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Jon Noring wrote: Patrick Turner wrote: Volker Tonn wrote: Jon Noring schrieb: In the last couple of years I've posted various inquiries to this and related newsgroups regarding high-performance, tube-based AM (MW/BCB) tuners, both "classic" and modern. Have a look into the "Collins" S-series. These are state-of-the-art tube sets 'til now. At least it's not the tubes alone but the fabulous mechanical IF-filters giving outstanding results for a tube set. Manuals with layout diagrams should be available on the web.... Since Mr Noring says he has regularly trawled the Net for everyone else's expertise on AM reception, but got nowhere, because he's still doin it, why doesn't he gird his loins and put his shoulder to the task of learning all about AM and radio engineering as spelled out so clearly in all the old text books, and then damn well build his own perfect AM radio??? Thanks for sharing your frank coments. They are acknowledged. The important thing is that the replies to my "trawling" have been very informative, including yours Patrick, and are not only benefitting me, but are benefitting many others who are following this thread in real time. Whether my trawling is successful or not for my purposes is immaterial -- if I fail, I fail -- I don't fear failure as some do -- the discussion is further adding to the information pool for the community of those interested in some aspect of tube-based AM tuners, and in that regards I think it has been successful. (With Google archiving the newsgroups, this information is now being preserved, and is searchable.) I don't mind sharing whay I know, but you will be the one left to decide what works or doesn't work, so you shoukld get away from the PC, and ito the workshop to try out ideas mentioned in all the responses to your query. I for one haven't time for the R&D, but if I was more passionate about good AM than I already am, it'd be to the workshop I would go, armed with ideas, and solder on towards lower thd and more BW. There are obviously two sides to the engineering of radio receivers: 1) the basic theory and the basic categories of design approaches (which I am studying -- it helps in that back in 1974 I had the equivalent of one years' worth of basic electrical engineering courses at the University of Minnesota, which is now all coming back to me), and 2) the real-world engineering of receivers/tuners, using real rather than theoretical components, and the attendant compromises and work-arounds which inevitably result. I do agree with Patrick's implying that there is no such thing as a "perfect radio". I am not seeking the "perfect radio", but a modern-design tuner "kit" sufficiently meeting the various requirements I have previously set forth. I believe once a good design results, that PCB boards can be made, coils can be built by someone or some company experienced in doing that (I mention coils since that is the one component difficult to buy right off the shelf -- thank god no one has to build their own tubes!), and the schematic with detailed instructions and guidelines sold through diytube (as an example.) There already have been several excellent SS kit designs for decent AM released by Oz makers in past years, but its 35 years since any tube based kits were available. Nobody seems to think it'd be commercially viable to present yet another AM kit, because 90% of folks listen to FM. So you are on your own wanting to make a kit design that could be sold, and I wish you well with the prototyping of coils and circuits. The target market for the "kit" are those who build their own tube- based components for their audio system, and want every component to be a high-performer, approaching audiophile-grade in performance (yes, AM broadcasts are not "audiophile", but audiophiles want a tuner that brings out the best in what is there in the signal.) They don't want to spend their limited time building junk, they don't want to build a Radio Shack beginners' crystal set. They want very good performance (which is admittedly a "fuzzy" word), commensurate with their other components. They just want the tuner kit not to be overly complicated in design, to work if they follow the instructions and guidelines, and to meet their (collective) expectations. And these kit builders are not novices, either, at wielding a soldering gun, and in chassis and cabinet design -- they are mechanically- and electronically-inclined, and are now building audiophile-grade amps and preamps from the many kits now out there. I also believe that some of the vintage radio collectors, who are experienced at restoring radios, will also take an interest in the AM tube tuner kit. (For those who don't know, I'm now restoring a Philco 37-670 console, so I'm not exactly out-of-touch with the radio collecting world.) Based on my experience with building audiophile-grade tube amps and plugging into that community, I think I've laid out pretty well what they want and expect. Most are not going to become radio design enthusiasts, they will not live and breathe tuners, building hundreds of circuits on cake pans in their basement (and I am not disparaging those who do!) They simply are going to listen to the tuner they laboriously built from the kit, happy with its performance, and happy for what they have learned about how radios work "under the hood", in a general sense. Some will no doubt get the radio bug, and join the people here, rescuing old radios from the landfill, and restoring them. Maybe my focus on TRF-based designs and "channel-based design" have been diversions. But, from what I've read about real-world TRF designs (John Byrns messages have been great here), a TRF-based design has some nice attributes from the audiophile kit perspective, and there are clever real-world solutions around the selectivity and gain limitations of the "what's taught in textbooks" regarding basic TRF design, as John Byrns and others have noted many many times, but which seems to fall on deaf ears of those who believe that the best high-performance receiver (however "high-performance" is defined) *must* be super-het in basic design. But obviously, the vast majority of commercial designs of high-performance tube-based radio receivers from the mid 1930's to the 1950's are super-het designs, and many of them are great performers, so I'll post a parallel message with another call for candidate radios to inspire the AM tuner kit. After all, if one is to put together an AM tube tuner kit, it makes a lot of sense to base it on a proven design from the past -- why reinvent the wheel? For example, diytube (at http://www.diytube.com/ ) has taken the venerable Dynaco ST-35 amp design, modernized it some (and to further improve its audiophile performance), and is now selling the PCB board with schematics and instructions to diy audiophiles. it is an excellent performer (I know firsthand -- it is a *very nice* sounding amp.) diytube is now working on a high-power monoblock tube amp kit based on the Eico EL34 amp of old -- can't wait until it is released. Just some thoughts... Jon Noring We await with ardent expectations of the fruit of your your efforts in your workshop with a saleable prototype tube based AM radio tuner kit. Patrick Turner. |
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