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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 06:58 AM
  • Join Date: 7th November 2006

Blog

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Latest Blog Entry

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

Posted 28th May 2016 at 02:18 AM by googlyone Comments 1
Posted in Uncategorized
In my previous post I presented an idea spawned from a very bad place, primarily boredom and probably too much alcohol. Plane trips from Australia do that...

The Amplifier of 100 Transistors was the result.

Between that posting and this a few things have happened. I finished the design - adding extra decoupling and 100 Ohm base resistors to all 104 output devices. I did this because I sincerely thought I was building more of an RF oscillator than amplifier.

And I built it.

And I got it working.

This is the beast from the back before I loaded the "output devices":

Attachment 1980

Note the ludicrous number of emitter and base resistors! Half way through I concluded that I was bonkers, and wasting several days hand building a complete folly.

Then again, even with the thing running, it is still a folly!


With the output devices loaded....

Posted 14th May 2016 at 03:48 AM by googlyone Comments 4
Posted in Uncategorized
As a kid, which depending on my wives mood could be stated to be "right now" right through to "you have never been a kid", I once made the statement that "if it can't be done with a BC549 it is not worth doing".

this statement was made in jest at the time, and probably stolen from a similar a similar assertion about the NE555. (those of you who are < 30 years old probably haven't seen these used in real anger!)

Here I am travelling, and flying from Adelaide (Australia) to the USA. This is a long, boring flight. In a fit of boredom I set myself a challenge.

So what is the challenge? Something cool and completely different for once. Hmm. Make a power amplifier using BS549's. If you have seem my play room, amplifiers are made to scare speakers and annoy the neighbours. So this can't be a lightweight 100mW job. It must be something that actually works, and is able to make real noise.

OK, it...

Posted 5th January 2016 at 10:48 AM by googlyone Comments 1
Posted in Uncategorized
I have been asked for the CAD files for the distortion meter I recently built.

NOTE 10 Jan 2016 : I have changed the clock driving and distribution PCB as it really needed to be more versatile to me to run a mix of CS and AKM ADC and DACs. The change allows selection of MCLK at different multiples on the ADC and DAC via jumpers on the board. Again this is prpobably a bit more "hard wired" than a generic consumer device would be, but allows stable operation for fixed sample rate systems.

WARNING:
This project is not a super straight forward "chuck it together and it will all be fine" sort of build. I am providing what is essentially a collection of USB interface (MiniDSP), power supply (mine - open source), backplane, clocking and galvanic isolation (mine - open source), A/D and D/A (mine - open source) and a differential interface and attenuator (Silicon Chip magazine), though I am strongly tempted to do my own.

...
Recent Comments
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
Did you HFE match the...
Posted 3rd June 2016 at 08:22 AM by erik777 erik777 is offline
Hide this!Advertise here!

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