tube fanatic

To determine exactly how much power is needed you will have to determine the maximum sound pressure level you desire at your listening position. The easiest way to do that is with a sound pressure level meter (Radio Shack used to make a nice one for around 50 bucks- not sure if they still have them). Once you have that, you can determine the power needed. Your speakers can each produce approximately (approx, because the output will vary with frequency) 102db at a distance of one meter with one watt of power applied. The level at, say, 10 feet will be lower. But, with that in mind, you can still extrapolate somewhat by considering that you need to double the power for each 3db increase in output from the speaker. So, for 105db, you need 2 watts, etc. Considering that the auditory pain threshold is, if my old memory serves me, around 120db, you could achieve that with around 64 watts. But, we're talking about each speaker providing that level of output. So, in stereo, with both speakers driven, the power requirement per channel is far less. Also, don't compare the Palladiums to the RF-7s as they are not as efficient and will require more power for a given sound pressure level. So, I hope this helps you a bit. The bottom line, as mentioned before, is that you have more than enough power.

Unless your RF-7s are in an enormous room which is filled with all kinds of heavy sound absorbing materials like rugs, curtains, hundreds of books, etc, 5 watts/channel would be more than enough! With the amount of power that your receiver provides you could create sound pressure levels that would break your eardrums before you would run out of "steam." Don't even give it a thought!!! 2.83 volts is equivalent to 1 watt into 8 ohms.

Well, I know that my opinion will start a raging controversy, but what the heck! Stick with the cheap stuff. For interconnects that are relatively short, say less than 3 feet, it probably doesn't matter what you use as long as they make a good electrical connection to the jacks. Put a little De-Oxit on the plug center pin, and on the outside of the jacks, and you should be in good shape. Since the cheap interconnects may not be as well shielded as some of the more expensive ones, be sure to keep them away from your AC power cords to avoid any potential coupling which could induce some hum/noise in a worst-case scenario.

You can power up just the one channel. However, depending on the power supply design, the decreased current draw from running only one channel can cause the voltages to be elevated. So, while it shouldn't hurt anything to try it briefly, I'd not run it for too long without knowing if the tubes are being subjected to an overvoltage situation.

Try a new tube, but if it happens again, I'd suspect a shorted or leaky input electrolytic cap in the power supply which is a far more common occurrence than a pure tube failure.

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.

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.

I had posted a comment, but deleted it.................

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.

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.

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.

Keep in mind that only the tubes for each channel should be matched, so you don't need quads, just pairs.

A few inches difference is of no consequence unless you are using very high capacitance coax.

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.

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.

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.

You can get them from: www.vacuumtubes.net They are reliable dealers and ship internationally.

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.

Just found these links about the company: http://www.daveswebshop.com/bursteinapplebee.shtml http://www.ominous-valve.com/burstein_applebee.html

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?

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.

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.

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.

What do you mean by the power tube is fluctuating? Please clarify........

"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.