last Activity: Yesterday 11:11 PM
  • Join Date: 2nd May 2004

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Latest Blog Entry

Posted 2nd February 2016 at 08:11 AM by rjm Comments 7
The discussion thread at the headphone forum is here, but I wanted to throw out the problem to the general blog-reading community here at diyaudio to see if anyone can nail this.

The earthed chassis (light blue) must connect to the circuit common i.e. "ground" (pale green). I do not know where the best place on the circuit ground is to tie that connection.

Suggestions please!

(COM and GND are completely equivalent pads on the circuit board, while IN- and OUT- also pads on the board but physically further away on the ground plane.)

****

Answer: as long as it connects at one point only, or the same point of both channels, it doesn't seem to matter at all. I have it connected at the ground tab of the headphone jack and that seems to be as good as anywhere.

****

The noise is a 60 Hz waveform, a positive spike and a negative spike once a cycle. It appears to originate from the current flowing...

Posted 24th January 2016 at 12:48 AM by rjm Comments 2
Ladies and gentlemen, please try to keep a straight face while browsing the following link.

http://www.entreq.com/products/ground-boxes-17667704

I'm not sure whether its possible to build a passive, permanent device that dissipates/neutralizes electrical charge. But the scientist part of me finds the claims that you can interesting.

Static electricity will eventually dissipate by attracting counter ions from the air. This happens more quickly if the humidity is high.

So seriously, if you just stuck a wire into a bucket of dirt, how much "earthing" would that actually provide? Is there any way to amplify that effect by using special materials or even passive electrical components?

Posted 30th October 2015 at 01:49 PM by rjm Comments 7
Original version is here.

I've been meaning to get around to updating this by folding in the improvements to the diamond buffer stage made during development of the Sapphire 3 headphone amplifier. Here is the first look of the bboard v2 under LTSpice.

I've gone back to simple emitter resistors on the input, running under much lower current to keep the input impedance high. The output is simplified to a basic Sziklai compound transistor pair with the bulk of the bias current running in the second transistor.

In terms of distortion, for line level output level, CCS loaded input has no advantage. I'll have to double-check PSRR and a few other things before signing off on this version though.

FYI only, not a production circuit.

Posted 9th October 2015 at 11:46 PM by rjm Comments 0
https://www.asus.com/Essence-Hi-Fi-A...r_Essence_STX/

I admit I did not give ASUS the benefit of the doubt and seriously consider their Essence STX soundcard as a replacement for my Onkyo SE200-PCI. ASUS make nice motherboards, but unlike Onkyo have no previous expertise in high end audio.

I am happy to report - a bit late in the game, the card came out in 2009 - that they've done a really good job with it and the drivers for Windows 10, technically still in beta, work just fine.

*****

Asus updated the design recently to the STX II. The PCB has been redone, but the only visible change is the PCM1792A DAC has been moved towards the top of the card closer to the IV conversion op amps. An second LDO regulator IC, U34, empty on the STX, is now populated. A "TXCO" clock source is added next to the ASUS audio controller IC. The four film caps next to the output IC are replaced with WIMA brand. It's basically identical, so it...

Posted 8th October 2015 at 08:35 AM by rjm Comments 3
Apologies for the Google-friendly title, I'm hoping people experiencing the same problem will find their way here.

Onkyo download page: http://www.jp.onkyo.com/support/pcau...d/se200pci.htm

Current version is 5.60C, last update was 2012 to be compatible with Windows 8. Driver package 5.60C installs without issues on Windows 10 64 bit. The AudioDeck utility installs as well.

However, all is not well:

On installation, Immezio 3D effects are enabled. This locks the sample rate at 48 kHz. 44, 96, and 192 kHz cannot be selected. Deselecting the Immezio 3D effects prompts a reboot, but the Immezio 3D effects remain enabled after rebooting. The card is stuck at 48 kHz. 3D effects (which enables the DSP processing such as Qsounds, EAX, A3D) cannot be shut off.

I see three possible workarounds:

1. Find a command line switch, or edit the installation batch file to disable Immezio 3D on installation...
Recent Comments
I did consider snubbers,...
Posted 8th February 2016 at 09:35 AM by rjm rjm is offline
I love the copper cummerbunds....
Posted 8th February 2016 at 01:04 AM by abraxalito abraxalito is offline
For a tiny bit of help,...
Posted 5th February 2016 at 04:19 PM by disfunctionalshadow disfunctionalshadow is offline
That looks promising!...
Posted 4th February 2016 at 12:55 AM by rjm rjm is offline
One bridge rectifier...
Posted 3rd February 2016 at 02:35 AM by rjm rjm is offline
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