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googlyone googlyone is offline

diyAudio Member

About Me

  • About googlyone
    Biography
    Electronics engineer, worked on digital, RF, systems engineering, software. Now in management :(
    Location
    Adelaide, South Australia
    Interests
    Strong interest in electronics, particularly analog, power audio and DSP. Hands on, try it out type
    Occupation
    Operations Manager in product design and manufacturing company
    Country
    Australia
    Real Name
    Phil

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  • Last Activity: Today 07:32 AM
  • Join Date: 7th November 2006

Blog

View googlyone's BlogRecent Entries
Latest Blog Entry

Posted 31st August 2015 at 12:50 PM by googlyone Comments 1
Posted in Uncategorized
I recently set to work the guts of the audio analyser:
- MiniDSP USB Streamer
- Interface card
- ADC
- DAC

The ADC and DAC were from an old project. the tests I had been able to do on these were done using simple test gear, I knew the distortion was fairly low - but had been unable to really bottom out the level.

I did know the DAC was down in the 0.001-3% level or below.

Imagine my chargin when I fired the system up, got all the bits running and measured something closer to 0.01% distortion at -1dBc!

I was initially convinced that there was something wrong. After cranking the level down to -10dB, the distortion dropped to 0.001%. Further tesing (I ran the DAC at -1dBc and attenuated the output) proved that it was the ADC dominating the measurements.

Attachment 1698

Much fiddling led to me concluding that the ADC buffers were the culprit. I would like to blame...

Posted 21st August 2015 at 05:16 AM by googlyone Comments 0
Posted in Uncategorized
Over the years I have played with measuring - well - just about everything in audio.

distortion measurement has been one of these preoccupations, not the least because it is hard to do, and using commercial gear, expensive.

I have built analogue hear to do this, used mixes of analogue and digital and of late played with using modified commercial sound cards. My efforts on the Sound Blaster x-Fi were interesting but ultimately not rewarding enough for me to leave the mods in there.

I have also been playing with using the A/D and D/A converters from my DSP crossover for this purpose. These are modular and use a common I/O plug with power MLCK, SCLK, LRCLK and Data (alone with I2S for the CS4398 and sometimes a digital volume control).

--- notwithstanding the fact that in previous tests I have shown the digital volume control is the MAJOR source of distortion - I will plug ahead with this, and likely leave that out of the test...

Posted 29th March 2015 at 12:51 PM by googlyone Comments 2
Posted in Uncategorized
I have been playing with measuring distortion of signal sources and amplifiers a bit over the last year or two.

I am serious enough to spend some time and thought on this, but not serious enough to sink significant cash into application specific test equipment.

I have a couple of USB Sound Blaster X-fi Music (SB1240) sound cards I use for measurements. The original intent of these was for speaker test and general music. I am pressing these into use for more serious measurement.

The ADC in these is the Cirrus Logic CS5361, which is a pretty good ADC. The DAC is the AKM4396, which is a decent DAC.

When making measurements I hit a problem. The raw performance of the CS5361 is specced to be -99dBc guaranteed an -105dBc typical for THD+N. I couldn't get this.

A few things quickly went onto my list of things to try:
-1- Switching - the sound card has a lot of this - how was it implemented?
-2- Op amps...

Posted 27th January 2015 at 02:07 AM by googlyone Comments 0
Posted in Uncategorized
I recently picked up a pair of, I guess, 1970's Richard Allan three way speakers. The line-up are RA drivers with which I am not familiar. Bass, LP10B, midrange LP5B and tweeters - long dead and replaced with mismatched dome tweeters.

Richard Allan was reasonably popular in Australia in the 70's and 80's, and did some pretty good gear. I was interested to see how these went, but did need to do something about the tweeters.

On pulling the drivers out, I noted a few things:
- The LP10B is a 10 inch bextrene cone woofer, using a 1.5" voicecoil rather than the HP10B's 2" coil. It is also very much an "acoustic suspension" driver - read on.

- The LP5B is very much like a 5" version of the KEF B110 - as used in the LS3A. I read somewhere that Richard Allan made a version of the LS3A under license, but that might be an "internet fact".

- The crossover was made by KRIX, a local speaker manufacturer...

Posted 26th January 2015 at 08:39 AM by googlyone Comments 2
Posted in Uncategorized
The Engineer in me led to plots and graphs, but no pics of the speakers!!!

Attachment 1540

With a neat old badge...

Attachment 1545

The bass driver is a classic Richard Allan unit, you can tell them a mile away by the red (sometimes blue and black) felt:

Attachment 1541

The midrange has a fair bit of the B110 about it's looks, though it is smaller and behaves quite differently. This thing is very much a product of it's era (1970's):

Attachment 1542

The surround on the midrange is stated as PVC in some literature I found. I kind of believe this, though it has been coated with something sticky. It is not sticky on the back.

The cabinets were in moderately good condition. There were some coffee stains on the top of one, and water stains on the side of the other. In the end I sanded and revarnished them.

The timber...
Recent Comments
The input buffer (presumably...
Posted 2nd September 2015 at 12:50 AM by abraxalito abraxalito is offline
The sound blaster is...
Posted 21st August 2015 at 04:56 AM by googlyone googlyone is offline
How does this unit compare...
Posted 13th August 2015 at 05:54 PM by Harry Manback Harry Manback is offline
Yes it is a philips...
Posted 27th January 2015 at 02:04 AM by googlyone googlyone is offline
The tweeter is not a...
Posted 26th January 2015 at 08:10 PM by Boden Boden is offline
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