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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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General Information
  • Last Activity: Yesterday 01:03 AM
  • Join Date: 7th November 2006

Blog

View googlyone's BlogRecent Entries
Latest Blog Entry

Posted 13th July 2014 at 02:26 AM by googlyone Comments 1
Posted in Uncategorized
What sort of amplifier do you build to go with a funky retro subwoofer and "Ikea Salad Bowl" speakers?

How do you reconcile this with the fact that you have a "metric shitload" of DSP stuff laying around?

I have run into this problem, and concluded that I need to mash these into something that is not new and higher tech than old style.

This has resulted in me trying to train smash "new and old" into what I am hoping will be a retro styled, but thoroughly high tech-on-the-inside amplifier. (Stopping short of going class - D which I hold aesthetic objections against).

So lets get started with the basics. The amplifier will not be square - it will be a parallelogram...

Attachment 1332

And to follow up with my (albeit young) recollections of the 1970's, it CANNOT be black.

This amplifier needs to be the most acid driven shade of orange that I can find....

Posted 1st June 2014 at 12:20 PM by googlyone Comments 1
Posted in Uncategorized
A while back I built some Ikea bowl speakers using Vifa bassmids and tweeters. The performance came out very good indeed, but when you are dealing with a 5 odd inch driver, there will never be masses of bass.

A subwoofer was always on the cards.

Attachment 1298

Given the spherical speakers perched on the retro "rocket like" stands, I initially thought of doing a spherical subwoofer - but in the end concluded that while I could do this, I was looking at using fibreglass on a "fit-ball", placement in the room was looking to be a challenge.

So I chose to do the absolute opposite - and came up with an off the wall approach to a conventional sub.

Attachment 1296

Attachment 1297

The idea was to move the implementation of a conventional sub well away from the "box with a driver stuck on the front".

I find it fascinating that...

Posted 17th March 2014 at 10:49 AM by googlyone Comments 2
Posted in Uncategorized
It must be close to 12 months ago that I saw the PIC32MX450. I was convinced that a chip that included two I2S audio interfaces, and ran at 100MHz implementing 32bit arithmetic in pretty snappy time would surely be able to do some fun audio stuff.

I started with getting a board designed, and porting the code that I use to control my Analog Devices audio DSP. Then I generated the code to implement a direct digital synthesiser. These worked fine.

Over the last couple of weeks I have completed the "core code" for a digital crossover all implemented in the PIC32 itself.

The basic implementation is:
- An analogue to digital converter
- The PIC
- A digital to analogue converter
(Oh and an interface PCB done on veroboard to route the MCLK and power to the A/D and D/As. I am kind of tempted to re-spin the PIC32 board to do this for me...)

The PIC drives the I2S interface as master, generating...

Posted 25th January 2014 at 01:37 PM by googlyone Comments 0
Posted in Uncategorized
I was asked if I would share the code for the audio DDS I was playing with.

It is here...

Attachment 1230

I think this is all the files you need.

To show just how lazy I am, the main function is the file titled "dig_cross.c" - as that was the main function I edited as the base of this code. There is also a file "ad1940.c" which contains a bunch of the SPI stuff. This is yet another illustration of my bone idle-ness - as this module is probably a decade old. It is used, but has nothing to do with an AD1940 IC....

No apologies

There is a bunch of comments in this, but some general overview comments are:
- About 95% of the source code is about:
- Running the user interface
- Generating the display (rather utilitarian implementation)
- Reading from the EEPROM, and doing limit checks on data
- Writing to EEPROM

...

Posted 24th December 2013 at 01:40 AM by googlyone Comments 9
Posted in Uncategorized
Well now I am on holidays over XMAS I got the time to really put in a solid chunk of time on the DDS based synthesiser.

Previous blog entries describe the PIC32MX based core to this. The thing works like a charm...

To get decent precision on the sinewave I have implemented an interpolation on a high precision Sinewave lookup table.
- The DDS references into a 12 bit "long", 24 bit "amplitude" precision sinewave LUT.
- Of itself this gives mediocre spurs, which in a DDS are heavily dependent on the frequency, but seem to result in 85-90dBc spurs. There is a fair hash of these without treatment.
- By adding a linear interpolation between samples in the Sinewave Lookup table, the spurs come out as shown below...

Attachment 1199

- The interpolation is actually quite simple in concept:
- The top 12 bits of the DDS Phase Accumulator looks up the "Sine Sample"
...
Recent Comments
looking forward to the...
Posted 13th July 2014 at 09:50 PM by wintermute wintermute is offline
Very nice indeed
Posted 21st June 2014 at 01:53 PM by SteB SteB is offline
Quote:
Originally Posted by CharlieLaub
Nice! A little short
...
Posted 21st March 2014 at 11:45 AM by googlyone googlyone is offline
Nice! A little short...
Posted 19th March 2014 at 04:39 PM by CharlieLaub CharlieLaub is offline
Quote:
Originally Posted by gene_klein
Hi googlyone,
...
Posted 25th January 2014 at 01:17 PM by googlyone googlyone is offline
Hide this!Advertise here!

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