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kevin gilmore

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Everything posted by kevin gilmore

  1. Kevin's review of the B52 from the pictures ray has posted. THE GOOD The aestetics of this unit are very nice. Still way to many ray samuels logo's and the logo's are way to big. But i happen to like the looks of the thing. KG's rating---- A- The quality of assembly, the quality of the parts, the quality of the layout. Outstanding. A particular company north of the border should look at how things are supposed to be done. KG's rating---- A At least the box is finally big enough so the electrolytics won't burn up due to the heat. Still a few more holes in the main board would definitely help. THE BAD Circuitry description. Differential amplifier on the input. Turns unbalanced signals into balanced or amplifies balanced signals. Output capacitively coupled to the 4 channel dact step attenuator. Output of the attenuator goes two places, one is the cathode follower preamp output stage, and the other is the balanced srpp headphone amplifier stage. KG's rating ---- C- Yes in fact as far as a headphone amp is concerned its 2 raptors in one box. As a preamp it has a cathode follower output stage, so it actually really behaves like as a preamp. Output impedance of about 2k is far better than the 100k impedance of the stealth. I feel sorry for all those stuck with stealth's which are now completely worthless. Yes the headphone stage is TWO SRPP stages in series with TWO output capacitors in series with the headphone. Double the output impedance. Double the slush bucket bass into low impedance headphones. THE UGLY What is this thing. A preamp?? If so where is the remote control. A Headphone amp?? Where is the low output impedance. Instead of doing one thing right, it does two things wrong. First thing if you really are going to use it as a preamp, chuck the 2 x 12au7 preamp output tubes and replace with 6n1p (after dealing with the filament voltage issue). But really with the same number of tubes and deleting the headphone output it would be easy to design a new board that fits into the same chassis and turns the thing into a conrad johnson clone. Plenty of room now for composite triodes. FOR A FEW PENNIES MORE ray could have actually added 2 wires into the power supply cable and avoided contaminating the high voltage ground with the grunge produced by the ultra cheapo fillament switchers. The B52 really is the best thing by far that ray has ever done. Stereophile should eat the thing up.
  2. Aerius please pay attention. That tube is completely and utterly useless for otl audio applications. Look at the Rp. Look at the fact that the sweet spot is 2500 volts and about 500ma. Decent output caps for that thing would be about the size of a gallon of milk. EACH.
  3. Rayvistors, right you are. I still can't find any of the boxes... But here is a new one. JVC's brand new 1080p 3 chip dila projector is called the "RS1" about $10k list, 8k street. I'm on the list for one sometime in early february.
  4. Yes i have designed one. The wj211 tube last time i checked was about $8900 each. You need 2. 4 for balanced.
  5. yes i believe in some current production tubes. Unfortunately virtually none of them are usable for audio unless you are completely nuts. Eimac (now independent again) makes wonderful ceramic triodes and tetrodes. The new western electric makes some pretty good 300B's. Way better than any other chinese junk, but still not as good as the originals. Hammamatsu makes some truely amazing products. In fact they make an amplifier tube so linear (and 50 ohm output) that works great as a headphone amp tube. Trouble is they are about $650 each. You need 2, and they would last virtually forever. Watkins-Johnson makes some very nice stuff too. They also make a 50 ohm output ultra low noise amplifier tube. You don't want to know the price.
  6. I agree with number 4. There are however tons of tungsol NOS 6080's available.
  7. I believe they were called hornets. I have a few somewhere.
  8. Actually it is still up. I figured someone would have taken it down by now. The people at the kindercare next door were all cheering my sign. I thought the area i live in was died in the wool redneck republicans, but maybe not.
  9. I put this up yesterday afternoon. http://gilmore.chem.northwestern.edu/impeach.jpg
  10. Could it be that adding a tube preamp with a high output impedance driving solid state monoblocks with whatever cables were used significantly changed the frequency response and what you think you were hearing was actually a change in tonal balance?? Fact is that there really is only one tube otl preamp out there with an output impedance less than 200 ohms. And its not cheap.
  11. billy i have found the perfect iem's for you to go with your new tomahawk... http://www.audiocubes.com/product/Elecom_EHP-AIN30_Rhinestone-Studded_Heart_Eardrops.html
  12. I dunno billy, there are so many better REAL tube/solid state balanced preamps available Here are three Audio research LS17 all tubes $3995 BAT VK30 all tubes $2995 Pass Labs X2.5 solid state $3990 All of which have a low output impedance and are actually capable of driving cables and power amps.
  13. The head-fi ray samuels marketing machine will be there to help ray sell the b52's. That and i bet stereophile will just eat the thing up. Then again, maybe not. As a preamp its output impedance is going to be way to high. A CJ-ART it isn't. I estimate 50k ohms. quoting conrad johnson "Even high-conductance triode tubes (such as the 6DJ8 and 6922) would normally have too high an output impedance. The traditional solution is to add a buffer stage (cathode follower) to the circuit. What we have done instead is to construct a composite triode made of several sections of 6922. Each doubling of the number of sections reduces the output impedance by a factor of two. The ART uses 10 sections... the Premier 17LS uses 4. In the case of the 17LS, the resulting output impedance is about 800 ohms." Yet i expect it to be priced more than the 17ls... No remote control, no input switching... As a headphone amp it is 2 raptors in series. What's worse than one raptor And the tomahawk, how many people will buy that piece of shit and not pay attention to the fact that it won't drive regular headphones and want to send it back. And as far as krell, ray's thing is definitely a slap in the face of real gear. I'm planning on a fork lift upgrade coming in february as soon as i can get a firm delivery on the new jvc HD projector with 10k:1 CR. Then a new krell preamp and a pair of krell monoblocks. All my current krell is now 7 years old...
  14. And while i'm at it... 5 wires between the amp and power supply chassis. only ONE shared ground wire between 2 asychronous switching supplies that are guaranteed to sing to each other and 2 x 250 volt high voltage supplies. One of the main ideas with a balanced unit with dual mono power supplies is seperated grounds... ?
  15. Someone just pointed this out to me... On the power supply, male pins with 250 volts DC on them. Ray had better fix that before someone dies...
  16. Does anyone think it is a very lousy copy of this?? http://www.krellonline.com/krell_component.php?id=87&page=EVO202
  17. Filbert at that other forum has said this (probably soon to be deleted) I'm not trying to troll you guys or make your lives difficult or whatnot. When I comment on something, it is in an effort to be helpful to the person I'm responding to. My comment was out of a genuine interest and concern. The current a portable amplifier outputs is going to come from the batteries, and the batteries are limited in capacity. In order to achieve a desired battery life, your current draw is going to have to be sufficiently low. You have to take into account not only the quiescent draw of the amplifier circuitry, but the draw of the headphones as well. As a result, based on the duration quoted here, it seems that it would have to drive your IEMs on a couple or few mA of current (depending on battery capacity), which is probably doable, but then there's a question of why you need an amplifier in the first place since many devices' internal amps will already source and sink that much current with pretty decent linearity and they're designed to handle the sort of load a headphone brings, whereas many micropower op-amps aren't (and even fewer could do so reasonably well). In order to get the equation above that level, it would take AAAs of a capacity I've at least never seen before or seen anything even close, but I'm not ruling out the possibility. I mention micropower op-amps as they're about the only thing that will get this low a quiescent current at this voltage, as well as the use of some of them might help explain artears' comment. I considered the use of micropower op-amps in some of the circuits I built over the summer, so I'm not unfamiliar with them. Thus, to me at least, it seemed as though my comments were reasonable. I would have made them irrespective of who made the amplifier. People who talk to me regularly I imagine will tell you I discuss the designs of a variety of devices, not just Ray's. I have to agree 100%. Many of the ipod and ipod like things i have checked into in the last few hours have at a minimum 4.8 volt batteries, most have 6 volt batteries, and i even found one with a 7.2 volt battery. All of these devices are going to be able to drive headphones better than something that runs on 3 volts.
  18. From a lousy picture i was just shown it certainly looks like one big electrolytic (evidently ray's trademark) even though AA batteries really don't need it and one 8 pin soic package. So its not the maxim part, but it certainly could be the boomer part, or an ad8617 if he uses the split between the batteries as ground. The input and output jacks are the same kind of jacks that i have on a couple of my video cameras. They do seem to work, but boy are they cheap. So i'll downgrade my parts cost to $25 Evidently ray is trying very hard to keep decent pictures of the board from ever showing up. I guess i don't even understand why he is making such a product. Its probably identical to the chips already in many of the ipod and ipod like devices, whats the benefit??
  19. The energizer non rechargable lithium l91 batteries are 4500 mah... at a current of 7ma you can certainly run a max4410 on these batteries for 400 hours. We will all know whether or not he is using a rail splitter on 3 volts as soon as a picture is taken. I'm sure ray needs new advertising to spruce up sales...
  20. Nope, not an ad8397 as that can't run on 3 volts. My crystal ball is warmed up, so i predict the following Just about has to be this chip http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3459 Will know once i see pictures of the board. Which i will see sooner rather than later No rail splitter necessary. No honking big cap either. Total cost to build $30 Initial introductory price $199 Thereafter $250
  21. Its the simplest of SRPP designs. It sounds like all amps of that particular topology. The output cap is size constrained. For high impedance headphones it is ok if you like that type of sound. It is nowhere near as bad as the hr-2 or hornet. It is not something i will likely listen to again. If i had to grade it i would give it a C-. There are so many things i would give a D- or F to... I think that fits into the "fairly good" range...
  22. Well when i heard ray's system about 1.5 years ago it was just plain awful. For a whole bunch of reasons. Absolute crap turntable. Not sure what cartridge was in it. Ray's $5k phono preamp with absolutely no subsonics filter. Seriously underpowered amplifiers that were wasting 90+% of their power whacking the woofers around due to the subsonics. 2 way transmission line speakers with dynaudio drivers that remided me of an old eton madisound kit... Now ray has replaced those seriously underpowered amps with new cary amps and has replaced the turntable with a high line VPI which i'm sure has a lot less rumble. So his system is now up to just lousy. The only nice thing i can say about ray's speakers are that they have a wonderful paint job. Which seems to be the only thing ray actually cares about, the look and feel of his stuff. Those are $8k speakers ray said. I own wilsons, B&W, quad esl63's and celestions. Trust me, those ain't $8k speakers anymore than the phono preamp is $5k.
  23. YES people 2 amps in series!!! An unbalanced amplifier drives one wire of the headphone and the other wire goes to ground. It has a specific output impedance. Take 2 of the same amplifiers and drive both sides of the headphone. The maximum output voltage swing doubles. The maximum available current does not change. The maximimum available power is 4 times. THE OUTPUT IMPEDANCE DOUBLES!!! Now if you have a solid state amplifier with an extremely low output impedance in the first place, doubling the output impedance has little effect. But when you have a tube amp with a 120 ohm output impedance (and you are kidding yourself if you actually believe that number for the raptor) you now have a balanced amplifier with an output impedance of 240 ohms. Really no kidding. This is how every single krell amplifier since the fpb series works. This is how every single solid state balanced output amplifier also works. (krell, parasound,big pass labs,crown....) If you really want to hear what a tube amp can do, get your hands on a pair of the small atmasphere amps and hook them up balanced to your headphones. You will be blown away. Circlotrons really work well for this.
  24. What do you expect when you take 2 amplifiers with an output impedance that is already too high and put them in series? Something that can't even drive hd600's...
  25. The whole thing is a joke. If you do replace 2 resistors in the raptor it sounds quite good with hd600/hd650's as you would expect out of the simplest of SRPP designs. For anything 150 ohms or less however it stinks. At least it does not start on fire anymore.
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