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Erik Mandaville

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Everything posted by Erik Mandaville

  1. I can supply the schematic and parts list. That's really pretty amazing that you haven't gotten your amps yet, Kev. Had they been shipped and lost, I wonder....
  2. This level of ambition is very respectable. What a great learning experience. Measure 15 times; cut once![] Erik
  3. I honestly don't know what is going on with W. Labs. I just remember the time a decade ago. If you need a copy of the schematic and parts list, I would be happy to send them to you, as I did for another forum member. Just let me know. I believe congratulations on another pair of SET amps -- that is neat, and the Horus is really a wonderful sounding amplifier. It's open to some modification, too, as I had done with the pair I built, but any of the changes, as you have seen on the forum, can always be reversed. Leok's shunt-feed Moondogs were very, very similar to the Horus I built as far as the output stage, but the 5687 driver in the Horus is pretty nice, I think. That in conjunction with a grid choke on the 2A3 instead of the more common resistor makes for a special sound, IMO. I used the MQ grid choke (FAR more expensive than its grid-leak resistor counterpart) in my Moondogs, too, that had also been modified with the DRD Ultrapath (I'm sure you're familiar with that). That 'ultrapath' part of the DRD goes back many, many years, just like parallel-feed outputs. I'm building a component right now, that, while not an amplifier per se' nevertheless uses the same approach, along with a plate choke on the output tube. Thanks for the invitation, Erik
  4. Great! The schematic is available, I believe, but I would rather not post that information. Perhaps try Welborne Labs again. The assembly manual probably suggests twisting the AC filaments for 60Hz hum rejection. Your amp looks nice, though. Moondogs can play very loud with Klipschorns, and I bet they are wonderful with Oris horns. I wish I went for a pair of those to use with my PM2As. They are the reason I first got a pair of La Scalas. I was going to use the bass bins with Oris 150s or open baffle. Good luck. edited. Erik
  5. It's interesting to see the evolution of (Klipsch) crossover design from the earlier to later, somewhat more contemporary approach. Note the tweeter connection. Just FWIW: This is not to be automatically contrary, but rather to offer the idea that mylar capacitors aren't inherently bad and in need of immediate replacement. That might be another subjective sort of call -- just as the NP electrolytic shunt element has been 'discussed' here by some to be more appropriately replaced by a plastic film type (though I'm in the same camp that would use the MUCH cheaper and MUCH smaller NP electrolytic). A passive network for the Jubilee had been posted here that in fact specifies mylar. That doesn't mean a poly film type might not sound better to some, but I think could indicate that if they were so obviously inferior they would be avoided altogether by engineers. I've had the opportunity to change the mylars in mine on many occasions, and it's work that would take me several minutes. They sound fine to me. The new tweeters are a fabulous upgrade! ....and still, even with that there are those who think the original alnico or mud-mag K77s are more musical. A very large portion of all of these changes is subjective. The alnico tweeters sounded comparatively dull and uninvolving. I want a tweeter that will help make a sizzle cymbal sound like what it is rather than an ambiguous hiss somewhere in the background. The C125s were a big improvement without sounding like they put a microscope on the recording. Good luck on your Heresy freshening up! Erik
  6. ....or find/save-up-for a pair of K400 horns and use those.
  7. I guess I think, too, that if you can experiment with this while trying to preserve the original shape and dimensions of the horn, the possibility of learning through trying is sometimes worth the effort. If nothing else, it could help lead to other insights and possibilities. On the 500Hz crossover for the La Scala, I hope someone will correct me if I'm wrong, but I believe the La Scala low-end response, while very mildly down above 400Hz, is still reasonably strong quite a bit beyond that. Erik
  8. However, you can alter the values of two of the elements in the type A network for that frequency. In other words, compensate on the crossover end rather than altering and possibly damaging the horn.
  9. "I also agree with all the above comments that properly setting up a crossover point (and slope) does require measurement equipment, but some of these measures are already available." We should note, too, that many of the older Heritage networks (the type A is always a good example) were designed around established criteria that is available to anyone. The fundamentals of designing a crossover include the impedance of the drivers being used, the desired crossover frequencies, and attenuation networks (where needed) for adjusting gain. Certainly compensation circuits such as impedance equalization, notch filters, and so forth require measurement, but the type A (among some of the other Heritage designs) do not use those special circuits. This can be very simply verified by the fact that the value of the single series capacitor in the squawker branch of the type A is selected according to nothing more than the (reflected) impedance of the driver (which happens to also include a sort of built-in attenuation network) and cut-off frequency. On-line calculators will provide a virtually identical value, as do design tables in books on crossover design. The same is true for the woofer, which uses a single series inductor, the value for which, once again, is derived from known figures -- impedance and frequency. In many cases, driver manufacturers will specify the precise network to make -- such as 18dB/octave @ 3,500kHz for a tweeter. And that's it. No mention of Zobel network, notch filter, or anything else. Given that information, there is a very specific way of designing an 18/dB network for that crossover frequency and driver impedance, and the information needed to create that type of network need not be made more complex than it is. In the case of the tweeter I'm using, it involves two capacitors in series with the driver, with a shunt element (an inductor) between the two capacitors. That's all, and in doing this one would be following the design suggested by the company that designed the driver. What if you were to find that the tweeter was too loud compared to the other drivers? There are formulas for making very simple L-pad circuits -- or these days, very conveniently, on-line calculators where all one has to do is punch in a couple of numbers. These work by the way, and I have tested them against formulas I have in books on the subject. Loudness doesn't need to be measured with anything more than one's ears. If it's too loud, turn it down until it sounds better to you. Just to be clear: Obviously very high order passive crossovers (which IMO may, depending on associated equipment, bring about other compromises) MUST be thoroughly tested and fine tuned. Using loudspeakers drivers with unknown behavior, as was indicated above, is another case where measurement would be important. My point has to do with the fact that the type A (which also happens to be a favorite of many) does not contain compensation networks or circuits of any kind. It was designed around nothing more than simple and readily available information: driver impedances, reflected impedance, desired crossover frequencies, and desired amount of attenuation. The squawker doesn't even use a true band-pass. It's an extraordinarily simple design, which IMO is one of the reasons why it may sound as good as it does, particularly with lower power amplification. I agree that new capacitors might be an improvement for you, and also that it's (possibly) not necessary to spend overy large amounts of money on expensive capacitors. If you can afford the likes of Hovland and others, absolutely let your own ears decide what works best for you. In many cases, mylars can be very satisfactory, but in this case I'm speaking of some of my own experiences in building speakers and crossovers. As others also indicated, you may not know what you're missing until you try for yourself. The autoformer and inductors do not wear out with time in the same way, and so a simple cap switch might do the trick. Solens are good for the price, IMO, and I have experimented with all types, cheap and not cheap, for a long time. ALK makes beautiful crossovers, and the ES versions border on electronic sculpture. Because of the complexity and number of passive components, they may not be an ideal choice for really low-pwer SET amplifiers (I'm talking about a couple to few watts max), but then again, maybe there are those who use them very happily with single-ended 45 and 2A3 triodes. I prefer not to tell someone what they should or should not like. Have fun! edit: Bob C. also sells capacitor upgrade kits, which may have been mentioned, and that will make things more straightforward. Erik
  10. Kevin! Thanks for the compliment (and willing greeting, too). All is good here -- I hope you guys are having a good summer also. Hopefully the house isn't filled with flocks of summer origami birds! I had the parts to make this more traditional type 'A' (except for that tweeter connection), so I can just have it on hand (as if I need another). I need a temporary closer match for the sort the center channel I've been putting together from parts over the last year. I just now closed the back to put into service. Later, I can build one of the 4k-3rd-order band pass 'things' I was using in the K-horns. Still no 511Bs, although I'm sure they sound great. I've just decided to keep that part original to the speakers. Kg4: Very good job! I know you're going to like them. I'm trying to get a little tube transmitter finished so I can broadcast oldies tunes from my CD player to our 1937 Philco radio, and I'll get those parts installed on a board for you. I've been doing too many things at the same time, and need to get this project finished hopefully in a couple of days. Erik
  11. Hi, Michael: Thanks. I had been looking around for some of the motor capacitors I've liked so much, and was able to find 3uf locally for cheap. A longer, narrower board helps with these larger capacitors. Since they don't have leads of their own, a little more point-to-point wiring is necessary. I also think the original Klipsch ground buss works extremely well, and is simple. It's very much the way a common ground is done in tube amps, although I know that some don't care for it. What is good is that it's one solid piece of wire that does not rely on extra connections and crimps of smaller pieces of wire. Each to his or her own there, I guess. To see if something like what is shown might work for you, you could cut a piece of paper to 6" X 10" to see how it fits in the bin with the barrier strip at the back. It's sometimes been discussed in the past how the type 'A' seemed to have a slightly higher tweeter output or a little 'brighter' sound than the AA, and I think part of that may be due to a possible mild reduction of series resistance in the 'A' HF branch. The tweeter filter in the AA is also of higher order. In the network shown, I chose to wire the tweeter completely separately from the squawker section, meaning it's connected directly to the input rather than after the 13uf capacitor (that's one extra element that might impose some additional series resistance in the circuit). So, in using the 6k cutoff for a first-order circuit with an 8ohm driver, I needed about 3.3uf for the tweeter filter. I remembered I had some .33uf Solen coupling caps, found them, and replaced the .47 mylars shown in the first picture. The 10uf in parallel with the other 3uf motor run is a Sprague polypropylene. Someone asked me to post a picture of a type 'A' network, and until the other day I didn't have one. Erik
  12. kg4: I'll put those parts in a type 'A' configuration and send them before the summer is out and school starts again. The 13uf cap is going to be made of an 8uf, a 2uf, and a 3uf in parallel -- all of which I have just sitting in a bin. Erik
  13. Jim: Will works on lots of Baldwins that are in fact PP Parallel, so it's something that could very easily misunderstood. Erik
  14. How are you doing, Dee? I owe you an email! Erik
  15. That is really coming along nicely! I found a box I had forgotten I had, and what would I find inside but an additional two autoformers and single woofer choke. Someone very kindly gave me an original Heresy I network (very good condition) for the center channel project, and I decided to build a couple of type 'A' networks to match the Heresy high frequency crossover point. All three front speakers now use the same tweeter and midrange horn, although the Heresy is obviously smaller than the K-horns. I'm going to take out my other 4kHz/non-autoformer networks to play around with the 6,000 crossover point. When I can get the parts I need to do a 4K crossover with the Heresy, I'll switch back. I have enough parts to make another pair of 'A's that I can send you to play around with when your La Scalas are done. Here's what I put together yesterday for the Klipschorns. I've always liked the sound of combining different cap types, and frequently parallel them for the needed values -- just like small value plastic film types are often used to bypass electrolytics. The tweeter section on these is also connected directly to the input, with a minor change in capacitance value (close enough to what I needed) to keep the roughly 6,000 cutoff for this first order circuit.
  16. Push-pull parallel is shown below. The monoblock on the left is a Baldwin with four output tubes configured for PP-parallel
  17. "Keep those Moth amps as now that Moth is defunct. I thought their work was Art." Absolutely. I have no intention of ever selling it. My wife arranged with Moth for us to purchase one of the last available, and I bought the parts, chassis, and schematic to put it together myself for a savings. With regulated DC filaments for both the input and output tubes (2A3s are usually heated with AC), it's among the most quiet SET amps I have heard. Welborne Labs DRDs, and the Wright 2A3 monoblocks I've had here were also very quiet. I can't remember the name of the person who helped with the aesthetic aspect of Moth components, but they really are very Jules Verne-like. They formed a new company called Eddie Current (that's a bit of a pun, as some will catch) that specializes more on headphone amps, which is also how my 2A3 is setup. It's a great headphone amp.
  18. "What exactly is Parallel Push Pull? If I were to assume it would be multiple pairs of power tubes but I am not positive exactly how it works. I have seen amp for sale where there called parallel but only had two a channel. Do the poster just have their facts wrong?" Great question! push-pull and parallel output stages both offer increased power over the use of single tubes -- such as a single triode like the 2A3 or 300B. For example, instead of using just a single 2A3 or 3OOB, it's possible to use two of those tubes per channel, and wire them so that each section of the triode (the grid, the cathode, and the plate) is in parallel with those elements of the other tube. This will give twice the power output that can be obtained from the same grid voltage used by a single tube. Push-pull operates differently, but is able to supply not only greater output power, but with comparatively less (measurable) distortion and lower noise (due to inherently better power supply rejection) than single-ended or parallel single-ended designs. This isn't to say one is necessarily better than the other, because we know rather well that there are different preferences. Push-pull outputs require greater grid voltage than paralleled single-ended tubes. Some people don't care for the sound of paralleled triodes, and prefer to use them just in single-ended mode or push-pull. So, if you've seen amps described as having paralleled outputs, that's what is described above. Erik
  19. "I thought the use of using two monaural amps as stereo...I would like to know as well..." That can work fine and is a common thing to do! I have a couple of vintage 6V6 PP amps that I use the same way sometimes. Both are integrated amplifiers with their own volume control, which makes it possible to balance channels easily if the gain of one might happen to be different from the other. Erik
  20. Jim: You are most welcome, and Will and I are both very glad you're enjoying it! I think the push-pull parallel description may have just been a slight error; it's in fact push-pull only, using two 6L6s per channel. Push-pull parallel, as Craig pointed out, would use a total of eight tubes with four per channel -- consisting two pairs of output tubes that are wired in parallel with each other but operated in PP with the other paralleled pair. It may help to think of each paralleled pair as essentially a single tube. Erik
  21. You might also just be curious about some of the other amps from Trascendent Sound, such as the new Cathode Follower and T-16 amps. The new Cathode follower amp (which does use output transformers) and the T-16. Bruce Rozenblit is a very talented designer. www.transcendentsound.com Erik
  22. We also shouldn't neglect to mention that while Klipsch Heritage speakers are among the several 'out there' that will work well with low power amps using triodes like the 45, 2A3, and 300B, there are MANY extremely good sounding push-pull amps that Klipsch owners love. I use and enjoy both, and can't help but admit that there can be a subjective improvement in low-end response and control with more powerful amplification. That has been my impression, but there are of course other factors other than just watt-strength associated with that, but I just wanted to mention that it might be an idea to audition some different topologies and tube-types if possible. Even small 6BQ5s in push-pull can be very impressive, as can EL-34s, 6L6s, and so forth. Discussions over power have been interesting over the years; though ludicrous is probably more of an accurate description than 'interesting.' Have fun! Erik PS: Look at all the tubes on this single-ended amp! it gets very warm for not even 2 watts per channel, but those two watts are among the very best I have ever heard, and you don't have to worry about the quality of output iron. It doesn't use it.
  23. Those were a nice sounding pair of Moondogs. I remember them, too. As others have said, 300Bs and La Scalas will be wonderful. I've used that tube, single-ended, with Klipschorns with great results, and find even the tiny handful of watts from the Moth amp I made incredible. Very nice work on those tops with the Altecs, BTW! (....just don't touch that autoformer in the crossover!) Here's my beloved Moth 2A3, mildly modified.
  24. I knew there had been some concerns, and I hope he is feeling himself again very soon. I loved his amps, but they are nothing when it comes to health. Erik
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