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  1. BuzzK

    Tutorial: Tube amp build with layout steps and adoption of PCB circuit to point-to-point wiring?

    I'm building another amp from scratch. I want to use a mu-follower driver circuit, which was originally on a PCB, but I will do a point-to-point conversion (no PCB) instead. I propose to explain how I decide to lay out and wire the amp, and the various considerations for optimization...
  2. BuzzK

    Onwardjames rocks on!!

    Onwardjames purchased one of my tube amps in good faith, and what a delightful experience it was (as a seller) from start to finish - and beyond.
  3. BuzzK

    Dynaco PAS3 Blend Switch resistor(s) question

    I see there are two different sets of resistors on the blend switch used with the Dynaco PAS3. The (presumably) older version has 560K & 270K resistors in the network between switch pins 2,3 & 4. The PAS3X uses 68K and 33K in those positions. The ratio is essentially the same, but they are...
  4. BuzzK

    Eico HF-85 Redo

    An AKer and a great customer prevailed upon me to fix up a cosmetically nice Eico HF-85. The HF-85 gets mixed reviews: a lot of people like it, but its inherent problems (aside from needing new caps & etc.) are acknowledged if not well-known: • Hum. An unshielded power transformer on a...
  5. BuzzK

    Vinyldavid is -- like his name implies -- groovy.

    Had a very nice transaction on some used gear with vinyldavid. He took pains to communicate thoroughly and accurately, and packed the items to survive shipment. One piece was much better than expected (or advertised). Thank you and thumbs up!
  6. BuzzK

    Opinions sought: Borskie's Aikido vs. CCDA line stages

    Looking for opinions from people who have built or heard them both. The CCDA is like an "Aikido light" with 1/2 the tube set. It also inverts. Thanks. BuzzK
  7. BuzzK

    Passing the PAS2/3: Ultimate upgrade for the PAS Dynaco Preamp?

    This is a work in progress . . . I'll be getting the prototype PCBs soon. The PAS2/3 series preamplifiers were immensely popular as well as [relatively] affordable. Here's a link to an interesting blog article, in which the author calls it "the most important preamp in the world"...
  8. BuzzK

    Buzz's custom tube preamp with 417A/5842 phono section

    Erno Borbely designed a FET phono stage that was later adapted for tubes by Joe Tritschler (audioXpress Jan 2010). I had two PCBs made with his circuit, but with a couple of mods including the ability to add Lundahl step-up transformers and switch between MM & MC cartridges. I had discussed...
  9. BuzzK

    Dynaco PAS2 /3 Question

    Can anyone tell me more about the microphone connection (the dotted line on the preamp circuit)? How is it used? If it is omitted, what (if anything) does that change?
  10. BuzzK

    A real mess . . . :-)

    Just pulled this one out of storage; made a couple of mods, and fired it up. Might still be my favorite tube amp, although the driver was a real P.I.T.A. to install. VERY musical, with good soundstage and space between the instruments.
  11. BuzzK

    Out of mothballs . . . Borbely DC100 amp build from TAA 1984

    The original circuit for this 100 WPC MOSFET amp was designed by the late, great Erno Borbely. It was a project featured in 1984 in the Audio Amateur magazine (what a fun publication that was!) I'm guessing I bought the circuit PCBs and most of the parts in the 90's and is has taken this long...
  12. BuzzK

    Specs for Magnatek UST20N20 & UST20P20 MOSFETS?

    I bought some of these parts many years ago, and can't find any specs via Google search. This are similar to the BUZ900 series lateral MOSFETS (essentially two 2SK134 type die in one TO-3 package). I'm trying to find the input capacitance values for each. Anyone have specs? THX
  13. BuzzK

    Eico ST-70 conversion to 6550s redux

    I posted about this project (now finished) in the past, but the inability to use the search function prevents me from appending to it. There were a number of contributors to the concept and the designs, including Gordon W. and Dave G. But Dave G. saved my bacon (once again) on this project. I...
  14. BuzzK

    Mike LeFevre (Magnequest)

    I don't know if Mike was a member or if it is appropriate to post this here, but I saw of Facebook that he recently passed away. Many of us had dealings with Mike at Magnequest, his transformer manufacturing company.
  15. BuzzK

    JJ = Just Junk?

    I bought a couple of "matched" quads of JJ EL84s from Viva and Tube Depot to populate a pair of SCA-35 amps. When buying quads now, I think it's a good idea to get 5 matched tubes instead of 4, in case one dies. I built my own tube matcher, and the quad wasn't what I would call a good match...
  16. BuzzK

    LEDs for cathode bias on small signal tubes?

    I'm interested in folk's opinions and experiences with using LEDs for cathode bias in preamps or line stages. 1. Advantages & drawbacks? 2. Is it "musical"? 3. Do you prefer capacitor or resistor bypass (or a combination of the two) 3A. Are bipolar electrolytic capacitors better or worse...
  17. BuzzK

    Tube amp burn-in . . . Fact or fiction?

    A lot of people believe that it's necessary to "burn in" a tube amp for some period of time, in order to get the best sound. Various "explanations" are offered, but likely most are unprovable or specious. While it is true that various parameters of tubes and electrolytic capacitors change from...
  18. BuzzK

    Iron placement question

    I've got to make the best of some chassis real estate. On the top of the chassis I have a large 5H DC choke. On the bottom I'd like to place a 28V bucking transformer, a Hammond 166J28 series, which has a dual bobbin construction. I'll probably have to elevate the choke on top with washers to...
  19. BuzzK

    Resurrection and upgrade of an Eico HF-87 Amp

    A customer purchased an amp from a third party who shipped it to me. The back story is that the seller had not used the amp after acquiring it elsewhere (good decision). It was immaculately packaged (some of the most care that I've seen) and arrived undamaged. At least from shipping. :) The...
  20. BuzzK

    Exceptionally good purchase experience with FB Night

    I recently bought an SCA-35 from FB Night. The unit arrived exactly as described, but and better condition than I expected. I thought I did a decent job of packing tube gear, but FB Night gets first place for the care and attention he spent in making sure that the amp arrived without the...
  21. BuzzK

    Dynaco SCA-35 Repackage Idea?

    I bought the iron for an SCA-35 from a guy on another forum. I'm thinking about installing it in one of my "universal" preamp / amp chassis, along with Dave G's PCBs; a relay input board; a motorized remote volume control (with mute), and a 12VDC power supply. I laid out all of the parts...
  22. BuzzK

    ST-35 capacitor question . . .

    A fellow audiophool buddy asked about the green capacitors in a Dynaco ST-35 marked "POM." Anyone know who made them, and what the dielectric is? Thanks in advance, Buzz
  23. BuzzK

    Opinion(s) re: 6922-EH tube?

    I'm interested in what folks think about this tube, esp. suitability for replacement of 6Dj8; reliability & lifetime; noise, sonics, etc. I'm contemplating using a pair in a phono stage. Thanks in advance, Buzz
  24. BuzzK

    Scratch build of a tube preamp with external power supply?

    I don't want to wear out my welcome with yet another project, but if there's any interest, I'll document the build of a tube preamp using mostly parts I have on hand, with an external DC power source to minimize A/C hum, with schematic and such. BuzzK
  25. BuzzK

    Way above & beyond by 57esquire!

    A few days ago, this AKer posted an ad in Bartertown for some Infinity speaker parts. I have a pair of the same model, but one is missing a grill, so I asked if he had one for sale. 57esquire (Tim) didn't have one in salable condition, but he had a busted one I could use for a template. He...
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