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googlyone googlyone is offline

diyAudio Member

About Me

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


Total Posts
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  • Wiki Comments: 0
  • Recent Wiki Activity: googlyone has no recent wiki activity
General Information
  • Last Activity: Today 01:39 PM
  • Join Date: 7th November 2006


View googlyone's BlogRecent Entries
Latest Blog Entry

Posted 21st March 2017 at 11:49 AM by googlyone Comments 0
Posted in Uncategorized
Years ago I moved from the country back into the city. This was a move that required me to clean out heaps of stuff that I really didn't want to clear out. In our old place we had two houses on the block, one of which had been converted into an enormous studio room with NO walls, and a 14 by 14 metre shed. To say that I amassed a collection of speakers and stuff would be an understatement.

One of the things I got rid of were a pair of Richard Allan CG-10 drivers that I never got around to sticking in a box. Indeed, I never even got around to measuring their parameters.

Recently on EBAY I came across a pair of these...

Attachment 2323

Attachment 2324

I was surprised at the condition of these - the cones look new. Needless to say they are not, the date code is 1973.

I have measured and used the CG-12, HD-15 and a bunch of other Richard Allan drivers in the past and found them...

Posted 12th March 2017 at 04:49 PM by googlyone Comments 0
Posted in Uncategorized
in my electronics workshop I have always had a stereo. Eight years ago I looked on the shelf and decided there was all the makings of an integrated preamp - DSP - Crossover and four power amplifiers.

That is the price of always making an extra board or two when I build a "thing" - you end up with a massive collection of bits.

I duly shoe-horned this lot into a case that is about 3" high. Tuned it up and didn't think a lot more.

Fast forward 8 years to two weeks ago, and there I was listening to the radio while wondering what to build next, and I thought the left tweeter sounded a bit low.

I swapped input to the amp L-R, and yep, it was. Odd - as the DSP treats L and R exactly the same, there is no balance control in there. So I swapped the speakers. Hmm, it wasn't the tweeter. It was inside the "box".

So I popped the lid, and found this...

Attachment 2322

Posted 8th January 2017 at 01:35 AM by googlyone Comments 0
Posted in Uncategorized
Well here I am at the end of another summer holiday - with yet another thing I have built for which I have absolutely no plans at all!

I have over the years built several (several dozen I would expect!) discrete operational amplifiers. The challenge I set myself here was:
- Actually get some proper measurements of it's performance, now that I have some test gear that is up to the job.
- Make the device in something close to a DIL-8 package. (slight fail here but close enough)
- Discrete
- Use some of the multitude of parts I have collected of late.
- The ability to configure the op amp as a buffer or amplifier with non-inverting gain. This means adding feedback resistors and a DC block cap.
- The ability to include input RF filter (typical few hundred ohms series and 1nF across the input)

The schematic won't surprise anyone - over the years I have designed ridiculously complex and simple amplifiers, and have run...

Posted 4th June 2016 at 04:42 AM by googlyone Comments 2
Posted in Uncategorized
I finally got around to rolling out the distortion test set and the Amplifier of 100 Transistors to measure its performance.

I would like to say that I don't care - and that the whole thing is an engineering abortion. A complicated joke, and that the measurements don''t matter. The fact that I am making the measurement would however show me to be a liar - as if I didn't care, then why did I do this?

Anyway, with low distortion measurements, getting your head around the baseline of your test gear is key. With all gains / levels being equal, here is the loop-back distortion of the test system:

Attachment 1984

Which is fine, rolls along at about 0.0003% across the band.

Then I ran a sweep of the Amplifier of 100 Transistors with NO load at 3dB below clipping:

Attachment 1985

OK, this is saying the amplifier distortion raises it's head above the noise floor at 1KHz and is...

Posted 28th May 2016 at 06:39 AM by googlyone Comments 2
Posted in Uncategorized
And then there were two! A lot easier simply loading just the "output devices" and testing.

The second one initially looked super stable, but after I got it quite warm by running an almost clipping sinewave into a 4 Ohm load, I did find just a tough of oscillation on negative excursions.

The first amp had envelopes of oscillation at 3MHz. The frequency of the second amps oscillation was 13MHz.

In the end removing the capcitor between the bases of the output devices (what was it there for anyway?) tidied things up.

These Amplifiers of 100 Transistors seem to breed!

Attachment 1983
Recent Comments
this is rare... must...
Posted 10th November 2016 at 09:08 PM by luisitoloco22 luisitoloco22 is offline
This is a awesome project,...
Posted 21st June 2016 at 10:32 AM by MR Overclock MR Overclock is offline
Have you put any thought...
Posted 10th June 2016 at 05:47 AM by erik777 erik777 is offline
Nice..deserves a thread...
Posted 5th June 2016 at 02:36 PM by kasey197 kasey197 is offline
No, not specifically....
Posted 3rd June 2016 at 02:03 PM by googlyone googlyone is offline
Hide this!Advertise here!

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