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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
    Engineer
    Country
    Australia
    Real Name
    Phil

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  • Last Activity: Yesterday 12:29 PM
  • Join Date: 7th November 2006

Blog

View googlyone's BlogRecent Entries
Latest Blog Entry

Posted 29th March 2015 at 12:51 PM by googlyone Comments 0
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...

Posted 6th December 2014 at 04:10 AM by googlyone Comments 0
Posted in Uncategorized
Over the last couple of decades I have built an awful lot of power electronics stuff, especially power amplifiers.

So I have bought and used a commensurately large number of power electronic devices.

As a young hobbyist this started with salvaging bits from refuse - especially in the late 70's and early 80's larger power devices were far from cheap. This generally worked really well, as I never did really trust what I pulled out of refuse gear, and I tested stuff that I used. (also not the least as data on power devices came from "equivelant devices" books such as the "Towers guide" and if you were really lucky you found a datasheet somewhere (on paper!). no intenet....

Why the digression?

Oddly with the advent of the internet and subsequently things like EBAY:
- I could get all sorts of things that you just could not buy locally in small quantities.
- Unscrupulous buggers out there started...

Posted 2nd November 2014 at 04:03 AM by googlyone Comments 0
Posted in Uncategorized
About 6 months ago I finished off a CS4398 (DAC) and PIC32MX450 (microcontroller) based direct Digital Synthesiser.

I recently packaged this into an instrument case, and added a power supply cum interface card that allows this to all neatly plug together. As a final chapter to the development of this synth, I have tried to measure the harmonics it generates and to use it to test an example amplifier.

What does it look like? Not super fancy, but neat enough and laid out pretty reasonably I think:

Attachment 1437

The larger home made board at the back is a power supply - well five of them in fact - to allow clear isolation between a number of digital and analogue rails.

The square board on the base of the case is the PIC board. This runs the human machine interface and more importantly does all the calculation of the waveforms. You can generate any waveform you want, provided it is repetitive and can be...
Recent Comments
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
OK that is hardcore!!...
Posted 4th November 2014 at 06:27 AM by wintermute wintermute is offline
Yes, the repair worked...
Posted 31st October 2014 at 09:56 PM by googlyone googlyone is offline
Nice job googlyone....
Posted 27th October 2014 at 11:14 AM by wintermute wintermute is offline
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