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Solving the intersample DAC clipping problem for about ten euros
Solving the intersample DAC clipping problem for about ten euros
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Old 14th February 2018, 11:00 AM   #21
MarcelvdG is offline MarcelvdG  Netherlands
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They compete on dynamic range and SINAD numbers measured with sine waves of 0 dBFS and less. Taking headroom reduces those numbers. I think a user-settable input attenuator (preferably with clipping indicator) would be a good solution, though.

Another issue is that the person who defines the specs is usually not the same person as the one who designs the circuit. It could well be that the marketers who set the specs have no clue about intersample overs, or simply don't care as long as their customers don't complain.
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Old 14th February 2018, 11:11 AM   #22
Max Headroom is online now Max Headroom  Australia
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So much modern stuff is unlistenable imo/ime because of normalising to 0dBfs or close to.
Switchable in/out and switchable absolute polaritry and you're on a winner.

Dan.
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Old 14th February 2018, 12:36 PM   #23
rfbrw is offline rfbrw
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Marketeers do not set the specs. Entities like the EBU and the SMPTE do.
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Old 14th February 2018, 08:47 PM   #24
MarcelvdG is offline MarcelvdG  Netherlands
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Quote:
Originally Posted by Max Headroom View Post
So much modern stuff is unlistenable imo/ime because of normalising to 0dBfs or close to.
Switchable in/out and switchable absolute polaritry and you're on a winner.

Dan.
If you don't mind hearing a click when you switch over, the circuit in post 1 can be switched in/out with a switch to ground and a pull-up resistor connected to the active-low set input of the second flip-flop in the bottom row. Changing absolute polarity can be done with an EXOR in the data line, if you don't care about the 1 LSB offset that gives you.

In fact you could use an 74AHC86 quad EXOR as polarity changer, clock buffer and delay circuit to prevent hold time issues.

Last edited by MarcelvdG; 14th February 2018 at 09:13 PM.
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Old 14th February 2018, 08:52 PM   #25
MarcelvdG is offline MarcelvdG  Netherlands
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Originally Posted by rfbrw View Post
Marketeers do not set the specs. Entities like the EBU and the SMPTE do.
That's only true for specs that are standardized, like interface standards, not for performance parameters such as dynamic range or for things related to cost.
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Old 14th February 2018, 11:14 PM   #26
rfbrw is offline rfbrw
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Quote:
Originally Posted by MarcelvdG View Post
That's only true for specs that are standardized, like interface standards,
Such entities cover a little more than just interface standards.

Quote:
not for performance parameters such as dynamic range or for things related to cost.
Those aren't specifications. They are performance requirements and the factors that govern them are varied but I doubt those who design,make and market the equipment ever get a look in. Can't say I ever saw a marketing representative of Neve or PMC calling the shots in a suite. Unless, that is, by marketeer you mean those more traditionally known as clients.
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Old 15th February 2018, 04:38 AM   #27
MarcelvdG is offline MarcelvdG  Netherlands
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As an integrated circuit designer I'm used to getting lists of requirements I need to meet, and usually there is a header "Specifications" above the list. It could be that that's sloppy language, but it is the terminology I'm used to.

Sometimes the specifications or whatever you call them come straight from a customer, sometimes they are the result of negotiations between potential customers and a marketing department, sometimes they come from some international standard, sometimes they are derived specs that were derived from a system spec by a system designer.

Anyway, it seems that this is a semantic rather than a technical discussion.
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Old 15th February 2018, 06:34 PM   #28
rfbrw is offline rfbrw
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Seems you miss my point but no biggie.
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Old 18th February 2018, 04:27 PM   #29
Panelhead is offline Panelhead
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Default Another solution to intersample peaks

I have been wanting to swap an AK4413 dac chip with an AK4414. This is a 32 bit chip replacing a 24 bit.
Read and reread the data sheets and it is 50 pages of identical specs and graphs. Using as a four channel dac so not parallel.
The current chip is almost the same specs. Only THD is better, the graphs showing THD vs freq with different decoupling on Vref. The AK4414 has 2 - 3 dB lower THD.
My original reason for installing a 32 bit chip was to get more bits for digital attenuation. But it looks like the date is LSB justified. Or there would be 8 zero buts in front of the signal. An additional 48 dB of digital headroom.
I still want to swap out these dac chips. This is a 12 dollar part.
With this change yield headroom for intersample clipping, 8 more bits for attenuation, or a just the potential for a couple dB reduction in THD?
This is a 10 euro tweak also.
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Old 18th February 2018, 06:11 PM   #30
Panelhead is offline Panelhead
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Default Another solution to intersample peaks

I have been wanting to swap an AK4413 dac chip with an AK4414. This is a 32 bit chip replacing a 24 bit.
Read and reread the data sheets and it is 50 pages of identical specs and graphs. Using as a four channel dac so not parallel.
The current chip is almost the same specs. Only THD is better, the graphs showing THD vs freq with different decoupling on Vref. The AK4414 has 2 - 3 dB lower THD.
My original reason for installing a 32 bit chip was to get more bits for digital attenuation. But it looks like the date is LSB justified. Or there would be 8 zero buts in front of the signal. An additional 48 dB of digital headroom.
I still want to swap out these dac chips. This is a 12 dollar part.
Will this change yield headroom for intersample clipping, 8 more bits for attenuation, or a just the potential for a couple dB reduction in THD?
This is a 10 euro tweak also.
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Last edited by Panelhead; 18th February 2018 at 06:12 PM. Reason: Spelling
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