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Old 20th March 2013, 06:26 AM   #2151
1audio is offline 1audio  United States
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Quote:
Originally Posted by davada View Post
This is very impressive. Is there a way of improving the efficiency.
With no load it's drawing 218mA.
The shunt will draw whatever is necessary to pull the supply down to the target voltage. Efficiency be damned if you are going this route. Its the least efficient regulator possible. . .

R9 is a simulated load. That's where most of the current is going. Remove it and add your circuit there.

I have not looked at or run the simulation in a long time. The series resistor from the 5V supply is what controls the current.

I may cook up a two quadrant variation on the concept and see what it does.

I had to build a very special test fixture to measure the noise of this supply. If there is interest I'll post the details.
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Last edited by 1audio; 20th March 2013 at 06:28 AM.
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Old 20th March 2013, 08:17 AM   #2152
borges is offline borges  Norway
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Quote:
Originally Posted by davada View Post
Because they are two boards. I.m cutting them down the middle.
David, one thing you might consider in designs like that is to add a straight V-cut line down the middle. The the boards are going to come apart nicely. The other alternative is to use a routing tool >2.0mm between breakaway tabs.

Some board manufacturers want to charge extra because they see that there are now two boards in one production panel. But it is easy to find ones which don't charge more. I've used PCBCART - Professional China Prototype PCB Manufacturer quite a bit.

BÝrge
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Old 20th March 2013, 08:18 AM   #2153
borges is offline borges  Norway
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Quote:
Originally Posted by 1audio View Post
I had to build a very special test fixture to measure the noise of this supply. If there is interest I'll post the details.
Please do Demian!

I'm eager to learn more few-transistor analog magic.

BÝrge
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Old 20th March 2013, 08:24 AM   #2154
borges is offline borges  Norway
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And a bit of promotion: The AB-1.2 has two unpopulated layouts of Demian's series LDO regulator on the PCB. The various loads on the board can be easily strapped to these regulators. Or the regulators on the AB-1.2 PCB can be populated and strapped into whatever you want. I did populate one, and the output voltage was dead-on 3.3V. Adding a pair of XOs as a load didn't change it at all. Follow my signature to the AB-1.2 schematics to learn more.

Picture of regulators: http://www.qnktc.com/AB_12_01.jpg

OK, enough promotion for now :-)

BÝrge
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Old 20th March 2013, 02:15 PM   #2155
davada is offline davada  Canada
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Quote:
Originally Posted by 1audio View Post
The shunt will draw whatever is necessary to pull the supply down to the target voltage. Efficiency be damned if you are going this route. Its the least efficient regulator possible. . .

R9 is a simulated load. That's where most of the current is going. Remove it and add your circuit there.

I have not looked at or run the simulation in a long time. The series resistor from the 5V supply is what controls the current.

I may cook up a two quadrant variation on the concept and see what it does.

I had to build a very special test fixture to measure the noise of this supply. If there is interest I'll post the details.

I haven't done power supply for my OSC so I'm interested. We can discuss this over in the OSC thread if it doesn't fit here.
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Old 20th March 2013, 02:23 PM   #2156
davada is offline davada  Canada
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Quote:
Originally Posted by borges View Post
David, one thing you might consider in designs like that is to add a straight V-cut line down the middle. The the boards are going to come apart nicely. The other alternative is to use a routing tool >2.0mm between breakaway tabs.

Some board manufacturers want to charge extra because they see that there are now two boards in one production panel. But it is easy to find ones which don't charge more. I've used PCBCART - Professional China Prototype PCB Manufacturer quite a bit.

BÝrge
Hi Borge. I use a 1mm or 1.5mm fishtail chipper router bit for PCB cutting. I built a nice table with a moveable fence and a Proxxen drill press. The neat thing about cutting this way is it doesn't matter what angle the bit is approached from I always get a straight clean cut. I took a chance and tried to fool then manufacture to save money. Make PCB didn't seem to care.

I'll try PCBcart next time.

Thanks,
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Old 20th March 2013, 05:50 PM   #2157
1audio is offline 1audio  United States
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Default Low noise measurement preamp

Here is the circuit. Its based on a surplus Geoformer I found on eBay. The transformer has a 35:1 ratio. I used a low noise preamp on the output to boost the overall gain to 80 dB. The equivalent input noise resistance is about 3 Ohms or .2 nV/rt Hz. Which means you can measure below the .7 nV/rtHz of a typical low noise transistor.

Calibrating this is a pain. I made a resistive divider 1000-1 50 Ohms in .05 Ohm out. Its pretty load insensitive. And to measure the noise floor I used a decade resistor and increased it until I got a 3 dB increase in noise, between power line harmonics. My FFT analyzer has a uV/rt Hz mode that makes measuring noise easier and more rational. Used with this preamp the whole process is pretty easy.
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Old 23rd March 2013, 06:24 PM   #2158
davada is offline davada  Canada
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Here is the divided board.
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Old 5th April 2013, 08:52 PM   #2159
Turbon is offline Turbon  Sweden
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Default So, next gen...

What is in the pipeline?
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Old 6th April 2013, 02:55 AM   #2160
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Originally Posted by Turbon View Post
What is in the pipeline?
1. Isolated i2s AW's:

Click the image to open in full size.

http://luta.7u.cz/imgLinks/audioweb/...eft48k-4dB.png

2. Using TI C5535 dsp as the engine:

C5535 eZdsp USB Stick Development Kit - TMDX5535EZDSP - TI Tool Folder

The list price is $99 but you can get promotional price for half of that sometimes.

The stock ezdsp5535 comes with uac1 firmware allowing 16bit 48khz audio in adaptive mode.

We have developed firmware for the ezdsp5535 with its on board AIC3204 codec:

a. AC2 stereo playback at 32 bit (of which 24 significant bits passed to AIC3204) at sampling rates of 44.1/48/88.2/96 khz (limited by the AIC3204).

b. Current version of firmware customized for Linux ONLY for development and testing. Another version of firmware will be available for MAC OSX in future. Another version with an ASIO driver will be available for Windows in future.

Join the audio-widget google group if you are interested in downloading an experimental boot image file for your ezdsp5535 to play with. The software is still under active development and is open source. The source code is in github:

git://github.com/alexlee188/C5535.git

The ezdsp5535 will be the engine for a line of AW with 5.1 and even 7.1 playback capabilities, as the C5535 DSP has 4 I2S ports. Plans are underway to use the expansion port of the ezdsp5535 to connect to external DACs such as PCM51xx to confirm 32/384 capabilities and the SQ.

3. Capture Widgets:

This is in the conceptual stage.

Alex
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