John Curl's Blowtorch preamplifier

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#19,302
PMA said:


It is an issue of high frequency interference. RF, cell phone GSM gateways. I am referring to an image shown here:

http://www.diyaudio.com/forums/showthread.php?postid=810164#post810164
Click to expand...


My question referenced the issue of tying the input and output grounds together with the chassis vs. a "different" ground reference point, like a star someplace else... so is that an issue in that it might create problems back down in the audio range while avoiding RFI??

_-_-bear
 
#19,306
Andre Visser said:


Not that my subjective opinion will count for much but here it is if you are interested.

A friend of mine import Furutech products and he asked my opinion on their fuses. My reply was that I can't imagine that it could make a difference because they are not directly in the audio path (OK I know everything is in the signal path in the end). He imported some anyhow and we tested them one afternoon in two sets of identical Class A monoblocks.

At first I replaced the fuses in the ac as well as dc lines, it took a few amp swops to detect a change but once detected the difference was quite obvious. Then I've tried with the fuses only in the ac and only in the dc lines, each time a difference was noted (although not as much as with all fuses replaced).

To give my opinion on your question, yes they do make a difference in SQ, whether they are worth the money, I guess that will depend on how much you value detail and accuracy in your system and of course the size of your wallet but that is besides the point isn't it.

André
Click to expand...
as i've said before, it's all in the circuit
all the way back to the power co. generator.
fuses, power cords, even panelboards.
so then, how can we minimise the effect?
enter power supply design.
a brick wall
then fuse differences, etc should not be audible
 
#19,307
Many many things "should not be audible".

This is the rub.
In many systems many many things are not audible.
In other systems, with other ears far too many things are strangely and confoundingly audible far too much of the time.

But that a power supply was a brick wall... brick, missing some bricks and mortar??


I think that part of the holy grail of audio is to make "environment independent" equipment. Not so simple, facile or easy.

_-_-bear
 
#19,308
john curl said:
Against doctors orders, I am writing this short note. I won't be around for awhile, good luck!
Click to expand...

I spoke with John about this yesterday. He had eye surgery, Dr. says it may take 2-3 weeks to recover enough to use the computer.

I wished him a Get Well Soon, and told him to keep me informed. John is a good guy. I'm sure all you guys will keep this ball rolling, but don't post questions to John for a while. He won't be able to read them or respond.
 
#19,309
Re: Re: Current source/sink IC

janneman said:


Hi Chuck,

If you read the material carefully, you will find that it is great as a DC source but that the dynamic impedance and performance deteriorates rapidly with frquency, and that all kinds of 'band aids' are shown to prop it up at AC. And some of the more interesting areas (for audio) are conspicuously blank in the data sheet. Nice, but no thanks. My 2cts worth.

Jan Didden
Click to expand...

Thanks for the analysis and input, Jan.
 
#19,311
Bottleneck, eventually, for low power nano transistors. regarding the frequency of the gene.rated noise.
Theory from larger transistors predict wrongly.

Intesresting and good report.
Shows that there are still new problems and benefits to discover.
When electronics goes into a new 'shrinking age' .. to save some power.

By no coincidence saving power in computers and elctronicvs
coincide with 'warming the globe' and 'lack of oil' theories.

We call it often paradigms.
Now is green, environment low power age, we live in.
The beginning of 😎

/Line 'linie' Lineup - Article writer - with Full Copright reserved.
(if you see this article at one of my audio websites - it is mine!
 
#19,312
bear said:
Many many things "should not be audible".

This is the rub.
In many systems many many things are not audible.
In other systems, with other ears far too many things are strangely and confoundingly audible far too much of the time.

But that a power supply was a brick wall... brick, missing some bricks and mortar??


I think that part of the holy grail of audio is to make "environment independent" equipment. Not so simple, facile or easy.

_-_-bear
Click to expand...

perhaps i am unclear?
the power supply is within our control.
we should strive to make the supply a brick wall, such that fuses and such don't matter.
i think it's doable.
 
#19,317
syn08 said:
PMA said:
In case you want to avoid high frequency interference issues, the box (if only one is used) must be the reference ground. The cable shield must be connected to the box outer surface and no unshielded wire may get through metal walls. Any violation of this rule leads to interference related problems.
Click to expand...
What is a "reference ground"? A schematic would certainly help here.
Click to expand...
Pavel is talking about AES48-style of construction/cabling, I think. Which is sort of a mimimum to avoid HF problems (google "AES48", first hit). The rest is in Ott's book. Or just ask Pavel, he knows this stuff very well from all I've seen and read from him so far (no wonder, given his day job). And, of course, only as far as I'm entitled to judge, not being a full-blown EMC expert (but I have some experiences, learning things the hard way -- designs that didn't pass EMC tests because I only eyeballed the problems).

Now to the Ref-GND, we are talking about unbalanced gear here, hence Shield==Ref-GND is an unavoidable consequence of this (at least for HF, for DC/AF there are some options).

Do you quys do the cell-phone test? I still have to find a CDP (for example) in my neighborhood that isn't prone to TDMA-noise when you hold your sending/transmitting cell-phone close to the display or tray... ok, a true HF-proof CDP is not easy to do... but also many power amps react unduly to a cell-phone close to the speaker leads...

- Klaus
 
#19,318
Sorry, "shield is the reference ground"??

Shield is not inside the unit!

Is the power supply ground at the same potential as the shield?
There are no ground currents circulating about the chassis then?
These and other questions...

So I am wondering where inside the chassis (or on the chassis?) do we find the groundiest ground point?? Or, "the reference ground"?

Does it not matter?

_-_-bear
 
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