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tube fanatic

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Posts posted by tube fanatic

  1. I would love to get some of you guys in a level matched blind listening scenario! You wouldn't believe the conclusions that you would reach, some of which would shatter your current notions. And, to answer Dr. Who's question earlier, yes it is very possible to achieve the midrange/top end smoothness of a triode while maintaining the bottom end of tetrode/pentode designs. I often accomplish that for folks with SEP designs and judicious use of voltage feedback at the output stage only, among other things. Drop me an e-mail if you want to discuss the electronics behind this- the forum isn't the place for long tutorials. If you do, I'll try to answer within 7-10 days as time permits.

  2. I have the sense that some folks involved in this thread have the impression that push-pull amps are the panacea for a "sounds good with all music" scenario.

    Yes, and all of the high fidelity amplifier manufacturers in the 1950s and early 1960s must have thought that too, because none, absolutely none of them were still manufacturing single-ended power amplifiers back then. You could find lots of single-ended power amps back then in cheap radios and in low end guitar amps, but none that I ever saw were SETs, they all used pentode output tubes. Back then the "hi-fi nuts" found that the added power and lower distortion of PP sounded better, so that topology became the standard.

    Well, having been involved in the industry at that time, I can tell you that the switchover to push-pull was seen, in part, as an expedient for getting much more "bang for the buck" in terms of output power and lower claimed distortion specs. But, with that in mind, and not getting into tutorials about amplifier design, the ability of a push-pull amplifier to deliver on its "promise" is dependent, in part, on having a perfectly balanced output stage with a perfectly balanced phase inverter. Throw the balance between the tubes out, and then see what you get. Most manufacturers of push-pull amplifiers also used a feedback loop between the opt secondary and earlier stages to get improved bandwidth and lower distortion, except that doing so often caused phase distortion problems. And, not everyone from that era was totally satisfied with push-pull pentodes/beam power tubes either. Hence the work of Hafler and Keroes with ultralinear designs (http://oestex.com/tubes/ul.html). As a "hi-fi nut" from back then myself, my own experience is that push-pull is not necessarily better sounding than single ended. There are too many other factors which can either enhance or detract from sound quality with either design.

  3. There is no way to predict which receiver/amp/speaker combinations will sound to your satisfaction. What may be pleasing to me may be annoying to you, etc. Do you have any friends who own speakers of interest? The only way to know for sure is to have the speakers connected to your receiver so you can listen critically.

  4. I have the sense that some folks involved in this thread have the impression that push-pull amps are the panacea for a "sounds good with all music" scenario. That simply is not true as they have their own set of ills which can noticeably affect the sound. There is simply no one amplifier design (whether tube or solid state) which will sound good with everything. If one is fortunate enough to find an amp/speaker combination which they find pleasing most of the time, they should consider themselves lucky!
    A case in point is one of my audiophile buddies who has used his Krell "arc-welder" with his B&W 801s for years with good overall satisfaction. Recently, he acquired a pair of Acoustat Model 4s which he's using with some crappy Yamaha solid state gear from the early 90s. Guess what? The sound quality of that combination blows away the other system with virtually all of the music we compared them with, regardless of the level at which we listened. So, what's the answer?

  5. How do you know that the resistor is damaged? Is it blackened/burned up, split, etc? If it did burn, it's because of excessive current running through it, which would suggest that there's something else going on with the amplifier. I recommend that you have it serviced by a competent technician in the interest of avoiding more costly repairs later on.

  6. If you had your speaker wires connected for a long time without being removed and re-installed you may have had some slight oxidation between the wires and posts which is the likely cause of the difference you describe. Electrically, it makes no difference which set of posts you use as the resistance of the straps is insignificant. It's a good idea to disconnect/reconnect all of your speaker leads, interconnects, etc. twice yearly; and it can be very helpful to treat the contact areas with a light film of deoxit which will allow an even better electrical connection.

  7. The dilemma you have outlined is very common and reinforces the fact that one amplifier type can't be everything we desire for all musical types (which is why so many audiophiles go chasing the elusive "sonic nirvana" only to find themselves going in a big circle over time). In addition, there's so much variation in recording quality that the issue becomes even more compounded. The solution, for those who can afford it, is to have a SET amp, and a pentode based amp (personally, I prefer SEPs with enough negative feedback to extend the bandwidth and smooth the highs as needed, as opposed to push-pull designs). In my own installation I can switch between amplifiers to better match the characteristics to what I'm listening to. Also, psychoacoustics come into play- i.e. depending on your mood, you may prefer the laid back sound of the SET one day, but on another day you want the more punchy pentode sound with the same musical selection. So, I've never recommended two systems to my customers, but rather, two amps to cover the bases.

  8. How much is the person asking for the large Advents? They are truly amazing speakers which can produce useful bass down to 30 Hz and can image magnificently. As mentioned above, you need to be careful about the woofer foam surround condition, but if the price is right, there are people who can do a professional refoaming for you at a reasonable cost. But, their age doesn't necessarily mean that the foam is bad. Two months ago my wife found a pair at a garage sale (hanging out with me for a lifetime has rubbed off!)- the foam surrounds are original and look as if they were just installed. Much depends on where the speakers were used; i.e. how much heat and moisture they were exposed to, among other things. I currently have them installed in a 25X15 room, feed them with only 12 watts/channel, and they throw a positively huge and deep soundstage with bass ouput which rivals that of a small subwoofer. I last heard them in the mid seventies and forgot how terrific they are. So, please don't rule those out either......................

  9. Yes, they were a popular maker of radios back in the 40s and 50s, but marketed under that name through the 70s if memory serves. The ECL82 is the same as a 6BM8 which combines a triode voltage amplifier with a pentode power amplifier in the same bulb. It's a nice sounding tube which should be good for maybe 2-3 watts output. If you have an actual model # for the amp, I can look at the schematic this afternoon and provide you with more technical information if you need it. Definitely worth having restored!

  10. I've never heard the WA5, but can tell you from many years of experience that the combination of the Cornwalls with SET amps is absolutely wonderful. Over the years I've designed and built many SET amps for folks to use with Cornwalls, K-horns, etc, and the synergy has been truly amazing. If you can accept the fact that the bass end with any SET amp is going to be a bit softer and less punchy than with pentode designs you are likely to be totally satisfied. In my opinion, the incredible midrange and top end offered by SET amps is without equal.

  11. Use my previous link and write down the specifications of the MOV you want to replace including its dimensions. Go to:

    http://www.newark.com/jsp/content/printCatalog.jsp?cat=catalog128&page=379&display=zoom

    You will find an enormous selection of MOVs from which you can choose a replacement with virtually identical specs. Be sure to change all of them to the new type. You need to check your space allowance as some of the replacements may be larger than the 14181.

  12. They are both very nice vintage amps, and if the price is right, why not grab both? At the very least, they should have all electrolytic and paper capacitors replaced. As far as longevity goes, it's not likely that there would be any difference if everything is electrically sound. Cost of parts is indeterminate- if an output or power transformer goes, a replacement can be costly, depending on whether you can find a modern replacement, or have to rely on buying a vintage part. Tube cost will depend on whether you want to use new old stock tubes, or modern replacements if available. Sound may be quite different between the two amps as a result of their circuitry, so it's worth bringing them home to listen in your room, with your speakers, if possible. How much is the guy asking?

  13. I do almost all of my listening with RF-15s (still around if you check online) which are very similar to the RF-52s. The imaging and soundstage is absolutely phenomenal. Your two watt Decware amps would be an incredible match for them, assuming you aren't looking to create enormous spls in a large room. Bass performance is also phenomenal (if you can accept that you're not going to get much below around 40 Hz, although the RF-52s are supposed to go lower than the RF-15s). Obviously, with tube amps, the bass is going to be a bit more "mushy" than with solid state. Having owned K-horns and Cornwalls in the past, I have to say that the RF-15s are actually more enjoyable to listen to, and allow much greater involvement in the music. Look at my equipment profile for room size, and mode of listening. Why not buy a pair of the RF-52s from a dealer which has a return privilege if you are not satisfied with them? I doubt that you will be disappointed.

  14. If the receiver has electrolytic capacitor problems, they need to be replaced if you are to avoid potentially catastrophic failures down the road. It's unwise to rely on fuses, or protective circuitry, to prevent this (i.e. I could have retired 30 years ago if I had a nickel for every device which came in for repair with intact fuses/protective circuitry which didn't do the required job!).

  15. The G series receivers employed protective circuitry to sense any DC appearing at the speaker terminals. If that condition exists, the relay which controls the output to the speaker terminals will not close, and you will not get any sound. Apparently, after the 10 minute interval, the situation corrects itself and operation is restored (hence the click that you hear shows that the relay is closing). Since both channels are affected, you probably have some electrolytic capacitor issues, although there could be other causes as well. If I recall correctly from having these come through the shop periodically, there's a display on the front panel which says "safe" when the receiver is operating properly and the relay is closed. In any event, this is not something that can be serviced by someone who does not have a great deal of technical expertise. I suggest that you look around for a qualified technician in your area who has experience with vintage solid state equipment (I'm mostly "retired" and now do this stuff only for friends or I'd try to help you out). It's a nice receiver, so if it can be resurrected at modest cost, it's worth doing so.

  16. My inquiry hinged with design of the cap..which is a better design (axial or radial)?

    Most of the caps in the audio path used in XOs are typically axial. Since this bypass cap is being used as a power source bypass and not in the audio path, is it a concern which dersign to use if there is an option and if so, why, (or) is it simplier to just use whatever will fit at the desired value?

    There is no difference in performance between axial and radial designs.

  17. It all depends on how loudly you intend to play the system. If you crank it up to the point that the amp is maxed out and goes into clipping you can certainly blow the speakers. I can't imagine, however, that you would be able to stay in the room (or possibly in the house!) with anything remotely approaching that kind of power and distortion level.

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