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Everything posted by TNRabbit

  1. OK, hard times are forcing me to sell these subs. First choice goes back to dkalsi per our deal; if he doesn't want them, it's open to the forum. $750.00 firm, you pick them up in Southern MD.
  2. That's called a "jog" wheel; don't recall seeing one on anything lately....
  3. I cannot believe you aren't getting enough slam from your setup. Somethign isn't right somewhere. Where is the sub located? What size/dimensions are the room? Got any pics? 95% of issues with "it doesn't sound like I thought it would" are due to improper speaker setup. We need more info to give you informed opinions.
  4. Why not a DVD player?? Any of the Oppo models are an excellent value for the money & will play just about any disc short of BluRay. Their customer service is exemplary. I picked a 980HD up on woot.com for $99.00 http://www.oppodigital.com
  5. http://www.samsontech.com/products/productpage.cfm?prodID=1735&brandID=2
  6. More amp than you'll ever use: http://cgi.ebay.com/Sunfire-Cinema-Grand-Signature-Series-II-19-5-Ch-Amp_W0QQitemZ270364778873QQihZ017QQcategoryZ14973QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
  7. ...I'd be scoping out that parking lot for a few days...somebody would be getting a baseball bat thumpin'...
  8. TNRabbit

    SVS help

    Personally, I would NEVER use a sub that size above 50 hz....
  9. Get one of the Marks-A-Lot or Sharpie King Size permanent markers with liquid inside. They are BLACK and don't have that blu-ish tint...just touch it to the bare spots but don't go over the black areas. It will "bleed" into the open wood.
  10. It is my undestanding that practically ALL output tubes are microphonic..?
  11. I agree completely with this assessment. In addition, I thought the second recording was a little bright, possibly due to the apparent live nature of the room/hall....*SEE EDIT BELOW* Of course, that version of "Claire de Lune" is one of my all-time favs for piano, so maybe I'm a little biased... [] EDIT: I've had another listen, and I don't think it's fair to use these two different performances to compare recording techniques; they are too dissimilar. #1 was recorded under the piano top while #2 sounds like it was recorded for 30 feet away. There are a lot of unnerving room reflections in #2. I noticed in one of the particularly rambunctious sections of #1 that there was overmodulation; was this the original recording or the re-recording (this sounds like an old 50s or 60s performance)? There are too many questions here to make an informed, unbiased evaluation.... 2nd EDIT: Armed with the further information stated about these recordings, I went back & listened on a pair of headphones (AKG-K701), I find the File 1 recording much more enjoyable to listen to, with the exception of a GRANDLY irritating distortion/buzz (overmodulation?) in the right channel which may or may not be part of the process of copying to mp3. I find it hard to believe that could be on the original recording... I just wasn't as happy with the File 2 recording. The imaging/phase shifts were very disconcerting.
  12. This is already posted on every audio forum on the planet...
  13. I second Jim' sentiments[:'(] Looking at Bob's arms you would think they weighed 90lbs each He's not that big of a guy... ;-)
  14. I've had mine for almost 2 years now, and it's gotten plenty of workout. I've not had any issues with this at all. Is there something else that is near the left passive that could be causing your problem? Chemicals, fumes, etc.?
  15. Interesting Q&A from the auction: Q: Hi Bob... glad to see the latest set of amps here on the BAY! I wish that I could run a set of these for even a week! Are they able to be strapped together so they can run a set of speakers that need a common ground design amplifier? And have you thougt about a stereo tube design? Mar-12-09 A: Hi 'john1, Hope you like these red ones on the Bay! Yes they can be strapped, and yes I have thought about a stereo tube design for about thirty micro-seconds. The problem is they would be too heavy for me to easily lift if I designed them the way my inner voice says. Thanks for your enthusiasm... means a lot to me, Bob Carver Q: dear bob....I know what voltage you have to use on the output plates.....but what are you using for the screens?? Just curious cordially neal Mar-12-09 A: Hi Neal, I love questions about screen voltage because it gives me the opportunity to talk about screens. What I did regarding the screen voltage was to perform a series of converging experiments at the time I designed these amplifiers. The experiments were quite involved, but here are my conclusions: Ultra-Linear screens reduce the maximum output current too much for me, and hence the ultimate performance of the amp. Ultra-Linear screens also saddle the output tubes with dangerously high voltage essentially equal to the plate voltage, often causing catastrophic and unexpected arc-over failures. I don't like that. I concluded, for better or for worse, that Ultra-Linear was scant more than a money saving method simply because it eliminated a second power supply. As far as the triode-like output impedance that it yields, KT-88's with a DC restorer and screens fed from a separate power supply can easily yield performance superior to the best Ultra-Linear configuration. Stu, Tim, and my own experiments taught me that. I operate the screens at exactly one half the plate voltage, or 330 volts DC. Good question; thanks for asking, Bob Carver Q: Hi Bob - You are my hero!!!!, you and Nelson. I had an off the wall inquiry, can Joe work on old Western Electric gear? I'm a recording engineer and I need a WE mic pre spec'd out, recapped etc. can you get me his email? Thanks so much. Mar-12-09 A: Hi '265, I felt like a hero yesterday, but today I cannot find my red cape and flying goggles, so I'll have to be a hero without them. You are making my day! Thank you '265. Joe can literally work on anything, especially old Western Electric gear. I'll forward this to him, and you are very welcome. Hero...Hmmm...Bob Carver Q: Do I need a pre-amp to run these? Can you recommend one if so? Do you have one? do you have recommended speakers for these amps? Can I call you with more dumb questions? I am new to the tube amp world anf have a few more questions. Mar-12-09 A: Hi 'comm, Yes you need a preamp. A vintage Citation I, Carver C-1, or Audio research SP-3. Others as well. I have lots of preamps. Their ARE no dumb questions except those that are never asked, so call anytime! Enjoy the tube amp world...it's lots of fun and very musically rewarding. Hope this helps, Bob Carver. Q: WOW, Bob Carver himself. It's great to see you back into tube equipment. I have a question about these amps, if you won't mind explaining. Sweet amps! Gorgeous! How do they get more power out at six ohms since they have output transformers that match loads? Thanks for your time, Chris Thomas - Texas Mar-11-09 A: Hi.... Hey, I just answered that question! Warmest and best, Bob Carver Q: WOW, Bob Carver himself. It's great to see you back into tube equipment. I have a question about these amps, if you won't mind explaining. Sweet amps! Gorgeous! How do they get more power out at six ohms since they have output transformers that match loads? Mar-11-09 A: Hi '33, Here's how: a pair of KT-88's are rated for 100 watts of audio. Since I'm using three sets for 180 watts, or 60 watts per pair, they are operating conservately and are substantially underloaded. Now suppose the amp is delivering 180 watts into eight ohms using the eight ohm transformer tap, and suddenly the load changes to six or even four ohms (as can easily occur in a complex speaker load) as the frequency changes. Now the amp is more heavily loaded, and the power output can increase to almost three hundred watts ON THE EIGHT OHM TAP! The irony is that if the speaker were then connected to the four ohm tap, the power would drop back to 180 watts. This tube amp is really surprising that way (in that the power goes up as the impedance goes down) as those six mighty KT-88's continue to deliver ever more current and hammer on unfazed. They can do that in large part because of the separate power supply for the screen grids. Great question, thanks for asking. Bob Carver More Q&A for the record. I don't understand this stuff but I'm sure it's pure gold to the tube guys: Question & Answer Q: Bob back again...so the solution was back to the sliding bias scheme to shrink the cathode resister as the tubes draw more current.. this time I use an led driver firing off 3 optocouplers which gradually turned on a transistor in parallel with the cathode resister.. a few extra resistore and trim pots and I got the same results lively dynamic sound ,efficient cool operation. This time around I abandond the big output tubes in favor of the russion military version of the 6bq5...I think they are fabulous. I just keep paralleling tubes to match what every Dyna OPT I choose, from the little bitty ones to the MK6 They are really tough.. I am using near 500 on the plates and 250 to 300 on the screens.. reading your description of you biasing scheme you MUST be using a sliding bias if you are idling at 25% normal...What is your method for shifting bias..just the general concept..your amps are the first I have ever seen in 20 years of looking over the world that got it right..... Mar-16-09 A: Wow! I truly admire your thinking and your tenacity regarding the age old bias problem. Your transistor idea across the bias resistor is nothing short of inspired. Do you sense current or do you sense voltage to turn the transistor on? I like your scheme because the delay that will naturally occur is rendered irrelevant by the energy contained in the the cathode bypass capacitor, as it MUST deliver the required current during the time it takes for the control circuits to respond and turn the transistor on. My DC restorer is not a sliding bias approach, rather its purpose is to keep the DC value on the control grid at design center even in the presence of signals that have a DC component. Thank you '541 for sharing your thinking with me and with all of us. Was a real treat. Best wishes and warmest regards, Bob Carver Q: Bob about the magnetic lag at the polarity flip...the solution was to use TWO transformers one for push one for pull each one never leaving one polarity...Did it make a fifference? yes it did and quite noticable (But not as much as the dynamic bias...) not very cost effective but worth it if you have the iron By the way ,when I say I hear an improvement I go thru eons of time setting up two identical amplifiers with just one change,in one of them ,making sure the levels are the same and blah blah blah the worst mistake to make is to THINK you hear a change based on MEMORY...Have to constantly make 'reality checks' and never assume anything. So at this point I quit audio and went 'underground' with life's necessities.. Next chapter: I surfased again again 10 years later thinking I was now in love with cathode bias scheme what with self balancing and 'plug and play' feature..Didnt' take long to realize that a big resister for idle wasn't cutting for heavy use.(continued) Mar-16-09 A: Continued next. Q: Bob..back again. so I could set the idle for 12 t0 15 ma and the max to whatever level I wanted even Way BEYOND what would be considerd safe or acceptable. This is where I thought it sounded the most lively and dynamic. Since the tubes were always trying to revert to the trickle bias condition (the troughs between the peaks, it was very efficient operation...one set of tubes should equal a lifetime. the heat didn,t seem any more than filaments at idle,,,no melting plastic cords here, and under operating conditions never did the plates glow and just faitly in the dark under heavy use,,,this is high voltage mind you. so it was the best of all world..best sound high effeciency ,long life At this point I had to put audio away having more pressing needs to look after,,,but not before I looked into the possibility of eliminating the the magnetic lag in the OPT just at the point where the push becomes pull and vice versa ,,this is where the magnetic polarity flips (contined) Mar-16-09 A: Continued next. Q: Bob..back again...so I could set the idle for 12 to 15 ma and the max on heavy peaks normalor safe even WAY BEYOND what would be considered acceptable or safe. This is where I thought things were really sounding good and dynamic....its as if the burst of bias current added to the signal induced flow of electrons...here the really interesting part..even under extreme conditions the plates never got to glowing,,in the dark just faint glow.as looong as it was music and apeech.. stedy sine waves was a different story...the thermal stree was just a fraction of normal run bias because the tubes were doing everything they could to revert to the idle trickle condition... this is going on every trough between peaks on the waveform...I could actually put my hand on a tube at idle, and although hot I didn't feel I was going to get burned most of the heat seemed to be filament this is really efficient operation and cool operation in my book.the best of all worlds ( to be continued) Mar-16-09 A: Continued next. Q: Bob...ok I'm back....as I mentioned pentode sounded the best and the strss on the screens was taken care of but with hi voltages 'normal bias' bias ran the tubes too hot....since I knew that the tubes sounded just fine with real low bias current when playing really soft (I mean each half still looked like class A on the scope) but quicly caved in when pushed. it seem obvious that what was needed was a sliding bias which would manipulate the bias depending on input...it needed to mimic the dynamic nature of speech and music... I couldn' find any information anywhere,,so I was on my own...the solution took the form of an led driver which sequentially lit up three leds coupled to three cadmium sulfide cell( I didn't know about optocouplers at the time) the changing resistance in parallel with one leg of a voltage divider in the fixed bias supply..I few resisters to trim things out and by gosh it worked perfectly...I could reduce idle to about 12 to 15 ma. ( to be continued) Mar-15-09 A: Hi Neal '541, Good to have you back! Your solution to the high voltage and bias problem is extremely creative, and provided you listened to it deeply, carefully, and found it to have just the right dynamics for music, speech and our human hearing mechanism, a tip of my hat to you Neal! Well done. Well earned. Bob Carver Q: Greetings again. I have another quick question for you about these amplifiers. I am currently running a pair of Carver Platimun speakers. Would I better off using these amps on my speakers using the original passive crossovers that are built into them, or would I be better off finaly bi-amping my speaker, and using these amps on just the ribbon drivers and using my existing amp for the bass drivers? Thank you for any advice you can offer. Mar-15-09 A: Hi 'io, Either way will work, but here's what I would do. Separate the woofers from the ribbons while retaining the passive crossover, drive the ribbon part of the crossover with these tube amps, and the woofer part of the crossover with your existing amp (probably a solid state amplifier). You would then be able to independently adjust the level of ribbon-to-woofer for the balance you like the best. Or you could bi-amp them and build an external EQ circuit. The EQ is necessary for the ribbons in order to voice them properly, and to blend them seamlessly into the woofers. This headache is avoided if you use the built-in crossovers (The work has already been done.) with just a small loss in drive voltage due to the passive nature of the crossover. And these amps have lots of power and current, so not a problem. Great question, Bob Carver Q: I have searched around on the net trying to find contact info for "Tubular Joe" to no avail. As a very pleased owner of one of your earlier brown sets I'd like to ask Joe some questions about their construction. Could you pass on my contact info, please? Mar-15-09 A: Hi 'rama, I haven't heard from you lately; it's good to hear from you, and yes I will tell Tubular Joe this afternoon. I'm sure he would love to answer any questions about the amp he so lovingly built. He is the best! Hope this helps, Bob Carver Q: hello Bob....near as I can tell , you put together an amplifier using the concepts I came up with about 15 years ago. I wanted to see what would happen with jacked up plate voltages on the outputs and soon ran into distressibg observations ....the plates were starting to glow even at idle and the screens glowing on and off like light bulb filaments under dynamic conditions...there had to be another way....then I found out thar el34s are perfectly happy with 800 volts on the anode and 400 on the screen...its right in the tube manual...I was surprized at how low the screen voltage could be reduced and the tube stll function fine.....Pentode mode allows this and I always thought pentode sounded more lively and musucal than UL or triode...I never could understand the infatuation with triode mode......both triode and ultralinear have a severe internal feed back mechanism working wihin the tube...pentode mode eliminates most of it to my understanding..(to be continued)...... Mar-15-09 A: Hi '541, Your love of amplifiers shows in your passion for trying different ideas, and you are absolutely on the right track! It took me awhile to notice that ALL the tube amps I really liked for sweetness, detail, envelopment and just full blossom power output always turned out to possess pentode output stages in their purest form. Pure classical! Q: oops i fell asleep during last message hope i didnt bungle it up Mar-15-09 A: Hi Randy, Yes you did, and I could not make sense of your message. The beauty of it all is we have all the time in the world, so try again friend Randy, and I promise to get out my Captain Marvel decoder ring and properly respond. Bob Q: Bob, One more question if you don't mind.... These are transformer coupled right ? What about OTL designs ? Mar-15-09 A: Hi'52, I love questions, the more the better! Yes, these are transformer coupled. OTL designs are great too, but Bob's my name and powerful amps are my game. OTL designs just don't have much current output capability, and therefore cannot easily drive difficult reactive speakers to satisfying levels. But that's just me, still, they can easily drive vintage horn speakers (and some others too) when we want to reproduce the sound of wind-chimes at realistic play-back levels. Feel free to ask more question, please don't be shy. Anybody! Bob Carver. Q: if you had your preferance would you run these with a set of brysyon 7b or the beautiful jewwls you hold. as the magnapan tympani 1 B are quite power hungry and i believe 10 watts at 96 db's could be off here a bit but it isn't much would these develop the lows needed to warm things up. i also realize that magnapan developed the tympani 3a's four panels of woofer material to off set the lack of lows in the ones i have. i would love your advice here. of course i have bi-amping questions i would hate to bore you with but i can run thre top end with either two bridged a-760's or two pm900s or run them ftraight with these or the brystons. i love ur stuff and genuis. randy hart Mar-14-09 A: Hi 'hart420, I'd hook these amps straight into the Maggies...the lows would warm up a lot because their impedance rises nicely on the low-end. The extra coherence and warmth you would get by running the amps full range into the Maggies would more than offset the extra volume level you could get by bi-amping. Bi-wiring (some units had bi-wiring capability, some did not) or straight in is my recommendation! Glad you love my stuff... hearing that helps make my day. Thanks for writing, Bob Carver. Q: Hello Bob, Nice amps. I have recently read that to control a speaker you need lots of amps (current). Like 100 A. What do these provide ? What is your opinion ? Thanks Mar-14-09 A: Hi '52, Controlling a loudspeaker is a complex, deep and non-trivial issue. Still, and just the same, the notion that 100 amps is needed is a false belief. The damping current required for total speaker control is never more than the peak input current at any given instant in time....micro-second to micro-second. That's why both two watt and 200 watt amplifiers work, and work very well. The maximum output current these amps provide is three times the maximum plate current of each KT88 (Three pair) times the turns ratio of the output transformer = approximately 26 amps p/p. Thanks for writing and for the illuminating question, Bob Carver Q: Hello Mr Carver, Thanks for the straight on shot (picture), You didn't forgst did you? It will certainly be of help to me. I will ever be greatful to you Bob. Best Regards, "jay" Mar-14-09 A: Hi Jay, I'm pretty sure I sent you a "straight shot". The chassis shot in this auction is the only one I have, and close inspection should reveal all. I now have an assistant to help me keep track of my promises, and if I promise to send you something she will make sure I don't forget. I hope I didn't already forget; if I have, let me know. Bob Carver Q: WOW, just like I want to build! I still own my Phase 400 from 1974 with warrantee cards. Anyway, Bogen used voltage regulation for the screens on the KO100 (2 EL34) and the DO-70 (2 EL34s). The DO70 uses the grid voltage sent to a 12B4A regulator tube to derive the screen current and the KO100 uses a winding designed into the power Transformer to an EZ81 rectifier tube to derive screen voltage. It seems that the design using the grid voltage (regulated via 12B4A) to supply the screen voltage is more stable. Since you have vintage iron, my question is: does your power transformer have a winding dedicated to the voltage regulator (DC restorer) OR did you just use the grid voltages regulated down to supply the screens (easier to do). The design I am looking at also uses a 6C4 also, which monitors the EL34 current. Did you accomplish the same job with a 6AL5 or am I off track. Thank You, Mar-14-09 A: Hi 'frank, I don't know who designed the Bogen amps, but I wish I did. He or she got it right: separate power supplies for the screen grids(often regulated), a very modern hi-tech output tube, British style stability compensation for the output transformer, nice high plate voltage,I could go on and on. These amps of mine have a separate power supply for the screens, which operate at approximately 330 volts. The 6AL5 has nothing to do with the screen voltage, rather it's purpose is to maintain the correct DC signal component on the control grids through the entire audio signal swing, allowing each tube to idle at about 11 watts instead of 32 watts, for any given distortion level and at the same time eliminating DC shifts and bounces. Hope this helps, thanks for writing, Bob Carver
  16. I absolutely cannot understand how a passive could "blow up" when the active driver did not, unless there is something REALLY wrong with the passive radiator. What exactly is happening to the passive? Do you have any pics?
  17. What's wrong with your RT12d? Those are relatively new; you shouldn't be having problems with it. Should be under warranty...?
  18. He's already sold3 or 4 pair; they've brought between $4500 and $6300.
  19. Yeah, they're HEAVY, too! I've seen a pair; they're about 48 lbs each...but they sound INCREDIBLE.
  20. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=180336122951&ssPageName=ADME:B:FSEL:US:1123
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