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Everything posted by kevin gilmore
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pico vs predator, real measurements
kevin gilmore replied to kevin gilmore's topic in Headphone Amplification
Ray has sold more than 800 of them at $295 each. === $236k Thats the biggest and only plus point i can think of. Unity gain and less power than what you hook it up to... -
pico vs predator, real measurements
kevin gilmore replied to kevin gilmore's topic in Headphone Amplification
Ray is one of those people that likes to count his chickens before they hatch. And he likes to sell at least 500 of a portable before he moves on to the next one. So if he could sell 500 @ 425 that would be $212K justin is eating into that at a rate of more than 50% so ray will be lucky to sell 200 @ 425 and that would be $85k. So ray is by the way he measures stuff at least $127k in the hole. -
pico vs predator, real measurements
kevin gilmore replied to kevin gilmore's topic in Headphone Amplification
My guess is that one of those two vendors is not happy at all. -
Yes the prototype is in the basement. But really it was so much easier to buy a pair of bigass krell monoblocks. The older i get, the less i build stuff especially if i can buy it instead. Which means justin owe's me at least 4 more amplifiers. (all electrostats)
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Design of the B24 and my uberamp of about 6 years ago, virtually identical. Especially the cross coupled feedback with all the benefits from that. Uberamp scales very nice up to about 800 watts per channel into 8 ohms. With appropriate parts and +/-125 volt rails the B24 will do the same thing. Plan on many square feet of heatsink. And a power transformer that requires 2 people to lift it. As shown it is good for at least 100 real watts rms per channel into 8 ohms.
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The Headcase pico Lovefest: Post your impressions here
kevin gilmore replied to thrice's topic in Headphone Amplification
The least he can do is send me front and rear panels for the amp, and maybe a cardboard box for the power supply... -
The Headcase pico Lovefest: Post your impressions here
kevin gilmore replied to thrice's topic in Headphone Amplification
Here is one for you, that you might not expect It is the only DAC/amp combo that i have tested (and i have tested a number of them including a couple of 2704 versions) that works with a SunBlade 1500 and Solaris 10. Which is very convenient for me... Not sure why the others don't work. -
No i have not said anything to Ti about this. He either should know about it, or will soon. Ti ==== Ti Khan. TI ==== texas instruments There was a very long thread on the nelson pass forum at diyaudio.com which i'm sure is still there about how TI desperately tried to stear clear of nelson's patents on a particular chip, but were unable to do so and ultimately licenced nelson's patents. I think that nelson is a reasonable person, and for diy like things (as in virtually no commercial potential) he is likely to give his permission. I have seen him do so in the past. But if you don't ask first, well....
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Yes it is sweet. However it absolutely violates Nelson Pass's SuSY patent. (in fact so does my Uberamp) So if he wants to sell boards, he had better talk to the man and get permission first. TI ended up paying nelson big bucks to buy his intellectual property on this issue. I still think i can show prior art and that nelson's patent is null and void, but that is a legal battle i would never want to fight.
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pico vs predator, real measurements
kevin gilmore replied to kevin gilmore's topic in Headphone Amplification
Dac's both powered from the usb port. Both units run from batteries to avoid any possible ground loops. Same intel based computer used for both. I think i know what all the IMD crap is on the predator, but until i get some time to test and verify, i won't say anything. Lets not forget that jude absolutely loves the predator. Can anyone continue to trust jude's recommendations at this point? Slightly biased maybe, no never... I think it is the same problem where the predator makes lots of hiss on some laptops... All i have to say is Induced Harmonic Compensation. Yeah, that's it... Ray is copying Rudistor. Truely classic. -
pico vs predator, real measurements
kevin gilmore replied to kevin gilmore's topic in Headphone Amplification
Actually this is exactly what you would expect from a tle2426 (or compatible) rail splitter that has to fight a low impedance load. Ray decided to seriously lower the values of all the feedback resistors on the opamp such that at medium and high gain positions each channel puts about 120 ohms of internal load to ground. That is 60 ohms that the rail splitter has to drive before you actually add any headpones. So without any tantalum low impedance caps on the output of the rail splitter where they would actually do some good, the output of the rail splitter is going to sap up some of that seperation. -
Done by a 3rd party who happens to own both units. Someone I trust who has no hammer to pound with. I see no reason not to post this, as it should be clearly duplicatable by just about anyone. http://gilmore.chem.northwestern.edu/picovspredator.htm
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I'm not done yet, more sillyness to follow. Since i have a NC lathe at my disposal i was thinking of making some bells to ring with the hammer. Turns out the science for making bells is very complicated.
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Got to start watching those cut and paste's... Actually with the glass shop at northwestern university shut down, i have stashed one of the 3 glass lathes. So i do in fact have the necessary stuff including bakeout ovens and turbo pump down systems to actually build tubes. Even have a 50 year old RF generator suitable for flashing the getters. The nichrome wire and the rest of the stuff is easy except if i want to do thoriated filaments or indirect cathodes. The cathode material is nasty. Getting new getters probably not so easy either. The bug and butterfly were cloisene'd enamel.
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with that video of a home made tube going round these days... (and it turns out that guy was someone i worked with back in the midwest hifi days 30 years ago) I figured i would show a picture of a tube i made by hand in 1976 (at zenith) Has a couple of bugs in it. (actually a bug and a butterfly) http://gilmore.chem.northwestern.edu/tube1.jpg http://gilmore.chem.northwestern.edu/tube2.jpg Proving without a doubt that i was nuttier, longer than just about anyone. (made from picture tube necks)
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I managed to get one of those hd-dvd players at wallmart for $99. Did not even have to wait in line. Just for chuckles i bought it. Filled with software bugs like i've never seen before. Won't even play one of the startrek remasters (which are glorious by the way) all the way thru, you have to go back to the menu and play it title by title. Think the blu-ray players are any better, think again. Go to avsforum and look at all the titles that various players won't play, or do stupid things with. Its not the price for me, i want something that works right out of the box and not have to install firmware every week for the next year. Plus some of the firmware fixes allow some disks to play, and then break others. So if you want to watch disk A you need this rev of firmware, and this disk you need a different rev... But evidently you can't go backwards in revisions on most of the players. The only player that works perfectly is the PS3. Very sad. By the middle of this year you will see lots of blu-ray players for $299 or less. In fact you can buy a blu-ray computer drive for that now...
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I started counting headphones in that picture, came up with at least 21, probably more like 30. Then i started counting everything in my house, dynamic and electrostatic, and can come up with almost that many. What i'm obviously sorely lacking is enough closet space to do that. I would have to throw out half my wardrobe (ahem) to pull that off. Damm
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Thanks billy, It really means a lot to me. Maybe I'll let you play with my new hammer. (i just got a couple of miniature pumpkins) http://gilmore.chem.northwestern.edu/hammer3.jpg
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Does 19 pair of electrostatic heaphones and a pair of esl 63's qualify as an electrostatic fanboy??
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My opinion is that all the meridian cd players i have seen are mediocre sounding units with a fancy front panel and a price 3 or 4 times what they are worth. What did you expect from tuberoller's massive pitch for them at the time. Still has not worn off. And lets not forget the $50 computer cdrom drive as the transport. There is to this day no fully complementary silicon process. You cannot make perfect npn transistors AND pnp transistors on the same piece of silicon at the same time. One has to be lateral, and the other vertical. So most opamps are virtually 90% npn transistors. No matter how hard you try you are not going to get identical slew rates for rising and falling edges. If you are in the fully differential, fully balanced, fully complementary camp as I clearly am, then opamps are not going to cut it for the seriously high end stuff.
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From the duracell and prismatic web sites... duracell alkaline 9 volt battery internal impedance 1.7 ohm duracell aa alkaline .12 ohm duracel aaa alkaline .25 ohm have not found the numbers for the carbon zinc versions, but it has to be much worse. lithium ion prismatic .06 ohm Now to find the ESR of that 15000 uf cap...
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Certainly not compared to lithium batteries.
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hornet does not have any output capacitors. Neither does the tomahawk or sr71. raptor and b52 have output caps. 50 to 100uf. electrolytics. all of mikhail's tube amps have output caps. He typically goes much bigger. 470uf.electrolytics. the zana deux has a 50uf output cap (i think) Bigass film cap.
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Both true and meaningless in this context at the same time. If the capacitor was an audio output cap, or coupling cap, then the change in the dielectric might be audible. Across a battery with a relatively low output impedance none of this applies.
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Of course the numbers are doctored. I've yet to test a rudistor amp that comes within 30% of rated specifications. Same thing with the complete bullshit numbers on the apache. >120db signal to noise ratio. Absolutely impossible with an amplifier with a gain of 65db. Fact is even under the best conditions, johnson noise will bring the signal to noise ratio down to about 108db. Unless of course you plan on running the thing in a bath of liquid nitrogen. 2hz. Again absolute bullshit. Those chassis are what about 1.5 inches thick. Output caps big enough to give 2 hz frequency response would be bigger around than the chassis depth. Or really shitty electrolytic caps. How about that power supply. Anyone see any chokes on the top of that supply. They sure aren't going to fit inside the case. Which means that if the supply is actually regulated, then it is solid state that is doing the regulation. Completely ass backwards. You might want solid state rectification, but you want a pass tube for the power supply if what you are after is the tube power supply sound. Rudi's opamp unbalanced/balanced to balanced input stage has a gain of 13db. At least the version in his latest dynamic amp does. All the voltage gain in that amp is all in the cheap opamps. It may be built better (because its actually built in the UK) than the old junk, but it is still a piece of shit. A very expensive piece of shit. Somebody will buy one sooner or later, then we will get pictures of the insides. If rudi is not showing pictures of the insides like he has done with some of his other units, you know there is a reason.