John Curl's Blowtorch preamplifier part III

Status
Not open for further replies.
Jump to Latest
#34,845
RNMarsh said:
What do we have here? That rather dramatic differences.....

-RM
Click to expand...
Keep in mind, that difference is all the content that the filter decided to remove. That is not the problem..

The problem is only when stuff that was removed is envelope information on frequencies we can hear.

If the content is purely ultrasonic, but not envelope information, we do not care.

That was the whole purpose of the 5/20 test scenario. It demonstrates that the filter being used to limit the signal prior to sampling has the ability to remove information that was in the upper sideband of the modulation. Almost everyone got hung up on not knowing the trig identity, or not thinking about how and where the information of the modulated signal lies. The purpose was to show that sidebands contain information necessary to preserve the signal integrity.

As such, it is not a sampling issue, but a filtering one. If we up the sampling rate, the filter break can go higher and there will be less possibility of removing envelope information.

Understanding that the envelope can create sidebands that may go above the input filter is the simple takeaway here. And that having the filter remove sideband content will not retain full waveform fidelity.

Far more difficult is trying to figure out what >20K content is actually the sound, and what is put there by envelope modulation of the sound.

Seems more like audiologist work. All we can do is try audibility test comparisons, perhaps a little better informed now.

jn
 
Last edited:
#34,846
scott wurcer said:
Thank you for a new word, prosthaphaeresis. I will note the Fourier spectra of both sides of the equation must be the same. The right side is done by convolution (product) and since the difference between the sine and cos is simply a sign flip of the negative frequency there is cancellation leaving the same two original lines. There are no new frequencies via the trig argument.

BTW - I prefer Euler's formula for trig stuff.
Click to expand...
Where do you come up with these multisyllabic words???

I prefer to not even do trig..

jn
 
#34,848
You are smarter than my mac.

//
 

Attachments

  • pros.png
    pros.png
    94.1 KB · Views: 188
#34,854
Hans Polak said:
I’m sorry, but you didn’t even try Electroj files that he carefully prepared, or at least you didn’t mention it afaik.
As long as you haven’t reported your findings, your opinion is just an opinion but without reference. When you want to take the safe road with HD that’s fine, but stop telling that 44.1/16 is not perfect without coming with any prove.
Click to expand...
Nothing, never, is perfect.
I tend to prefer the Beatles to the Rolling stones, but I cannot prove-it.
BTW, I had answered to the Ultima Thule pool: we will see.
 
Last edited:
#34,855
TNT said:
You are smarter than my mac.

//
Click to expand...

Smarter than a MAC that's easy.

Aside: weirdly enough, these product identities were used before logarithms were invented in order to perform multiplication. Here’s how you could use the second one. If you want to multiply x times y, use a table to look up the angle α whose cosine is x and the angle β whose cosine is y. Look up the cosines of the sum α + β. and the difference α – β. Average those two cosines. You get the product xy! Three table look-ups, and computing a sum, a difference, and an average rather than one multiplication. Tycho Brahe (1546–1601), among others, used this algorithm known as prosthaphaeresis.
Click to expand...
 
#34,858
RNMarsh said:
😱

I bough one and was going to use it until I saw all the I/O opamps were 741's.

OMG. No HF filter on input, either. Good features but that killed it for me. It would be the sonic bottle-neck in my system.


THx-RNMarsh
Click to expand...

The MiniDSP uses the ADAU1701 directly for analog outputs. Its has no opamps. Furthermore, there is an HF filter on the input.

When you mentioned in this thread, eons ago, that you were running your M2's with a MiniDSP in between them and a DACIII, I remember posting that imo the MiniDSP is decidedly mid fy. Good, but not high end. You questioned that at the time.

This is all rather confused. Also, if I remember correctly, they were in your system when you and Mark did the test with the gunked Threshold.

When my daughters went through puberty, I let them freely use every word ever used by man. But OMG would be sanctioned.
 
Status
Not open for further replies.
Top Bottom