diyAudio - View Profile: googlyone
Go Back   Home > Forums > Members List

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

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 12:34 PM
  • Join Date: 7th November 2006


View googlyone's BlogRecent Entries
Latest Blog Entry

Posted 7th September 2015 at 11:35 AM 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 11:47 AM 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 12:50 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...

Posted 21st August 2015 at 05:16 AM by googlyone Comments 0
Posted in Uncategorized
Over the years I have played with measuring - well - just about everything in audio.

distortion measurement has been one of these preoccupations, not the least because it is hard to do, and using commercial gear, expensive.

I have built analogue hear to do this, used mixes of analogue and digital and of late played with using modified commercial sound cards. My efforts on the Sound Blaster x-Fi were interesting but ultimately not rewarding enough for me to leave the mods in there.

I have also been playing with using the A/D and D/A converters from my DSP crossover for this purpose. These are modular and use a common I/O plug with power MLCK, SCLK, LRCLK and Data (alone with I2S for the CS4398 and sometimes a digital volume control).

--- notwithstanding the fact that in previous tests I have shown the digital volume control is the MAJOR source of distortion - I will plug ahead with this, and likely leave that out of the test...

Posted 29th March 2015 at 12:51 PM by googlyone Comments 2
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...
Recent Comments
Yep, you are dead right....
Posted 5th September 2015 at 02:00 AM by googlyone googlyone is offline
The input buffer (presumably...
Posted 2nd September 2015 at 12:50 AM by abraxalito abraxalito is offline
The sound blaster is...
Posted 21st August 2015 at 04:56 AM by googlyone googlyone is offline
How does this unit compare...
Posted 13th August 2015 at 05:54 PM by Harry Manback Harry Manback is offline
Yes it is a philips...
Posted 27th January 2015 at 02:04 AM by googlyone googlyone is offline
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 06:32 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2