erik2A3

Kevin: 95dB would really be pushing it for me, as well. I might do that with the likes of Genesis, King Crimson, Yes, and occasional heavy metal (fun sometimes), but my main musical diet is classical (piano sonatas, Baroque, guitar, woodwinds), and acoustic jazz. Turning such music up too loud does not sound natural to me, can obscure fine detail, etc.

All very helpful responses to that question -- I do appreciate it! That is a very nice amp, by the way! Those are Sophia Electric 6SN7s, aren't they? I think I may have an idea about what that circuit is, and may in fact be very close to the one I built last year. 300Bs can sound much bigger, IMO, than what their output horsepower might suggest. That's been my experience, at least. The way I've been listening to these La Scalas lately actually came about by an accident: I don't know what I was doing.......switching out crossovers or amps or some other thing (the usual neurosis), when I had one of those ubiquitous jaw-dropping experiences when I began to listen in the near-field, which may sound odd for speakers that have the power to blow the windows out. Truly, something happened in a really nice way, and the effect and sound is not unlike listening with my Grado headphones. I used to listen at probably twice the distance, but much prefer the closer position. It's hard to describe sound to someone else in a way that's meaningful, and I do appreciate the effort you guys made to give me your impressions. I would very much like to try the well known Tractix sometime. I have split Industrial La Scalas, and it looks as though all the squawker connections as far as attaching to the baffle are the same as a standard La Scala, so it should be too difficult to put into place. Josh, thanks for the kindness in offering an audition. I wish I knew how to make paragraph breaks that actually work! erik

Descriptions of music reproduction are often vague, I agree. By 'sharper outlines' I mean the manner in which instruments are presented in space -- either more clearly or diffused. What does "true to the music mean"? A system's fidelity to a recording is hard to measure unless one happened to be present in the studio when it was taking place (IMO) Kind of an of an offshoot of that (which we aren't discussing here) is when some say their systems reveal the artist's intent. Thanks for responding, I do appreciate it. Sometimes things like this just require a leap of faith. I've never had any trouble...ringing or shouting, etc. Of the original horn, but am curious about the Fastrac. Erik

Thanks. By better detail do you mean MORE, as in sharper outlines and greater clarity? A more precise kind of presentation, maybe? Erik

BE36: I am greatly interested in what you think of your Fastrac horns compared to the k400. Would you mind if I asked you to characterize some of the differences you found -- not in the sense of 'better' or 'worse' (which can be ambguous) but rather the nature of the sound produced by one compared to the other. I would appreciate it! Erik

In addition to the above I would suggest trying different networks, in addition to different crossover points, and base decisions upon your very individual preferences. There is no 'ultimate' in any of this. Where there are options, there are slots for personal tastes.

I use the Type A, somewhat modified, with our La Scalas.

I should have tried the AL with my 300b amps. Actually, I may have soon after I got these la scalas, but had to address some issues that surfaced with the speakers soon after I got them home. No fault anywhere, could have been during the time they were moved. 300b triodes can sound pretty powerful, and certainly capable of more than 1.5 watts trying to hack their way though all those inductors and caps. To simply write it off as 'bad' or 'terrible' leaves something to be desired, IMO, and specifically in terms of equipment in front of it. It's a dance of compromises, as someone once observed, though I can't even begin to remember who that someone was.

66hr Would you share some details about your 300b amp? I have been surprised at just how strong the 300b can be, even with speakers in the 87dB/watt/meter range. I built a pair of monoblocks lasr year based on a direct-coupled 6SN7 into the 300b that are outstanding. It's possible to see how they would be satisfactory with the ES networks in K-horns. Had you ever used these amps with the type A?

...and good grief, of course a very sincere THANKS for your kind words. The original plan was simply to make it work again, but I found so much more possible in terms of voicing, grounding, and power supply rejection that it developed into quite a project. I would like to say, though, that this particular Baldwin amp has been moderately common in DIY vacuum tube audio electronics circles. Doubtless there are many very good examples out there being enjoyed as primary reference amplifiers. erik

Dee I appreciate that. Thanks

66hr -- Great!

Blvdr: I have heard that before about Al's Extreme Slope networks, which as you know is not a reflection of the quality of ALK's design but a case where 'more' (in terms of many inductors and capacitors -- all of which are of great quality) doesn't subsequently mean 'more' in terms of necessarily improved performance. Totally agree with you. The AL was honestly not just good, but really quite good with the big SS amp I mentioned, yet sounded honestly sort of broken with our sub 2-watt amplifier. An organ amp I rebuilt, push-pull and in the 20 watt range, was another story. It sounded significantly better with the AL than the SET amp. Interestingly, using the more powerful amplifiers with the far simpler type 'A' was also an equally inappropriate network for high wattage; the response seemed very peaky, shouty, and just sort of overly charged in a way that was not natural (to me) I guess it's a case of balancing and compromising in order to find what works best with what.

Actually, no. The answer is that there is no simple answer. Let me clarify: The Hafler amp belongs to my wife. Using with the AL network was an experiment, and I was impressed with its performance with a crossover that has received rather less than flattering reviews in the past. As someone who builds his own amplifiers and preamps, specifically the single ended, directly heated triode variety, I have generally preferred dividing networks with insertion losses as low as possible, and that usually equated with simple, 6dB/ octave types, or, in the case of lower crossover points to the tweeter, 12dB for some extra protection for the HF driver. What I would suggest to the author of this post is to try a few different designs and choose which one sounds best to HIM, not the one people tell him (or her) NOT to get or use because of the opinions of others. There has been a significant correlation, in my experience with Klipschorns, La Scalas, and Heresies between the type of amplification one is using and the species of crossover that serves the most preferred performance -- based on listening, not measurement. Moreover, it would be important to not that this correlation has, for me, not so much to do with certain magical synergy, but rather another "simple" part of the equation: physics. Erik

This past weekend I had been experimenting and listening to the type A (I've also done 4,500, 4000, and 3,500 Hz versions of that) and one of my own based on the recommended crossover point (and slope) of Bob's tweeter manufacturer. Both were very good, although I prefer the tweeter on its own capacitor rather than in series after the input-to-autoformer cap). As a quick experiment (my networks are installed outside the cabinets to make changes easier), I tried the infamous AL that came with the La Scalas. With a one or two watt amp, the AL was very unsatisfactory. It sounded completely lifeless, detached, etc. Disconnecting the very low power OTL amp I'd been using and replacing with with a 100+watt vintage Hafler power amp, which in the right situation can be an exceeding good sounding amp, completely changed the tonal characteristics of the presentation via the evidently otherwise terrible AL. I like to keep in mind that individuals with rather exceptional qualifications designed the AL network and made it available to the public for a reason: That perhaps being that it had potential to sound startling good in the right circumstance. With the high power amplifier, that crossover shined wonderfully. Seriously. With all other SET and OTL amps I own, except for the direct-coupled 300B monoblocks I made last year, the La Scalas were not at all happy with such a mass of inductors, caps, and other shunt components that reside in the AL. With the right amp, the AL can be, IME, very balanced and image remarkably well. The subjectivity of all of this can't be overstated.

Dee You are welcome! I'm preparing the teardown and rebuild of my own in the not-too distant future. I was interested in taking this great old amplifier in a direction, based on my experiences, it hadn't been before. I'm very, very happy with the result, and really don't plan anything different from the one to which the post above refers. The main thing I need are suitable output transformers. Had a pair once that would have been great, but don't now. I have some other ideas regarding that, but we'll see how things go. erik

Back problems are surely not much fun....I've been there, and have continued reminders on some days. On the two channel front, I'm slowly beginning the second Baldwin amplifier rejuvenation, having found a completely stock example of the same one shown earlier in this thread. In addition to a complete rebuild of the earlier example shown, I found I was able to extract a quality of sound from that thing that truly surprised me. With some real care and attention, it is capable of becoming a thoroughly engaging and captivating amplifier, with dead-quiet performance during quiet passages of music. Much of this I attribute to its simplicity of design, but it has much of the air, space, presence, and immediacy of an SET amp (with the right speakers in the right room), but with a talent for punchy bass and really scintillating highs that are addictive -- but with the added benefit of more power that we need in our larger listening area. A couple of key parts in the circuit were removed, with addition of metal film resistors in some places and other types elsewhere. I look forward to the process of restoring another one of these for my own family. I'll post a picture of this 2-channel system to share when its done. erik

Bruce: That's interesting about the dropping resistor. With the schematic by my side as I type this, we have a 6.3 volt secondary winding off the main power transformer. R14 is installed immediately, on the upper (as shown in the schematic) leg of those two filament leads. R14 (the resistor in question) is then followed by the bridge rectifier, C9, the ripple filter capacitor, and the parallel wired 6SN7 filaments. My schematic is dated 1998. With Ron's permission, I'd be happy to send it to you for comparison. I guess it would seem rather odd for a schematic of the same vintage to indicate such a difference, but maybe some change was made without notice (??). Stranger things have happened. As I remember, your amp is wired the same way, R14 being before the rectifier. All of that notwithstanding (I'm clear on where that resistor is on the schematic I'm looking at), I am glad you're still enjoying your amps! I sure do mine, as well! Do let me know if you'd like a copy of this. As I said, the copyright date is 1998. The only real difference between your model and the one I have, if I remember correctly, has to do with the change from MagneQuest (your Moondogs) to ElectraPrint (mine) in the heavy iron dept. They are a great match with La Scalas though, aren't they!? Enjoy! erik

Neo: It's good you got the problem solved. I remember pretty clearly how you badly you wanted these Moondogs. The CD louder than vinyl issue may have to do with the amount of gain out of the CDP vs whatever phono stage you're using. Perhaps it's not a problem as such, and can be remedied by turning the volume control up a little more when playing LPs (??). If you want to try to balance the gain between the two, it's possible to use in-line atttenuators such as 6dB, 12dB, etc. As an EE, I'm sure you know how to install one of your own design on the CD input into the preamp. Deafbykhorns: Seems Ron had reworked that portion of the filament supply. It's been so long since I've been under the hood of my own pair, that I forgot I had switched to AC filaments. I always seem to have good success and quiet performance, and use the common simulated grounded center tap supply via two 100 ohm resistors on each AC to ground. I use AC on the filaments of the 300B monoblocks I built last year, and have very little residual hum through the horns. My Moth amp, purchased as a chassis, box of parts, and schematic, uses regulated DC for all filaments, including the 2A3s, and doesn't make a peep. Have fun if you build a pair of Moondogs.

Hey, deafbyklipschorns Well, we have a difference here:) I found the schematic online, actually (which someone had posted) and reconfirmed that the dropping resistor is on one AC leg just before the bridge, which is the case with my own pair of Moondogs. Your point is interesting, though, because there may be some differences in different editions of this amp. In fact, as I'm sure you know, it's more common to drop the voltage after the bridge, via CRC, then the filaments. Thanks, too for offering to help Neo with the problem -- I hope he takes you up on the offer. erik

Maynard: okay, gotcha. I don't even have my moondog schematic anymore - for some reason. It's a simple amp, though. Bruce has a nice pair, filled Kiwami resistors if I remember it right. After rebuilding a Baldwin organ amp to send to another forum member friend, my current project is also solid state -- an unbuilt Dynaco PAT 4 preamp! I'm heading back towards vinyl, and will use for a bit until I build a tubed phono stage, most likely 12ax7. Good luck with the Sony, erik

Tube fanatic You had been curious about the schematic, so was just mentioning that I know the amp well, and if you needed more info on the circuit could share with you whatever you may want to know. Erik

Don't do anything unless you know what you are doing. There are nearly 400VDC present in that amp when it's energized, and if you're not sure what pins are the filaments on a 6SN7, there is a good possibility you will not be sure of where the high voltages reside in the Moondog. deafbykhorns: Just for clarification, the dropping resistor is on one leg of the AC filament supply BEFORE the rectifier, not after it, followed by the rectifier and filter capacitor. Have a good day all. erik

tube fanatic: Please let me know how I can help you with this. I know the entire Moondog circuit by heart, and I can share any aspect of it with you. The AC portion of this filament supply is not on its own, meaning that there is not a separate 6.3 volt filament transformer. I agree that it's highly unlikely that the winding is shorted, but I am uncertain of the quality of connections associated with it. 9 volts on one end and 2 on the other is odd to me, because the filaments should be wired in parallel, and they are connected to the same 6.3 volt source. I would like to know how this voltage has been measured in terms of the positions of the filament pins we've discussed above. Again, please let me know if I can help you troubleshoot in any way in terms of information you'd like regarding the schematic. I'm comfortable sharing that with you because it's obvious to me that you are very familiar with vacuum tube circuits. Bruce: are you measuring this without a load (tubes installed?) 8.31VDC is high, and should be dealt with for longer tube life. Are you familiar with Ohm's law? you can calculate the value of resistance needed to bring that back down to a more appropriate level. I measured the voltages on that amp when I had it here, and they were within spec. at that time. What do you measure with tubes installed? erik

Neo An EE is great ( I am honestly impressed), but how one views a tube socket, from bottom, top, or one end or the other makes a difference. My concern about this has to do with the possibility of certain conditions that may make additional powering up of the amplifier to test filament current potentially unwise. I would add that the problem has aleady basically been diagnosed and tested with the tube, itself -- since as you say the heaters glow fine in the other monoblock. If the filaments were getting adequate current in the faulty amplifier, the amplifier would still be working and we wouldn't be discussing it. Since we are talking about DC, the problem is a little more complex because of the other parts involved. Do you know how to safely bleed down the storage charge in a high voltage filter capacitor? Depending on how you view the amp, one of the holes in which you insert a meter probe may be the plate (that means high voltage, Neo). It would be helpful to know the orientation of the amplifier relative to how you're viewing it. From where did you receive your degree in electrical engineering? Best of luck with what should be an easy repair. Erik