mikebse2a3

Erik you are very welcome. The "Radiotron Designers Handbook by F. Langford-Smith" is a wealth of information for anyone interested in electronics and tubes especially. An experience I had once about the important role of paying attention to impedance issues was when I built a very high quality passive pre-amp using 50Kstereo volume controls with both sections paralleled to create a 25K control for each channel. I was using a CD Player with a Tube D/A Converter into the passive when I picked up a Creek OBH 10 Remote Passive Volume Control. The Creek Control's Values where 50K and the sound was much better in the bass and clarity was better than with my Homebuilt Unit. I decided the Tube D/A Converter must not like the 25K Load of my Homebuilt Unit so I rewired it as a 50K Control and sure enough the sound was every bit the equal of the Creek. This is one reason I would advise not using low impedance attenuators if possible especially if you might want to use Tube Equipment with it. With Tube Equipment a range of 50K to 250K is often used with 100K being a good overall compromise. mike[]

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A few pages from Radiotron Designer's Handbook about Attenuators. See Fig 18:12 for the L Type that we have been talking about. mike[]

Maybe this will make it easy to see why I say that changing the volume control's value will not lower the volume settings(Assuming same taper rates and both turned half way) as long as the source componet can handle the lower impedance load of a 50K versus 100k control(Or Any Value We Choose). The voltage presented to the grid is the same in both examples only the current demanded from the Source has changed. As can be seen the voltage potential from ground will be the same for either value control. mike[]

Eric if you are talking about a resistor or control used as R1 in my example without R2 in the circuit then yes I agree with you. You will be creating a voltage divider(using R1 and the Volume Control) that as you point out will give you a reduction in voltage to the volume control. The thing for someone to look out for doing it like that would be a chance that the preamp could be a little more sensitive to noise/hum due to the input stages higher impedance with that method. mike[]

Eric said: The only way one can help calm down a hyper sensitive volume control is 1) replace it with one of LOWER (not higher) value ----------------------------------------------------------- I don't believe simply changing to a lower value volume control would work. Eric lets take for example a CD player with a standard 2 volt output level capability then look at my example circuit in my previous post you will see that the 2 volt potential will be available with even a lower value control as long as the load we present to the CD players output stage isn't driven beyound its capability(current supply) thus causing a voltage drop due to current starvation. Looking at it another way: if both controls have the same taper then turning the control half way down would still have the same voltage potential applied to the grid of the tube in my example from either control. The lower resistance control would just demand more current from the CD players output stage. mike[]

Many volume control circuits in tube preamps are wired like this simplified schematic. (Example One) Just changing(Lowering) the Volume Control's Value would only increase the load for the Source Componet. If the source has a beefy output stage that can handle the increased current demand then the output voltage will stay the same across the Volume Control. If the output stage can't deliever the increased current demand then the voltage will drop and distortion of the source's output stage will increase. Example Two: Shows an Attenuator installed(R1 & R2). R1 & R2 Values can be chosen to maintain the desired input impedance with the amount of attenuation desired. For Example: If your (Volume Control is say 100K) and R2 is 100K then make R1 50K and this would maintain the orginal input impedance of 100K. I have found that it usually sounds best if you use the minnimum amount of attenuation possible to acheive your needs. mike[]

I posted the Spec. sheets in updates and mod section for anyone interested in them. mike[]

Spec. sheet page2 mike[]

Spec. sheet page1 for anyone interested. mike[]

If you look at this subject of accuracy deeper then we need to realize a few things: No Human Voice or Instrument comes from two or more locations(ie:speakers) so their is nothing natural abought how we record or playback music now or how we listen to it. We have just been tricking our ear/brain for an illusion of reality. If a Band is recorded at realistic live levels then it seems to me the only way we will maintain that Tonal Balance is to playback at those live levels and any other level is going to shift things Tonally. So if where you listen won't allow those levels of reproduction the best you can do to create the illusion is to alter your tonal balance to sound as natural as possible in any given situation and for recordings(which vary all over the place). My personal Goal and Point is GO FOR REALISM of your Music in your own situation the best you can. You should feel free to use the tools we have now whether it is Loudness Controls, Equalizers, Surround Sound and Etc... to acheive this goal of realism in our own situations. I see nothing very accurate about the method of how we reproduce Music at the present time. If we accept the inaccuracy of using two speakers to reproduce the illusion of a central image(NOTHING REAL IN NATURE HERE) then how is it any more inaccurate to use Loudness Controls and other Methods to acheive Realism in Reproduction? Enjoy Your Music!!!! mike[]

I will join others when I say that the Khorns shouldn't sound as you describe when they are working correctly and the Equipment, Room, and Setup compliments its needs like any other high quality speaker I've ever heard. If you find no fault with the speakers then it very well could be that your room/setup is the area that is giving you the problem with the Khorns. The Khorns will play your room much different than the Cornwall because as you noted the drivers are vertically lower than the Khorn's Midrange and Tweeter which will change the reflections patterns from the room walls and even more because the Khorn is located in the room corners your room modes for better or worse will be different. when I've heard Khorns sound edgy in the treble one thing that can cause this is a lack of diffusion in the room. Diffusion will generally help any room to sound much smoother with a better tonal balance with whatever speakers you choose to use. PWK realised long ago that his Khorns could be blamed for bad sound when installed in certain room conditions and he realised diffusion would solve alot of those problems which is why he advised the polycylinder diffusor in the past. A really good sound system requires all factors(Speaker/Room/Componets) to compliment each others needs and because most of us have certain things that we can't change or choose not too change the best we can do is find what works for our unique situations whether its different speakers or equipment or dealing with the room acoustics. JTA said: Reluctantly, after that, I made some tone adjustments turning the treble down a few dbs and the bass up a bit. That certainly helped but I have always taken comfort in leaving the EQ flat as I feel it offers the purest undistorted sound. Though improved with the EQ adjustments, they still have that PA speaker bright, unmusical sound. JTA I just would like to add that our rooms are equalizers in themselves both in TIME, FREQUENCY and AMPLITUDE. So an Equalizer used PROPERLY can be one tool for us to use to deal with what the room is doing to our sound! GOOD LUCK JTA with whatever you choose to deal with this problem. mike[]

Sure wish I could have came this year! I was lucky to tour the plant and museum a couple of times in the late 80s and early 90s. Anyway I did get a picture of an early prototype of the Belle circa 1970 in the museum when I toured it. Early Prototype Belle circa 1970 mike[] How bizarre! Is that grille fabric in the interior of the tweeter and midrange? Looks from the photo like it's glued to the horn itself. Thanks for the pix. Michael Yes the Tag on top of the speaker said; The Belle Klipsch was introduced in 1971 and named for Paul's first wife, Eva Belle Klipsch. This early prototype Belle has an experimental grille cloth treatment. circa 1970 mike[]

I have spent many hours reading his works over the years. Thank you F. Alton Everest ! We should all be so fortunate to work at something we love! mike

Sure wish I could have came this year! I was lucky to tour the plant and museum a couple of times in the late 80s and early 90s. Anyway I did get a picture of an early prototype of the Belle circa 1970 in the museum when I toured it. Early Prototype Belle circa 1970 mike[]

THANKS dragonfyr!!! I really appreciate the MANY articles that you post on the forum. mike[]

ka7niq said: The tweeter sounds "spitty" to me. Perhaps its the amp ? i am going to change some things around, and see. The Klipschorns are 15 feet apart, and I am 15 feet 7 inches away. They dont seem to be pulling together, and I can clearly localize sounds in the right and left channels. I am getting a resonant coloration in the lower mids that I got in the Belle's. Honestly, at this point, I am far less then impressed. ----------------------------------------------------- Something just doesn't sound right here! Khorns shouldn't have a problem with a good centerfill with a setup as you described above. I would suggest you recheck all the drivers/crossovers wireing for correct polarity. Many times I've went to someones home to find that the polarity of some of the drivers had been turned around causing sound problems similar to what you have described. If you have any good test CD Disc I would suggest you use those to investigate at what frequencies you are loosing your centerfill image and also maybe to help identify where some of the sound imbalance is coming from before worring about different crossovers and drivers/horns. You should be getting better sound than what your describing so far. mike[]

http://www.acousticsciences.com/index.htm http://www.acousticsciences.com/tubetrap.htm http://www.rpginc.com/products/modexcorner/index.htm http://www.rpginc.com/residential/index.htm Not sure how involved you are wanting to get or if you have seen these sites Steve but here are a few sites to check out for Bass Traps as well as other acoustical treatments and some very good articles to help a person understand some of what is going on in a room acoustically. Also if you haven't read it "The Master Handbook of ACOUSTICS" by F.Alton EVEREST is a good place to begin to learn also. The above companies and their products are thourghly tested and have specifications that can be provided. I'm not familiar with the Aurlex Products. I spent a little time on their website but didn't see any measurement specifications provided. I would be curious to see test of their products so does anyone know if measured performance specifications are available? Edit: Found the Measurement Sections. The Syn-Aud-Con Newsletter was interesting on the Aurlex bass trap. mike[]

If you have a meter you can check to see if the voice coil is open by measuring it. You should see a reading of about 6.2 ohms. If you don't read the proper resistance you can pull the tweeter out and recheck it right where the rivet(THIS IS WHERE THE VOICE COIL IS ACTUALLY SOLDERED ON THE K77M) for the hookup terminal is and if you get a good reading there then you might repair it yourself if you can solder.(I've repaired several K77 tweeters that weren't working right by repairing this weak point in the design.) You most likely have the K77M and the way the hookup terminal is joined to the voice coil by a rivet can develope an open or a very high resistance connections. You can gently move the terminal "slightly" and see if you get any sound by doing this and if you do then you can possibly repair it yourself. If the above proves to be your problem then the way I have solved it is to take a very fine copper wire and soldered it inside the rivet where the voice coil is soldered and then leaving a little slack start to wrap the wire around the hookup terminal and solder there also. The reason for a little slack is so if you slightly move the hookup terminal it want break the wire. You can get a real small gauge wire to do this from a Scrap AC Cord if you have one. Any other problems with the tweeter would probably be best if you check with member Bob Crites (BEC) mike[]

http://www.littelfuse.com/cgi-bin/r.cgi/prod_parts.html?LFSESSION=yTy2PodKDG&PartID=602 This is a good sight for questions on fuses. This is a search result on the AGC 2.5 mike

I've sent you a PM Bill with my e-mail address and phone numbers Additional information I forgot to add yesterday is that there is almost no volume out of left channel when playing a record. Also, I didn't disconnect the wires at the cartridge because when I disconnected the connect from the tonearm to the TT, the hum still remained (I thought that ruled our the cartridge which is only a couple months old - am I wrong on that??) -------------------------------------------------------- Ok lets simplify this so where on the same page now. You can take the right channel(THIS IS OUR KNOWN GOOD SIGNAL) from the turntable and plug it into the left channel of the preamp and if you get plenty of volume and no hum then again this tells you that the preamp is OK and that again the left channel of the turntable has the problem which again I would look at the wires connecting to the cartridge or the cartridge as the problem since you already swapped interconnects out yesterday. If you determine the problem to be at the turntable then again swap the left and right wires hooking to the cartridge and if the problem hum and no volume changes channels then your problem is a bad cartridge. If the hum and no volume stays in the left channel then look at your wiring very carefully coming from the cartridge to your interconnect sockets of the turntable for a broken wire. Bill I might have confused you a little on this but because of the highgain phono input circuit it really isn't the best way to just unhook the wires to trouble shoot your problems because just doing this allows this circuit to pickup noise and hum because it isn't loaded properly. Using the shorting plugs was a trouble shooting method to see just how much Hum you had in the Phono Circuit of the Preamp without the chance of introducing hum from having no input connection on the phono inputs of the preamp. The best trouble shooting method is what we are doing now and that is taking a known good signal(RIGHT CHANNEL FROM THE TURNTABLE) and feed it to the left channel monitoring the results which in your case if we feed a good signal into the left channel and we get good sound out of the left channel of your stereo then we know your Left channel from the Preamp is GOOD and your problem is a BAD signal from the LEFT side of your Turntable Cartridge or Wiring. mike[]

The reason the hum is greatly reduced by using shorting plugs is you have reduced the sensitivity of the input " THINK LIKE IF YOU TURNED A VOLUME CONTROL ALL THE WAY DOWN" and thus any noise you hear then will be from the circuit itself and any local interferance close to the circuit created by its design provided everything is operating as designed. In your case you can't really just unhook wires because you are dealing with a high gain circuit and if the input is left open you will get some induced noise/hum. By the Hum being greatly decreased with shorting plug (and also moving to right side in one test) and you tried different interconnects it sounds to me like your problem is in the cartridge/cartridge wiring. Your left channel still having some hum at a lot higher volume setting could be a seperate issue possibly. If you E-mail me your phone number I can maybe call you and get a better idea of how to help you narrow down the problem. Just put klipsch in the subject line please so I don't accidently delete it. mike[] Edit: Again I would ask is the volume normal in the left channel even though you have humming when you play a record. I really believe I would swap wires at the cartridge at this point to see if the hum changes sides.

Good! now if you haven't, swap the left and right phono interconnects at the Preamp and see if the hum moves to the right channel or stays in the left(AND THAT THE LEFT STOPS HUMMING). If the hum shifts to the right then look at the left interconnects all the way to the cartridge for the problem like a bad ground. If it is easy for you to do you might even swap the wires at the back of the cartridge to see if the hum changes sides. You could have a bad cartridge if you swap the wires at the cartridge and the hum moves to the other channel. If you play a record is the volume the same on both channels except for the hum problem? mike P.S. I always Keep some shorted RCA style plugs for putting on inputs to elliminate sources for problems such as this. When you unhooked both phono interconnects and thus left the inputs open its possible you will pickup noise and hum in the highgain circuits like a phono input so by using a shorted input plug you can eliminate this interferance to see if the circuit is quite on its own. You can make your own shorting plug real easy if you have a cheap interconnect you don't mind cuting up. Just cut the interconnect close to the plug and tie the wires together thus shorting the plug. Then plug this on the phono input thats giving you the problem hum and if its gone then you know the preamp is OK and the problem is from the source like again in your case possibly a bad interconnect, broken wire or cartridge maybe.