erik2A3

I have a single-ended OTL that runs really warm (actually HOT), that's good for a whopping 1.5 watts/channel into 8 ohms. With speakers that have an efficiently of 104 and 106 dBs/watt, it is probably one of the top three best-sounding amps I have. Even with Heresies it was really amazing.

Craig, that's really a gross over-simplification. Thinking and design are far more advanced than conventional valve amps. Surely you know that!?

Hey Pats3of4 Sending a PM

I have all the drivers (K55V or K55M for midrange), woofer's, tweeters, but not the crossovers. I will sell them all for less than you could buy a pair. I slowly acquired these over the years to build a pair, but have too many other audio projects going on. More than that, I need space in my workroom for amp projects in the works. Send me a note of your interested. I don't buy or sell here often, but my wife and I have perfect eBay feedback. PS:. I just remembered that the tweeters were very kindly given to me by another forum member years ago. I would not feel right turning around and selling them (some might do that; I won't) I pass that gesture on, so the complete set of tweeters will be at no cost. Add to that the points I'll get from my dear wife for clearing out some of my audio madness, and I will come out just fine. I promise a very fair deal. Just don't have the crossovers, but Heresy I networks come up on eBay all the time.

Al, I have an extra pair of K400s. Are you looking for just the horns, or horns and drivers?

Agreeing with Craig, here. I've used the above triodes in different configurations for a long time, and yeah, they can be great -- but consider also the circuit; there is more to just the output device used. Single-ended EL 84s can sound amazing with Klipschorns. I did that for a long time too, and IMO gives the far more costly big triodes a real run for the money. I have some insanely expensive 2A3s and 300Bs, and love the the El 84. PS: my wife bought me a Decware mini-Tori a few years back, one of the few amps I didn't build myself. It uses single-ended 6V6s (or others in that family), and while a great little amp, I recently bought some nice OPTs with UL taps at 40%, and also mades some other small changes, including feedback removal (just my preference). Those old triodes are nice -- particularly in a parallel-feed application -- but consider some others too!

Mark51, I had to chuckle about the doorbell wire! Me too! I went through what now seems like a pretty crazy wire experimentation phase about 20 years ago -- everything: doorbell, garbage disposal power cord, bunches of coax, bare silver, twisted pair fine transformer wire for ICs (excellent), low voltage landscaping, tons of stuff. One of the things people should keep in mind about caps in x-overs, is that they see very, very small voltages, where a 50V cap is good for 100watts or more (approx.- forgot the exact spec when I was studying all of this in the late 80s, early 90s). When I see networks using 630V caps, it makes me wonder a bit. Those big caps, particularly the PE and Teflon dielectric films, get really, really expensive, and that voltage rating is simply not necessary. But that's just my opinion, as well as that of some other builders I know. People should use what they feel best using. Using less expensive plastics such as mylar or poly -p at such low voltages is ok (for me) because they do not suffer the same stresses as those seen in high-voltage applications. I've used Illinois caps for old radios and other vintage equipment very successfully. Again, just me, and am totally comfortable with it providing the working tolerance is met, and I'm using the correct amount capacitance. I've always been much more interested in design and circuits (as I said before) than I am about the passive parts used in them -- which sure, can a do make a different. My experience with spendy caps is that, yes, they can sound different, but my premise is that the difference may not always be for the better in a specific application

Oh C'mon Dean, Let's do autoformers again...for old time sake... the Wild West forum saloon days!

Lol! Done.

Mark51: Right and good! And what Bruce said, and the substance of what wdecho said. I was building speakers and crossovers more than 10 years before I joined this forum in 2002 -- and then also took a badly needed long break. Things got really nasty here..... I am able to afford whatever capacitor brand available; I know about all of them, and have used and experimented with most of them. In either frequency dividing networks, interstage coupling in line and output amplifiers, bypass positions, etc., etc., etc., etc., etc!!! The cost of a condenser (aka capacitor) does not make it sonically superior -- unless the user in question, in his/her own listening space and with his/her associated equipment - judges it to be better. BEING ABLE TO HEAR A DIFFERENCE BETWEEN BRANDS AND TYPES IS NOT THE POINT. THE POINT IS WHETHER THE DIFFERENCE IS ONE THAT TO THE PERSON IN QUESTION (not the builder of the network, unless, as was my case, the person in question and the builder are one and the same) PERCEIVES THE DIFFERENCE TO BE BETTER (OR POSSIBLY WORSE) without respect to cost, construction, or anything else. Beyond that, another question remaining has to do with the fact that the difference, even if thought to be for the better, still may not justify the often exponentially greater cost. BUT! If ANY difference or change for the better is worth the price of admission (whatever it happens to be), it is most certainly someone's right to spend his or her money as they so choose (As Schu stated above). As Mark51perceptively and independently discovered, good results CAN be obtained with a minimal investment. I have also replaced a $60 film cap for an NP electrolytic (because I'm a fool and an idiot who doesn't know better?) No, because I COULD tell a difference and preferred the NP electrolytic -- likely because it DID have slightly higher measurable ESR than the expensive film cap, and thus seemed to mildly attenuate what I perceived to be a peaky, somewhat grainy HF driver. Done, end of story. I don't obsess over capacitors -- circuits and design interest me much more. So many designers I have read and followed, and who have published project articles along with schematics, almost invariably ask that interested builders stick to the values of L,C,and R shown on the schematic, but to "season-to-taste" with preferred cap and resistor types and brands. PS: My all-caps (not a pun!) in the sentence above is not intended as shouting; please don't take it that way. It's because it's the same statement I've made here for 16 years. Anyone who knows anything about audio electronics knows that what really matters most about these pesky passive components, is that it's not the type or brand -- but the color of final, decorative, outer wrap.

Right. I've been a Lowther owner for a long time. Some install zobel networks, swamping resistors, baffle step compensation etc., with the hope of correcting the response -- all of which sound terrible to me. I don't like damping material, either. Silver voice coils, despite their higher conductivity, are also heavier than copper or aluminum (the other options), and that slows the driver down somewhat. The mini torii with La scales, Heresies, etc., is outstanding.

Also tried them with 106dB/watt Lowther horns, which were not nearly as nice a match as the others. The problem really had more to do with power transfer function into the Lowther high (15 ohm) impedance.

Mini Torii (the output stage and part of power supply of which have been reconfigured for UL operation). This necessitated replacing the original output transformers for single-ended OPTs with UL tap and secondary impedance of 6 ohms.) One connection left -- chassis earth ground. Aesthetics are quite nice, with the much larger output transformers, although I will say the amp was really nice stock. I'll post a picture when I'm done with it this weekend. edit: Forgot speakers: La Scala, Heresies I, Electrovoice 2-way (vented enclosure).

Rick - We both could have gotten more for them

Greetings gentleman and old friends! I was poking around the Garage Sale here, and was so very pleased to see that this old pair of K-horns has found another great home within the forum family. Awesome! The gent I bought them from (also for $1,200) told me his dad was a dentist who loved classical music, and thought the Klipschorns were the perfect speaker for that genre (I have to agree!). They were originally raw birch, and had been painted chocolate brown. There was not even a hint of wood grain left, and my wife and I labored over them for days, carefully removing the paint. If I remember right, the original networks were the type AA, which couldn't be found at first. They had been removed from the cabinets for some reason, and were found outside in unfortunately very poor condition. I happened to have all the parts to build my preferred heritage type A network - as was correctly stated in comments above. The motor run caps shown should be good for a long time still. And so, Kevin, they have in my mind sort of come full-circle - I bought them with the funds from the sale of those black La Scalas so many moons ago. Remember? When I bought the K-horns, I told the owner I would honor the very fair price I bought them for by passing that on to any future owner if I decided to sell them. Thanks, Rick, for remembering that! I have to say I missed them like crazy after I sold them. As it turns out, since we are now in Arizona in a house without suitable corners, it is just as well. I bought a pair of nice La Scalas from a guy in Phoenix this time last year, and they are working out perfectly. In turn, this current pair of LS replace the pair of industrial LS we had that just didn't compliment our room decor in the least (which personally didn't bother me). My poor wife has very patiently put up with this audio insanity forever, and so it was my choice to find something a bit more room-friendly. Enjoy!

Amps with and without hum-null pots: The Wright 2A3 single-ended amplifiers are designed with low impedance driving the output stage via a larger than customary interstage coupling capacitor, as well as incorporating a different filament hum reduction approach, using fixed resistance rather than a variable potentiometer to balance the AC filament supply for minimum 60 cycle hum. When using three element tubes such as the 2a3, 300B, 45, etc., the cathode is also the filament, so hum is more problematic than a tube with an indirectly-heated cathode. The power supply is also unique -- I talked with George Wright about it years ago. Such a gentleman, he was. The other more simple solution around AC filament hum is to use filtered DC instead. The Moth si2A3 as designed by Craig Uthus uses regulated DC for all filaments, and is thus an inherently very low noise amplifier. Every time I compare the two (AC and DC filament supplies), I always tend to prefer AC; and so installed dedicated AC supplies in the Moth amp for both input and output stages. OP: As others have already pointed out, you don't need to adjust the bias on those amps. Enjoy them, they are marvelous amplifiers.

Hey Bruce, Absolutely. I couldn't find my old posts on this either, and decided I was probably going about it the wrong way...or something along those lines, and gave up. It's great you still have your old Moondogs! They are such great amps! I agree they are a bit busy under the hood as originally designed. That's of course NOT a reflection of the efficacy of the circuit, itself, but rather related to the fact that it enabled the kit builder to more easily keep track of what's what during construction - despite the fact that each mono block subsequently used a bit more hook up wire to and from the terminal boards than if caps and resistors (etc.) were wired directly to tube pins and other terminal points. That puff of smoke should be really easy to track down and fix; I'm sure they'll be howling at the moon again very soon! I rebuilt my own pair around 300Bs, but was just thinking the other day that 'llI put the separate 2.5V filament transformers back in for 2A3 use. When I bought mine, Welborne Labs and Lowther America had gotten together to sell a large kit package for a significantly lower cost. It consisted of the pair of Moondog kits, very large, back-loaded horn enclosures (unbuilt flat pack), and Lowther PM2A drivers. Maybe I imagined this Bruce, but do you no longer have your La Scala? Am I thinking of someone else, maybe? Hope you and your family are well, too. After a 3rd major back surgery and move from Houston to AZ last year, things are getting better. I also had four separate surgeries on my hips to repair torn cartilage (that's what running on concrete got me), but have been once again been able to do some hiking. Very thankful! erik

Moth Audio kits: Bruce, Moth Audio did not sell kit versions of their products. We (specifically my wife) contacted Craig U. to make an offer for the Si 2A3 in the form of an unassembled and unwired parts package, including output transformers, power transformer, and all passive parts and hardware (including chassis and custom wooden shipping crate) to build the amp. I already had an assortment of driver and output tubes to choose from. And that's what he agreed to sell us, based on the understanding that I can read schematics and know how to build. The regulated DC filament supply on the output stage doesn't use hum null pots; however, I have converted the 2A3 heaters to AC, balanced with pots for minimal hum. Even with AC on directly heated triodes, it's still a fairly quiet amp in terms of 60 cycle hum. I just prefer the sound of AC over DC filaments, which is probably also partly related to the fact that I simply also prefer that more historically traditional approach (such as a grounded center-tapped filament transformer, etc.) The zero-cap-in-signal-path design was inspired, as he explained to me, by an amp designed by his dad. I am responding here for clarification. erik

dtel, You and I both!

DizRotus, You and I joined this forum the same year. If we go back to those early years and consider the amount of rudeness and character-bashing that took place then compared to now, I think we would both agree things have changed very much for the better. And on the whole, I agree with you in terms of just leaving nasty and unkind commentary alone. In a social context such as this, though, when a fellow forum member, or his or her costly and carefully chosen audio equipment is ridiculed, disparaged, or otherwise unfairly and/or rudely criticized, it would not be unexpected for another forum member to pass on the reminder that we are here to share ideas and thoughts about a common strong interest - not to use it as a platform for flinging insults at others as a way of inflating one's own ego. It depends on how it's handled, I think. To not respond to inappropriate, bullying behavior is also another way of allowing it to continue. It is NOT ok. We should abide by mutually agreed-upon forum etiquette, where such behavior is not only not allowed, but also not tolerated. A little bit of healthy argument is good; bullying or criticizing others is not good. You obviously felt strongly enough about this to comment on it yourself, which, while it is yet another contribution to the subject under discussion and does not simply ignore it, I do appreciate your attitude and your effort.

Just for the record, there is another matching cabinet. The one shown above was pulled out for illustration purposes. The black rectangular area below the driver cutout is the horn mouth. These are extremely sturdy, well-built cabinets.

So, perhaps not adopted...... Anyway, Dimensions: 41.5" tall X 18" wide X 15" deep Weight per cabinet guesstimated to be about 100lbs sans drivers. These were designed around the Lowther PM6A driver, which is one of the shallower alnico drivers. I use PM5As in my rear-loaded horns, and the magnet is so large it won't fit the compression chamber in these cabinets. I acquired them to use with DX series of Lowthers. I hate to see them go, but we simply don't have space.

JMON - Totally! I care about these cabinets, but am so happy they are going to one of our forum community members who I know will appreciate them.

Apologies, I forgot the eBay link. See here: http://www.ebay.com/itm/Lowther-DX3-Fullrange-Speakers-Pair-/120705540484?hash=item1c1a9c6184:g:fnEAAMXQHDlRe9jN

These drivers would be ideal, but as mentioned above, Common Sense Audio has a line of drivers (Audio Nirvana) that have been very well received (I also own a pair) and are much less expensive. With the Lowther DX3 drivers, I estimate the efficiency in the boxes I'm giving away to be in 100dB/watt range. Once driver surrounds are loosened up and broken in (taking several hundred hours), they sound extremely good with such music as acoustic Jazz, lighter classical, solo guitar -- so for me are very, very satisfactory. Moreover, they are true point-source drivers, and have zero insertion loss associated with passive crossovers.