jitter and noise performance of 74xx AC and VHC series?

patwen · 22nd November 2004, 09:39 AM

Hi,

What is the main difference between the 74xx AC and VHC series, especially in terms of jitter and noise performance?

I went through some of the datasheets (74AC161/74VHC161, Fairchild), I am unable to find any relevent info, can someone help?

Which series, VHC or AC, has better jitter and noise performance?

Thanks

PW

Søren Kramer · 22nd November 2004, 12:25 PM

I had very good sonic result using better filter (L 10uh) and decoupling (lots of smd 805 cg0 and x7r) of this chip for clock in pd75/65 player. Only a few tweaks have been sonic better; as lowering pll.

I am no expert but as I understand it this inverter has low psrr, and is often used without enough "speed" in decoupling (also groundbounce) -> jitter.

Se this - it is in danish - but go to:
"Optimering nr. 4. – Jitter optimering"

http://www.hifi4all.dk/forum/forum_p...730&KW=optimer

As a general rule, use only the nessesary speed. A rise time of 4ns is only nessesary if signal travels for longer distance.

Ouroboros · 22nd November 2004, 12:31 PM

In general, 74AC devices produce more supply-rail noise than VHC ones, so this may translate into jitter problems. (Although having said that, modern 74AC parts seem to be a lot quieter than the earlier ones).

If you are using 3.3V rails, then 74LVC or 74LCX parts work very well.

22nd November 2004, 09:39 AM	#1
patwen diyAudio Member Join Date: Jan 2002	jitter and noise performance of 74xx AC and VHC series? Hi, What is the main difference between the 74xx AC and VHC series, especially in terms of jitter and noise performance? I went through some of the datasheets (74AC161/74VHC161, Fairchild), I am unable to find any relevent info, can someone help? Which series, VHC or AC, has better jitter and noise performance? Thanks PW

22nd November 2004, 12:25 PM	#2
Søren Kramer diyAudio Member Join Date: Mar 2004 Location: Århus	inverter Toshiba 74HCU04 I had very good sonic result using better filter (L 10uh) and decoupling (lots of smd 805 cg0 and x7r) of this chip for clock in pd75/65 player. Only a few tweaks have been sonic better; as lowering pll. I am no expert but as I understand it this inverter has low psrr, and is often used without enough "speed" in decoupling (also groundbounce) -> jitter. Se this - it is in danish - but go to: "Optimering nr. 4. – Jitter optimering" http://www.hifi4all.dk/forum/forum_p...730&KW=optimer As a general rule, use only the nessesary speed. A rise time of 4ns is only nessesary if signal travels for longer distance.

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22nd November 2004, 12:31 PM	#3
Ouroboros diyAudio Member Join Date: Dec 2003 Location: Nottingham UK	In general, 74AC devices produce more supply-rail noise than VHC ones, so this may translate into jitter problems. (Although having said that, modern 74AC parts seem to be a lot quieter than the earlier ones). If you are using 3.3V rails, then 74LVC or 74LCX parts work very well.

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