John Curl's Blowtorch preamplifier part II

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Interesting. It would be interesting to know some numbers (peak current levels, for instance). Why do you think it was because of asymmetric signal (maybe making you turn the volume up higher for subjective signal level?)
Could be. I was quite astonished at the peak to average on a single played note by trumpet or trombone---something of the order of times 8 to times 12 in voltage! I should add that I didn't hear that much of a problem, but the peaks were barely being accommodated.
 
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I was not familiar with the brand of speaker. Nice rosewood finish. Decent sound for a two-way.

For the trade show Andrew Jones loaned us a good-sized pair of his. It sounded quite decent, and I was told that people came into the room with many of them sneering at the little circuit board and heatsink, and the absurd transition between the connectors to anaconda-sized cables snaking across the room, from Audioquest (complete with their battery packs, not, I stress, my selection). The amps were derived from an IR reference design and managed less than about 30uV unweighted of output noise. The Bel Canto DAC also on loan strongly dominated the overall output noise, which was detectable in a quiet room if you put your ear next to the tweeters.
 
There are reasonable changes in one's gear, but there was a certain discussion about changing rectifiers making *huge* changes that makes it pretty much impossible for me to take your listening impressions seriously.

You're welcome to setup a time with me, and I'll demo the difference in diodes for you. I upgraded a guys amp (made be me) with diodes and a larger common mode choke, I asked him if it was worth the price, he said, "it was more like a $3000 upgrade." So I assure you it's not just me. BTW the difference in the CMC'S was icing on the cake, it wasn't the leaping difference in sound the diodes made.

Guess I'm totally crazy with my brain leaking all over... After all the fellow isn't a PHD who performs a double blind study to check differences in his personal stereo, to confirm he's enjoying it... :rolleyes:
 
I enjoy my stereo just fine, thanks, and the more I play around with it, the more I enjoy it. But you won't hear me say that it makes a huge difference (3k could mean an entire system, which would be a big change or it could be absolutely no difference in sound... money at the high end is utterly divorced from performance) unless I back it up with some measurements.

Likewise, if I enjoy the music, I could hardly care what the equipment is.
 
I never said they don't measure differently.

$3k isn't much $ for retail. I've priced out things not using any non-measurement-zone parts that cost that much, in just parts. $3k for DIY might get you something special though if spent right. His speakers are $3.2k, so the stereo is a FAR cry from the diminishing returns/bad you're talking about. He's a big Bel Canto fan, who's a measurements sorta guy.
 
Step one: prove the higher end stuff actually more revealing. :D

I mean my speakers are seas excels and a SS9500 tweeter. Pretty dang good stuff.
Computer + decent, albeit generic sound card and an older panasonic class d amp that I use for multichannel amping. I know how horrified you all are.
 
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not all of us have your magical imagination when hearing things, either.

That kind of language may have a tendency to incite more insults. What do you expect him to say back? "Oh, you're right." Or more likely, "It's just that not all of us are stone deaf like you." And then you get to think up something worse to hit back with, and so on. We could do that, but do we really want to?
 
Of course I shouldn't have written that if I didn't want to incite a riot. So, yes, I am helping to perpetuate the cloth vs golden ears. But the irony of someone wanting reconciliation out of one side of his mouth and calling people who wish to have measurements to validate claims idiots out of the other is a bit too rich. At least some members are honest enough to throw the baby out with the bathwater.
 
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Know that feeling. If I were flush I'd have snapped up the pair of Gedlee Nathans currently for sale on this forum. For my limited space they are possibly the ideal solution. And pretty efficient. Oh and would offend many sensibilities as they appear to break many rules are were designed by science rather than the marketing guide to high end audio :)
 
God/Buddha/FSM forbid you offend the cost-at-all-object crowd. :D

(Yes, I acknowledge there are plenty of very expensive, very well performing systems... there's also a lot of rubbish)

I mean, soon enough I'll be gainfully employed, but until then... (and after that I'll live pretty much the same anyhow)
 
Daniel, I have been in your situation, but I was not completely satisfied with it over the decades.
It reminds me that I built my own Eico oscilloscope kit back in 1962 and used it for years. It wasn't perfect, but it did the job well enough, I thought at the time. Then someone loaned me a Tektronix 585 oscilloscope and I realized how much more I could do with it, and my Eico went to the back shelf.
It is better to have 20/50 vision than be legally blind, but don't think that you are in the best position to see differences. It is the same with sound systems.
Close by my place is a new audio shop, Berkeley Stereo, who deals almost exclusively in used equipment, going back to the beginning of hi fi. Everything sold there works, and is usually reconditioned to look almost like new, but it does not sound like a SOTA hi fi playback system. It is interesting how each electronics component sounds kind of different, yet many here would think that they all should sound pretty much the same, given the 0.1% criteria, and 20-20K frequency response. Not necessarily bad, but often opaque, or colored in some way. Yet, I started with this sort of equipment, first buying it used while in college, then working in a hi fi store that sold and repaired it (tubes mostly), until I finally started making my own designs, and retiring my Dynas, Fishers, etc for better designed and sounding components.
Once, 25 years ago, I had a SOTA system, but it was destroyed in a California firestorm, so I had to start all over. Well, back to used Dyna tube amps, second hand speakers (loans), inexpensive Grado cartridge, donated turntable, etc.,and yes Radio Shack wire to connect it all. After a year or so, as I recovered the rest of my life, I started improving my system. I got one of my old preamp designs used, and one of the power amps that I was currently designing for Parasound. I upgraded the speakers to something somewhat better, and finally after several years, to the WATT 1's that I bought used. I could have stayed with these speakers, and I still have them, but I was given something even better that I am still working on. The point is that even when I had replaced the reference hi fi that I had lost in the firestorm, I learned by living with the inexpensive replacements, once again, what I had missed with the early system of my college years, and that to be happy with my system, I had better try to work to make a better audio system, and I continue to do so today.
 
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On the subject of power or current requirements, I think there's a thread here (or maybe it's at AVS forums?) about what kind of PEAK amplifier power we actually use. Using the fact that a DAC can't produce more than its FS peak value, and using the volume settings people use to listen with, and a voltage measurement of a FS sinewave with that volume setting, the resulting value determined by all who tested was rather amazingly low.

Related, a couple of years back I made a very fast clipping detector circuit and mounted it my power amplifier, along with a 2 second pulse stretcher so I ccould know when the amplifier clipped, at all. 100W ampllifier (at 8 ohms), 4 ohm speaker, about 86dB SPL/1W/1m. I found that it never clipped at any level I listened at. I blasted it with some R&R at high level to make sure that detector hadn't broken -- the sound when if finally tripped was very much louder than anyone in my house (and probably my neighbors) would tolerate.

The speaker was a mag planar (not ribbon) type above 350Hz, (dynamic below that), and the impedance didn't dip below 3 ohms, though, so there are sure to be speakers and carefully selected program materials that could make it clip at muck lower volumes. But still, I was amazed (and stopped worrying about whether my amps had enough power or could deliver the needed current to keep the feedback loop tracking).


Seems at odds with what I've seen on a 'scope while playing certain music sources.

I've seen clipping fairly often with moderate power level amplifiers.
In addition I think this plays a reasonably significant role in how amplifiers are perceived subjectively - because they are often driven into the "rails".

(one "advantage" of a triode in A2 or AB2 is the "compression" effect on peaks - never a hard sharp clip, as one can see with bipolar amps)

With the simple assumption of 90dB/1/1m, and assuming for the moment that this is a sufficient level for average listening (probably it is low since you're not listening at 1m distance) also assuming an average to peak level requirement of 20dB, then the amplifier power required to avoid clipping is ~128watts. Once you go from 1 watt to 2 watts, we're up to double that, 256watts. Your speakers were "86dB" so I would expect that to avoid clipping you'd have needed more power.

Of course if you are using commercial recordings, the average to peak is usually "governed" so that may explain why you did not see clipping?

Also, not sure what sort of "pulse stretcher" ur referring to, but recording studios (as you probably know) used "peak hold" circuits on meters for this same reason... (being able to "see" a transient peak).

_-_-
 
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