John Curl's Blowtorch preamplifier part II

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#99,061
Markw4 said:
Full of it in what way? Some of them may have not have imagined some reproduction artifacts they don't like the sound of. In trying to figure out some causal explanation, its likely some or many of them have arrived at mistaken beliefs about some of the underlying mechanisms. I would probably agree with that.

On the other hand, if by "full of it" you mean they are imagining the existence of every low level reproduction aberration they claim to hear, that would seem unlikely.
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Yes, mistaken beliefs about the underlying mechanisms. There are many people on this forum who are completely convinced of things such as: op-amps sound bad, op-amps sound bad when used as I/V converters, sigma delta converters sound bad, switching power supplies sound bad, digital filters sound bad, etc.
 
#99,062
zenelectro said:
The DAC1 used AD1896 ASRC which was the first really decent ASRC chip.

By the sound of their marketing blurb, one would think they cooked their own ASRC but you are right. I just did some searching so apologies for re-hashing all this. Does anyone know what the effective jitter rejection CF is on the SRC4392. G Marsh did some specific testing years ago.

T
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Yeah, the newer ones all use the SRC4392. I can't recall the exact source, but I believe the SRC4392 has good jitter rejection and the TI ASRC core that debuted in the SRC4192 was supposedly updated at some point to address that perceived deficiency. I think Bruno Putzeys did say that in his original testing of the SRC4192 that the chip had two filter modes and would have good rejection with small amounts of input jitter anyway.
 
#99,063
What designers are concerned about is improving products, not saying that products are perfect as they are. I appreciate some of the suggestions here regarding the 9038's potential problems. I also have looked at the schematics and see other potential problems. I will address the op amp potential 'problems' first, because I have the solution in mind already. I hope to find if there is any audible difference.
Of course, Scott would not even consider a Benchmark for playback, it is too good for the human ear, just as it is today! '-)
 
#99,064
scott wurcer said:
Why do we continue to have mainly folks sitting in their ivory towers doing sighted listening and pontificating on what they hear as irrefutable fact. I've given up on "mistaken beliefs about some of the underlying mechanisms" with folks that should really know better.
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Scott, what can-you say between two amps, one with less distortion than the other ? Just that one has less distortion than the other, it is easy, reassuring for an engineer and this can be "irrefutable fact" if the measurement has been well done.
Witch one will sound better, if both are low enough distortion ? No idea.

And neither you, because no one knows the distortions audibility thresholds etc. ?

The name of this forum is DiyAudio. So it seems normal to me that we talk, from time to time, about subjective listening impressions. Because, yes, we can use 'operational amplifiers', but we use-it for audio.

I was a customer of AD and PMI. But my orders were not based on your (nice) data sheets. Numbers are useful to make a présélection in order to find parts that match technical needs. The final choice can only be based on subjective listening, thanks to the samples.
Well, who consider his choices as "irrefutable facts". We can just hope our preferences in a given situation will match the ones of our customers.

This said, I agree with you if it is about snake oil, or strange things like Bybee magical, op-amps sound bad, cable's sound, silver is better etc... But what's the hell ? Near everybody smile. ;-)
i believe we all have our little quirks ?
 
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#99,069
The operating pressure (peak) for the 10mm pistol with the 135 gr (doubletap) FBI load is only 33,000psi (SAAMI). At the muzzle it will be much lower.

The muzzle Velocity is 1600f/s.

So does the rapid expansion of the of the gas under pressure create a shock wave with a greater velocity of propagation than the absolute pressure differential?
 
#99,073
That .22-250 is the one cartridge I want, preferably in a Remington 700 series varmint rifle. Right now everything is chambered in .308, .303 Brit and .22 LR. The .308 will be very close to the .22-250 in loudness I would think.

It will be the big test one day. I have to see if my shoulders have healed enough to shoot with. Otherwise everything may as well be sold off. 🙁

-Chris
 
#99,074
sorry to hear about your shoulder Chris.

.22-250 should be easy on your shoulder. The projectile mass is low.

I used to shoot 45-70 with a 470 gr projectile in competition (BCPR). Pound through 150 rounds in a weekend and you are talking sore, even with a chicken-pad.
 
#99,075
Hi Chris,
For a demonstration, I fired a single shot from a 32 ACP indoors and in the dark (special circumstances).

After that one shot, I was blind and couldn't hear anything. So forget follow-up shots in the dark! Anything you would fire after that is a blind shot. You'd probably do better squeezing your eyes closed and blasting away afterwards, but your rounds are very likely to strike something or someone you don't want to shoot. That was a .32 ACP, I can't imagine what it would be like with a 9mm or .45 ACP. Blind and deaf longer I would imagine. Not a good plan at all.

So to sum it up, fire a shot in the gloom and you will be completely helpless.

-Chris
 
#99,076
I once went through 32 rounds of .308 in an afternoon. My chest-shoulder was one massive bruise. It was a great afternoon. Not a mark on my cheek, but any more and I probably would have developed a flinch and a face bruise.

So the .22-250 recoil is lighter? Sharper I would imagine. A semi-auto would be even easier to fire. A Browning BAR might be a good rifle for me.
 
#99,077
I also shot DCM on several occasions in order to get an M1-Garand through DCM. Range was 300,600,and 1000 yards. Total rounds was near 125 including sighters.

I shot M14-M1A using a 168gr BTSP with 41.5gr IMR-4064 at 2750 f/s(?). The trick is learning how to pull the rifle into your shoulder.

The M14-M1A has more perceived recoil than the M1-Garand, even though on paper it is less. I attributed it to the relationship of the thrust line of the barrel to the rise above the but-plate causing lower muzzle rise but more direct recoil.
 
#99,080
The Ar-15 has almost no recoil and minimal (considering...) overpentration. In many countries legal ownership is a potential problem. No defense caliber firearm is really safe to fire indoors, especially in a residential area. Every round is your responsibility, wherever it goes, and there are no "accidents". As of course you already know, but is often forgotten these days in some places.

All good fortune,
Chris
 
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