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Old 5th February 2012, 02:33 AM   #1071
rsdio is offline rsdio  United States
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Quote:
Originally Posted by borges View Post
input on:
- The purpose of the diode in the regulator and wheter a generic 1N4148-ish SMD can replace it.
I have not looked too closely at the power supply schematics in this thread, but a diode in a regulator circuit is probably being used for a very specific voltage drop. You might need a Zener diode with a particular voltage drop. On the one hand, whatever diode is called for in the original circuit is probably available in an SMD package. Substitution is not necessary to get an SMD package, so I would avoid substitution unless someone carefully looks at the consequences of changing the diode.

No point in fabricating a special regulator circuit if changes to the BoM renders its performance worse than a standard regulator.
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Old 5th February 2012, 04:14 AM   #1072
ianrt is offline ianrt  Australia
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Default Diode in regulator circuit

I assume the diode is to protect against reverse Vbe on the transistor and can be a generic 1N4148.

Ian


[QUOTE=borges;2891194]

I'd like your input on:
- The purpose of the diode in the regulator and wheter a generic 1N4148-ish SMD can replace it.
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Old 5th February 2012, 05:00 AM   #1073
1audio is offline 1audio  United States
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[QUOTE=ianrt;2892398]I assume the diode is to protect against reverse Vbe on the transistor and can be a generic 1N4148.

Ian


Quote:
Originally Posted by borges View Post

I'd like your input on:
- The purpose of the diode in the regulator and wheter a generic 1N4148-ish SMD can replace it.
Bingo-
The diode is to prevent reverse current from the base of Q1, which can degrade the noise performance of Q1. Its a precaution that is unlikely to be necessary in this circuit but almost free. A 1n4148/1n914 would work fine.
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Old 5th February 2012, 06:16 AM   #1074
rsdio is offline rsdio  United States
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Quote:
Originally Posted by 1audio View Post
A 1n4148/1n914 would work fine.
Assuming that there was a particular reason to specify the 1N914 in the original schematic, how about the MMSD914T1G? That's a readily available part that I've used in other USB designs.
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Old 5th February 2012, 07:28 AM   #1075
1audio is offline 1audio  United States
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Quote:
Originally Posted by rsdio View Post
Assuming that there was a particular reason to specify the 1N914 in the original schematic, how about the MMSD914T1G? That's a readily available part that I've used in other USB designs.
It would certainly work. The 1n914 and 1n4148 seem to have the same die inside. This probably also has the same die. Should be about 5 cents.
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Old 5th February 2012, 09:54 PM   #1076
UnixMan is offline UnixMan  Europe
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Quote:
Originally Posted by borges View Post
- Pinout for external I2S interface, its driver / flip-flop and the direction of MCLK on such a thing.
mmmh, what about a small plug-in board to allow for different pinouts / I2S signal levels?

At least in my case, MCLK should come from the widget/AB to the DAC.
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Old 6th February 2012, 07:00 AM   #1077
1audio is offline 1audio  United States
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I updated the regulator circuit to quell the angry tl431. Here is a link to the updated info (rather than crossposting) Asynchronous I2S FIFO project, an ultimate weapon to fight the jitter . I compensated the device to prevent it oscillating. The actual device doesn't seem to have this issue and the three pin version I use doesn't have the comp pin anyway. The curves look more like what I see with the actual circuit.
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Old 6th February 2012, 08:27 AM   #1078
borges is offline borges  Norway
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Thanks guys!

Quote:
Originally Posted by 1audio View Post
It would certainly work. The 1n914 and 1n4148 seem to have the same die inside. This probably also has the same die. Should be about 5 cents.
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Old 6th February 2012, 03:01 PM   #1079
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Default USB5102

I neglected to post the results of Alex's mod for allow filter switching on the PCM5102.

His new firmware and WidgetControl.py works fine with my USB5012 board. The filter selection is persistent between power cycles. I can't hear the difference between filters but that is my hearing not the filters fault.

We now have our first hardware specific control line and have the first steps toward DAC configuration via I2C lines.

There are still a few of the USB5102 kits left if anyone is interested.

George
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Old 6th February 2012, 06:00 PM   #1080
Turbon is offline Turbon  Sweden
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Börge.

When do you expect the AB-1.2 be available? Can it be bought as a replacement in box to replace the AB-1.1 board? The MCU board will fit in just fine? I know, a lot of components will be thrown away but it is now as it is so far. In what positions are you planning for external PSU's optionally to be added as replacements for the built in ones? So... To be able to NOT changing the whole AB board the need is to move the DAC to somekind of piggyback board - is there a problem doing this? Money not an obstacle until you reveal your price :-) ...

Brgds
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