erik2A3

My point is that to some they not only might but DO sound terrible, horrible, nasty, yuk......whatever. Some people also think horn speakers are extremely colored and so stay clear, regardless of high efficiency. As the 901s don't sound right without their EQ, nor would many speakers without their attendant crossovers -- which often include fixed pads to either attenuate or boost HF response. The EQ for the Bose is an integral part of the system, so I guess I just prefer not to consider one without the other. My tube amp also sounds -- actually doesn't sound at all -- without its tubes. They are intended to go together. Again, though I don't have 901s, I corresponded for a time with someone who was completely taken with them, as I am with La Scalas or our Lowther rear-loaded horns. We discussed different systems in the spirit of enjoying music and an interest in audio. Agreed, it is very much in the application!

I have something of a suspician that what is better or worse in terms of the Bose 901, Klipsch, Martin Logan, Lowther horns, Quads, or any other speaker -- shouldn't matter. Most speakers systems, including Klipsch do in fact incorporate a certain amount of equalization in terms of impedance equalization and other related circuits within the actual crossover in order to achieve a desired result, which in the case of the 901 enables adjustments at the individual user level. The myriad crossover modifications done on Heritage speakers by forum members is arguably not very different -- people are making changes using variuous parallel and shunt combinationsmof L,C, and R in order to achieve a certain desired response -- that is supposed, and perhaps in some cases, may, sound better than before. People use EQ a great deal, which ultimately influences that last component in the chain -- the speakers, regardless of manufacturer. I've heard 901s on a couple of occasions, and, as an owner of Klipschorns and La Scalas (which I adore), the 901s were slamming good! Seriously. With a very powerful amp, they were truly impressive; and that was the element that impressed me, not the fact that the sound I heard had been partly influenced by a few user adjustable EQ parameters. I don't have 901s, but I know of people as devoted to them as Klipsch users are to Klipsch.

Dee What an interesting subject! And what a surprise to see two of my favorite composers, Erik Satie and Brian Eno in the same thread! Eno's Ambient series has captivted me for years -- it still does. His "Music For Airports" is fascinating. ...hope that Old Baldwin is still glowing. erik

What was done on the Dyna 70 to cure the internal ground loop problem? This is actually rhetorical. I already, rather clearly, know.

....very easy to confuse the two since iron core frame types like these can look very transformer-ish.

Just for the sake of clarity in terminology, it might be helpful to refer to the topic of discussion as an "autoformer" rather than "transformer" (as also indicated above at one point) This device is really more of a multi-tapped choke or inductor, as can be seen in the diagram, with a single winding (also. Above) where a true transformer will have both a primary and secondary section.

Some prefer apples, some prefer oranges -- though I'd submit both need to be tried to find the one most favored.I have heard dynamic driver systems that sound extraordinarily open, with very good clarity and transient response.

We are all just sharing personal opinions. Everyone responds differently to reproduced music, and while my main speakers are Klipschorns and La Scalas that are side by side, I can say I have heard some truly outstanding non-horn loaded speakers, including both more conventional dynamic driver-based designs and electrostatic panels. I have been a very big fan of horns for many years, but have seen more than one instance where a former ultra high efficiency horn user/owner drifted to a hefty transistor amp and less sensitive loudspeakers devoid of anything that remotely resembled a horn. Never hurts to try something new...... It's just stuff, after all....

Many have also loved the Dynaco ST-70, a number of very competently restored examples (some better than others), can be found on Audiogon, some of which have really nice visual elements in addition to performance. They are right in your budget range, depending on how much work went into chassis refinishing and/or powder coating, etc.

Efficiency is also related to what's in front of it. If one only happens to have a pinch more than a single watt, as is the case with what is probably the best sounding amplifier I own, 90/dB for a watt will run out of headroom pretty quick. If on the other hand one happens to have on tap 250+ behind one's music, and depending also, somewhat, on the genre of music and preferred listening levels, such moderate effieciency could be more than adequate. As others mentioned, have a listen and please let your own tastes and impressions be the deciding factor. I almost bought a pair of Polk SDA -1 floorstanders years ago because they sounded really, really good. Go with an open mind and check em' out! Is there a chance you could arrange to listen to them at home to get a better idea of what they will do in your own space and with your electronics?

With others talking about 60'watts, I guess should mention that one of the amps mentioned above is a whopping 1.5 watt/channel and is a staggeringly good amp. My choice for among the best I have heard.

I have wondered on more than one occasion how this interesting speaker might respond with the Transcendent Sound T16 or SEOTL amplifier in front of it. I regret I've never heard the RF-7, but the Transcendent amps on Klipschorns and La Scalas, for me, are a special match. ....but then there is the vintage Baldwin organ amp I recently rebuilt. Transformer coupled as it is, that thing was truly a jaw dropper. This last one sent on to a good friend, I have another on the bench (okay, it's actually upside down on the floor awaiting surgery..), and I can't wait to get going on it! The RF-7 is an elegant and very interesting looking speaker.

Good morning, Sebastien There is extensive information here regarding the type A network, which I believe was in use from the early 1960s to early 1970s. That is a rough estimate. It is among the most simple Klipsch Heritage designs, and seems to be favored by many who have low powered amplifiers -- as in the 1 to 10 watt range. It uses the least number of parts, with just a couple of capacitors in the Mid / HF branch of the network, for a crossover point around 6 kHz, and a single series inductor for the low-pass section. Because of the low order slope, there is greater overlap between the drivers, however there is also less insertion loss, which is a benefit if one does not have too many watts to begin with. I have also had excellent results with this network sans inductor on the woofer, for an even simpler design. Because of its simplicity, it is also an extremely easy network to use as a basis for experimentation. Many enjoy modifying the original design with like-value modern capacitors of various brands and construction. One can season to one's taste as far as that goes.....the "which-capacitor-is-best" battles of past forum history are rather silly (including my own contributions) though entertaining. The type AA is slightly more complex, but also very much liked by some owners. If you do any DIYing, these crossovers make very good first build projects; they involve only a small handful of connections. They are also available new and well-priced on ebay from a very capable gentleman. You can also find used ones that are not too expensive. Apologies for the lack of paragraph breaks in my text. By the way, the lower crossover points mentioned above are NOT suitable to the stock K77 tweeter. They are used with the tweeter sold as a drop in replacement.

I would like to,also mention that, using the same Crites tweeter often mentioned here, I have experimented not only with the 4,500 cycle crossover point, but also wound my own, precisely measured inductors, for crossover points of 2,500 and 3,500 Hz. I used third order networks in these lower ranges to provide a sharper cutoff and protection for the tweeter, but maintained a simple bandpass and variable or fixed L-pad for the squawker. There are a number of ways of mildly altering the overall tone of these speakers, such as methods of making them sound less bright . I have done some of the published changes that have been posted over the years, And agree that some of the brightness was reduced, but unfortunately so was much of the character that first captivated me when I heard a pair of Heresies in college but couldn't afford at the time. What sounds good to one person, whether a brand of capacitor, a crossover design, or anything else -- might be a completely different story for someone else. Erik

I also have my crossovers outside the la scalas, which are positioned next to our klipschorns. As you have read, the autoformer is just a way of balancing the output of the squawker relative to that of the woofer and tweeter. As mentioned above, it is essentially a multi-tapped choke, since it does not have a true primary and secondary winding. Most loudspeaker systems do NOT use autoformers, but rather single series resistors or a so-called L-pad, one in series and the other in parallel with the voice coil of the driver. More recent Klipsch speakers do not, to the best of my knowledge, still use the autoformer - some have indicated it was a choice based on higher cost of the autoformer.....an assumption with which I do not necessarily agree. There are often debates over whether resistor based L-pads or autoformers are better, though it's my opinion, based on extensive listening to identical networks -- where one provided midrange attenuation with an autoformer and the other using non-inductive resistor based L-pads -- that the autoformer seemed somewhat opaque or veiled compared to the network using resistors. ALL of our listening impressions are entirely subjective, however, and I can only speak for myself. Some systems use variable L-pad controls, which function by maintaining a constant impedance load for the amplifier, but make it very easy to turn the squawker up amd down just like a volume control. It needs to be said again that changing positions for the squawker output from the autoformer causes a change in impedance. Since crossover frequencies and subsequent values of capacitance are based on the impedance of the drivers in question, one ideally should not simply change taps on the autoformer without also altering the value of capacitance appropriate for the resulting change in impedance, such as would be found if changing from tap 4 to tap 3 on a type A network. We have Klipschorns in corners about 22 feet apart, with La Scalas to the insides, about 18 feet apart from one another. As others have indicated, I also agree that the K-horns offer a more comprehensive snd balanced frequency response, but I prefer the La Scalas on some genres of music, such as classical guitar and Baroque, jazz trios, and so forth. For me, the most transparent of the Klipsch crossover networks for the Klipschorn and La Scala has consistently been the type A. Doing some experimenting with much more power than I normally ever use, I found the type AL extremely satisfactory, yet very dull and lifeless when the same network was used with our usual diet of sub 5 watt single ended triode or OTL amplification. Have fun on this journey! Erik

The auto former is handy like that, I agree. There is a change in reflected impedance, however, that may benefit from a subsequent change in value of capacitance on the input to said autoformer, as may be needed to maintain the same crossover frequency. Not hard to do or calculate, and just thought I'd mention it.

Either solid state or tube, a preamp with low output impedance would be preferable. I have had excellent results with both solid state and a variety of vacuum tube preamps, and my own opinion is that either output device of the preamp will not destroy the desirable quality of the single ended triode amp. ANY component can color the sound in some small way, and I suspect it sort of depends on what you like. If the Korneff amp requires a strong signal, a "passive" preamp, either transformer or conventional potentiometer-based, might not be adequate -- but possibly would be great. I would certainly try your solid state preamplifier to see what YOU think about the combination. I use one with my Transcendent T16 amplifier, and the two work very well together.

Yup. That's why it can be very nice to get rid of the OPT altogether. OTL, well designed, is rather spectacular, IMO.

BTW: If you're still reading this thread -- I also happen to very much like the Electra-Print transformers. This is another entirely subjective element, but I've heard the EP and another brand of also highly regarded output iron, and preferred the Electra-Print. My Moth Audio 2A3 amplifier also uses Electra-Print output transformers. The Moth 2A3 circuit is the best I have heard in terms of a conventional SET amplifier, and very close to a parallel feed output configuration, which is distinctive. erik

I may be thinking of someone other than Korneff as far as the parallel output design topology. Been such a long time since I've poked around at those amps, but there are a number of such designs, including Bottlehead stuff (formerly Electronic Tonalities, for those of you that remember that...) The Horus, which I also built, was one of these amps. Users of Moondogs and other common SETs can also subjectively easily (just time consuming) replace the existing OPTs on their amps with a high quality parafeed design from MagneQuest, as well as the necessary large plate choke for the DC component. This is an extremely WORTHY modification, at least from what I heard. There was another forum member and Moondog owner that used to contribute here that performed this precise modification to his Moondogs, and never turned back. Again, all subjective, and capable of being changed back if one wants or is interested enough in the investment of time and money to complete the task.

FWIW: Another amplifier in the same power range as the 45 triode is one that subtracts one of most important aspects of its (or any transformer coupled amplifier's) performance is one that does not rely on one (an output transformer). They're referred to as an OTL, and many who have heard them have come to prefer them for a number of reasons to more conventional single-ended amps that use more conventional air-gapped output transformers for impedance matching between amp output and loudspeaker. I own several single ended amplifiers using the 2A3 and 300B triodes, and also find myself using one of the two OTLs I own from Transcendent Sound. The OTLs referred to above do not use hollow state rectification (vacuum tube diodes), but rather solid state counterparts with significant filter and storage capacitance. There was a time I wouldn't consider anything that did not rely on vacuum tubes, but thankfully stepped away from that notion.........which, just speaking for myself, was ignoring some potentially highly sophisticated circuitry with outstanding sonic performance. And as always, there is not a single audio component that fits everyone. Some have tried OTLs and ultimately returned to their comfortable single ended triode amps (which I do from time to time too......depending on my mood, and depending on what music I'm listening to, etc. The human element constitutes a very significant part of the equation, IMO. I'd like to suggest too, that as much of a fan I am of the lower powered OTLs and SET amps, there are also some not just good, but extremely good sounding higher powered tube amps using EL-34s, 6L6s, etc. And then there are also the very high powered designs from Transcendent Sound (with whom, by the way, i have not a single connection other than for owning some of their amps and building, or in three cases completely rebuilding, them for others). You might check the website and forum for more information. Interesting stuff! The single ended SEOTL, which is the one in the same ball park in terms of power as single ended 45s, is IMO staggeringly good for such a low power amp, and I far preferred it to any 45 amplifier I have heard. If I'm not mistaken, Korneff's 45 is of a shunt (aka parallel) feed output topology, which is different from the usual output transformer that has to deal with both DC current and music signals, and I have built a couple of this type of amp using both the 300B and 2A3. They ARE different, and about as close as you can get with an output transformer to not having one at all................but not quite. Try to listen to as many as you can, enjoy the process. Erik

...but thanks for including the link, Tube Fanatic.

If the description of 2v into 10 k ohms, as djk mentions above, is right, he is also right. That's not the output impedance of the player.

KC (spooky pic, by the way!) 10K still seems on the high side to me, and I can't seem to find a spec listed for your CDP, but I'm sure you're getting it from the manual, correct? In any event, if it is a correct value, then you are right in terms of what we both know about the 1:10 ratio -- thus my suggestion to "experiment" as you are intending to do. I do understand your curiosity about this, and I guess I'm just going through a kind of less-is-more sort of stage in my audio development, or something... ALL in this hobby as far as perceived sound quality is entirely subjective. Go by what you like, and not necessarily (to say the least) by how something measures, etc., etc, or what others (like me) might say about extra circuitry or anything else. You might try a buffer stage and love it.

Oh. That sounds more in keeping with what I would expect. The general rule is that a source output impedance should be 10 times less than that of the load it's driving. As a personal and totally subjective approach, I would want as little as possible in the way of extra circuitry (including the inherent impedances and potential Miller capacitance effects related to it -- all of which can potentially impose signal degredation) between my sources and preamp. A good valve line stage, though, might be an idea to try. Anyway, experiment!