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erik2A3

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  1. erik2A3

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    Totally understand and can relate. I would have bought it from you if in the position to do so.
  2. erik2A3

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    I hope someone jumps on this. The A23+ is an incredible amplifier -- very flexible in terms of power-on options; significant output power; line level outputs; input level controls; great workmanship and construction, etc. Being such a single-ended triode diehard for the past 30 years, I confess I don't think I had ever heard the crack of a snare drum so realistically reproduced until I inserted this hefty component into the system. We are using it with modified RF5s in a large room with a very high ceiling, and the Parasound/RF5 combo fills and loads the room with little effort. Better still, the A23+ is not an amp that needs to be turned up really loud to sound good. Its sound remains full, even, and balanced at frequency extremes even at lower SPLs. In my experience. We listen to all genres, but the way the system opens up with the likes of Alice In Chains, Tool, Perfect Circle (and others) at quite high volume levels is definitely impressive. My wife was the one who researched and bought this amplifier for us, and the aforementioned bands are some of her favorites. We've had Klipschorns, La Scalas, Chorus IIs, and Heresies, but the RF5s, for which I purchased RF7 high frequency drivers (I can outline the necessary crossover rework some other time), honestly represents some of the most coherent and just plain great sound we've ever enjoyed. The Parasound Halo A23+ is what seems to tie everything together so well. GLWYourS!
  3. Excellent information, and I would add that whether the crossover in his K-horns (which I also owned for years, along with a few pairs of La Scalas), is suitable for single ended 300Bs perhaps depends more on the crossover in question. The lower order designs, such as the type A and/or AA actually are very suitable for SE 300Bs, 2A3s, 45s, PX4,s, and so on. It's when the amplifier is forced to contend with higher-order designs, such as the type AL (rather infamous on this forum, but actually sounds quite good with enough power in front of it -- IMO), that lower output amplifiers (eg most single-ended triodes) start to run out of steam -- not so much from wild impedance swings, but rather the insertion losses associated with higher order crossover slopes. When one's amplifier is able to squeeze out only 1.5 - 8 watts or so, the greater number of passive components required by higher-order crossovers, the more the situation becomes like a 4 cylinder, 2-wheel-drive sedan trying to navigate through deep, soft sand, mud, etc. In other words, the fewer the number of chokes (aka inductors), capacitors, and resistors (as in fixed or variable L-pads), the more single-ended-amplifier-friendly a crossover tends to be. And when a network starts adding even greater complexity in the form of resonant peak filters, Zobel equalization networks, and so on, things just get worse. I've worked with all of those in the past, and what one ends up with, particularly with such tiny amplifier wattage, is a linear response that sounds like a thick felt pad was draped over what would otherwise be crystal clear sound. This is one of the reasons that there are those (and I include myself among them) that really like the sound of very high quality single, full-range drivers that don't use crossovers -- except sometimes for the parts required (or more accurately, desired....I don't care for them) for baffle-step compensation. To the OP: That's really neat you've corresponded with PWK in the past! Very special indeed. We might remember, as well, one of this illustrious gentleman's comments regarding amplifier output. "What the world needs is a good 5-watt amplifier." I hope I have that at least mostly correct. I used single ended triodes with our K-horns and La Scalas (and Heresies) alike for decades, and was able to get extremely high, undistorted volume levels from all of them. However, what's loud to one person might not be the case for someone else; so one can't discount the importance of listening tastes and priorities. In general, though, and in my own experience (which is unique to me, as well as some other old timers here who enjoyed the same speakers with low power amplification), I am absolutely comfortable saying it's possible to obtain very, very good sound quality from single-ended amplifiers and Klipschorns. I would agree that a constant reflected impedance can be beneficial, but I would humbly submit it's most certainly not mandatory. If it were, Klipsch would have been more aware of that characteristic than we during those earlier years. I built my own 6db/octave crossovers for my k-horns and la scales, often with a true band-pass for the midrange. Moreover, I found I actually preferred a variable L-pad to the autoformer, the latter of which (just for me, mind you) seemed to sound veiled in comparison. Moreover, one did not have to change values of input capacitance to the mid-range horn as one does with the changing of taps (in order to attenuate) on the autoformer in order to maintain original crossover frequencies. Despite the fact that (I think) Klipsch is now using another vendor for crossover repairs and upgrades (rather sad and unfortunate in my personal view just in a historic sense as it relates to this forum), I could not give the Crites family http://critesspeakers.com a higher or stronger recommendation for their understanding-of and experience-with Klipsch crossovers. The same can most certainly said for ALK Engineering, and Dean (although I think he may not be doing crossover work any longer). All three of the above have spent decades offering upgrades and repairs...and kits...of extraordinarily high quality. I've used my own 300B amplifiers with both the type A and AA networks, and they absolutely sang through the monster heritage horns. Good luck in your search!
  4. It's not unusual for a large tube like the 300B to tilt to one side or the other - and still be perfectly operational. I'm looking at mine right now, and one is not perfectly perpendicular to the chassis either. It was working just fine last night. The four pins don't have to be very tight; they need to make contact with the socket pins consistently, though. Considering the physics of this, things expand in the presence of heat, which in this particular instance regarding the output tube socket, would probably just help improve the contact with is associated pins on the tube. By the way, I think you mentioned the socket base being slightly loose, and you're able to gently move it side to side. That's actually not that big of a problem, unless it got so aggressively twisted that the leads coming out of the base of the glass envelope itself become fatigued and break. The socket base can be fixed, and there are a couple of way of doing that. Removing and reinstalling the 300Bs may have cleared/cleaned oxidation or some other contaminant that was preventing adequate electrical contact, and so you found that you were able to listen without problems for several hours. It's helpful that you can navigate around a schematic. I know you've been here awhile atto, as have I under my old avatar; although I don't remember if you have some technical ability in terms of using a multi-meter. This may be a case where tube socket re-tensioning might help, though. If you do know how to use a meter, measure residual charge in reservoir capacitors to confirm they've bled down. If you have the schematic, also check if there is a power supply bleeder resistor on the output of the power supply to common (ground). CAUTION! POTENTIAL SEVERE ELECTRICAL HAZARD (Please understand this is not intended as an insult to your abilities, experience, or knowledge). I can't count how many times over the past twenty years I've been associated with this forum that otherwise well-intentioned suggestions of working with high voltage equipment was expressed as if doing so was as harmless as playing with that old Fisher-Price farm toy, where the barn doors go 'moo,' like a cow, when you open them! Clip one of the meter probes, and with one hand in your pocket (as I think Curious George (smartly!) mentioned awhile back), use the other hand to take the measurement. If there is still any voltage present, LEAVE IT ALONE. Let someone else work on it who knows how to bleed that voltage away. A guy in Germany once sent me a large OTL amp to repair that uses a total of 22 tubes (I built two of those amps myself), and, since it came all the way from Europe, I was certain it would be fine to work on it, and that any voltages that were in the huge PSU caps would be gone. I just did the usual quick check (some of you know what that entails, but I'm not going to describe it here), and POW!!! , accompanied by a bright blue-white flash. My workroom is upstairs, and my wife, who was all the way downstairs at the time, called up and asked if I was ok. Assuming things is not the best practice (with anything), and can represent a potentially fatal mistake in the presence of high voltages - and especially high current. With the amp turned off and DISCONNECTED FROM THE WALL SOCKET, and if you've confirmed that storage charges are no longer present with your meter set to DC, then (and only then!), and depending on the type of four pin sockets the amp uses, slightly adjust the contacts of the socket pins (gently) so that they grip the pins on the tubes just a little more tightly. It would be good at this time to re-tension all sockets, the signal tubes usually being a bit different from the 4-pin outputs. I use Dental tools and picks for those. You can also give them a short burst of De-Oxit spray (or other good electrical contact cleaner), following the directions for use on the can. (I apologize for all the safety verbiage here. I taught both college and public school art for over 30 years, and safety precautions were always important. When you have a college-age junior (a Business major) ask you if his head would get burned if he stuck it in a 2,000 F ceramics kiln, one learns to not make assumptions). Or the high school senior in a linear perspective drawing class who rose his 18-inch-ruler-holding hand and asked, 'How long is one inch?' I looked at him for a moment, and could tell he was actually sincere. 'Ok, look at the end of the ruler opposite the 18" end on the right. Do you see that? Great. Now follow the markings until you come to the number 1. That's 1". He was a great fella, and I thought very well of him - called his parents to tell them so, too. One just never knows what someone else might or might not know. There are a few other things that I know of that can cause this kind of problem. Does the amp use a vacuum tube diode rectifier or SS diodes? are there coupling capacitors between the input and driver stage and final stage (going to the 300B)? What components are in front of the amp? Are you using a line stage preamp ahead of it? The system is a chain, and in order to fix a problem you have to isolate the failing link. edit: Despite my otherwise being an absolute bimbo-fool with modern technology, I can type fast. Lots of practice, obviously!
  5. You might also achieve a little HT sag with a different rectifier (obviously with suitable current specs). I’ve also had good results using a thermistor between mains input and PT primary. Great project, and I have to thank you and other contributors here for inspiring me to get back to my workbench.
  6. Plate dissipation and triangle waves aside for a moment, something as simple as checking (and correcting as needed) filament voltages on vintage equipment originally designed for lower mains supply is also important. If you’re planning on using a variac long-term, not an issue, as you of course know. I did the same work on a LEAK ST20 ten years or so ago. Push-pull or single ended, EL84s are really good. Easily the equal of some of the outrageously priced output triodes. As always, your workmanship and attention to detail are among the very best we see here. Very nicely done.
  7. I do like and prefer your choice of words and tone here. Well said.
  8. Great! Sort of a matter of semantics, I would say. I'm familiar with gyrator loads, and I suspect I'm just sort of a more traditional sort of builder. I'm of course also very familiar with CCS active loads, which you probably know can be achieved a few different ways. I've used them in two or three preamps I've built over the years What you're explaining is really not a benefit to me, if that's what was intended. I'm actually pretty well-versed on this - and I will be the first to admit that the more I've learned, the more I've also learned about how much I don't know, as well as what I prefer. Hopefully you are the same in that way. Use your gyrator; I'll stick with the hefty choke. Plus! that big anode choke is much heavier, which we know just adds to the cool factor, and thus subsequently automatically improves sonics. Wink. Grid Chokes: I'll choose them over a resistor, which in my view -- and to use your words -- is technically inferior to the ubiquitous grid leak resistor. It was really just mentioned because not many builders that I know of use them...a few do, and I had to learn about them myself way back when. And you're right. There isn't anything wrong with preferring one thing over another. Again, I am comprehensively aware of their function and how they operate, although I'm sure there are others here that enjoy techno-jargon. Building for me is often an intuitive sort of thing, within reason and observation of operating parameters. Designing is something of an art to and for me, and most often has to do with extensive experimentation and listening comparisons -- and, good grief, not the quest for ultimate linearity. Build the way you wish and enjoy the process. That's what this is about. And YET again, a plate choke (or your gyrator if that's what you prefer - even though I don't care for them) is absolutely needed in a parallel-fed (LOL) output final stage. Good? Good.
  9. A rather long and tiresome story. They were truly incredible amplifiers, but, in short — and this is intentionally vague — the forum was very different back then. My old avatar is Erik Mandaville, my name obviously. You can probably check archives, card catalog, or whatever, and find images and text. I used to write ludicrously long posts.... They used extremely high quality parafeed transformers and grid chokes from MagneQuest, and I sold them for the price of parts alone. Parallel-feed is a very old yet extremely good sounding topology in a well-designed circuit; and the Horus 2A3 mono blocks were/are most definitely an extraordinarily competent design. I have no problem admitting errors when I make them, and selling those was not well-thought out. Again, the Klipsch forum back then, as many of the longer-term members here will remember, was kind of like the old west with egos on horseback. I loved the grid chokes in that amp.
  10. In parallel feed, a plate choke is used for B+ on the output valve. The grid choke to which I referred is superior, in my view, to a grid leak resistor for a number of reasons, none of which I'm going to take the time to explain. I did enough of that here 15 years ago. Use your gyrator load; I'm comfortable with my choice.
  11. I have. In short, the benefits FAR out-weigh any negative elements you may be perceiving associated with that capacitor. More than that, some of the the most capable designers I have known will enthusiastically opt for parafeed (which is sort of a lazy way of referring to its more descriptive 'parallel-feed') over the conventional air-gapped SE OPT. One of the very best sounding amplifiers I ever built was one such design -- called the Horus 2A3 (designed by a very capable guy - Jean Francois Lessard). While it was based on some of the work and research done by Gordon Rankin (Wavelength Audio), Dan Schmalle (Bottlehead -- or, some of you, as I, might also remember him from Electronic Tonalities) , and others, I came up with some quite good-sounding modifications to better suit my own priorities, tastes, etc. Nevertheless, I could not have done any of that work without the roadwork of the others mentioned. My abilities pale in comparison. It's about as close as one can get without going altogether OPT-Less, which can be staggeringly good sounding...in my opinion. I don't cringe too much at a decent coupling cap. Many extremely good products make use of them. Note that a large plate choke is also needed in the finals stage. If you've never built one, I STRONGLY encourage you to give it a shot. I sold mine, and that most definitely was one of my dumbest 'audiophool' mistakes. It was the design that got me addicted to extremely high impedance grid chokes over the more common, dust-cheap grid leak (for those of you know what I'm blabbing about....). Quality iron is key in such a design.
  12. Very nice!!! ...what always amazes me is how imaging and soundstage collapse if one happens to remove the wooden side panels!
  13. "It was a typo, I meant to write 1/2 watt not 1/5 watt. My book 400mW with a 1/2 watt resistor is yes within limit but not good engineering practice. I will go back and edit the original post." The period and back slash are neighbors on the keyboard -- easy mistake! I thought that was likely the case -- you've been at this a long time! Totally agree on the power issue. Being conservative is SMART!
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