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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 8th September 2009, 04:07 AM   #1071
1audio is offline 1audio  United States
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John Curl's Blowtorch preamplifier part II
The ability of a human being to understand any audio communications over SSB is a testament to the resiliency of the audio processing engine, since it has almost no relation to the original spoken voice.
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Old 8th September 2009, 04:13 AM   #1072
Wavebourn is offline Wavebourn  United States
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John Curl's Blowtorch preamplifier part II
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Originally Posted by 1audio View Post
The ability of a human being to understand any audio communications over SSB is a testament to the resiliency of the audio processing engine, since it has almost no relation to the original spoken voice.
Right, it is a quint-essence of unnaturalness of a sound.
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Old 8th September 2009, 08:32 AM   #1073
jan.didden is offline jan.didden  Europe
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Quote:
Originally Posted by Steve Eddy View Post
Sorry, Jan! I missed this the first time around and only just caught on what your bump post was about.

Thanks for providing the article. Though I really don't want to get in to the whole TIM/DIM/PIM debate.

It's just that y'all were arguing over what was shown in fig. 3. You'd previously labeled some of the peaks in it, and John questioned whether or not they were accurate.

So I thought I'd use some of my CAD/graphics skills to get a better fix on what frequencies the unlabeled harmonic components were.

se
Steve,

Reason I posted it is that Matti and Eero actually give some formula's about that modulation and discuss the build-up of the spectrum. I'm not very good in that area so I'll stay out of it, but thought some of the heavy brains here could do something with it.

As to my labelling of the unlabelled peaks, remember these were the peaks that were actually mentioned in the paper, I just went and put them up.

I also think we should be very carefull to treat that fig 3 as a precision drawing; it must have been scanned and printed umphteen times, and measuring points that are themselves several mm wide with a micrometer doesn't inspire confidence.

jd
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Old 8th September 2009, 02:42 PM   #1074
Bob Cordell is offline Bob Cordell  United States
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Quote:
Originally Posted by 1audio View Post
The ability of a human being to understand any audio communications over SSB is a testament to the resiliency of the audio processing engine, since it has almost no relation to the original spoken voice.
Try cell phone-to-cell phone; that is my pet peeve. It seems with each new generation of cell phone technology the quality and intelligibility goes down (as the compression goes up).

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Old 8th September 2009, 04:12 PM   #1075
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by janneman View Post
Steve,

Reason I posted it is that Matti and Eero actually give some formula's about that modulation and discuss the build-up of the spectrum. I'm not very good in that area so I'll stay out of it, but thought some of the heavy brains here could do something with it.


jd
Thanks Jan, this was informative. 1) They clearly used the word inharmonic for any AM/PM sidebands. I think this was an unfortunate choice of words. 2) Their simplified analysis only "expected" the labeled sidebands causing more confusion when looking at a real amplifier.
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Old 8th September 2009, 04:24 PM   #1076
BV is offline BV  Slovakia
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Two measurements with modified DIM100 signal, 3200Hz+15000Hz.
First picture is uA 741, and second is??
Attached Images
File Type: png uA741.png (26.2 KB, 280 views)
File Type: png what.png (26.2 KB, 280 views)
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Old 8th September 2009, 04:33 PM   #1077
simon7000 is offline simon7000  United States
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Ladies, Gentleman and Regular Posters,

As I see it the question is why the spike at 2F2-9F1 is so high. It seems to be about 15 db higher than it should be. This would imply that there is a peak in the frequency response of the D.U.T. around 28.62 to 30 khz. This is clearly not the case for such a simple circuit even with a 741.

One possible hypothesis is that the transit time for the signal through the 741 is changing due to signal level. The delay for a 741 seems to range from .25 uS to 1 uS. It is also not the same for positive and negative going signals.

As the feedback is inverting to get the required other 180 degrees of phase shift to make the op-amp unstable with a wildly rising gain would require a delay of 16 uS. I have trouble with an overloaded op-amp becoming this slow.

If this actually happened it would act as a pitch shifter for signals inside the circuit as the delay stretched. This would modulate the 3180 F1 fundamental to about 3025, which I also do not see happening.

Any other hypothesis as to why 2F2-9F1 is so high?

ES
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Old 8th September 2009, 05:08 PM   #1078
Steve Eddy is offline Steve Eddy  United States
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Quote:
Originally Posted by janneman View Post
Reason I posted it is that Matti and Eero actually give some formula's about that modulation and discuss the build-up of the spectrum. I'm not very good in that area so I'll stay out of it, but thought some of the heavy brains here could do something with it.
Ah, ok.

You'd posted it in a reply to me so I thought you were intending me to do something with it.

Quote:
As to my labelling of the unlabelled peaks, remember these were the peaks that were actually mentioned in the paper, I just went and put them up.
Which paper? If the one from jocko, I don't recall seeing them mentioned with any real specificity.

Quote:
I also think we should be very carefull to treat that fig 3 as a precision drawing; it must have been scanned and printed umphteen times, and measuring points that are themselves several mm wide with a micrometer doesn't inspire confidence.
Actually, in spite of how many times it may have been scanned and printed, it held up rather well.

When using the labeled frequencies along the bottom, the resulting graph was a near perfect match when overlaid on fig. 3. Near enough that the peaks you'd labeled as 2F2-6F1 and 2F2-8F1 couldn't possibly have been at those frequencies as they were off by far more than the fudge factor of the relatively poor quality fig. 3.

se
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Old 8th September 2009, 05:26 PM   #1079
jan.didden is offline jan.didden  Europe
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Quote:
Originally Posted by scott wurcer View Post
Thanks Jan, this was informative. 1) They clearly used the word inharmonic for any AM/PM sidebands. I think this was an unfortunate choice of words.[snip]
I wasn't sure about that, thanks for confiming my suspicion. I think we should at the very minimum agree to the terms used when discussion these things. Are IM products 'harmonic' or 'in-harmonic' products?

jd
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Old 8th September 2009, 05:30 PM   #1080
jan.didden is offline jan.didden  Europe
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Quote:
Originally Posted by Steve Eddy View Post
[snip]Which paper? If the one from jocko, I don't recall seeing them mentioned with any real specificity. [snip]se
See attachment here:

http://www.diyaudio.com/forums/showp...postcount=1010

I posted it to help JC to remember what he wrote 30+ years ago ;-)
This is from the same paper as Fig 3.

jd
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