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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. 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
  2. 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
  3. 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
  4. 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
  5. 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
  6. 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
  7. 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
  8. 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
  9. 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
  10. 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
  11. imaging ?

    There's no question that near-field listening is a very easy way to achieve astounding imaging. I see that the OP has Heresys and LSs, both of which work extremely well in that application (as do the Reference series towers). Try setting up either in a 5-6 foot equilateral triangle (very minimal toe-in) with the listening spot and, if available, drive them with a pair of mono SETs. With listening levels in the upper 60s to low 70s db range you should experience immersion in the music (obviously, as was stated above, rotten recordings will still be rotten) which is without equal. And, the best part is that room treatment is rarely needed. When I set up systems that way, I use certain favorite recordings to get the imaging to be as desired (if you like Alison Krauss, Gravity or Paper Airplane work really well). If you try it, please post your experiences. One last point is that such near-field arrangements require so little power as to border on the ridiculous. With LSs, for example, a few milliwatts can sound equivalent to 100+ wpc in a large room system. Maynard
  12. Plate current vs cathode current

    With pentodes cathode current is a combination of plate current and screen current. As to proper bias for your amp, the best thing is to set up the tubes per the manufacturer's instructions. What amp are you talking about, and can you post its schematic? Maynard
  13. Flea Watt Amp Recommendations

    Low power and powerful bass are not mutually exclusive at all!!! There are many considerations before you get into flea power after living with a high power ultralinear design. Definitely post in the tubes section... Maynard
  14. Building an amp (for those who are curious!)

    There's nothing wrong with good, old fashioned, 60/40 rosin core solder. Of course, as with anything, it takes practice to learn how to use it correctly, not have cold solder joints, etc. The flux does leave a residue on every kind of tip that I've encountered over the years, and it does build up somewhat after multiple connections are made. It's possible that the amount is related to the alloys used in a particular tip. For example, the Radio Shack tips I use in the Weller 8200 gun (yes, I still use a 100W gun most of the time- after 60 years of doing so it's hard to change!) build up more residue than the tip of the Weller WP-25 which I use for PC work. At the power supply company we used various solder stations, different kinds of solder, different kinds of flux including water soluble, and tips had to be cleaned to ensure proper connections. While I'm not arguing that some don't consider it necessary to ever clean a tip, I find it difficult to imagine that at least wiping the heated tip with a moistened sponge would not result in better connections. Maynard
  15. Restore or Mod A Maggie 6V6 Console Pull

    Where are you located? Maynard