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tube fanatic

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  1. If you can buy a restored/calibrated mutual conductance tester within your budget from a reliable seller, that's great. Usually, the better units, like Hickoks, go for $500 give or take. But, if you just want to know if a tube is good or bad, look around for something like a Sencore Mighty Mite tester. They can often be found in the $75 price range and are very reliable testers within the context of what they can do. What makes you think that the tester that you have doesn't work? Do you have the manual and tube chart for it? If not, those can usually be found online for free from various sites.

  2. The tube tester in your picture is an emissions type unit. This type of tester will tell you if the tube is "working," but not what it will do under actual operating conditions (with such a tester, tubes can sometimes test "good" and not work, and at other times tubes that test "bad" may work fine). The tube tester's circuitry is usually fairly simple, so the unit you have may be easy to repair by a knowledgeable technician. To get a better idea of how a tube will work you would need to have a mutual conductance (aka transconductance) type tester which can be quite costly. These are very rarely seen in the price range you specified. Such units also need to be electrically restored and, most importantly, calibrated to be of any real use. If improperly calibrated, a tube which seems to test within specification may actually be terrible. Frankly, though, the only way to really know if a tube is good is to put it into an amp, etc, and see what it does under its actual operating conditions. If it performs well, and its measured voltages are within spec for the device in question, you know that it's good. As far as the tubes in the caddy, it's hard to see the type numbers. If you can post a list it will be easy to tell you if there are any worthwhile audio types there (the large tube in the tester does look like a KT88 though).

  3. The transformers are in the pro unit only and are used for isolation

    between the ground of the source component and what follows after. The

    PC version does not have the transformers from what I can tell. In

    either case, both are simply passive line level attenuators. Another

    negative with this unit is that it doesn't allow for any kind of balance

    adjustment between the 2 channels. NHT makes a point of the tracking

    accuracy between the two channels, but that's a moot point since most

    recordings are not balanced, and neither are our ears.

  4. i consider myself handy but i would not want to try and take on a task of building one of these because my technical knowledge of how to properly do so is limited let alone it would not look good at all when done.

    Does anyone know of another unit that is cheaper and could replace this one?

    Tell me exactly how you want/need to use the device. Would only a single input suffice? I have a friend who may have something that he can loan you so you can test the concept of a passive line stage without incurring any expense.

  5. This discussion reminds me of an optician friend who does not put price tags on his frames. Although he likes to make the largest profit possible by selling ridiculously priced "designer" frames, he has found that it's far better to let people choose their frames without the influence of price or status. Often, when he tells the person the cost of the frame, they are shocked that it wasn't double the amount...........

  6. You can't necessarily correlate price with sound quality. Some of the exotic, ridiculously expensive, speakers out there are priced so that they are considered "status" symbols but don't sound all that impressive. Many use rare woods which do nothing for the sound quality, but just add cost. The same goes for the drivers themselves; just because the frames use some rare metals doesn't mean that they work better than plain steel or aluminum. People are easily convinced that if something costs more, it must be better. Would you feel differently if Klipsch raised the price of K-horns to say 30 grand per pair, or Palladium 39s to 50 grand?

  7. You need to be careful if choosing "band type" tube gear for home audio use as many of the units out there are not designed for the kind of frequency response needed when listening at home. In addition, distortion levels which may be acceptable, or even desirable, for band use would be totally unacceptable for home listening. If you are looking for vintage gear, I'd stay with the "old reliables" like Fisher, Scott, Marantz, Macs, etc. Also, a great deal of wonderful tube gear was around in the 50s and 60s from Lafayette Radio, Musicraft, Allied, Heathkit, and even Radio Shack! So, if you see any of this kind of tube gear, and the price is right, grab it!

  8. So, unless you are looking to blow out windows, a 2 or 3 wpc amp should be plenty.

    A bit of rhetoric here...and I will take a point of order on this...I think that you will need more, and you will hear the effects of having added headroom from your amplifiers, and that is not opinion...but, if you don't mind tube amps "soft clipping", then amplifiers capable 3 Watts RMS into 8 Ohms won't bother you... if you don't mind harmonic distortion products at concert levels.

    Some folks don't mind...I do, however. Big Smile See enclosure. The Crown D-60 is a 35 W/channel into 8 Ohms (20 Hz-20Khz) at 0.05% THD amplifier.


    As mentioned in my original post here, it all depends on how loudly one listens. PWK's power calculations in Vol. 16, #1 also allow for 10db of headroom; so, actual power need is in fact lower than that stated. Besides, if an amp can deliver say 3 watts at 5% THD, the distortion isn't even going to remotely approach that at .5 watts which may be all that the listener requires. Having another 30 watts in reserve isn't going to make a difference. And, very low distortion (as you mention for the D-60) isn't necessarily the key to good sound- how often have we listened to a solid state amp with vanishingly low distortion and find that it sounds like garbage? To use another analogy, what advantage would there be to driving a formula one racer down Main Street at 25 mph when a 60s Beetle would be sufficient? So, again, it all depends on how much power is needed to satisfy a given listening level.

  9. Thanks to all for the great feedback. I think I will start with refreshing the LS's.....new caps and maybe the CT125 tweeters from Bob....I'll also check the gasket on the mid horn. Overall, the bass is very acceptable. I may look at adding a sub down the road, but not a priority now. I like to listen around mid/high volume (about 9 or 10 o'clock on the Sansui dial). If this doesn't remedy the issue, I'll then start looking at replacing my amp and/or CD player.

    If I end up replacing the amp (hopefully I won't need to), would a 3 or 4 watt tube amp give me enough power....in comparison to the Sansui AU-717 (which I believe is 85 wpc)? I don't know how many watts I usually use of the Sansui when volume dial is at 10 o'clock.....I know it is pretty loud.....floors are vibrating a bit. Of course, right now I have to choose the right music to play at that volume.....no thin vocals.

    I really appreciate all the great advice you all have added.

    There's no way to correlate volume control position with power output as there are other factors which will affect it- loudness of the recording, output voltage of your source, the taper of the volume control, etc. To get some idea of how much power you need, try this sound pressure level calculator:


    Also, according to Dope from Hope, Volume 16 #1, the La Scala will produce a 100 db spl in a 3000 cu foot room with only 1 watt/channel. So, unless you are looking to blow out windows, a 2 or 3 wpc amp should be plenty.

  10. Try switching the RB-10s between the right and left channels of your amp to see if the volume difference follows. It's also possible that the volume controls of the amp don't track exactly the same. I presume that you had to turn the volume controls up higher for the RB-10s than for the Heresys due to the difference in efficiency- it's possible that at the setting needed for the RB-10s the controls may be slightly farther out of spec with each other than at the lower settings.

  11. How loudly do you play the system? You mention not being able to afford tubes; however, if you only need a few watts/channel due to your listening habit (remember that these speakers can produce enormous sound pressure levels with minimal power- a friend drives his family out of the house running only 4wpc into his Cornwalls which are not as efficient as the La Scalas), tubes can be an extremely affordable alternative. Granted, you may still have to replace the caps in the crossovers, but that's a cheap fix. La Scalas and tubes are very synergistic! As an example of what's out there in affordable, and decent, tube equipment check this out:



    Both of these have received favorable press and would serve as a nice introduction to tube amplification. The first one even comes with a lifetime warranty!

  12. Looking at your pix, I'm not sure if this is a commercial amp, or one that someone built (probably from the 40's to early 50's). The 4 jacks on the side and 5 controls to the right of the on/off switch suggest that it could mix multiple inputs, so it may have been used for PA purposes in an auditorium, school, etc. If you give me the # of the UTC transformer I can reference that- it may be an interstage or output transformer. The two matching components behind the power transformer appear to be chokes for the power supply. What's nice is that it appears to be totally original under the chassis! Often, equipment like this turns up significantly butchered. Please post whatever other info you can locate on it.

  13. The Marantz will probably sound different, but whether it is an improvement or detriment is unknown (you would have to experience it in your system and be the judge). It is a bit more powerful than the H/K, but the difference won't be of any value unless you're pushing the H/K to the point where it's clipping. If the price is right, I'd grab it. It was a nice unit in its day and can still deliver much enjoyment if it is working properly.

  14. It's often very difficult to quantify changes in sound quality, and placebo effect certainly can enter into things. Years ago, when I was extremely active in audio circles, blind/level matched listening tests made all the difference in the world. People who knew that they were listening to a $10k Levinson amplifier, for example, raved about how much better it sounded than whatever it was being compared with. But, when a blind test was conducted, they often said that the Levinson was nothing special. Regarding deeper bass/better highs, that can be related to many factors (including length of the wires between the speakers and amp, gauge of the wires, capacitance of the interconnects between the source and amp, etc). Sure, having more power is never a bad thing; but if you are running an amp/receiver which can deliver say 50 watts, before the onset of clipping, at no more than 20 watts peak, you're not likely to gain anything by going to something more powerful (it's kind of like buying a Nascar race car to drive down Main Street at 25 mph). One option, however, for evaluating something different is to order it from a mail order place which allows you to return it if not satisfied. Yes, you will gamble a few $$$ in return shipping charges, but better to do that than get stuck with something which you find unsatisfactory.

  15. If you are pleased with your current system there's little justification to make any changes. Sure, another amplifier or receiver may sound different, but not necessarily better. If your receiver is powering the RF5s to the levels you desire, then it will certainly be more than powerful enough for Cornwalls. Do any of your friends own a good quality amp or receiver which they can bring over for you to do a comparison? That's a nice way to get an idea whether a change is likely to be worthwhile.

  16. Do you just want an amp, or a receiver, and do you want something with a built-in phono stage, or can you go with an external preamp?

    Also, keep in mind that if you are maxing out the power of the Denon, doubling the power will only get you another 3db in output from the speakers. So, you really need to get the power up to at least 150wpc to start realizing significant loudness increases.

  17. I have a quad of Mullard ECL86 from a Penncrest console stereo receiver. I've pondered a ECL86 PP amplifier circuit using the original Penncrest receiver output transformers, or a SE spud amplifier. But I'm not sure what the proper primary impedance would be for a SE output transformer when using ECL86.

    I guess I could try it with a SE 6BQ5 OPT, and see how it would work out...

    The ECL86 is a nice tube to use as a single ended "spud." You could run 250V on the plate and screen with the bias set by a 270 ohm cathode resistor (I'd bypass it with around 1000uf). The load impedance would be 10k. I doubt that the transformers in the Penncrest would be up to real audiophile standards (and you would have to measure their impedance to know if it is compatible with the voltage I specified). A nice choice, if you're not looking to spend a fortune is the Hammond 125ESE. Although it's rated frequency response doesn't look that wonderful, in reality it's capable of producing truly amazing sound, and significant bass output down to 35-40 Hz. Or, if you have some bucks to spend, the Hammond 1638SEA is truly excellent. I would also consider contact biasing the voltage amp section in this application, for simplicity sake. If you need any other info, send me an e-mail and I'll do my best to help you out.

  18. Since this thread hasn't burned out yet (see what you started Joe!) I'll raise a question which, to my surprise, hasn't been discussed in the context of using low power SET amps- has anyone experienced a "spud" amp (i.e. a single pentode, directly driven by the source component)? This represents the ultimate simplicity in tube amp design- one tube per channel and minimal support components in the signal path. A couple of years ago I heard a demonstration of an Ah Tjoeb cd player (which can put out around 5 volts, as opposed to the typical 2 volts) driving an amp using one 6EH5/channel to around 700 mw output into Cornwalls. The sound was amazingly clean, with smooth mids and highs, and much tighter/fuller bass than is usually available from SET designs. Given the efficiency of the speakers, the guy was able to produce extremely high sound pressure levels (far greater than I could tolerate, in fact). For those who have source components which can output 3 volts or more, this may be a nice avenue to explore.

  19. I don't know the Patrician IV at all and was thinking maybe I could trade it for another matching Klipschorn. I guess maybe I need to do some research before I make any rash decisions. I have it hooked up now and it sounds incredible, absolutely incredible.

    Please do NOT even think about getting rid of the Patrician. Try to find another one! Then you'll be in for a sonic treat that you can't even imagine. I'm jealous!!!!!

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