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Old 7th July 2003, 03:04 PM   #1
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Default 74vhc74

Hello everyone,

I want to build the ASRC like Fedde's Nonoz DAC. But I can not get the IC 74VHC74, could I use 74HC74 instead of 74VHC74?

What is the difference between 74HC74 and 74VHC74?
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Old 7th July 2003, 03:06 PM   #2
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I used the 74ac74 before. I think it's slightly less good, but certainly worth a try!

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Old 7th July 2003, 03:48 PM   #3
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Thank you Fedde.

I am still confusing the meaning of alphabets between 74 rather.
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Old 7th July 2003, 03:48 PM   #4
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Lightbulb Re: 74vhc74

Quote:
Originally posted by Marlowe
Hello everyone,

I want to build the ASRC like Fedde's Nonoz DAC. But I can not get the IC 74VHC74, could I use 74HC74 instead of 74VHC74?

What is the difference between 74HC74 and 74VHC74?
Hi marlowe,
Just have a look here:
http://www.diyaudio.com/forums/showt...664#post151664
I tried AC, HC and VHC. The latter gave the best sound.

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Old 7th July 2003, 04:58 PM   #5
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This should help you. The article do not mention VHC type. I think VHC means "Very High Speed CMOS"

http://www.xs4all.nl/~ganswijk/chipdir/ttl.htm
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Old 7th July 2003, 06:42 PM   #6
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Thanks Elso and PRBS.

And then, how the clock frequency is recommended?
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Old 7th July 2003, 06:53 PM   #7
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Faster is not necessarily better. They may produce more RFI (or they do!) and that can be harmful... Faster logic demands better pcb's (homebrewed may not be good enough), even multi-layer and advanced decuopling.
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Old 7th July 2003, 07:32 PM   #8
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Quote:
Originally posted by peranders
Faster is not necessarily better. They may produce more RFI (or they do!) and that can be harmful... Faster logic demands better pcb's (homebrewed may not be good enough), even multi-layer and advanced decuopling.
and even then I'd stay away from logic that is faster than required as the internal groundbounce cannot be reduced by external layout.

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Old 7th July 2003, 11:33 PM   #9
chijen is offline chijen  Taiwan
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Quote:
Originally posted by peranders
Faster is not necessarily better. They may produce more RFI

You are right!

(or they do!) and that can be harmful... Faster logic demands better pcb's (homebrewed may not be good enough), even multi-layer and advanced decuopling.
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Old 21st July 2003, 03:52 PM   #10
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I've built the ASRC circuit using KWAK-CLOCK 7 with 48MHz crystal and three Philips 74HC74 chips reclock the three pins from CS8412 to TDA1543 in I2S mode, but it can not work.
There is no sound I heard.
The output DC of ASRC are 0V (SDATA) and 4.97V(WS & BCK).

I have tried to connect CS8412 to TDA1543 directly (bypass ASRC), and then the DAC is ok.
So the focus of problem is on the ASRC circuit I think.

I measured the pins of 74HC74s, the DC of VCC, PR, and CL all are 4.98V, GND is 0V. Q1 of SDATA is 0 and of WS and BCK both are about 4.97V. D2 and Q2 all are same as Q1.

How can I to do something to test and debug?

thanks!
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