Erik Mandaville

Now I just have to resist the urge to collect consoles for the sake of their contents, as disposing of the carcass is kind of a drag in my neighborhood (transfer station silliness WRT "construction debris.") I totally understand that, same problem here. My wife got so tired of seeing an old beatup but nevertheless really cool Sears console from the W II era that she stripped the nasty green paint off it (I helped), and turned it into a nice display shelf for her hand-made teddy bear collection. I saved some of the tubes and transformers, and dumped the rest. There is something so captivating to me about those old things. I've gone the smaller or at least more portable route from two decades or so earlier.

"But you have to kinda quit assuming that everyone is totally ingnorant to the subject." The title of this thread is "Should I bother? Beginner Tube amp Question" Based on that, would it be correct in your estimation to assume the person involved has a comprehensive understanding of high voltage charges in storage capacitors? If that's an assumption you would like to make, that is your business; however I will pass on a warning simply to remind about safety regardless of what others think about it. For me, based on the knowledge I have and experience with being shocked in the past, it would be a serious professional compromise to not mention it to someone who, by the nature of the title of the thread, seemed uncertain and was a self-described tube amp beginner. He pointed out his experience with working at very high plate voltages, which I acknowledged, and then explained that the safety warning was intended for anyone else who might be interested in getting started in electronic DIYing. I have had a number of non-posting members ask me questions about things like this. If you would rather make the assumption that people ARE aware of very real safety issues concerning potentially fatal shock hazards, that's your business. I would rather make my error on the side of preventing that from happening to anyone. I have friends who are pros at this who have admitted becoming so familiar with the work at times that they forget to be afraid -- and gotten zapped by a careless mistake, such as forgetting to turn a component off before soldering. I think we sometimes forget that our conversations about such things as this, where people can be very seriously injured or worse, are viewed only by the small handfull of participants within a given thread. The fact of the matter is that it's global, and we simply CAN'T know who is following along, and possibly ready to jump in and have a hand at whatever is being discussed without being warned of the potential dangers. You can expect me to continue to make some of those concerns public where I think appropriate. It was not meant as an insult, and the author of this thread seems to recognize that. No offense taken, Erik

The schematic above is the same for my Heresy IIs. Erik

"Regarding safety... I play with CRT projectors with 35kV anodes. I'm good! Thanks for the concern, tho!" Sure. It's intended for anyone reading this, (which may be many) who are interested in the same thing yet may not have experience working around high voltages -- which you certainly do. There have been a number of occasions in the past where even long time forum members with solder slinging skills have reported very bad shock experiences in working with these components. Others have talked about working on and soldering in energized equipment, which is not good anyway one looks at it. 'Yes' on the 6.3 volt filaments supply. It may be fine, although one way to lower that, as well as provide some in-rush current suppression is to use an in rush current limiter as part of the AC input into the amplifier. For a stand alone power amp, it could be as simple as replacing the volume controls (which might be in the range of .5 megohms or so) with a fixed grid leak resistor (from the grid of the input tube to ground) in each channel. If you can find a shematic, the location will be easy to see. Have fun, Erik

Whether vintage or modern: Keep in mind that filter capacitors can store strong electrical charges for days. Not all power supplies are complete with bleeder resistors, and you have to be careful. Don't assume the component is safe just because it's been turned off and unplugged. There are several places inside the amp and tube sockets that, if you touch them, will drain the filter capacitors very quickly -- into you, and that's not a good thing. This is a fun hobby, but you just have to remember (and respect) the fact that these things make music through the use of dangerously high voltages. Erik

I remembered Townshend Super Tweeters. I was seriously considering a pair of these a few years ago, but haven't yet. They are pretty expensive at $1,500 (the last I saw) but have gotten some outstanding reviews. They have a built in gain control to match the output of the main speakers, and of course can be moved back and forth on the top of the cabinet as needed for best sound. Erik

Fostex makes a number of top-mount tweeters just for this purpose. Madisound sells a kit that uses one of them, and it's simply a matter of installing a capacitor in series with it to establish the crossover frequency (usually quite high) Stereophile has done this a number of times in the past, and the same is also done with full-rangers like Lowthers (and again Fostex). A friend of mine recently bought four of the Fostex super tweeters, but were not the really expensive ones. These were in the $150 range, I think @ www.madisound.com He likes them. It's one of those things, I suppose, that someone should try for themselves to see if it's an improvement or not. I'm going to get a pair for my Lowthers one of these days, but don't feel the need to use them with the Klipschorns. Bob Crites' new drivers did the trick for us there. I tried a pair of add-on car audio tweeters, which actually were okay for some recordings. On others they sounded tinny and not very musical. I think those from Fostex I'm thinking about are in the 106dB range, so in some cases might need padding down. Erik

"Cheaper than a SET kit even so what the hey ya know?" It's true, some of the SET kits available are expensive. There are alternatives, however -- good for beginners, and has gotten some good reviews considering the cost. Probably the least expensive tube kit available, or at least that I've seen. Go to: www.tubesandmore.com See the menu on the left, and scroll to 'Audio' Click 'Audio'. See the stereo amplifier kit for $185.00 complete with all parts and instructions. There is also a monoblock version. Parts are installed on a wooden base, very much like old radios from the 1920s. With some minor modifications, the circuit could be installed in a simple chassis for greater safety, with short screws into the bottom of the base. Wood won't conduct, so it's insulated. The vintage stuff is always cool, and can sometimes turn into something pretty involved. Line voltages are higher now than what they used to be, which means filament supplies (the things that make tubes glow) can run on the high side (not so good as far as tube-life goes); filter capacitors usually need to be replaced or reconditioned; resistors replaced that have drifted in value which can throw off correct operation. They or neat though! If you have a variac, that would be good as you begin to check it out. Something like this was how I got zapped a long time ago. An old 6V6 pp amp, with no fuse and an un-earthed line cord. I was able to let go by throwing it -- all the way across the room. Those kinds of shocks are hard to forget. Have fun but be careful Erik edit: Correction: Go to the website, and first click on 'Kits' on the menu. From there scroll down to 'Audio' as mentioned above.

"Hooking the tweeter filter cap to the junction of the autoformer input (pin5?) and the 13uf cap causes the tweeter roll-off to react as a second order network electrically rather than first order. Dr. Eugene Patronis calls this an "improved 3 way network" in the 3rd edition of Sound System Design by Davis and Patronis. Hooking a tweeter filter cap directly to the xover input will allow more tweeter output below cutoff." I pointed out once in the past the notion that I thought the original tweeter connection on tap 5 was possibly of a higher order than its frequently referred-to first-order status. As would be shown in a schematic diagram, the "input - 13uf - #5 tap - 2uf - voice coil" arrangement closely resembles a third order design (not saying that's what it is); however,my point at the time was simply to state that I found a greater sense of presence and HF energy, as well as clarity overall, with the autoformer completely out of the equation. For me, that was a more significant improvement overall than what was derived by simply connecting the tweeter filter to the input IN FRONT of the 13uf cap. With the tapped choke gone, the tweeter, as you pointed out, would be connected directly to the input, and a true bandpass would be connected in series with the squawker. That is another benefit, IMO. In any event, a response plot of the original setting in the type 'A' was posted, indicating an essentially first order slope (if I recall correctly). It was posted in response to my suggestion that the autoformer might be having some influence on the behavior of the tweeter. I also pointed out the value of capacitance normally used for a 6dB tweeter network @ 6kHz would generally be different from what is used in the type 'A' example -- which has certain implications........... What matters is that we are satisfied with what we have, and that is the case for me until I am able to sort of 'liberate' the system of passive chokes, caps, and resistors. Erik

And for the record: The illustration of the network above is for informational purposes. I in fact would prefer to get rid of it completely and never look at it again -- despite the fact that to me it looks kind of neat on its own. The aesthetic issue has ZERO to do with the fact that I can't get away from the fact that it is nevertheless still a passive dividing network, consisting of hundreds of turns of thick wire, capacitors, and resistors. Erik

"Well, Paul disliked L-pads...and he felt the need to attenuate the tweeter so it had to be adjusted by an autoformer" Sure, I'm aware of that. Simple enough. However the example I gave had to do with a specific network ('A') which does not attenuate the tweeter. Rather, the tweeter is connected in series AFTER the capacitor between the amplifier input and autoformer. In theory, this might possibly also increase related ESR, which is a characteristic that has been addressed in the past in relation to potentially lower tweeter output and perceived HF response with older capacitors. I was simply making the point that the tweeter filter in THAT particular network should not have to be associated with the autoformer in any way in order to functional properly and effectively. The question you are asking is something I have done quite a few times. The main job of the autoformer is to increase (or decrease) the load impedance 'seen' by the amplifier, which in turn will bring about either and increase or decrease in gain. Since the values of capacitance and inductance in crossovers are in part based on driver impedance, it would be correct to assume that alterations of impedance imposed by the autoformer would require an appropriate change in values of associated capacitance. I have switched between tap 4 and tap 3 on the autoformer many times without changing the value of the primary capacitor, and the only change in response that I could detect was the resulting attenuation brought about by the impedance increase from one tap to the other. The response might not measure that way, but there is not always a direct correlation between measured and perceived response as it relates to sound quality. The breadboard version of the network below was to test the quality of a type A network that used a resistive L-pad to attenuate the squawker rather than the autoformer. It was an experiment. The result was a design that to me had an obvious increase in high high frequency response and presence. The tweeter filter, which at that time was a first order design, was also connected directly to the input of the amplifier rather than behind a 13uf capacitor. My question had to do with whether or not there was a possibility that the perceived increase in the amount of HF energy and presence had anything to do with the tweeter being separated from the midrange branch of the crossover network. I do know that Paul Klipsch did not care for resistive L-pads, and certainly respect his choice in that as a designer. I'm reporting the change in sound that I witnessed with the removal of the autoformer.

"There is also nothing wrong with using 2 autoformers, except cost." Of course this is true, and cost certainly is a significant factor. If one were to maintain the use of the autoformer for the squawker, a far more common and widely used approach to reduce tweeter gain is a variable L-pad. It can be adjusted by the user 'on the fly' to dial in the exact amount attenuation desired, and requires no change in related passive part since the original load impedance is maintained. Suggesting that two autoformers can be used, to me, implies that the tweeter circuit can be treated individually and does not necessarily have to be associated with the primary capacitor between the network input and autoformer (EX: Type 'A'). Can we identify the specific reason for not connecting the tweeter filter directly to the amp input? Erik

"On the other hand, you can use a transformer winding as an inductor." That is very true.

"This is the most germane crossover discussion I've seen in a while. We tend to think of the autoformer as just a level control without considering that it is after all a tapped inductor..." Agreed it's a good discussion. The fact that the autoformer is a multi-tapped inductor has been actually brought up a number of times in the past. It's somewhat related to how it functions as an attenuator. As was pointed out above, an eqaully effective crossover can also be designed without it. I know that from experience myself despite the number of times Mr. Klipsch's work to the contrary is brought up in response. (please note that I have great admiration for his work, just a different pair of ears that I'm trying to please). Autoformers have been described as sort of more 'transient perfect,' however I didn't find that in comparisons I've made using both types of the same network order using the same crossover frequencies. ANY of the older Heritage networks can be made using a pair of resistors rather than an autoformer. It consists of a bandpass (series connected coil and cap) on the squawker, followed by an L-pad calculated for the impedance of the driver and desired reduction in output. The tweeter is connected directly to the input by way of a single capacitor. Very simple; very effective. One just needs to keep in mind that, when calculating the desired values of capacitance and inductance, the actual impedance of the driver is used rather than the reflected impedance imposed by the autoformer. You can also design a mixed order network fairly easily, such as using a lower x-over frequency for the tweeter accompanied by a sharper cutoff, such as 18dB/octave. That's what I use on my own networks at a frequency of 4,000Hz. Best not to do that with the K-77, though. For reduction in tweeter gain minus the autoformer, an additional fixed or variable L-pad is needed, however, which is something I admit makes the convenience of the autoformer attractive. Erik

" Which drivers are these? Did you build the enclosures? What is the efficiency?" Sorry for the late response, here. The drivers are the older version (non-rolled-edge whizzer cone) PM2A. If I remember right, they are rated at about 97-98dB or so in free air, and around 100dBs or so in rear-loaded horns. The cabinets are the Medallion IIs from Lowther America, during the time Tony Glynn was at the helm. The cabinet is actually based on the original Lowther Acousta horn, which was wider and not as tall. The Medallion II was designed by Jennifer Crock of Jenna-Labs. I was going to build the horn from scratch, but just did not have access to a decent table saw in order to make the odd angle cuts of the internal folded horn. So, I purchased the flat kit, and put them together. This was back in '98 or so, when Welborne Labs and Lowther America put their heads together and offered an outstanding value: Welborne Labs Moondogs (complete unbuilt kit with tubes) and the Lowther PM2As and unbuilt/unfinished Medallion II cabinets. Lowthers have an almost electrostatic like transparency, a good thing, but also have some drawbacks (there are always compromises). I've heard that AERs, such as those recently sold in the Garage, are much smoother, and all around better, but I'm attached to these old PM2As. They honestly sound better to me all the time. They have enormous magnets, and extremely low excursion, which is why they really benefit from horn loading. I know some people who experimented with both the PM2A and slightly more efficient PM5A in bass reflex cabinets, and very much disliked the results. Others were okay with it, but I've not tried them in a ported enclosure for myself. I also once filled the internal voids inside the cabinet, some of which are pretty big, with dry playsand to damp the cabinet (someone advised me to do that -- Tony Glynn said NO!!!), which it did. It took hours to get the sand in by duty-designed holes in the back, and I not only damped the cabinet completely, I destroyed the sound. I made a vacuum attachment for the shop-Vac, and sucked out every last grain of sand to get it back to where it was. Jennifer Crock also told me to line the entire length of the horn, or as much of it as I could get to with felt, and I had meant to give that a try but never did. She called it the Medallion Completion kit. She makes some nice wire, but kind of expensive. I used a long pair of Jenna-Labs ICs for awhile back then, but decided not to keep them. I had been looking at Lowthers for a few years, being really interested in the single, (sort of) full-range driver approach. This, in addition to the SET 'thing' gave me a good way of getting into both, but I admit I had to sort of close my eyes and jump. I loved the sound, but the drivers did take quite a bit of time to break in. The surrounds tend to be tight, and just need to work in. These things taught what music can sound like without a crossover in the equation, which I'm sure is very much like what those using active frequency dividing experience. Jim: Yah! Erik

Our HT is all Heritage as well: Klipschorn R/L, Heresy center, Heresy surrounds. It seems really ideal for movie soundtracks, but I also sometimes use just the Klipschorns for stereo listening via a 2-channel bypass mode on our Lexicon processor. Carefully adjusted surround can be remarkable for music-only listening. Erik

Lowthers with SVS subwoofer -- it works incredibly well, although I was worried I would have problems combining the two because of the speed of the Lowther horns. It's fine. The Lowthers are very nice on their own, but fall off fast in the 60Hz range. Without a doubt the best addition I've made, but need to get another sub for the HT -- or pair, most likely. JL Audio would be nice! (just kind of $$$$$$$$ for me now). Erik PS: The radio at the bottom was custom designed and built by the dad's of one of our forum members. Probably the best point-to-point wiring I've ever seen.

"I'm probably wrong here Erik, but I ASSUMED every adult here "knew" they were allowed to exercise their personal preferences." I would truly like to be able to assume the same thing, Mark. You mentioned that radio in your previous post -- an HD, if I'm not mistaken. I've been interested in trying that myself. Take care, Erik

Hi Mark: You phrased the question about why people could like a pro audio amplifier in a very general and open-ended way, and the idea of how this particular amplifier relates to the concept of personal preference is one I have been interested in since it was first brought up. Your right about the safety concern, though, including cheater plugs. People have also been called 'chicken' because they preferred not to do electrical work in a live chassis. I don't mind offering my two cents worth if it might keep someone from getting hurt. To my way of thinking, personal safety and possibly preventing electrocution is not the same as choosing the sound of one component over another (if that's what you were referring to in bringing up the cheater plug issue -- I wasn't completely clear on that). The 'High End' comment: You didn't bring up that phrase, someone else did. Accept my apology for making that seem as if it came from you; I can see how you might have read it that way. Lastly, I'm always interested in defending personal preference, where people are weighing multiple factors in selecting components for their stereo systems. Historically here, phrases such as "You're deaf if you can't tell the difference" or "The fact that you like this (whatever it may have been) is proof of your lack of experience, understanding, and that you're an idiot." have been hurled over discussions ranging from capacitors, crossover topologies, amplifiers, and everything else. I'm not saying that's come up in relation to this discussion of pro audio equipment, and I'm not accusing anyone of using the phrases I just mentioned in this specific situation. I'm simply clarifying the reason why I have chosen to post in some cases in the past. Ultimately, you're right. It would be best to just skip along and do something much more... CONSTRUCTIVE! [] Erik

Interstage impedance matching is always an issue, whether 'home (approved) audio' or pro. That goes, as mentioned above, between preamps and amps, or within stages of components, themselves. I can attest to the attention Mark has given to this in his preamps; the amplifiers I have no experience with, but I'm sure the same is true. My argument has to do with something else concerning individual preference for these machines. Erik

"I'm still befuddled about what there is to "like" about pro amps in the home audio setting?" Why befuddled? What are you basing the judgement on, Mark? Some people have heard them and find them suitable. That's good enough for me. If they are not suitable for YOUR home audio setting, drive on. It's no different than the Paleolithic SET/PP debate. People have asked me very similar questions regarding our La Scalas and Klipschorns -- or....what is it you enjoy the sound of.....Belles, aren't they? "Horn speakers like that will rip your ears off!" "No," I reply back. "They rip your ears off." People have bought them and liked what they do for the cost. People use the same structures in the process of hearing, as do people also chomp T-bone steaks or creamed spinach (YUK) with the same 'chewing, and swallowing anatomy'. Doesn't mean they all like to eat the same thing.....and so on and so forth, etc., etc., etc. This isn't to say PCATs and other tube amps aren't equally likeable (obvious enough). I wish I had the piggy bank to afford a pair of your amps. I'd be interested in a schematic if you ever decided to make them available, though. Erik PS: What is a HIGH END audio amp? I admit the term is impressive sounding enough, but what exactly does that mean? I know that cost figures into the equation simply by virtue of the title. Add the term 'Audiophile Grade' onto anything and the price is jacked up 500 fold. I have a $75.00 amplifier that sounds as good or better than ANY significantly more expensive tube amplifier I own. That doesn't make it my favorite amplifier, because there are other associations about the components I have that are important to me -- the people that were involved with the fact that I own them. On sonic merits alone, the TEAC is a superb amp at 30watts X 3. Cheap, light weight, easy to not to worry about.

Dee: LOL! I would say pretty well-deserved, too. Evidently, someone else had bought them earlier, took them home, and then brought them back and asked for his money back! Too funny. I heard them playing in the background of a phone call just five minutes ago. Erik PS: We have a truly mint pair of early Heresy Is too (virtually flawless walnut veneer), and I paid, choke, nearly 700 times that. But I love them! Jim: Guess what!? I'm getting the ACTUAL Baldwin schematic for this project I mentioned. It will be KILLER!

Mark: "Jeff---who cares about "average" people in this context? I fail to see your point at all. OF COURSE average people don't hear differences, that is why they have Bose speakers or little boomboxes for stereos. Jeff---who cares about "average" people in this context? I fail to see your point at all. OF COURSE average people don't hear differences, that is why they have Bose speakers or little boomboxes for stereos. "Average" people do not own Klipschorns or Jubilees or even KG4s, nor do they argue about it on forums! "Average" people could care less about any of this. I fail to see your point at all. OF COURSE average people don't hear differences, that is why they have Bose speakers or little boomboxes for stereos. "Average" people do not own Klipschorns or Jubilees or even KG4s, nor do they argue about it on forums! "Average" people could care less about any of this.or even KG4s, nor do they argue about it on forums! "Average" people could care less about any of this." But many average people also enjoy the more easily available speaker models from Klipsch, and yes, Bose (those Bose jabs are handy, aren't they?). Nor, as you said, do they spend time arguing about it audio forums. I've said in the past that some of the most insightful impressions of how music sounded here, from preamps and amps I have built, or from the La Scalas, Klipschorns, Heresies, Lowthers, or DIY speakers -- have come from AVERAGE people. And you're right, people who could care less about whether a crossover or coupling capacitor costs $.50 or $100. Average people listen to music, not the latest resistor, op amp, or inductor upgrade (which, based on the price paid, better be good!) Or whether an amplifier, according to one person's measurement machinery, wasn't worthy of a life spent in someone's home audio rack. A good friend once said to me, "When are you going to start listening to music again for the sake of music appreciation -- the composition, rhythm, harmony, and other elements -- the thing as a whole?" "Sometimes it seems that you use it (music) as just another test for the latest experiment or so-called 'upgrade.' " I submit 'average' listeners might have something valuable to offer. And you also observed "Average" people do not own Klipschorns or Jubilees..." That's probably, true, but there are quite a few people in the so-called 'hi-end' that consider horn speakers in general, and Klipsch Heritage in particular, horribly colored, harsh, tinny, ear-bleedingly bright, and so forth. Very unflattering. Even a few of our more illustrious forum fellows had in years past said the same thing about the Heritage line. I remember listening to a pair of RF-7s a few years back, and I found them bass heavy and slightly dull compared to the La Scalas and Heresies. What was one of the design objectives for the La Scalas? Correct me if my history is wrong, but I thought good-quality PA use was one of them. And the Jubilees? Was the currently available model intended primarily for home use (I honestly don't know the question to this answer!) Based on appearances alone, which I admit can often be totally misleading, the Jubilees I've seen on the forum have a much more Pro-Audio or cinema sort of look than one expected to blend well in the......average person's home. "Who cares about average people in this context" (?) I do. Here's why: The average music listener is most often NOT someone who is worried about whether the capacitors in her crossover (or his crossover) has the word 'mylar' or 'mundorf' written on it. What matters is composition, artistic proficiency of performance, and so forth. They don't sit and worry about whether they should possibly consider NOT liking their new preamplifier because someone is doing measurements on it that might turn out to be not very good. LOL! Were I an audio engineer, which I am not, I would keep a very careful ear to average people who really like to listen to music. Erik

Mike: Dunno, I guess it's sorta like looking at a picture of a cool car, a cool motorcycle, or a bowl crammed full of vanilla ice cream and topped with a soft brownie and hot fudge. I appreciate quality craftsmanship even if I may not happen to have a personal preference for the actual function of the product. Al K's ES crossovers border on sculpture and are wonderfully well-made, but they are more than likely NOT the best match for some of the very low power amplifiers I have. Dean and I don't always see eye-to-eye on issues (yeah, I know that's probably an understatement if there ever was one), but there is no doubt in my mind about the quality of the workmanship evident in those pictures. I will never hesitate to give credit where it's deserved. To the best of my knowledge, they were also designed by a very capable engineer; and that fact in conjunction with high quality craftsmanship is what helps me say, without reservation, "hey, nice networks" -- the only thing lacking in that quote being the exclamation point that belongs at the end of the statement. [pi] ...oops, I think I just hit the pizza icon. Kinda funny, though, so I think I'll just leave it! Erik

As usual, I have to chime in with something like: "Hmmmm, that actually could be an interesting combination." (...but you just never know for yourself, for sure, 'til you try for yourself) Erik