Erik Mandaville

"So, I don't listen now to the 901's terribly often, but when I do, I still smile." I like how you phrased that. They struck me on an emotional rather than intellectual level, too. The Klipschorns do that as well, as do our Lowthers, so for me I'm not sure I look at this in the sense of one being universally better than the other. They are different, and all three can sound awesome. I've not heard the 901s in our own house though, and that might be a completely different story. However, that would be an application problem, not necessarily an example of inferior speaker design. Erik

" I have listened to other speakers, some very expensive, some not so. I still like the horn loaded speaker." I share that sentiment, and I was kind of surprised at my own response in that I genuinely liked them. On their own, I wasn't aware of any lack of high frequency detail, and was interested in what I perceived as bass response that was not only deeper but more controlled and tighter than other speakers I've heard with similar physical dimensions. I had thought very seriously about buying a pair, and had gone back to the same store for a second audition. That time around the sound was really strange -- not good at all. Music sounded disjointed, dull, out-of-phase (or something), and just completely different in a bad way from the first time. I looked around the display setup and noticed that the EQ was missing. I asked about why it wasn't there, and the store clerk replied, "Oh, someone came in and ran off with it about a week ago (meaning it had been stolen). "So," he said, "we just hooked everything back up without the EQ so it doesn't happen again." In light of this, I have heard that some people actually prefer the 901s without the EQ, but to my ears the sound was unacceptable. So, yes, I do seem to have an inclination for horn loaded designs, but I'm interested enough in most aspects of this hobby to be able to appreciate other designs. This isn't unlike my experience with the digital Teac amp. I remember when EVERYTHING had to have tubes. In terms of how I view that kind of thinking now, I will describe it (and I'm saying this just about myself) as probably a little naive. Some people have also thought it odd when I tell them that one of my favorite painters is Mark Rothko. "But you can't see anything recognizable in his work!" True, but that also wasn't his objective. Erik ....maybe I should buy a pair of those things. I still wonder what they might sound like here at home.

" The guy from humblehomemadehifi is hearing things. He also rates the AudioCap Theta below some metallized types, which is absurd." Dunno, maybe that's just his opinion. No more or less absurd than yours to the contrary.

"The ESR tests very good and that tells you everything about a cap." In terms of electrical characteristics -- perhaps not necessarily in terms of what might provide the best frequency balance in a given system according to personal taste and perception. Some capacitors I've used with great ESR specs didn't sound the best in a given application. My 2uf worth. Erik

"I also think that alot of folks' "bad taste" about Bose relates not so much to the 901's, but to experiences with the other "mass produced" stuff that simply cannot be compared to Klipsch speakers." Why can't they be compared to Klipsch speakers? The simple statement that they CAN'T be compared is in fact a comparison of sorts, is it not? They have been compared to Heresies in this very thread. Those present seemed to prefer the Klipsch, which is fine. Others might prefer the 901s. I love our Klipsch speakers, and found the 901s in the environment in which I heard them also very musical. They made a very favorable impression on me, and I also thought their build quality was in keeping with their price range. That they are mass produced is meaningless to me. My car is a mass produced product. I liked the way they sounded, but would add that some Klipsch products are possibly produced on a similar scale. To my way of thinking, that is not necessarily an undesirable thing. I think quality control is suitably high for both companies. Again: as much as I love our Klipschorns, there are those who won't even consider horn loaded speakers -- even those made by Klipsch. Erik

Chris: I just now saw this, and wanted to thank you very much for that kind offer. I honestly don't need something in that value right now, but just for kicks might order a couple to use in the Klipschorn networks. As you said, they are also reasonably priced. Thanks again! Erik

"That's the direction I'm leaning... After verifing that there is no shorts, that the "problem" being perceived is not really a "problem." A polarized cord, with the correct polarity, and an earth ground should resolve the 50/50 chance of having this chassis live to unsafe levels." I have to differ just a little -- with all due respect, of course. The perceived problem is very correctly described as a problem. You have high voltage on the chassis that as it is right now could kill someone or start a fire. That you have not been able to find a short does not mean one doesn't exist, and could be hidden in a place that visually you can't access. The 'drain' I mentioned you needed above was an earth ground connection for the chassis -- to send this voltage to ground through the chassis ground lead instead of through your body. That earth ground connection is protection for the user in the event of a problem, and that problem has made itself known. In order to find the problem, it may involve a complete overhaul and rebuild of the circuit, including power transformer replacement. The amp is not safe until you locate and repair this issue. Just as a remote possibility: what if the amp were sold, along with its newly installed earth-grounded 3-prong plug, and the person who purchased it read somewhere that it is a perfectly safe practice to use cheater plugs to defeat safety grounds, and then one day decides to pick up the amp with both hands, while it's energized, in order to move it to a slightly different location? What if this same person had his or her audio system in the basement, with a bare concrete floor, and he or she happened to be barefoot at the time? If you can't find the source of the high voltage on the chassis, please consider taking or sending it to a professional technician who is very familiar with vacuum tube electronics. Best of luck, Erik

"I will use the Clarity Caps in the future. I am pretty sure that they are used in the B&W Nautilus speakers (802 and up). I'm not sure if it will make a difference but why not if it is the same price?" Absolutely! I completely agree. That's the thing that is nice about learning how to solder: One does not have to rely on others to make the choice of capacitor, resistor, or whatever else. I have seen your networks, by the way, and you've done some neat work! My point again was just that we (as a collective) often perceive the sound quality of music differently, and can thus make individual choices about how to go about altering or shaping sounds to our own liking. I've learned to not make cost part of my decision making process, because I have found it unreliable in terms of its relationship to performance. I have used some of the most expensive capacitors available because they sounded best in a given circuit, yet on other occasions chose a very inexpensive part -- but not because of its lower cost. Because it sounded better. The price wasn't even considered. Another example: The drivers in our two channel system now cost over $2,000/pair for JUST the drivers alone. No cabinet. Our Klipschorns, including a total of six drivers and a like-new pair of complex horn-loaded cabinets were $500 less than that. Of course money comes into play sometimes -- I'm a public school art teacher, after all. I have just found, as far as my own tastes and preferences, that what sounds good to me in terms of passive part selections is not something that is (always) determined by cost in the sense that 'more expensive' universally equates with better performance. The Clarity caps sound like they might be a great value, and I can tell you are happy with your B&Ws. I know someone who has a pair of B&W monitors in his office system, and I was very impressed by the sound. Erik

" I lifted the transformer and its' potential to ground dropped (but not all the way to zero, interestingly) while the chassis stays hot" I assume you're saying you physically isolated the power transformer from the chassis? Go back and check the schematic in the area of the center tap on the power transformer. You don't know the origin of this potentially lethal current draw. Erik

"Thanks for the response! I'll heed your warning in it!" I'm not necessarily saying it's not worth looking into more, but If your interest is in a DIY tube project, you might consider some other options as well. As a collector item, someone might like it; as well as someone with a special interest in vintage Grundig products. It's a well-known company. Erik

I admit, 'Solen' and 'Dayton' don't have much of a catchy name -- like MUSIcap, or SONIcap, or CLARITYcap, or AURIcap, or JUPITERcap (they must sound out of this world). One of the best single-ended amp circuits I've built and heard uses INVISIcaps. edit: wink

"I'll never use Solen's or Daytons again now that I know about these." That's exactly my point. That you don't care for Dayton or Solen caps doesn't make them inferior, except for you. Try different types and brands; use what works best for the sound-catchers on YOUR head, not those of someone else. I think Solens and Daytons are great regardless of their price. Erik

"Without detracting, or treading on anyone's toes, and in keeping with my previous posts, on this thread, is this a likely good candidate?" I had the same console about 10 years ago. A shop teacher friend asked if I wanted it, and I thought it would make for a good project. If you could see behind the face plate shown in the picture, you would likely change your mind. They are very complex in terms of construction and the integration of the radio receiving/source sections and output stage (amplifier). If the one I had gotten hadn't deteriorated so much, I might have worked harder on it, but there was lots of damage and oxidation. Erik

It can be fun to trouble-shoot. That filter cap possibility is related to the question I had about B+ voltages. Have you checked anodes against the schematic yet? What might be done to get rid of the shock hazard of this dangerous chassis? If I may, I would like to suggest addressing the hot chassis problem before you do anything else. You need a drain. Erik

I meant to leave a link for this well-known Dynaco site: For someone who is interested in learning, the kit prices are really quite good, IMO. The Dyna 70 is great looking, I think. Kit building is a blast, too! Wake up early on a quiet Saturday morning with a hot mug of whatever like you like, and heat up the iron for a few more connections, check them off as you go along. It is really enjoyable. People readily pay these prices for crossovers, which is fine and a personal choice, entirely. Just for the record, the same amount of money can buy a working amplifier that you can be proud to have built and tested yourself. There is always lots of support as you go along, too. http://store.triodestore.com/diy35kit.html Erik edit: search Dynaco on ebay. The ST-70 kit with an inside shot of some very nice wiring can often be found. In my case, totally worth the expense. I didn't want what someone else may have made for the same price; I wanted to learn for myself.

I just wanted to mention again the other alternative of an inexpensive kit with instructions and new parts. Or possibly a competently restored vintage power amp that can be used as training ground for study, measurement, and minor modification. A chassis looking down at the ground from a height of 115 VAC needs to be encouraged back to earth very soon. I sincerely hope that discovery was made by way of a volt meter, only. Take care and good luck! Erik

Have you located the fuse in this amp? Erik

I hope you took that comment in the right light, just as a 'light' suggestion to maybe proceed with a little healthy cuation. It's how I am, probably because I'm a teacher by trade, or something. I mentioned earlier on in this thread that it was an amplifier very similar to this one that once lit me up like a mercury vapor rectifier when I picked it up. On vintage stuff, it's just hard to tell sometimes if insulating materials are in good shape -- that sort of thing. One never knows what sorts of 'events' or mishaps such an antique may have been exposed to, or what damage may have been done to power supply elements that can't be seen (but possibly really quickly felt). I'm curious to see how things progress. Thanks for reporting some of your findings. Erik

"Put me in the camp that believes that the quality of the caps do make a difference." I agree with this 100%. I also think that the difference a part makes has a closer correlation with the design in which it's used than what it cost. "Different" is not always better, in other words. For my part, there have been times the more expensive part was judged to be better, sometimes it wasn't; and the cheaper cap or resistor or choke was used for the component while the more expensive part was used to take up space in a parts bin -- then used for something else where it resulted in an improvement. Put simply: over the past couple of decades, I remember times where I tried a given part that was indeed constructed very well and would have lasted a long time, but just did not sound as good (or any better) to me as the decent-quality-but-cheaper part I already had on hand. Where one is able to try for oneself and/or learn very basic soldering technique, it can be extremely liberating to have the freedom to make a choice based on one's own preference, rather than be told by someone else that the more OR less expensive part will be best. Erik

"If you have not checked out Parts Express, you should. I buy from them, when I buy. http://www.partsexpress.com/crossover-capacitor-index.cfm In my few projects I've used the Dayton poly and sometimes slightly more expensive. I refuse to believe that the very high priced units are anything than functionally equivalent to the lower priced, just with more artful claims and a higher price tag. Granted, some people report wonders." As above. I've used Dayton poly capacitors many times, and they have been very good for the money; and every bit as 'good' (IMO, IME) as some costing many times the price, which I have also tried. If you are able, maybe it would be worth auditioning some different types and brands of the needed values, and let that help with discovering what works best for you. It's possible to pay extra for matched tolerance values, which has not been a worry for me. For others, a 10% rating may be too high, so that may be an issue for them. When I listen to music, the ability (or interest) to quickly distinguish between a 5% 2uf cap and 1% 2uf cap would be non-existent. If you can detect a difference and one sounds better to you than the other, and cost isn't a factor, it's entirely your call. Erik

Nice job -- kind offer. Erik

"(About 10.5VAC as it happens, probably a transformer leaking to ground???)" Really? That might be something you'll want to watch. Did you check plate voltages on the input and output stages against a schematic or perform resistance checks? I'm glad it's come to life and passed the first smoke test. Erik

These have been popular -- DIY projects from Angela Instruments. Also a good source for parts. From the attached link, scroll to: The How To Section for some other examples of SE 6V6 using more common input/driver triodes and tube rectification. A stereo amplifier could be built from scratch for a little over $200.00 or so. Do note they include a word of caution. This is building completely from scratch, which might be something after a restoration project, or two. I've gotten parts from them in the past, and they've always been good to work with. Erik http://www.angela.com/

Cancel that. Erik Added: I have the same pentode/triode in my Dyna 70 -- one of the characteristics of the original design that gets slammed so often (to me it's been a great sounding tube).

Nice schematic! The 7199 is direct-coupled to a triode configured as a cathode-follower into the output stage. What triode type is it? Erik