John Curl's Blowtorch preamplifier part II

[fas42]

Originally Posted by Joshua_G

On top of that, I found out that meaningful listening evaluations need prolonged listening. Few times it happened to me that when I evaluated various pieces of gear on my audio setup, on first listening it sounded good. After few listening sessions, on few consecutive days, some faults to sound quality emerged. Therefore, a brief, one time listening evaluations aren't the way for meaningful sound quality evaluation.

Interesting, completely the other way for me. I have a collection of really "nasty" recordings, as in that on most systems they sound pretty horrendous, unlistenable to in an enjoyable way, and it takes mere seconds to assess a completely unknown setup this way -- the faults absolutely scream at you; I'm speaking of the components working as a complete entity, not the recording ...

Frank

[morinix]

Originally Posted by fas42

I have a collection of really "nasty" recordings......

Care to grace us with some examples?

[Joshua_G]

Originally Posted by fas42

Interesting, completely the other way for me. I have a collection of really "nasty" recordings, as in that on most systems they sound pretty horrendous, unlistenable to in an enjoyable way, and it takes mere seconds to assess a completely unknown setup this way -- the faults absolutely scream at you; I'm speaking of the components working as a complete entity, not the recording ...

Frank

Well, I spoke about evaluating gear on my own setup.
When a piece of gear doesn't sound good, it's quite obvious very soon. It takes prolonged listening to find out that something really sounds good, without drawbacks.

I didn't like the majority of other setups I heard. Indeed, at times it takes few minutes to find out that you don't like a certain setup. On one case I found it out only after a whole listening session. Only after the second listening session I could pin point the reason for it: it is a setup (a fairly expensive one, about 4 times than my own setup) which has a great "Wow! Effect", but all music on it sound the same, and it is very far from being musical.

[RNMarsh]

Originally Posted by aeronautical

Mr. Curl, is that because steel or ferric metal can be excited into being a magnet in the presence of a magnetic field...thereby fixing one problem and spawning others?

Current flowing thru ferrous metals create a non-linear Z which translates into distortion... Ferrous metals within 2-3cm (1 inch) of a signal carrying wire is sufficient to measure the thd increase.

Thus, keep ferrous metals like the chassis might be - 1 inch or more away from the signal wires and pcb/circuitry. And, of course dont, therefore, use parts with ferrous metals in them.

The research done on this came from Japan... I think I recall who/company but not sure. -Dick Marsh

[aeronautical]

Originally Posted by RNMarsh

Current flowing thru ferrous metals create a non-linear Z which translates into distortion... Ferrous metals within 2-3cm (1 inch) of a signal carrying wire is sufficient to measure the thd increase.

Thus, keep ferrous metals like the chassis might be - 1 inch or more away from the signal wires and pcb/circuitry. And, of course dont, therefore, use parts with ferrous metals in them.

The research done on this came from Japan... I think I recall who/company but not sure. -Dick Marsh

Great...thanks. I can tig weld stainless and if I can get paint to stck to it, powdercoat it and bake it in Mrs. Aeronautical's oven.

One parameter resolved.

[john curl]

Richard is right. Of course, copper, silver, maybe Uranium might be OK. Can you afford it? I'll stick to aluminum.

[fas42]

Originally Posted by morinix

Care to grace us with some examples?

I've already mentioned driving boogie rock with strong cymbal content, rock with studio injected cavernous soundstages in another post. 80's new wave pop with layers and layers of synthesiser sounds and heavy reverb and other effects in the mix are hard work for a lot of systems.

In another direction, early 30's swing orchestras, with rows of brass blasting out crescendos well back in the soundstage

An Ambisonics recording by Nimbus of Franck and Faure chamber music, an extremely distant acoustic is conjured up.

The Essential Odette on Vanguard, live recording at Carnegie Hall, mastered at an extremely low level: full volume is just barely loud enough.

Ike & Tina Turner in concert, very, very dirty sound, plus full blown studio mixes on one CD. Massively energetic, raw sound, would be diabolical on most setups.

Jimi Hendrix Experience's Voodoo Chile recorded live, and done superbly. The drum kit is captured perfectly, and the Marshall amp growls and grinds menacingly. With excellent audience ambience. But will your system show it?

The list goes on and on ...

Frank

[aeronautical]

Originally Posted by john curl

Richard is right. Of course, copper, silver, maybe Uranium might be OK. Can you afford it? I'll stick to aluminum.

I think I still have a connection for stainless sheet metal. If so I can build my chassis out of that.

Now for the trivial things...like electrical properties.

Come on guys...lighten up...i WAS JUST KIDDING

I am trying to come up with some design goals but heck, I just want it to sound good, last a long time, and be within my abilities to build. Mr. Curl, I am looking at the schematic you posted earlier today. I would need a little bit of guidance but am willing to have a go at it. In the next few days I will try to figure out if I can buy the parts. I wish there would be others out there that would build this along with me...it would be a shame for these guys to waste good energy on something productive like building the best preramp we can build.

[fas42]

Originally Posted by Joshua_G

... and it is very far from being musical.

That's the number 1 criterion for me, the worst of the worst recordings have to be musical, in that sense I'm totally on your side here. And this musn't be achieved by doing the equivalent of throwing a thick blanket over the speakers, I've heard this system "sound" many times, and it is not the correct way ...

Frank

[morinix]

Originally Posted by fas42

I've already mentioned driving boogie rock with strong cymbal content, rock with studio injected cavernous soundstages in another post. 80's new wave pop with layers and layers of synthesiser sounds and heavy reverb and other effects in the mix are hard work for a lot of systems.

In another direction, early 30's swing orchestras, with rows of brass blasting out crescendos well back in the soundstage

An Ambisonics recording by Nimbus of Franck and Faure chamber music, an extremely distant acoustic is conjured up.

The Essential Odette on Vanguard, live recording at Carnegie Hall, mastered at an extremely low level: full volume is just barely loud enough.

Ike & Tina Turner in concert, very, very dirty sound, plus full blown studio mixes on one CD. Massively energetic, raw sound, would be diabolical on most setups.

Jimi Hendrix Experience's Voodoo Chile recorded live, and done superbly. The drum kit is captured perfectly, and the Marshall amp growls and grinds menacingly. With excellent audience ambience. But will your system show it?

The list goes on and on ...

Frank

Ok, cool