DRBILL

It would be a good discipline for all of us to go back and read or re-read Paul's technical papers with an eye to style and form. He acheived clarity through brevity and parsimony. He was a humble man who genuinely wanted to share his discoveries with others. He made his wisdom accessable. I almost didn't post this. It is not intended to be critical. DRBILL

---------------- On 8/23/2005 9:40:33 PM colterphoto1 wrote: "I've never had to cement rubbers on" Michael---------------- Which reminds me of an Aggie Joke. The sign said "condoms - $5" But when the Aggie checked out it was $5.19. "What's the nineteen cents for?" "Tax, said the clerk." "TACKS! --YOU CAN KEEP 'EM!" Sorry, but Mike started it. DR BILL

There is a new issue of SWITCHED ON BACH called SWITCHED ON BACH 2000 (Carlos 25th anniversary). It has the same Carlos programming but with improved MOOG voicing. Some parts are wonderfully better than the original while others are simply puzzleing. The original BACH tunings and temperaments are used which adds interest. TELARC CD-80323 DOLBY SURROUND DR BILL

Hum in the audio community is something like Original Sin. No matter what you do, a little taint of it still remains to remind you of your vulnerability. Remeber that you heard it here first. DRBILL

Nope. None of the above. Too permanent if it isn't right the first time. I have used common office variety rubber cement to good effect. You can always correct your mistakes. DRBILL

GIL, I appreciate your thoughts. This question didn't arise out of a vacuum. I had a Heathkit w-4 (Williamson) amplifier on the bench recently that was plagued by hum harmonics. After exhausting the usual suspects I was stumped. Then I noticed the Y-G lead from the power transformer which, on the schematic was marked "not used". I stripped the end and with a little trepedation, touched it to chassis ground. Hum gone. I'm sure the Heath engineers had a good reason not to use this lead, but I can't imagine what. I pulled all the power amplifier schematics I had out of my files to see how others treated this question. Dynaco favors a .02 disk. Eico has no center tap but uses the wire wound pot with the contactor to ground. My conclusion is that some people drip coffee while others perk it! I never sat for the Novice exam for fear of the five WPM code test! My dad was W5ESA and his rig was in one corner of my bedroom --home made: 807's in parallel push-pull. It could be exciting back there in a thunderstorm. I've had rosin in my system since I was in grammar school. In high school I had a bench at a local radio/TV shop after school. DRBILL

I think the laws of diminishing returns hold here considering the price. I have a pair of Mark IIIs with new cap boards and a slightly improved driver board using pairs of 6DJ8s and KT90s in the final. There might be some subtle differences between mine and the ones pictured, but I expect it might require instrumentation to detect it. Stock, and well maintained, the MARK IIIs are superb. All else tends to be gilding the liley. But, of course, I get out of patience with the "improvements" that some of the brothers claim to have made to Klipschorns. You can trust me on this, when improvements were needed, Paul made them --and never mind the cost. DRBILL

In the amplifiers that I regularly see, there are three ways to deal with a center tapped heater winding on power transformers. In some, the center tap goes directly to ground. Others connect to ground via a small value disk capacitor. Yet others bridge the heater feed with a wire wound pot identified as "hum balance" with the center contact and center tap finding the way to ground by various means. What are the advantages/disadvantages of each method. Is there a "best way"? Your input will be appreciated. THANKS DRBILL

In that case, you can use either kind. Yes, I am referring to the plug that goes into the wall socket. I'm sure you are quite familiar with the adaptor thingy with the little wire hanging loose! Or do you just cut the ground prong loose? The reason I ask, there can be some polarity issues that result in excessive hum. But that's a dissertation and is probably covered somewhere else on the forum. While I have you on the line I'll mention the filter capacitors in the Mark III. It is the weakest link in the system and is driven almost to the failure point. Its 525v volt rating leaves no headroom for an AC surge. This is yet another reason to continue using the 5U4 or to invest in an isotap. If a filter cap ever blows, don't replace it with another "twistlock". Invest in a "cap board" (many are available) that installs either under the chassis (if you want to preserve the original visual profile) or in place of the present can. "I could tell you more, but you would not be able to bear it!" Seriously, it is a splendid amplifier. I would never have anything else. I Have never had ANY difficulties with mine. But there is the voltage issue that your tech mentioned. Fortunately, there are fairly easy ways to work around it. You asked the right questions, early. BILL

DEE, ±122vac probably isn't much to worry about. After you have carefully set the bias, let the Mark-IIIs operate for about an hour, and in a dark room, inspect the plates on the output tubes for any suggestion of reddness. I think you told me that you are using 5U4s. That pretty much rules out any problems. Voltages tend to sag in the summer, so you might want to check again in the fall after everyone turns off the air-conditioners. As you get closer to 130vac, become nervous. I am using GZ34/5AR4s and I had nothing but trouble with rosy plates until I bought the isotap. I can set it to exactly 117vac which is the DYNACO specification. Look up isotap on e-bay. You can probably get one for $10 or so. The catch is the weight, so beware. They are like a boat anchor. You want the one with the third grounding prong on the line plug. If you play loud, heavy bass music, you will notice some sag using the 5U4. Is this starting to sound like "stone soup"?! BILL

Are you set up to post pictures? It would really help. DRBILL

I vote for carefully restored Mark III's. DR BILL

I think I would check all of my connections --both audio cables and speaker wires. Heating and cooling have a way of loosening things up. Just because an RCA jack seems tight doesn't mean that the center pin is making good contact. Good hunting. DR BILL

I just finished retrofitting two Dynaco FM-3 tuners with the Van Alstine recommended alterations. This was accomplished by "kits" supplied by Desmond Gillman whose wares can be had on e-bay in the Dynaco look-up. This brings the power supply up to standards, replaces some of the usual suspects such as coupling capacitors and undersized resistors. Most important, it changes the de-emphasis circuits in a major way. When the FM-3's were introduced, FM stations were rare, usually distant, of low power, and didn't have much to offer in terms of audio bandwidth. To cut down on noise, the FM-3's rolled off bass and treble very early. The kits correct this and bring the audio bandwith up to modern standards. These kits, together with a careful, painstaking realighnment, produce the best multiplex FM receiver that I have ever heard. I would put it right up there against a Mac or a Marantz. If you have an FM-3 mouldering on a shelf somewhere, you owe it to yourself to give this a go. I can remember few times that I have been so pleased with so few bucks spent. DR BILL

Try www.vacuumtubes.com. Michael Marx has an astounding catalog of NOS tubes at reasonable prices. His site is often under construction, so don't hesitate to call him or e-mail him. He is an encyclopedia of tube lore. DR BILL

DEE, My KT90's are EH. They are the only ones that I have tried. They have the "wafer" or sometimes called "coin" base to keep the height in check. They are REALLY big tubes! Michael Marx at SNDTUBES@vacuumtubes.com has the 6AN8 & 6AN8a for 6.00, (NOS), pot luck on brand unless you specify. BILL

Hello, Dee, The 6AN8 is appropriate for parallel-filament circuits and/or series circuits nor requiring controlled warm-up. For your application, either will work fine. I SO want you to try KT90's in your Mark III's. Direct drop-in. Just re-bias. They provide a few more watts, much smoother bass, and no danger of rosy plates when your house current exceeds 117vac. Ask anybody who has tried them. DR BILL

A member of my family has bachelors and masters degrees from one of the most prestigious engineering schools in <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />North America. The boy is ignorant. And it comes as no surprise. You should see his transcript. It is bereft of humanities. He attended an extremely rigorous and expensive trade school. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> Dont let that happen to your scholar. Equip him for life, not just for work. Send him to a top notch liberal arts university and have him major in math or one of the sciences. Make sure he gets a large dose of humanities and a language or two. There will still be time for him to gain his engineering credentials. It will be much easier for him because he will have learned the discipline of critical thinking. For years, I sat on the Board of Trustees of The University of the South (better known as Sewanee) which is always mentioned in the top twenty-five liberal arts schools. It has alliances with several engineering schools to offer courses that essentially lop a year or more off of the engineering degree. Im sure that there are many other schools that have similar alliances. At least, encourage him to send for some catalogs. DR BILL

That is stunning. I had to call my wife in for a second showing. MANY THANKS! DR BILL

---------------- On 7/31/2005 9:33:59 AM bkrop wrote: It's probably the nature of the brushes, as they don't start and stop cleanly, by design, they tend to sound "fuzzy". IMHO of course. ---------------- If these were brushes on so-called "sizzle" cymbals (the ones with loose rivets in oversized holes) the answer would be obvious. Like others, I would like to hear an AB comparison with a really good SS amplifier. The quality of the recording could be a large factor. There are just so many variables. And dare I suggest that Dee's amplifiers and top-notch speakers are passing along some undisirable recording defect that SS fails to detect. DUCK! (where?!). DR BILL

There is an earlier thread than this one. It is very comprehensive. DR BILL

---------------- On 7/25/2005 6:35:00 PM Parrot wrote: Father Bill, in what way do you find the Forum boring? In terms of lack of flame wars or in terms of lack of stereo info? I agree with Nick on guessing that the summer finds many Forum members outdoors. ---------------- Flame wars are a definite waste of kinetic energy. An old friend used to put it this way- "We are passing the saw through the same old slot without ever touching new wood." DRBILL

What is happening to the FORUM? Nothing of any great interest has hapened in a couple of weeks. Perhaps it is summer torpor. Maybe I'm just bored. But that can't be. I was just presented with my third grandchild. My 36 year old daughter had a boy. Her first child. He is beautiful. Thank God, he looks just like his Pop, mop of black hair and all. The rest of us don't favor much! 8#2oz, 19½". His name is Marlon Vaughn L. His Pop is bassist in the "Me Thinks" which was voted best hard rock band in the Dallas/Fort Worth area by the Fort Worth Weekly poll. His stage name is Merlin Von Bungy. Go figure. I'm tired. His mom REALLY is. DR BILL DR BILL

Is it just me, or has the FORUM gotten to be tediously uninteresting lately? DR BILL

I second The Varsity. As long as you are in the neighborhood, at least, take one of the tours of the Fox Theatre. It is a most elegant reminder of a past gilded age. Even better, take in a live performance. All-in-all, I find Atlanta to be a very gracious place. Even on the sidewalks you sense an aura of good manners. All bets are off when you get behind the wheel! Think Dallas on amphetamines. You had better know where you are going and what lane to be in when you get there because the next stop will be Alabama! Good luck DR BILL