John Curl's Blowtorch preamplifier

[john curl]

It can be shown that there is more than one approach to shielding. There is: 'reflection loss' which cables and a thin metallic sheld do OK, and there is 'absorption loss' which is proportional to the thickness of the shield material. In this case, thicker is better for 'absorption loss'. In the Blowtorch case, we cannot easily prevent low impedance based low frequency pickup, except that the output is balanced, so that the balanced line can cancel any low frequency noise pickup that gets by any electrostatic shield that may be picked up by the cable.
In the case of the blowtorch, the way that it is fabricated would make a THINNER outside case, even more expensive to make. We therefore keep it as thick as practically possible. Interference that we are most interested in, is the garbage radiated by switching power supplies, high frequency ballasted florescent lamps, computers, etc. The thick case makes it easier to relax the shielding requirements, INSIDE the box.

[anatech]

Hi John,
I think your premise is clear enough. Besides, you can only control what you build which is inside the box. What happens outside the box is quite beyond your control. Cable routing is the job of the installer and I don't see any of the top systems guys using conduit. They'd probably use plastic anyway.

So I don't see any progress in crying about cables. That's for a .........
........ ............. cable.... ......... thread .._

So let us talk about stuff that is with our ability to control.

-Chris

[Magura]

Would the assumption that metal Neutrik XLR chassis plugs would have reasonable shielding properties, be totally off?

Magura

[PMA]

Depends where you connect the shield. If on pin 1 only and this not connected to chassis, then you have very good antenna leading inside.

[Magura]

Originally posted by PMA
Depends where you connect the shield. If on pin 1 only and this not connected to chassis, then you have very good antenna leading inside.

But assuming that you make use of connecting the shield from the cable to the metal of the plug...that is connected to the chassis?

Magura

[jbaudiophile]

Hello, Anatech

And what about cable resistance/capacitance DISTRIBUTED filtering ??? Not a new idea, as a French company (SIARE) used it for loudspeakers filters and that was so innovative... that almost no guy bought them...!

But with mains rubbish, even if it can't be completely nulled, it can be a lot disminished BEFORE entering the amp or preamp!

I have here a lot of experiments running on this. No mains cables are made equal, and highly depend on your location all along the supply line. As well as on the world map...

So, no overall recipe to be just copied here or here.

BUT...

Bob Crump made extensive research about it, and we shared some local findings. But was shortly before he died

Far more interesting a question than the plain package thickness pr material... Would anyone add a 2 inches aluminium/steel.silver/... to his already owned equipment ??? For sure no ! But on developed stuff only... at spare time for 99.9% of us !

Here, John, I have to learn a lot (as well I can share some Europe study)... Sorry for, but a lot of guys missed to report for their own area, and itis NOT easy for me to contact them, eh ???

Jbaudiophile

[anatech]

Hi Jbaudiophile,
I don't know if I understand your point, but I'll answer the best I can.

All I said was that you can only control what you manufacture, or what is inside your box. That's all.

If a snazzy $3,000 US power cord were to be included, I'd probably not purchase the item because the power cord tells me the designer can't design a power supply. That and the darn thing is probably too stiff to use. Ever route semi rigid cables? It isn't fun.

And what about cable resistance/capacitance DISTRIBUTED filtering ??? Not a new idea, as a French company (SIARE) used it for loudspeakers filters and that was so innovative... that almost no guy bought them...!

Hmmm, could be because the product didn't work or was over priced. I am extremely skeptical about cables. The market had spoken. Bye bye product.

But with mains rubbish, even if it can't be completely nulled, it can be a lot disminished BEFORE entering the amp or preamp!

Why? This is the job of a power supply not a cable. Fixing one's hopes on a cable is foolish and feeble. I view this as similar to clutching a bible and sprinkling "holy water" on your gear will incanting some phrase over and over. You can more effectively do this once the cable is secure in it's socket at the rear of your device. If you are worried about your mains being that bad, install and audiophile generator. This frees you from all sorts of evils. This would seem to be the best fix actually. A pile of "Audiopile" (not an error ) cords would go a long way to setting one of these up money wise. Then you can listen when there is a power failure! Small draw devices can effectively use filters. Power amps require minimum impedance to the mains and should not be filtered, they can only make use of capacitive devices across the mains.

I have here a lot of experiments running on this. No mains cables are made equal, and highly depend on your location all along the supply line. As well as on the world map...

I agree. This is why the designer should know how to make a power supply that rejects noise. Eliminating the use of toroids is a good start. They have too much bandwidth. There are also times when one lives in an area where the mains are too noisy to use. Move. It's not unlike poor antenna reception. Move. There are times when technology can not supply a fix. Accept this.

Far more interesting a question than the plain package thickness pr material... Would anyone add a 2 inches aluminium/steel.silver/... to his already owned equipment ???

You don't want to know what I have seen people do to their equipment. Never say never. All the need is a flaky internet article to destroy their equipment. If the article is in print, more stereos will die.

I do not understand your post, but it appears to take me to task for comments I've made. That's okay. I stand by them.

-Chris

[Steve Eddy]

Originally posted by anatech
All I said was that you can only control what you manufacture, or what is inside your box.

That's certainly true for a typical commercial manufacturer, but I thought this was a DIY effort that was being discussed?

se

[anatech]

Hi Steve,

That's certainly true for a typical commercial manufacturer, but I thought this was a DIY effort that was being discussed?

Yes, that is true for an entire system. However, the thread discussed John's commercial product. I will extend this to say that if you DIY a piece of equipment, you should design to the standards for this equipment - at least loosely. If you wish to include a custom connection system, then do so! I mentioned this earlier in a thread. Can't remember which one.

As a designer though, I would accept chaos outside my equipment and design to accommodate and mitigate those effects as much as possible. How could anyone design anything will worrying about all the possible problems your design could face all over the world? Design for your known environment and anticipate as much as you reasonably can. State the expected operating conditions for your equipment and dissuade it's use outside of those parameters.

Lastly, I would not allow a design to depend on an uncertain cable for it's performance that is outside the normal spec. That's why highly capacitive cables can cause some amplifiers to burn up, they are outside the accepted normals.

-Chris

[Steve Eddy]

Originally posted by anatech
Yes, that is true for an entire system. However, the thread discussed John's commercial product.

Yes, with an eye toward folks being able to build their own versions of it.

I will extend this to say that if you DIY a piece of equipment, you should design to the standards for this equipment - at least loosely. If you wish to include a custom connection system, then do so! I mentioned this earlier in a thread. Can't remember which one.

Ok.

As a designer though, I would accept chaos outside my equipment and design to accommodate and mitigate those effects as much as possible. How could anyone design anything will worrying about all the possible problems your design could face all over the world? Design for your known environment and anticipate as much as you reasonably can. State the expected operating conditions for your equipment and dissuade it's use outside of those parameters.

And again this is good advice for the commercial manufacturer. But when you build something for yourself you don't have to worry about "all over the word." You only have to worry about your particular situation and your particular environment.

That's one of the beauties of DIY. DIY is what this board is all about and that's what this thread has ultimately been about. And that's why I'm wondering why you keep responding to my comments from the perspective of a commercial manufacturer.

se