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tube fanatic

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  1. Have you run a frequency response curve for the triode amp which is driving the mid bass horn? It would be interesting to know what it is doing at around 80 Hz vs 500 Hz.
  2. Since this discussion is back to swapping triodes with different characteristics, a way to achieve a workable situation is to "contact bias" the tube- i.e. grounding the cathode and using a very large, say 10 megohm, grid resistor. Although some consider this technique "non-audiophile," the results are quite fabulous; in fact, the distortion for a given plate voltage is often a bit lower than when the tube is self biased with a cathode resistor/capacitor. In the shop we often did this for people who insisted on having the flexibility of swapping 12AX7s, 12AT7s, 12AU7s, etc. The nice thing about this method is that the tube bias adjusts itself as the tube ages. Virtually all of the vintage triodes were actually designed to allow this method of use. Bass response is phenomenal as it is not limited by the often undersized cathode bypass cap. In summary, it's an easy modification to do for those with experience in working under the chassis; and, it's easy to change back if the results are not as desired.
  3. I had posted a comment, but deleted it.................
  4. Many factors contribute to how much power you need, including the size of your listening room and what you mean by "volume." Have you measured how loudly you enjoy listening with a spl (sound pressure level) meter? That will quickly determine how much power you need for the Heresys. Regarding solid state vs. tube power, watts are watts! The difference is in the distortion, particularly if the amp is pushed a bit beyond its means. Tube amps tend to distort (or clip) a bit more "smoothly," whereas solid state amps distort in a more abrupt fashion. The danger to the speakers is using them with an amp that is clipping. With the Heresys, unless you are listening at extremely loud levels, it's unlikely that you will ever need more than a few watts/channel; 15 should be plenty.
  5. Actually, the filament voltage and current is identical between the 2 versions. Even if one happens to heat faster than the other, the electrical draw is the same. Some have claimed that the "A" version is quieter, but in practical terms, any NOS 12AX7s produced from around 1961 on are all about the same. In the shop we used to select tubes based on microphonics (gently tapping the tube with the eraser end of a pencil to determine if it could be heard in the speaker) more than anything else. There were definite differences there from one manufacturer to another, and from one batch to another. If one wants to go to the trouble of doing that "test," slight sonic improvements may be gained in installations where the amp is subjected to acoustic feedback or vibration from the speakers- it makes a good case for keeping the amp isolated from any vibration when possible.
  6. In the applications you mention, there should be no problem. The "A" version (speaking about NOS tubes here; I'm not familiar with currently manufactured foreign tubes) has a slightly higher maximum plate voltage and plate dissipation rating. There may also be slight differences in inter-electrode capacitance, but I'd have to look up that info- again, not of importance here.
  7. Keep in mind that only the tubes for each channel should be matched, so you don't need quads, just pairs.
  8. A few inches difference is of no consequence unless you are using very high capacitance coax.
  9. What kind of an antenna are you currently using? If it's just a simple folded dipole, you can often improve reception greatly by increasing its height (tacking it up near the ceiling can work wonders). Alternatively, you can use any of the dozens of amplified FM antennas which are out there (Terk has always made excellent products). Lastly, you can use an outdoor antenna with a rotator; but, if roof mounted, you need to install proper lightning protection.
  10. I recommend going with NOS tubes if cost isn't a major issue. Mike Marx can set you up with two matched pairs: http://www.vacuumtubes.com/7868.html. It's hard to speculate as to why you experienced a reversal of the speakers which sound best with it. Are you able to verify correct bias adjustment yourself once new tubes are installed? If not, perhaps you can find a local technician who can assist you with that.
  11. If at all possible, try to audition speakers by bringing along your Proton preamp/amp. Some speakers will sound much better to you than others with your particular equipment. Any reputable dealer or private seller should be more than happy to connect them to the speakers you are interested in.
  12. You can get them from: www.vacuumtubes.net They are reliable dealers and ship internationally.
  13. Well, it depends in part on what brand of EL84's you have (Mullards have a design max. rating of 550V on the plate). Also, EL84's have a slightly lower plate dissipation than 7189A's. Basically, you can't go wrong by using 7189A's. I'd have to pull out the schematic of the X100 to check the plate voltages used- that amp was available in a few different versions during the early sixties, and I think some used a tube rectifier and others a solid state rectifier; so, the plate voltages may be different depending on which version you have.
  14. Just found these links about the company: http://www.daveswebshop.com/bursteinapplebee.shtml http://www.ominous-valve.com/burstein_applebee.html
  15. Burstein-Applebee was, if I recall correctly, in Kansas City back in the sixties. They were similar to Lafayette Radio, Olson, Radio Shack, etc. in that they sold various parts and components. Like the other companies, they had their own house brand of speakers, among other things. I can't tell you anything about how they might sound; but, if they're cheap enough why not try them out for fun?
  16. Over the years I've experienced many new tubes which were defective- in fact, a bad filament has been a common problem! Since they were matched, I would return the other one of that pair also so the replacement can be matched to the good one. Please post to advise after you get them replaced.
  17. Glad it worked out well for you. Forgot to mention to keep the volume control of the Fisher turned all the way down (having no speakers or load connected could be a bit rough on the output tubes if you turned the control up); alternatively, get a couple of 25 watt/8 ohm resistors and connect one across the speaker terminals for each channel. Then you don't have to think about it.
  18. Just saw your other note. If the filament is getting brighter/dimmer, then the tube should be replaced (actually, replace both tubes for that channel, and recheck the bias/balance). If you speak of the bluish glow, then that can be normal if the tube happens to have a bit more gas than the other.
  19. What do you mean by the power tube is fluctuating? Please clarify........
  20. "A DIY passive is just a few parts in a box--an attenuator. Adding more parts won't make the path cleaner." Agree totally. In fact, for those who are handy, and want to experience one with absolutely minimal expense, pick up a cheap aluminum mini-box, a couple of Radio Shack RCA jacks, a 10-15k metal film resistor, and a 10k pot. Wire the resistor between the center terminal of the input and output jacks; connect the pot's wiper (middle terminal) to the output jack, and the end to ground (viewed from the back, use the terminal on the left). Make one for each channel, or put both in the same box. You won't believe the sound that you get! Radio Shack's 10k pot with switch (271-215) used to be made by Alps and was extremely quiet (the switch can be easily removed). Less than 20 bucks for amazing sound- not too bad. If you are driving any of the Heritage speakers at reasonable volume levels, the passive attentuator will allow your amp to deliver more than enough power.
  21. An integrated amp is nothing more than a power amp with a preamp section. Going to a straight power amp is totally unnecessary. The easiest way to do the connection is to run cables from the "recorder output" jacks of the Fisher to the auxiliary, cd, or tuner inputs of the integrated amp and use its volume control to set your listening level. All of your source components are connected to, and accessed from, the Fisher. Assuming that the integrated amp has a decent preamp section, this should achieve your goal. Thinking back, I don't believe the Fisher allows its preamp to be used as a separate entity from its power amp (I can check the schematic if you want to know for sure). The reverb in/out jacks of the Fisher are probably in the circuit before the Fisher's volume control, so they can not be used as you desire.
  22. No active preamp can equal the sound of a passive line stage, assuming that your source can put out enough voltage to drive the amp to the power levels you desire. In the eighties, when passive line stages were more popular, we built many for audiophiles. Typically, we used a single high quality resistor (such as a Caddock) between the input and output; the volume control was either a high quality Alps pot, or a stepped attenuator with metal film resistors. Assuming the amp was quiet, the sound seemed to emerge from a background of total silence- absolutely no hiss or hum, even with one's ear against the speaker (back than we were using K-horns for the testing prior to delivery). By using short (less than 6 feet long), low capacitance interconnects, there was virtually no high frequency rolloff. Why the passive line stages fell out of popularity is beyond me.
  23. Feeding a low level signal from the Fisher to the input of your other amp is fine and will not cause any problems. Disconnect all sources from the integrated amp; even if you remove the jumper between its preamp and power amp sections there could be slight signal bleed-through from internal coupling which could affect the sound quality.
  24. You can't make the comparison based on cost; and comparing a tube to a solid state amp is comparing apples to oranges. Each will have a distinct sound. Then, tube amps can sound differently from one another based on the design- i.e. triode vs. pentode; single ended vs. push-pull. My experience is that any type of tube amp sounds better than any type of solid state amp; but, others may have the opposite view. The only way to know is to listen to different amps through your speakers in your listening room, and then decide for yourself.
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