tube fanatic

Assuming you have metal (as opposed to plastic) outlet boxes, and assuming that the boxes are grounded through the Romex or BX cable, and you connected the green ground wire from the cheater plug to the screw which holds the outlet plate to the box (with a good electrical connection) there should be no concerns.

Your question doesn't have an easy answer as much depends on the listening environment. How large are the rooms in which you listen? What kind of furnishings are there (i.e. carpets, drapes, rugs, book cases, etc.)? What type of music do you listen to and how loudly do you listen? Where is the listening position in relation to the speakers? Why do you feel the need to have a separate preamp and amp as opposed to an integrated amp? The one question which can be answered now is about going with monoblocks. Stereo amps, depending on their power supply design, can have varying amounts of crosstalk (i.e. interaction between the 2 channels which can reduce the perceived channel separation). Going the monoblock route limits the crosstalk to that of the source. Some people can hear crosstalk differences, and others can't. The bottom line, once you have made some decisions, is to find a way to audition the amps in your system. It's the only way to know if the sound is what you are looking for.

Pick up a Niles Audio AXP-1 switch box. It will give you 5 inputs to one output. If that's not enough, you can always get 2!!!

I just remembered having this bookmarked. It will shed some light on the electrolytic issue: http://www.niccomp.com/Products/General/Alumlyticlifeexpect.pdf

Exactly! Electrolytic caps which have say a rating of 3000 hours at maximum operating core temperature and working voltage may last 50000+ hours or more if operated at 1/3 their working voltage and a fraction of their maximum operating core temperature. Of course, this has to be considered on a case by case basis. But, that said, I have serviced vintage communications receivers from the 50s which had electrolytics which were absolutely fine. As stated by JL, a great deal has to do with how much use, and how often they are used; so your technician may be quite correct in telling you that it isn't necessary to replace the electrolytics at this time.

Go to Niles Audio's web site. They have switch boxes for virtually anything you might need. If they don't have any with as many inputs/outputs as you desire, you can always cascade a couple of them to get what's needed.

Contact Mike Marx at SND Tube Sales. He may be able to help you. http://www.vacuumtubes.com/

Electrolytic capacitors have a finite life span which is based on many factors. Check out the following tutorial which explains how they work in relatively simple terms: http://www.hans-egebo.dk/Tutorial/electrolytic_capacitors.htm Applying a very slowly increasing voltage to electrolytics allows them to re-form (see article for details about this) which, in many cases, can restore useful life to an otherwise "bad" capacitor (if the caps are installed in equipment, it is often done with a variac, a variable transformer). This does not apply to just tube equipment. All electrolytics, regardless of operating voltage, are prone to spoilage and failure.

Cabinets/covers for many 50s and 60s amps were an optional purchase since many users installed the amps in custom enclosures, book cases, etc. Since the cabinets were often costly (by the standards of the times), I always felt that the manufacturers were being considerate in not forcing consumers to purchase what they didn't need. Another advantage to having an exposed chassis and tubes is the greatly improved ventilation which translates into longer tube life (especially in designs which ran the tubes at or even above their design maximum ratings).

Keep in mind also that the position of the volume control does not equate to the amount of power the amp is putting out. Depending on the taper used (i.e. the amount of resistance change for a given amount of turn), and the resistance of the control itself, the amp's output can ramp up very quickly or very slowly. Years ago some commercial amp manufacturers used a taper which allowed the amp to ramp up power with very little turning of the control. It gave the illusion of an extremely powerful amp. Psychologically, if you had to turn the control to 12 o/c, instead of say 8 o/c, to achieve the same volume level you might think the amp less powerful than it actually is.

I told myself that I'd stay out of this discussion, but what the heck! Your observations about SETs vs PP tubes, etc., are valid and duplicatable (from the usual subjective standpoint). One factor which is contributing to the difference is that virtually all pentode based amps (whether single ended or PP) use some degree of negative feedback (degeneration) to extend the bandwidth, decrease distortion, and also as a means of taming the usual runaway high frequency harshness and abrasiveness. In my own observations, as well as in listening done with fellow audio nuts, as the degeneration in pentode amps is increased, there's a very discernable decrease in low level detail retrieval as well as a shallower and narrower sound stage. So, the advantage of going the SET route could be in part related to the fact that degeneration is not used in most designs of that type. I have yet to be able to duplicate the 3D, almost holographic soundstage of SET amps in any of my pentode designs. Close, yes, but as good never!

PM sent---

If it's the one that I'm thinking of, there should be a separate chassis for the amplifier mounted on the bottom shelf of the cabinet (the model number will be stamped on it). Another chassis, containing the AM/FM tuner and phono sections, is what is mounted on top with the controls and face plate. This is a nice find as the amplifiers used in such consoles are really nice and, once restored to ensure safe operation, can provide many years of terrific listening enjoyment!

Do you have experience in restoring vacuum tube electronics and working with potentially lethal voltages? If not, don't consider touching it; rather, seek the help of a qualified repair technician. If you can, post the model # of the chassis which it uses (close-up pix of the chassis, etc. would be helpful also).

If the power amp is on when you shut down the preamp, pulling a tube before the p/s caps are discharged could give you a bit of a "pop" in the speakers. While this would probably not damage a tweeter (in particular), it would be best to wait until the orange glow from the tube cathode is no longer visible. At that point no appreciable current is flowing through the tube so you'll be quite safe even if the electrolytics are not fully discharged. With small signal tubes like 12AX7s, the process will be very fast. Repowering after installing the new tube can be done immediately.

Much depends on the power supply design and how much of a reservoir the electrolytic caps provide. In most tube equipment, a bleeder resistor is used to discharge the caps in the event power is applied with the tubes removed or burned out (in which case the electrolytics can remain charged since no current is being drawn). A safe number, which should cover virtually any piece of equipment, is 5 minutes to allow full discharge. It may be much longer than needed for some units, but better to opt on the side of safety. I'm not sure what you mean by a hot cycle. But, if you are concerned about applying B+ (i.e. high voltage) to tubes with a cold filament, there's not going to be any damage to the types used in preamps or amps (some would disagree and claim that doing so results in "cathode stripping," but that has never been documented in tubes of this variety).

If testing them as 6GH8s (6U8s have the same pinout) didn't work, try testing them as 7199s. The latter have a different pinout from the former. If you have a copy of the schematic, try to correlate the pinout on the bottom of the tube socket with the tube types and you should have your answer (i.e. look at the components connected to each pin and then reference the schematic to see which is the plate, grid, cathode, etc.).

While we were moving things around to properly place the the Heresy's, we decided to do a blind A/B comparison between the two speaker pairs. I had a spare speaker switch (I save everything... I think I have the first patch cord I ever bought), so we were able to easily switch between the speakers without the listener knowing which speakers they were listening to. While both speaker pairs sounded great, it was obvious to the three of the people listening (all Klipschoholics) that the Heresy's clearly sounded the best of the two with vinyl and the Fortes clearly sounded the best with CD’s and digital feeds, all with the same amplification (the tube system)... almost like they were designed that way and maybe they were? I know when I first heard the Fortes, a CD was used, and obviously an LP was spinning when I first heard my Heresy's. Even though we were using tube amplication for this test, I would bet money that the Heresy's sound better using tubes and the Fortes would sound the better of the two using solid state (note I did not say they would sound better using solid state because when I was using the Fortes both both amps, they sounded better using the Eico's as well, even though the Onkyo is a great sounding SS amp). Thought I would share, as this experiment was a lot of fun, with some definite conclusions about heritage speakers and analog v SS at least. The only flaw in the experiment that you outlined is that you didn't state whether you level matched when switching between speakers. Without that, it's almost impossible to draw definite conclusions.

Sorry for intruding on a request from a specific forum member, but I have a free moment. The issue of a preamp is dependent on the sensitivity of the amp (i.e. how much driving voltage is needed for it to achieve full output). Some amps need only 0.1 to 0.5 volts to achieve full output and can be driven directly by a high level source like a CD player. However, if the amp lacks an input level adjusting control, some type of outboard device is needed. Some people prefer using what's known as a passive line stage between their source and the amp, as opposed to a powered preamp, to eliminate having an additional source of noise, hum, and other sonic artifacts. The passive devices, however, should be installed close to the amp through the shortest possible interconnects (of low capacitance) to reduce the potential for slight rolloff of the highs. The term integrated amp is usually reserved for amps with input switching for multiple sources, tape loops, possible phono stages, and so on. And, yes, there are fine tube amps of current manufacture available which do not break the bank. Companies like Decware, JoLida (in spite of their legal controversies), Cayin, and Prima Luna come to mind. As to whether such amps compare sonically to vintage, fully restored amps, only you can make that judgment by listening to them in your own system.

Can you cite the reference for the above?

Just to clarify an imortant point, there is no difference between the power generated by a tube amp and solid state amp. The distortion characteristics are different, and the behavior of the amp when it clips (i.e. driven beyond its maximum output voltage or current) is different. But, watts are still watts.

More than enough!

My '88 K-horns were also signed by PWK. Back then, the dealer who placed the order could request that he personally sign the tags, but it was dependent on his being in the factory at the time they were completed. When I sold them, having the signatures increased their value only slightly. Of course, with a different buyer, the signatures may have been worth more.

Although I totally agree with your opening statement, there are those who can make an equally compelling argument for solid state amplification (years ago Bob Carver challenged the audio industry by saying that he could make his solid state amplifiers sound the same as any other amplifier- iirc, no one took him up on it). And not all tube amps sound incredible- much has to do with the circuit design as well as the characteristics of the output transformers used. As far as why there's such excellent synergy between Klipsch (especially Heritage) speakers and tube amplification, it is partly due to the extremely high sensitivity and efficiency of the speakers so that minimal power is needed for high sound levels. If you look at the distortion vs power output curves for many tube amplifiers it becomes quite clear that distortion can rise rapidly as the maximum power output of the amp is approached. In the latter situation, even a well designed tube amp can start to sound lousy. SET amps are known to have less, or perhaps somewhat softer, bass than pentode based amps because with the former negative feedback (used to decrease distortion and widen frequency response) is not generally used. As a result, the variations in speaker impedance over the audio band can cause the amp to "lose control" of the woofer somewhat (I can go into more technical details about this if you wish- drop me an email any time). Perhaps you can find a local dealer who would bring over a tube amp for you to evaluate in your system. It's the only way for you really know what you're in store for in making the change to that type of amplifier.

Well, the Sams Photofact directory isn't coming up with the data for your particular receiver. They do show one with the same cabinet number, but different suffix (3092A). Unfortunately, the electronics are different. If it were my decision, I'd try to find a local tech who can trace the circuit from the power supply through the preamp/phase inverter/power amplifier and make the necessary restorations there. As far as the AM/FM tuner, if that's important to you it should be restored as well, although that can be a bit dicey without the factory alignment data. If you don't care about radio reception, I'd pull the tubes involved there. This will eliminate any possible signal bleed through or noise from getting into the preamp when using your CD player as a source. In addition, the decreased current draw from the transformer will result in much cooler operation which isn't a bad thing! If you run into a brick wall in finding someone, I'll be glad to help you out (keep in mind that I'm on the east coast, so shipping could be costly). maynard