John Curl's Blowtorch preamplifier

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#1,301
VivaVee
---he reason that Naim (and others) put the inputs on the right hand side is legacy. Typical turntables have the tonearm cable/wiring exiting on the right side. Therefore, placing the high gain RIAA stage on the right side, 'under' the tonearm, and placing the mains input cables/power supply on the left side, minimises the interference.---

This goes wrong when you place the preamp at the left side of the turntable which is an easier arrangement. I write and I read from left to right. I draw my schematics with inputs at left and outputs at right. I like my real circuits have some ressemblance with my schematics. Then audio electronics boxes I built have their inputs at the rear left when when viewed from the front (at right when viewed from the rear).
 
#1,304
It is really about which control you change the most often. If the amp sounds that good, the volume should be on the left. Max the volume control and leave it there. Then switch sources more often... hence sources on the right.

You guys should really try the copper tape used for stained glass work. Good adhesive, you can solder on it... it doesn't mind, readily available etc... You can even use it to cob up a decent circuit on a perf-board.



😉
 
#1,307
We are grateful here that electronics do work upside down ... otherwise nothing would work 😉

back on topic ... Ti-shield is a composite of copper/alloy49/copper that has been used in military shielding applications for awhile. All oy 49 is a nickel-iron high permeabliity alloy that provides shielding at low frequencies (both E and H fields). The copper layer is much more effective above 10kHz (E field only). The laminate is usually just 10mil thick!

A cheap but effective substitute is copper plated steel - this was used by Counterpoint during the 90s for their pre/amplifier chassis.
 
#1,308
poobah said:
I just got my new AOL CD in the mail... fun to stick in the microwave...
Click to expand...

You sure you're not breaking some sort of End User Software License Agreement there? I'm sure there are rules about disassembling software...


I'll back up the self adhesive copper foil suggestion. I used to use it all the time on guitars and suchlike, it works really well and is a doddle to apply. Just make sure you bridge the joins with a blob of solder, as the adhesive is a very good insulator.
 
#1,309
Hi VivaVee,
A cheap but effective substitute is copper plated steel - this was used by Counterpoint
Click to expand...
That was to keep the electrical noise in! 😀

Poobah,
Thanks for the copper tape hint. I'm gonna go buy me some.

You know, we could build a preamp in a copper pipe, the Pipe amp (or a straight pipe with gain).

-Chris :clown:
 
#1,310
If you're really serious about magnetic shielding and don't mind spending some money, Ad-vance Magnetics will sell you a kit with high permeability materials that you can form into shields. I got the kit to make some photomultiplier shields for another obsession of mine, but the stuff will work well in audio applications, too.
 
#1,312
Originally posted by poobah
I just got my new AOL CD in the mail... fun to stick in the microwave...

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blowtorch microwave-

http://margo.student.utwente.nl/el/microwave


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topic-

how low will the noise floor be with blowtorch type

circuitry?

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when enough people misspell a word, google will not present

a correct spelling
 
#1,313
What's the mechanism for the increase in distortion, and how much? Inquiring minds want to know. Are we talking in this case about a mu-metal enclosure at a distance (the way I was considering working it), or mu-metal in close proximity to a signal-carring wire?
 
#1,315
Please get some experience in audio design before criticizing the use of aluminum as a chassis material. I have worked with mu-metal for almost 40 years. Mark Levinson first tried it in 1973 and rejected it. I have a mu-metal shielded dual banana input connector. Its distortion contribution can be measured. Have you ever looked at the cost of mu-metal? Let's have some serious contributions.
 
#1,316
Guys,

You Gotta try those microwave tricks... awesome.

The toothpick one is way cool. I found that the colored toothpicks provide the most spectacular display! Nice plasma displays!

Great link tontt!

😀 :smash: 😀 :smash:😀 :smash:

I've blown up a lot of $1200 IGBT's... these are way more fun, and alot cheaper!!!!!!!!!!!

NEWS FLASH

I tried alternate methods for supporting the toothpick and stumbled on to something grand. Cut a potato into 1/4" slices... use the potato slices flat as a toothpick stand.

Do this when your wife isn't around... or get a cool wife.
 
#1,317
john curl said:
Please get some experience in audio design before criticizing the use of aluminum as a chassis material. I have worked with mu-metal for almost 40 years. Mark Levinson first tried it in 1973 and rejected it. I have a mu-metal shielded dual banana input connector. Its distortion contribution can be measured. Have you ever looked at the cost of mu-metal? Let's have some serious contributions.
Click to expand...

Maybe mu-metal related distortions has something to do with relatively easy saturation of the mu-metal? I know that some of the old signal transformers had a several casings, outernmost made of lower permeability material like steel and inner ones from mu-metal. Lower permeability outer layer takes most of the external flux and protects inner mu-metal shield from saturation.
 
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