John Curl's Blowtorch preamplifier part II

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I am thinking discrete power amplifiers, and particular some of the advances made in compensation design in amongst others. Beyond that, a lot of the stuff done by JLH and Baxandall for example was done 'after hours'

I just don't buy this professional/amateur thing when some of the amateurs happen to be leading lights in the field in their own right.
 
One might say boring sophistry. A $25,000 phono whose specs could be equalled by a JFET/IC op-amp composite.

Scott,

We really got to disagree on this one. There is no way a JFET/IC op-amp composite could meet all the same specs. Although it may match or even better all the presumed common measurements, there is one spec it would never match... the price.

ES
 
price is easy to adjust upwards - limited only by case appearance/weight/finish

not quite so nose bleed but look inside Ray Samuels Audio products - US$3k Dark Star headphone amp is 4 bridged OPA541 power chip amps - worse audio specs than LM3886
but really nice machining on the case, separate ps box, cones...


another example is a US amp manufacturer who contemplated closing, as last gasp effort went from sheet metal to machined cases, careful matching anodize apperance, integral eye candy heatsink machining, "jewelry" connectors - and 3-5x price increases

in an hr presentation at BAS they never once mentioned actual circuit design changes - now a regular buyer of full page Stereophile ads - doing great business
 
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there is one spec it would never match...

Write-Off

A new 750 does $45K here, used ones go under 20
(gets even worse when the 750PSU unit is included. one might think coils are a bad investment)
 

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Scott,

We really got to disagree on this one. There is no way a JFET/IC op-amp composite could meet all the same specs. Although it may match or even better all the presumed common measurements, there is one spec it would never match... the price.

ES

No, you just need to pot it in diamond inpregnated epoxy (for its thermal properties of course).
 
Slightly off topic. We are shipping out a small system this month. It is taking six trucks just to hold the loudspeakers. We book an entire truck to take our loads. Twice now, the truckers have tried to pick up our stuff and pack it tight enough so that they can pick up a partial load from someone else along the way and make a bit more money.

Our best technique to avoid that is that our crates are four and a half feet wide so that you can't put two next to each other and a standard four foot pallet won't fit either.

We do pay for the entire truckload for a good reason. The maximum insurance for a truckload is $100,000! So we have to keep each shipment under that.

So you would need a 53' truck just to carry two phono preamps! :)

Scott,

That means you could only get 7 ICs on a truck!
 
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Output stages are discrete Class A, rest is opamps (and coils)

Where are the discrete parts? Are there dual transistors in the heat sinked DIPs? The pinout or what I can make of it doesn't match any discrete that I know of. Looks more like a power buffer like the LT1010. Fixed bias? They aren't even using IC's in cans or ceramic packages. Where are the coils? Are you sure this isn't just the servo?
 
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