John Curl's Blowtorch preamplifier part II - Page 1861 - diyAudio
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Old 1st December 2011, 06:56 PM   #18601
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Quote:
Originally Posted by john curl View Post
Who cares whether the JC-3 can drive 600 ohms or so? It was NEVER designed for that, and it is the OPA2134 on the output that is the limitation.
If I may suggest, never put an (unbuffered) opamp only at the output of the hi-end line stage or phono stage. This would ALWAYS compromise the design and will never drive the cable well, though it may sound 'silly'. This is my know-how that I share here.
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Old 1st December 2011, 07:17 PM   #18602
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My interpretation of the Stereophile review is that the tested sample might not be representative of Mr. Curl's design and intent. What stands out the most is the disparity of spec'ed and measured gains, but the RIAA errors don't look likely either. But whadda I know?

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Old 1st December 2011, 07:41 PM   #18603
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Quote:
Originally Posted by PMA View Post
If I may suggest, never put an (unbuffered) opamp only at the output of the hi-end line stage or phono stage. This would ALWAYS compromise the design and will never drive the cable well, though it may sound 'silly'. This is my know-how that I share here.
Seems easy enough to avoid using cables made from unrolled capacitors.

se
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Old 1st December 2011, 07:50 PM   #18604
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Originally Posted by simon7000 View Post
(Hand to ear) Eh, speak up, why do you always mumble? (True unhappy client story!)

The cited blog came to the conclusion the article finding cable differences was flawed. I think the basis of comparison was flawed also.

Now 162 watts average into a loudspeaker seems loud, but I was just at a small ballpark. The loudspeakers I installed 18 years ago were rated for 103.1 db/w @ 1M. Someone else (Low bidder) had added speakers to cover new seating that were 90 db/w @ 1M.

So the new loudspeakers at 4.5 amps would have produced 105.8 db @ 1M (Power compression comes into play and that actually is a fairly good number for their maximum power.) As this is a minor league ballpark the level would need to be 95 db at the farthest seats. So the throw of those added speakers would be 132 inches! The ones I used handled a bit more power and could throw 54 feet, which was just adequate.

The operator mentioned they could not get a good level balance for the entire ballpark. It just wasn't loud enough for the new section no matter what they did.

So there really are cases where 4.5 amps ain't loud enough even for indoor use as some audiophile loudspeakers can be as low as 82 db/w @ 1M.
I would find 104dB SPL average in a room generally unbearable and the peaks for any real music would be near dangerous even in this extreme example. Why would anyone wire such a system with plastic coated #24 zipcord?
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Old 1st December 2011, 07:53 PM   #18605
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Quote:
Originally Posted by Steve Eddy View Post
Seems easy enough to avoid using cables made from unrolled capacitors.

se
But those are the kind of cables that are particularly revealing of preamp differences.
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Old 1st December 2011, 08:20 PM   #18606
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Originally Posted by scott wurcer View Post
I would find 104dB SPL average in a room generally unbearable and the peaks for any real music would be near dangerous even in this extreme example. Why would anyone wire such a system with plastic coated #24 zipcord?
104 db @1 M or only 90 at my listening distance. Loud.. yeah but there are some who listen that loud. Perhaps that is why they think I mumble.

Then the issue of 24 gauge wire is that it is not a reasonable choice but appears as if it were included in some "tests" proving speaker wire changes with level.

Yes some folks have sold 24 gauge as speaker wire, and it probably works just fine for their customers.

Now if you want to look at the new super alloys that are being made in triple processed vacuum furnaces, there actually are better choices for interconnect wires coming down the pike. And yes they will costs more and actually be worth it to the very few who have the rest of their gear up to the task.
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Old 1st December 2011, 08:27 PM   #18607
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Default More bad FET news?

LSJ74 seems to no longer be listed anywhere on the Linear Systems website. Anyone have info?
Just checked not in crossreference or selection guide either.

Had a good laugh looking around, from Gerorge Massenburg's website....

Their all-discrete, bipolar transistor circuit topologies are completely transformerless with no >>FET's<<, IC's, or electrolytic capacitors in the signal path.
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Old 1st December 2011, 08:43 PM   #18608
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Old 1st December 2011, 08:53 PM   #18609
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$8.74 each will keep them available for a while.
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Old 1st December 2011, 08:54 PM   #18610
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The 2sk170 must feel very flattered, to be "complimented" by this thing.
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