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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
General Information
  • Last Activity: Yesterday 12:25 PM
  • Join Date: 7th November 2006


View googlyone's BlogRecent Entries
Latest Blog Entry

Posted 15th November 2015 at 09:05 AM by googlyone Comments 0
Posted in Uncategorized
I have more or less completed the audio analyser based on CS4398 and CS5381.

In an earlier post I suggested I had reached the limits of these IC's. I was wrong. What I had reached the limit of was getting the grounding "OK" for a single (unbalanced) input measurement system.

I have since built a balanced front end - in fact I simply built a Silicon Chip PCB as it was pretty well what I would do - and integrated this to the ADC and DAC.

It looks a bit like this:

Attachment 1756

What you see is:
- On the left are two independent power supplies
- In the back middle is a MiniDSP USB Streamer card.
- In the middle back is an interface card that
- Does optical isolation of the MiniDsp USB Streamer
- Does more regulation for the ADC and DACs
- Generates local clocks for the DAC and ADC
- Feeds these back to the MiniDSP Streamer

Posted 11th October 2015 at 01:10 PM by googlyone Comments 0
Posted in Uncategorized
I have been asked for the PCB file for the weller WPS80 like soldering station driver.

This is rock solid stable - have been using it for quite a long while now with zero issues.

The files are attached, in ALTIUM format.

Attachment 1743

Any questions just ask.

Posted 7th September 2015 at 12:35 PM by googlyone Comments 0
Posted in Uncategorized
On thinking over the sensitivity of the CS5381 to the drive and input filtering capacitor I decided to explore the capacitors further.

I was also interested to note that a number of manufacturers seem to recommend a range of different capacitor values here.

Purely because it was handy - i.e. right in front of me on the desk - I threw an extra 2nF capacitor across the differential input of the CS5381. Boom - the distortion dropped 6dB straight off.

I muttered a few choice profanities, which made me feel an awful lot better, then arbitrarily threw a 470pf NPO ceramic cap across that lot, just to be sure. Well given I was off doing such arbitrary things - why not?

On analysis, 5nF capacitance at 20kHz is about 1.5K Ohms (reactive) which is within the capability of the op amp to drive.

The results?

Attachment 1710

Which I found rather pleasing, as using the "default" 2n7,...

Posted 6th September 2015 at 12:47 PM by googlyone Comments 0
Posted in Uncategorized
I have had the time to play with the MiniDSP Streamer and my ADC and DACs now.

Initial results were disappointing - and led to me looking very closely at the ADC drive, and particularly the single ended to differential part of the circuit.

Given I pinched this circuit from an application note (and embarrassingly did not question it adequately) gives me little solace that I built, and used this!

Interestingly, Creative Labs did exactly the same thing on the sound blaster that I had so much trouble improving - the single ended conversion is just wrong. This solves the "Puzzle" that I noted in a blog a few months ago - now I know why I just couldn't get better performance out of that CS5381 drop in to the Sound blaster box.

In the process of improving the ADC drive, and to allow experimentation with the input op amps, I built two versions of the ADC drive, one using non inverting buffers and a second that uses inverting...

Posted 31st August 2015 at 01:50 PM by googlyone Comments 2
Posted in Uncategorized
I recently set to work the guts of the audio analyser:
- MiniDSP USB Streamer
- Interface card

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...
Recent Comments
Good work! Simple and...
Posted 9th October 2015 at 04:12 AM by braslet braslet is offline
Good work! Simple and...
Posted 24th September 2015 at 04:13 AM by braslet braslet is offline
Yep, you are dead right....
Posted 5th September 2015 at 03:00 AM by googlyone googlyone is offline
The input buffer (presumably...
Posted 2nd September 2015 at 01:50 AM by abraxalito abraxalito is offline
The sound blaster is...
Posted 21st August 2015 at 05:56 AM by googlyone googlyone is offline
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