John Curl's Blowtorch preamplifier part II

[bcarso]

I will be ordering some PC cards next week. Simple 2 layer FR4. So what test card should I use to measure how much the PC material really affects an audio signal? Should I lay out a winding long trace over a ground plane and drive it with a modest 10,000 ohm source and a high impedance 10 M load. Test this with square waves from say 20 -20,000 hertz?

Should I do an FET buffer with and without an input guard ring?

Again, it is claimed that modern board materials do not have significant hook.

 

[29285]

@Simon7k
So you are looking for some measuring setup to discover differences in properties of different pcb material. Measuring with enough resolution you will find some in the end, but - you are not sure what you are looking for. And you do not know the criteria in real numbers for what is relevant for audio and what is not.
So, what is the point?

 

[Kindhornman]

Bonsai,
Order yourself two of those, one for each room! $27,000 for a box of air and a few electronic components.

 

[rayma]

Levinson as well did stuff with a different dielectric, I think it was Arlon?

From the owner's manual for the Nº32 Reference Preamplifier:

The Mark Levinson Nº38 introduced revolutionary volume precision
and resolution to the world of high end preamplifiers, with the firstever
0.1 dB-step volume control. In the Nº32, this same approach is
taken to an even higher level in a discrete attenuator of Madrigal’s design
that uses 66 surface-mounted, precision resistors per channel.
Used in combination, this balanced volume control gives us over
65,000 possible volume settings between zero- and maximum-attenuation.
(Don’t worry, we don’t use them all.)

This design, implemented on an Arlon 25N printed circuit board with
local, discrete regulators, delivers greater transparency than any volume
control technology we have ever experienced. It also provides increments
as small as 0.1 dB, allowing you to select precisely the correct
volume for any given recording, and to do so repeatably.

 

[scott wurcer]

Stupid question;
Has actual glass ever been used as a substrate?

Just curious.

Sapphire has.

 

[scott wurcer]

Just to digress:- a $27k CD player.

Neodio Origine | The Ear

Don't lose sight of the fact that this hubris is over 44.1/16. That's 27k pounds not $ what a pile of shiet.

 

[rayma]

Has actual glass ever been used as a substrate?

And also for this (AVX, formerly Corning): http://www.mouser.com/catalog/supplier/library/pdf/AVXGlassDielectric.pdf

 

[bcarso]

And also for this (AVX, formerly Corning): http://www.mouser.com/catalog/supplier/library/pdf/AVXGlassDielectric.pdf

Yes I had thought to mention those. Very good for high temperatures, although not the very lowest dielectric noise (porcelain a bit better).

 

[rayma]

Yes I had thought to mention those. Very good for high temperatures,
although not the very lowest dielectric noise (porcelain a bit better).

I've tried them for RIAA use, and they didn't sound as good as the usual culprits.

 

[john curl]

Just think about making capacitors out of circuit board material, and testing it against a more accurate capacitor in a differential subtraction test. In fact, if you took a dual metalized circuit board (a copper film on each side), you could easily make such a capacitor. Then test.

 

[bcarso]

Just think about making capacitors out of circuit board material, and testing it against a more accurate capacitor in a differential subtraction test. In fact, if you took a dual metalized circuit board (a copper film on each side), you could easily make such a capacitor. Then test.

Yes, a differential measurement is advised.

 

[john curl]

I found this test to be possible and perhaps practical.

 

[Bonsai]

Don't lose sight of the fact that this hubris is over 44.1/16. That's 27k pounds not $ what a pile of shiet.

Yeah - about 38k USD.

Unbelievable.

 

[Bonsai]

Bonsai,
Order yourself two of those, one for each room! $27,000 for a box of air and a few electronic components.

I could just about do myself a Tesla for that figure. A much more worthy expenditure. Or take a holiday to Antartica. LOL.

 

[billshurv]

I thought the funniest part was the beginning 'my mate who makes awesomely expensive horn speakers loves this so I got one to listen to'

 

[marce]

rsavas wrote
“if you can't lay out your own pcbs”
not
“if you don’t lay out your own pcbs”





It might have been a problem in instruments for measuring pA (or fA on clean boards)

What is the Z of the audio circuits?

George

cheers, apologies to the injured party....

 

[Max Headroom]

Stupid question;
Has actual glass ever been used as a substrate?
Just curious.

I bought some glass screen protectors as an easy way to build 2 layer construction smd T&M jigs using stick on copper foil as tracks and earth planes.
Drilling holes (diamond bit) would provide 'vias'.
It may be interesting to see how these sound as an audio pcb....these glass protectors are 3 layers...tempered glass, plastic layer and an adhesive so may not have the same ideal electrical characteristics as plain glass.

Here's an intersting way using microscope slides - youtube.com - How to make Clear Glass PCBs

Dan.

 

[Destroyer OS]

Yeah - about 38k USD.

Unbelievable.

It's not actually the price that bothers me... It's that I can see a ton of cheap *** parts for that price in it... and some ******* that can't even properly twist wires put it together.

 

[marce]

I bought some glass screen protectors as an easy way to build 2 layer construction smd T&M jigs using stick on copper foil as tracks and earth planes.
Drilling holes (diamond bit) would provide 'vias'.
It may be interesting to see how these sound as an audio pcb....these glass protectors are 3 layers...tempered glass, plastic layer and an adhesive so may not have the same ideal electrical characteristics as plain glass.

Here's an intersting way using microscope slides - youtube.com - How to make Clear Glass PCBs

Dan.

Plating the barrels of the holes would be interesting...
Quite honestly though is there any point with the range of modern materials available today....
Better to use a high speed FR4 weave such as 7268 or even a high performance laminate...
https://www.altera.com/content/dam/altera-www/global/en_US/pdfs/literature/an/an528.pdf
why go to extremes with something that is totally impossible to manufacture a board reliably

 

[Bonsai]

It's not actually the price that bothers me... It's that I can see a ton of cheap *** parts for that price in it... and some ******* that can't even properly twist wires put it together.

Ha ha LOL