tube fanatic

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About tube fanatic

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    tube amp designer

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  • Interests
    extracting the best possible sound from single ended tube amps using modestly priced designs and tubes.
  • My System
    Currently using RF-15s in a small room, near-field, arrangement and driven by low power SETs. The soundstage is enormous, and the musical involvement beyond anything previously experienced.
  1. Civility is exactly why I mentioned competing businesses. The least civil discussions I have seen involved business owners feeling threatened by potential loss of revenue.... Now I really need to get to work. Maynard
  2. Neil, it's very difficult to work with this discussion while being euphemistic. Let it suffice that certain business owners are very well protected on here. When Ken, owner of AEA Audio, tried to become an active forum participant he was truly run off here because he posed a significant threat to the financial interests of ........ (fill in whomever you wish). It was so obvious that some of my non-social (they don't participate in forums) audiophile acquaintances instantly picked up what was going on. This problem is as evident today as it was when I joined this forum years ago. And, anyone who was reading the mail on here a few years ago knows why Mark and Jason left. I miss having guys with their intelligence and skill set with whom tube equipment could be discussed in electronic terms. Their insights and explanations would have been very instructional for those wishing to learn some audio electronics. You mentioned other forums. What I like about those such as Audio Asylum and Audio Circle is that manufacturers, or other industry professionals, are very clearly identified. And, in all the years I've followed the discussions on audio forums, I have NEVER encountered any of the industry identified individuals bashing or otherwise criticizing their competitors. And, if they did, it would have only hurt their business. Of course, on there, the moderators would have immediately dealt with the issue. Here, we all know that this is a permitted activity. William is quite correct in pointing this out in his comments above. So, the environment on here is absolutely different from other audio forums. The social media side of things is fine for those who enjoy the chatter. It adds a different dimension which some prefer. But, with all of that, I know guys who wanted to participate on here but were so disgusted by what is permitted that they chose to join other forums instead. To each his own. Wish I had time to continue but obligations call! Maynard
  3. The first sentence describes what happens on here far too often. And, in such cases, it is the obligation of those who see through it to point out the flawed statements to others. This is especially important when the person making the contemptuous statement is doing so with the sole object of self promotion. I've lost count of the number of times that someone, whose word is considered gospel by many, has said something to the effect that "brand XXX equipment is crap because I say so" (the unstated implication being that theirs is much better). And, when this is publicly pointed out, the individual gets terribly offended and starts the usual forum "war." Sadly, with this being a public forum which is read by many who do not participate, such misinformation must be corrected. Just the take of an old crab who has seen much over the years............... Maynard
  4. Joe, noticing some microphonics when tapping the chassis or tubes themselves is not necessarily a problem. The question is whether you notice anything not sounding right when listening. Given the weight of the Scott you would need an awful lot of acoustic coupling between the cabinet and the sound field of the speakers (whether through the air, floor, rack, etc.) to make the microphonic tubes "sing." And, the shields on the tubes also offer some degree of mechanical stability which would reduce any vibrational effects. So, if all sounds well when you spin records, I would leave it alone. Maynard
  5. It's impossible to make blanket recommendations of one amp over another as everyone has different listening criteria. However, if you post a very detailed description of your requirements (starting with which speakers you use) and describe your room, distance from the speakers when listening, level at which you listen, type of music you listen to, etc., some ballpark suggestions may be possible. Keep in mind that the only way to make a judgment of what will be most satisfactory to you is to try the amps in your own system. Making a purchase based on what someone else tells you is the best can be extremely costly. Maynard
  6. Very interesting to watch: Maynard
  7. There is no easy and short answer to your question. In general, tube output stages are designed to operate into a specific load impedance which is provided by the prmary of the output xfmr. Unfortunately, the primary impedance varies depending on the load across the secondary. These variations in primary impedance are partly responsible for changes in the amplifier's distortion. As William pointed out, speakers present a widely varying load. Some circuit arrangements, like SETs, are fairly immune to impedance variations. If you select the output xfmr tap which is closest to the minimum impedance (I think the LSs are 3.9 ohms but that needs to be verified), distortion will actually decrease with any impedance rise. This is good! Pentodes are much more impedance sensitive which is why negative feedback is needed to keep distortion low. A pentode, with a properly implemented fb circuit, can be as forgiving of impedance variations as a triode. There are many more variables at play here, however, such as distortion varying with output level from the amp. That can be a separate discussion at some other time. Maynard
  8. I just found Atkinson's measurements of these amps (say what you will about the reviewers, I've always found him to be very honest in regard to measurements): Getting back to my earlier comment about my discussions in the 60s, we all felt at that time that an input sensitivity of around 2.5-3V would be just fine and, if it was somewhat higher, it wasn't considered a big deal. Remember, we're talking about power amps which would only be used with a preamp. Integrated amps are another matter entirely. Besides, what's the point of having a power amp with an input sensitivity of, say, 0.1V? To me that's way off the chart. Maynard
  9. Of course Albert raised some excellent points here. However, I don't agree with the premise. The issue of required amplifier sensitivity is something I often discussed with some fellow NYC area amp designers back in the 60s, and we all concluded that it did not need to be overly high. We need to consider the design goal of the Horn Monos which was to provide extremely quiet operation when used with very high sensitivity/efficiency speakers which only require power levels in the milliwatt range (LSs being an excellent example) to create huge output levels. These amps have a voltage gain of around 9 db if I recall correctly and boast a s/n ratio of close to 120 db!!! That is a terrific combination in my book. So, for the chosen design goals, I think it is a perfectly executed product. Even Rozenblit addressed this issue in a paper (it is short and will give a much better understanding of this discussion for those who are somewhat less technically inclined): That said, I now have to challenge Albert to a duel to settle the matter in an appropriate way. Since we both are old farts it should be quite humorous............. Maynard
  10. Most noise in tube amps originates in the gain stages which precede the output stage. Mike's approach in using a very low input sensitivity is a wonderful way to deal with the noise issue when the amp is to be used with very high sensitivity/efficiency speakers. And, the measured performance of these amps is truly outstanding and far better than the majority of tube amps out there (including my own). Maynard
  11. There's little reason to use a tube rectifier given the availability of high quality solid state alternatives. Tube types are limited by fairly low peak current capability which is why the first filter cap has to be relatively low in value. Unfortunately, this results in a large amount of ripple (AC riding on the DC) which has to be dealt with. A choke is the only reasonable way to get rid of it in a power amp or other device which draws moderate or high amounts of current (there's also the issue of regulation which is a subject for a different discussion). However, in low/constant current devices like preamps it's not much of an issue and a resistor will often work just fine instead of a choke. In any case, when designing new equipment, I would rather use a couple of 50 cent diodes (which should last forever) in combination with a high value cap, than add another tube to draw filament current and add additional heat. Maynard
  12. Truer words were never stated! I paid Justin a compliment, and anyone who has read his posts on here or had personal dealings with him knows that what I said about him is well deserved. If anyone reads more into it they need help (perhaps one of our resident psychologists can be of assistance). What's pitiful is that the OPs thread was turned by others into a ludicrous discussion which, in my opinion, seemed to be intended to dilute his enjoyment of his purchase, focus attention on someone else, and served no purpose whatsoever. All this over a production run of 100 units of which 85% have been sold to very pleased customers. Maynard
  13. I'm sure you will have a lot of fun playing with the amp! What's nice is that when you try other tubes you don't have to deal with biasing them yourself. The auto-bias feature gives the convenience that single ended users enjoy. As to EL34s providing a great midrange and warmth, it is totally circuit dependent. In one amp they may be outstanding, and in another they may not be good at all. So, it's going to be a matter of choosing the tubes which provide the sound that you are looking for. Maynard
  14. Justin, your attitude is totally refreshing! You are not threatened by a competitor's limited edition product and have actually encouraged him to come out with more! And, you don't find it necessary to bash a competitor's product as a means of trying to elevate your own status. You are a true gentleman, and I'm sure your customers greatly appreciate dealing with someone like yourself. Maynard
  15. Trust me, you did not kick the nest at all, and I'm glad that you knew (as did I) that VPI was totally forthright about the amp. A very quick look online would have revealed this to anyone who had doubts about their marketing integrity. Companies like VPI have a great deal to lose if they try to dupe their patrons. I can't imagine they would ever consider anything but total honesty, unlike some other purveyors of audio gear. Enjoy the amp and don't let anyone "rain on your parade." Your opinion of its value is the only one which matters. Maynard