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Old 6th December 2012, 07:44 PM   #2481
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Default VAS CMCL

(regarding post #2479 )
By the way, talking about the 'simplest solution' , in principle, the Iq of a high gain complementary VAS can be controlled by a CMCL comprising only two additional trannies. (not recommended for utmost performance)

As for post # 2480, I have a lot of "subconscious agenda's": Iq stability, distortion, headroom. phase margin, clipping behavior, etc. .

Cheers,
E.
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Old 6th December 2012, 08:06 PM   #2482
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Quote:
Originally Posted by Edmond Stuart View Post
I have a lot of "subconscious agenda's": Iq stability, distortion, headroom. phase margin, clipping behavior, etc. .

Cheers,
E.
+1

Edmond, any news regarding the TIS?

Cheers
Stein
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Old 6th December 2012, 08:47 PM   #2483
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Quote:
Originally Posted by stinius View Post
+1
Edmond, any news regarding the TIS?
Cheers
Stein
Hi Stein,

Not yet. I'm still busy with perfecting my PC based distortion analyzer (DiAna). One of the problems is how to calculate the exact frequency (and other variables) based on sampled data of an external (not synchronized) sine wave source. With 'exact' I don't mean within a few decimals. No, I mean 16 decimals behind the comma. On the web I couldn't find anything about this topic, so I have to figure it out all by myself. Not an easy job!

I've also tested a couple of sound cards. Regrettably, most of them were cr@p, in particular the ones from Creative.

By the way, I just downloaded a new C++ compiler from Walter Bright (for free!), which support the Intel 80 bits FPU 'long doubles'. Just what I was looking for.

Cheers,
E.
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Old 6th December 2012, 11:06 PM   #2484
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Looking forward to your results!

Sounds like quite a challenge.
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Old 7th December 2012, 08:15 AM   #2485
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Hi Andrew,

Indeed, it is a challenge!
By now, I have spent three and half years on this project, not just by finding (and testing) the right algorithms, but also mastering Windows programming (WIN32 API).

Cheers,
E.
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Old 7th December 2012, 09:06 AM   #2486
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Yes, I have not tried any windows programming - only the embeded stuff.

Good luck my friend!

/OT
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Old 8th December 2012, 04:23 AM   #2487
Struth is offline Struth  Canada
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Hi Guys

For a computer-based distortion analyser to be of any true use, the interface has to have more than 20kHz bandwidth, which pretty much leaves common and even exotic sound cards in the bin. I've heard of a 32-bit converter that is very good but hard to get - and if you can there are no drivers for it. Having that kind of resolution seems important for measurement, otherwise you diddle around trying to keep generated signals and sampled signals as close to full-scale as possible to have the lowest THD out and lowest resolution errors in. But what you also need is 200kHz bandwidth.

I'm sure you've checked out the Dr. Jordan site and his descriptions of his software. For the software literate, the descriptions should give away enough for you to see what path he took.

Could we be more off topic? At least Bob's book has a chapter about audio measurements. Personally, I found ch.3 to be the most informative.

Have fun
Kevin O'Connor
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Old 8th December 2012, 05:01 AM   #2488
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Quote:
Originally Posted by Struth View Post
..... the Dr. Jordan site ......
Have fun
Kevin O'Connor
Any URL ?
Thanks.

Edit: This one http://www.dr-jordan-design.de/ ? Came up on Google.
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Last edited by ashok; 8th December 2012 at 05:04 AM.
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Old 8th December 2012, 05:27 AM   #2489
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my 5 year old PC has 192k settings for the motherboard HD chipset - should mean >80 kHz - which is a standard "extended" BW for THD meaurement
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Old 8th December 2012, 07:32 AM   #2490
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The bandwidth of my software (DiAna) is virtually unlimited and independent of the sampling rate. The BW of the whole setup is only limited by the anti alias filter in front of the ADC.

> Dr. Jordan (Win Audio MLS)
Come on Kevin, you can't be serious.

> keep generated signals and sampled signals as close to full-scale as possible to have the lowest THD.
The majority of sound cards produce more distortion at full-scale.

Cheers,
E.
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