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tube fanatic

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About tube fanatic

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    tube amp designer

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  • Interests
    extracting the best possible sound from single ended tube amps using modestly priced designs and tubes.
  • My System
    Currently using RF-15s in a small room, near-field, arrangement and driven by low power SETs. The soundstage is enormous, and the musical involvement beyond anything previously experienced.
  1. A budding audiophile!

    My grandcat is highly insulted! He would never allow a flea on his body!!! And, he's not really sleeping. He is analyzing the problem in the HT system and concentrates better with his eyes closed..... Maynard
  2. Dynaco ST-70 series 3

    Supposedly, this is getting closer to being available (at a price of $3k according to one source). I can't imagine that it will be worth almost triple the cost of a fully assembled ST-70 from Bob Latino. But, it is interesting to read about how they developed the design: http://www.dynaco.com/inside-story.php Maynard
  3. A budding audiophile!

    My daughter was working on her HT system and enlisted a helper. She said that the sound quality improved greatly with his intervention! Maynard
  4. So, what do you know? (audio expertise)

    Isn't it obvious? Maynard
  5. DIY Tube Amplifier Kit 6P3P + 6N8P

    There's a good lesson here for anyone contemplating building a kit like William's- don't assume that the transformer wiring is correctly phased as it is with the higher end xfmrs. In fact, it seems that even identical xfmrs may not be wired the same! So, the correct phasing can be determined by experimentation after the amp is built, or with a signal generator and 'scope before it is built. Who would have thought??? Maynard
  6. Finally pulling the trigger on a Bob Latino VTA 70

    An excellent choice for an amp! Most importantly, do you have any experience soldering (especially on a pc board)? If not, it would be worth buying a bag or two of old resistors/capacitors and a bunch of terminal strips (which you can mount on a board) and practice. There are many video tutorials around on proper technique. It is easy when first starting out to overheat a component which can cause it to fail, and it is possible to damage pc board pads with excessive heat. Any non-conductive surface is fine for doing electronics work and, if you are working on a concrete floor, a rubber mat under your feet provides an extra level of safety. I also recommend installing a GFI outlet into which you can plug the amp when testing and measuring. It's a very inexpensive way to make things much safer. Maynard
  7. DIY Tube Amplifier Kit 6P3P + 6N8P

    I'm not sure what they tried to accomplish with the dual fb loops either. I suspected that the global loop was causing excessive phase shift which triggered the oscillation. And why they didn't use a compensation cap across the fb resistor had me scratching my head as well. In either case, I have never found a global loop to be worthwhile even in a 2 stage amplifier (to my ears it seems to impart a "swishiness" when listening to the music). The simple plate to plate fb arrangement works well and, as William discovered, reducing the value to 470k made a big difference. The ringing should be eliminated with a little capacitance across the input jack (even as little as 1000 pf may do the trick without affecting the hf response since it is rolled off anyway). And I sure agree about the value in these Chinese kits. For what they cost, even if they only last for 10 years, it's still excellent. If I didn't have such a large stock of tubes from the radio/tv repair shop days I'd probably go that route myself and simply reconfigure the circuits to improve the parameters. Maynard
  8. Got a Fisher 500C for my Cornwall II's

    I see that you are in Utah so you're not terribly far from Ken and Lloyd at Analog Engineering Associates in California. In addition to electronic restoration, they offer some of the most amazing cosmetic restoration work that I've ever seen: http://aeaaudio.com/vintage-amp-store/ Maynard
  9. The "Little Bruiser" mono flea-power SEPs

    It's there, but is lost between the pictures. Attached is a separate link to make it easier. These amps are about as simple a design as I can come up with. If constructed with reasonable care they will give more than a taste of just how wonderful single ended tube amplification can be with Klipsch speakers. And, if wiring is routed appropriately, they should be dead silent as well. Maynard Little Bruiser 3.pdf
  10. The 6W6 was originally registered by Hytron in 1939 for use in the audio output stage of car radios. It enjoyed a very long and successful life until it was ultimately replaced by the electrically identical 6DG6. It is also one of the nicest sounding audio tubes I've ever heard. Power output of these amps is approx. 1.3W which is more than enough to allow very loud levels to be achieved with most Klipsch speakers. They are particularly well suited to systems which are set up in rooms which are not terribly large, or in near-field applications. One of the local guys has described the sound as being "smooth as glass" by which he was describing a very smooth midrange and top end. And, as is evident with the 320 Hz square wave shown below, the bottom end is very potent (and also extemely tight and well controlled). The "ear bleed" filter across the input allows tailoring the high frequency response to individual taste. The amps run very cool and can be played all day, every day, without breaking a sweat. Tube longevity should be extremely long due to the conservative operating parameters. Should you decide to build a pair, keep in mind that THESE AMPS OPERATE ON VOLTAGES WHICH CAN KILL YOU! DO NOT ATTEMPT BUILDING THEM IF YOU LACK THE EXPERIENCE TO WORK WITH SUCH VOLTAGES IN A SAFE MANNER. The schematic is attached as a PDF between the first two pictures. Feel free to post any questions and I'll try to answer them as quickly as possible. Maynard Little Bruiser 3.pdf
  11. Having A Senior Moment Caps in Series

    It's probably a neon bulb used for additional regulation in the meter circuit. It cannot be tested with a battery. Maynard
  12. The Mastersound is apparently parallel single ended as you stated. As to not hearing much difference between it and your Yaqin, it has nothing to do with the age of your ears! Not everyone is sensitive to amplifier characteristics, and some music and speakers may be less revealing of differences than others. I'd consider that a blessing as it keeps you from chasing your tail trying to find amplification which covers all the bases with all kinds of music. Maynard
  13. To me, a triode strapped pentode is as much a triode as an actual triode. It's the electrical characteristics which matter (a triode strapped 6Y6, for example, is a much better "triode" than some of the popular tubes which lack a suppressor and screen grid). Others take a different view and only consider DHTs "true" triodes and that adding a cathode changes the definition. As to push-pull pentodes (whether used in conventional pentode operation or ultralinear) I tend to agree with you. I find that many push pull amps, even when biased for class A operation, lack the sonic appeal which makes tubes worthwhile. If I needed much more power I'd probably go with SS myself as the differences between that and push-pull are small to my ears. It's a matter of personal taste as with everything else in audio. For me, single ended is the only way to go. Maynard
  14. Derrick, what kind of tube amp are you using that puts out 256 wpc (I may have misunderstood what you stated)??? Auto biasing is a very useful feature, especially for owners who are not technically inclined. It makes the amp operate as a plug-and-play device as well as keeping each output tube set for the desired operating point (theoretically at least). Another advantage is that it eliminates "bias obsession." You can't imagine how many guys are so obsessed with bias that they check it on a daily basis and won't tolerate even a 1 milliamp drift (which can occur from normal line voltage variations). Yes, it's worth keeping an occasional watch on it (like once/year after the first 100 hours of operation on the tubes) but it just isn't that critical. Not everyone agrees about ultralinear combining the best qualities of triode and pentode operation. It's a matter of personal taste. To me, it's the opposite- I generally find that it combines the worst qualities of both. One must experience it in their system to make a decision. Since many amps can be switched between triode and ultralinear operation while music is playing, it's easy to get an impression of both. There's no question about the inefficiency of triode operation. However, triode amps are not necessarily room heaters (it all depends on the design, power output, etc.). As to short tube life, that's totally design dependent. I find no difference in tube longevity between my SETs and SEPs. Distortion is also totally design dependent. It is possible to have a SET with distortion figures which remain low over the entire operating range. As to power needed with most Klipsch speakers, you yourself have measured that it doesn't require much to get blown out of the room. It's a matter of selecting the needed power output to satisfy one's listening levels. There's little to be gained by having an amp which can deliver 100X the maximum power required to handle the loudest level at which a person will listen. Maynard
  15. I like 'em big.

    The audible differences may have more to do with circuit arrangement than power. For example, comparing a single ended amp to one that's push pull will yield noticeable differences regardless of power. And then there's the issue of distortion levels at a given output power. A more fair comparison would be a 1 watt SET with a 8 watt SET, and so on. The bottom line is how much power the amp can furnish when needed. If a "normal" listening level requires 50 milliwatts (with Klipsch speakers that's often the case), and the amp can supply 5 watts at low distortion (for 20 db of headroom), there's really little need for more power. And, the required power is so easy to measure that I'm surprised that only a handful of guys gave it a try in the thread I started on that a few months ago. https://community.klipsch.com/index.php?/topic/170414-who-wants-to-measure-how-much-power-voltage-is-really-needed/ Maynard