John Curl's Blowtorch preamplifier part III

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1audio

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Border Patrol? They need a new marketing person. The performance looks similar to many inexpensive ($1.00) 20W digital amp chips. But no DSP!!

However as depressing as it may be the distortions are all below the known thresholds for human hearing. The response interactions are a different thing. I wonder if the source impedance curve changes with level or load? It would make it very difficult to know what it is. Probably very saleable.
 
gerhard

gerhard

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hoffmann-hochfrequenz.de
billshurv said:
Just a question in general. The attached doohickey is std fare in RF design for getting power in and out of ones hogged from solid boxes. Some neat little SMT ones these days. Not sure I've ever seen them in audio, which is a shame as they would seem ideal for what we are discussing, which is herding the RF into the chassis and not to your amplifier. Anyone had a play?

But to use them you almost have to double box your unit, not unlike LNAs which need 2 or 3 boxes to get 50/60Hz out of the way.
Click to expand...

like this one in post 390 of

< My version of the G = 1000 low noise measurement amp (for Ikoflexer). >

Cheers, Gerhard

(it may be unwise to expose that thread to the snake oil community, so be warned:
excessive amount of facts. )
 
SyncTronX

SyncTronX

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Shame on me.

You guy's are right. To get the most information I do need to sit in the near field. Typically I'm at the the boarder of it or farther out, +15 feet. Nearfield starts around 14.5 feet. So I was fooling around at about 10 feet and leaned in another foot or two and yes, much more imaging.

At least on Heart Felt World, Chris Isaacs.

Because I have a long room (33 feet) I'm typically around the 27 foot (dining room table) or 15 foot (couch) range with the music on. 15 feet is good with imaging, but 10 feet is better. 10 feet from a wall feels too close for me for listening. It is what it is.

Cheers,
 
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31697B

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SyncTronX said:
Shame on me.

You guy's are right. To get the most information I do need to sit in the near field. Typically I'm at the the boarder of it or farther out, +15 feet. Nearfield starts around 14.5 feet. So I was fooling around at about 10 feet and leaned in another foot or two and yes, much more imaging. Cheers,
Click to expand...

Great! You listened and you tried it and you heard. :)

The near-field may be even closer than 14.5 feet depending upon the speakers dispersion -- how wide it is.

Glad you tried and heard and learned.

THx-RNMarsh
 
Destroyer OS

Destroyer OS

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jneutron said:
You do not have to be sold at all. It's a discussion, no worries.;)
My focus in that set of drawings was two fold..
1. With all components bonded, the low frequency currents of the signal from the pre to the amp will take the path of lowest impedance, which would not be the IC shields, but rather the bonding grounds. That rears the ugly head of coupling between the amp haversine draw and the input signals. With no signal, all is quiet. But with major power, the input may be compromised due to coupling.
How one measures this coupling without disturbing the system is a big question, the coupling depends on the low resistances.
2. The loops allow field coupling of external sources. Big loops, big coupling. Big enough, near strikes will toast the equipment.. Sadly, been there, replaced that..:(

I am more than happy to be proven incorrect, that is familiar territory (anyone with kids knows this position).

Jn
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You don't have to bond PG to safety ground (in some equipment I've found there's no way around avoiding it to keep audible noise out, amps at the end of the chain are somewhat vulnerable). I like Schurter's DENO's to break the loop.

I do like the sound of eliminating lightening problems. I know first hand how things like to toast themselves with too much current through ground. I guess the question that really raises is a two part:

Does the layout affect sound? If so, is it worth trading the sound qualities for protection if the sound isn't as good?
 
SyncTronX

SyncTronX

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Correction,

Heart Shaped World, Wicked Game and Blue Spanish Sky. Nice indeed.

Yeah, I've measured it with my trusty radio shack SPL Meter. Walking forward from the back of the room. At about 14.5 to 15 feet is +3dB. The room is 14.5 feet wide. The Cornwalls are in the corners at differing angles pointing inward.

The roof is angled going from a height of 13'4" down to 8', so the different angles seem to help imaging. Yes this system images pretty darn well which is what I like. It sounds great cranked up through live levels.

At least for me another thing that I don't ever see discussed it walking around when listening to music.

It's what I've always done at venues too, that is walk across the near field from side to side, mid field from side to side the far field from side to side and hear how it sounds from various angles and distances. Yes, then I'll go fore and aft after side to side. I do the same at the house. Currently I'm going through my Onkyo '92 Silver Premium sampler disc. From 2 CV Citroen, thought Lacanau, through the Tik Tak Polka by Orchestre Pasdeloup to Ariel Ramierz "Misa Criolla" Kyrie, through Count Basie's "April In Paris" and to the end.

followed by Chris Rea, The Road To Hell. #4 Texas, need I say more?

Cheers,
 
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KSTR

KSTR

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jneutron said:
Ott, Johnson, Van Doren, that other guy(I'll remember his name 1 minute after editing is closed..:D.) Every time I read, or am at one of their presentations, I find I have to correct them on their misunderstandings.

That said, what I learn from them vs what they learn from me scales at about 100:1.
You are entirely correct.

John
Click to expand...
With regard to Ott's "Electromagnetic Compatibilty Engineering" (you sure have a copy, do you?) could you point out these misunderstandings that really have a consequence, that is, lead designers on the wrong track in understanding and preventing/fixing EMC problems?
 
Destroyer OS

Destroyer OS

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scottjoplin said:
Wouldn't that mean signal ground is not directly referenced to the chassis? Also a PSU fault may not blow the mains fuse unless the signal ground could carry the fault current
Click to expand...

Not directly, yes.

If you need the signal ground to carry a fault current from one piece of equipment to another in order to exceed the mains fuse ampere limit... you won't have a fault current unless SG can carry it. The worst part about that is having a faulty piece of equipment you don't know about until you try a new amp and find your source is kaput. It's actually not that desirable to have interconnects that hot, either. If the chassis is safety grounded, it insures you don't have it hot under any relative situation, which is nice and safe. The interconnects have no such protection unless they're XLR balanced, and even then it's likely to fail if it's more than a slight moment.

All of that really applies to linear power supplies. SMPS's are kind of another can of worms for the discussion. The likelihood with them is that they already have safety and PG.
 
jneutron

jneutron

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KSTR said:
With regard to Ott's "Electromagnetic Compatibilty Engineering" (you sure have a copy, do you?) could you point out these misunderstandings that really have a consequence, that is, lead designers on the wrong track in understanding and preventing/fixing EMC problems?
Click to expand...

I do not have a copy, and I am unable to recall who I told what to.

That said, I do recall some of the errors but cannot attribute..

"Twisted pairs do not communicate."

This is incorrect. Twisted pairs can communicate if their twist pitches have an integer relationship. Same twist is obvious by inspection. That is why cat5e has a specific twist pitch for each pair, and they are different.

"It is not possible to run a quiet unbalanced run across a room."

It most certainly is. I demonstrated that in a 450 seat venue with the mix rack 100 plus feet away in amongst many kilowatts so old school solid state dimmers (pre slew rate limited), a toro 700? Leaf blower, and a .5 mega volt van de Graf. In fact, I also ran mike feed in that 100 foot "snake" as well.

One of my drawings shows that, drawing "C" I believe.

Someone in a published book had drawn how a conductor skins incorrectly, messed up the magfield and eddy currents. IIRC, when the book's next edition came out, the drawing was corrected. I seem to recall 1994 timeframe. (Or maybe 2004?).

"Placing power conductors at 90 degrees to twisted pairs zero's any coupling."

No, it does not. It makes the coupling position dependent, and will vary sinusoidally as the power conductor moves along the twisted pair. If the power cable is also twisted pair, coupling will depend on rotation of the power cable.

Somebody said there is magfield on the inside of a shield caused by the shield. No, there isn't. The magnetic field within the dielectric is entirely from the core current, shield current plays no part in that. (My avatar is a field map depiction of a double braid coax.

I'll try to recall more, but 20 years is a long time.

Jn
 
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jneutron

jneutron

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