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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.

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  1. tube fanatic

    Audiophile Musicians

    https://www.stereophile.com/content/musicians-audiophiles-david-smith Maynard
  2. tube fanatic

    Speaker Switch with tube amps?

    Hot switching is fine as long as it’s done under zero signal conditions (i.e. no signal to the amp input). I don’t know how the myth got started that tube amps must have a load connected at all times to prevent them from blowing up. Maynard
  3. Interesting review. The amp measurements are not very inspiring but, as is mentioned, measurements never tell the real story about why certain amp/speaker combinations sound so outstanding: https://www.stereophile.com/content/borderpatrol-p21-exd-power-amplifier If I had a nickel for every "perfectly" measuring SS amp which sounded like absolute crap with most Klipsch speakers I could have retired many years sooner! Maynard
  4. tube fanatic

    Radio station coming through amplifiers?

    RF pickup in audio amplifiers is not unusual in the presence of strong signals. You said that you are picking up stations. How many, and can you determine the frequencies? Are both amps doing this? If so, is one louder than the other? Since there are many possible causes of this, let's start with the simple approach: Disconnect everything from the amps, turn the input level controls up all the way and note whether you still hear any stations. If not, you can rule out the amps. If they are still present, start moving the speaker cables (which should be no longer than is needed to reach the speakers) around a bit to note whether anything changes. Do the same with the power cords of the amps. Out of curiosity, have you done any rewiring in the house or listening room or any work on the rain gutters? I'll elaborate on this in the future if needed. I don't know when I'll be able to get back on here, but will try to keep tabs on the discussion whenever possible and provide more details. Maynard
  5. tube fanatic

    She Nailed It!

    This rendition gives me chills..... https://www.youtube.com/watch?v=xaWLsgxDzuw And, this rendition of Stairway to Heaven does the same for me: https://vimeo.com/226640440 Maynard
  6. tube fanatic

    Newbie question: Amp & Speaker combination

    Your question would be better served if you post it in the Talkin' Tubes section of the forum. The DB212 is a nice little amp. As Gary pointed out, it needs to be restored to ensure safe use and longevity. Regarding power, it should be more than enough unless you want to achieve "ear bleeding" levels (in which case RP-160s wouldn't be appropriate anyway). In general, the synergy between Klipsch speakers and tube amplifiers is outstanding. If you have never experienced the combination, you are in for a real treat (assuming the DB212 is working correctly). Maynard
  7. tube fanatic

    LaScala's and Tubes.

    It's impossible to rely on reviews or recommendations when making equipment choices. SETs are less affected by speaker impedance variations than SEPs (unless they employ negative feedback). One of the issues is the amplifier output impedance which is in series with the speaker impedance. That's why trying an amp in your system is imperative. If you want to experience quality SET sound without spending much, build a pair of Little Sweeties. They offer extremely good synergy with K-horns, La Scalas, and Belles and maintain very low distortion even when the speaker impedance drops (I believe LSs only drop to around 3.8 ohms). And, William is correct in saying that large opts are not usually worth the extra expense. In my experience, it's rarely worth using them in flea power applications. Maynard
  8. tube fanatic

    The long awaited "Little Sweetie" mono SETs

    Something wasn't working properly (I know it couldn't have been the crossovers!). There are guys running as little as 1/3 wpc from triode strapped radio output pentodes into La Scalas or K-horns in small rooms and the sound quality is beyond exquisite. As Richie pointed out, listening level is the key point. But, given how much acoustic output one can get from the above mentioned speakers, it doesn't take much to get blown out of the room. Maynard
  9. tube fanatic

    The long awaited "Little Sweetie" mono SETs

    That's a really nice implementation of the Sweetie design William! Those who accuse SETs of having extremely high distortion should take a good look at the FFT that you posted. That says all that one needs to know, and explains why flea power SETs are capable of sound quality which is so good that nothing can compare. When one looks at how little such an amp costs, it's very surprising that more guys don't give them a try. And the best part is that the tubes are not only inexpensive and abundant, but should last almost "forever." Maynard
  10. tube fanatic

    Knight KG250 integrated amp

    I don't know of any techs in your area. However, a wonderful source of assistance is a local amateur radio club which usually has many older members who know tube electronics better than anyone else. You are fortunate to have one right in your town! http://w5hsv.weebly.com/club-activities.html I'd join those gentlemen for breakfast and I'm sure you will have many offers for help as ham operators are among the friendliest, most helpful, folks you will ever meet. Maynard
  11. tube fanatic

    Knight KG250 integrated amp

    Has the amp been restored? If not, the popping could be caused by almost anything ranging from a resistor/capacitor/bad solder connection to a tube. It should be checked out by a competent tech. If you provide your location I may be able to suggest a tech in your area who can help you. Maynard
  12. tube fanatic

    Heathkit tube amps

    You can use dissimilar mono amps for a 2 channel system. However, even though they are both Heathkits, the sound characteristics can be quite different which you may find disturbing. There's also the issue of how well these units were constructed (you can't imagine how badly some amateur builders butchered units like these), and whether they have been restored. If unrestored, they need to be gone over by a competent tech to ensure safe operation. Maynard
  13. tube fanatic

    Leeds Radio NYC- tube dealer

    Excellent video about this place. Richard is an interesting fellow from whom I've bought many tubes. He is honest and reliable. It was interesting to hear him mention the founder of the business, Aaron Leopold, who was my neighbor when I lived on Long Island. In fact, his son and some of his grandkids were neighbors as well. One of the grandsons became the plant manager of Rectilinear Research in the Bronx with whom I did lots of business back in the day. Their model 3 speakers were outstanding and I have long regretted selling mine. https://www.youtube.com/watch?v=Sk5cCHP-XR8 Maynard
  14. tube fanatic

    Proper Ohm Tap for Chorus lls

    Moray, I can't agree with this. Differences in sound when trying the various impedance taps are caused by a slight shift in output stage distortion characteristics since the speaker impedance variations are reflected back to the opt primary. In the case of the HF-81, the global fb loop is taken from the 16 ohm tap so that almost the entire secondary (there is also a 32 ohm tap if I recall correctly- please tell me if that is inaccurate) is "active." And, of course, the nfb does make the output stage fairly immune to the impedance variations anyway. It's simply a matter of using whichever tap provides the most pleasing sound with a particular speaker. Maynard
  15. tube fanatic

    Plate current vs cathode current

    I had a moment to glance at the schematic and see that the 10 ohm resistor you are referring to is in series with the plate (pin 3), not the cathode which is grounded. If you measure the voltage across that 10 ohm resistor you can use Ohm's Law to calculate the plate current and plate dissipation based on the plate voltage you measured. You can also measure across the 200 ohm resistor in series with the screen (pin 4) to calculate screen dissipation which is also very important. Screen voltage can be measured from pin 4 to ground. And, you can measure the bias voltage from pin 5 to ground. With all of that information you can get an idea about operating conditions. I can try to look at this in more detail if you run into problems. Maynard
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