Deang

I want Craig to figure out how to turn a Scott 299B into a pure Class A amp --that's where the magic really is.

Have them now 13" from the wall, 21" from the side walls, with acoustic foam mounted to the wall, next to each speaker, extending about 3 feet out -- to handle the first side wall reflection. It seems like the whole wall is acting as a baffle -- and sound is everywhere. Speakers are now 8 feet apart, center of horn to center of horn (as opposed the 6.5 they were). Center image is still stable. Highs have smoothed out, and the bass seems more even. Interesting.

Craig, I love you man -- you're a trip. You're also full of sh!t. You'd have this thing on your test bench with a piece a paper, and have the whole circuit diagrammed out in 45 minutes. A schematic probably wouldn't tell you everything you need to know about the transformers anyway -- they're specciaal. Custom wound to his specs (whatever that means), and the associated info is not likely to be on the schematic.

No way. RF-7's would sound great a foot apart!

Sometimes, and to our shame -- Justin is the most 'adult' person here.

How much are you willing to spend? Two channel only? Do you HAVE to have tuner?

yah, me knows. I was only concerned about impeding the functioning of the port. So, it is 1.5. So now, do I have to factor in both ports (RF-7 has two 4" ports in the rear)? Thanks!

I don't think he was trying to be 'nasty'. I think he thought he was being 'funny'. Man, I don't know. I've got my Cornwalls 7 feet apart, and the couch is 7 feet back. It was the best I could do -- and it's borderline. The bigger horns really need some room to breathe. Being that close...I just think they're going to end up sounding like a P.A. system. The biggest problem you would have is the cancellation effects from the speakers being so close together. There is such a thing as too much speaker for a given room -- and I think this is one of those situations. Would you believe in this situation -- a set of Heresies would sound dynamite.

Well, they use a cathode biasing scheme, and I can run KT-88's, KT-90's, etc. I just have to make sure the tubes are matched using real voltages (under load) -- I think I have that right. The truth is -- they will always sound best with the EL-34's. Based on my understanding of cathode biasing -- it works good if you stay with the same tube type, not so good if you go to something else. Believe me, I have no problem with the EL-34.

I knew it was SS rectified when I bought it, and of course there is no rectifying tube. I wasn't much concerned about this, since my last three amps used it, and I was happy with all of them. I certainly think there is more to how an amp ultimately sounds than whether it is tube rectified or not. Yes, it is a very simple design. A little over a two dozen parts overall, and only 5 parts in the signal path. Kelly voiced some criticism over the parallel arrangement of the EL-34's. Most of what I read seemed to indicate it was more of a good thing. What sayest thou?

12AX7 & 12BH7. Can you guys tell by looking if that's a silicon diode for the rectification?

I've searched the web endlessly. I called Mike Sanders and though he was very nice about it -- said no way. I am most definitely interested in manual adjustable bias. That would be the bomb. It's the ONLY thing I don't like about them! Kewl.

"...about 3 feet apart if that, the couch would be about 4 feet away from the speakers." Close enough together to enjoy all the cancellation effects. I don't think you should do this. Seriously.

So Mark, you tell me -- what the hell are we looking at here? I paid extra for the duct tape.

Bad verbiage on my part. I simply meant rewiring, so a beam or pentode tube behaves as a triode. As far as the Quicksilvers go -- I have no idea where Mike Sanders got the circuit for these. They do sound very good however.

I think wiring Ultra Linear in Triode just gets you closer to the 3rd order distortion faster. I think at this point, I have just decided I am more interested in keeping the amps in Class A as much as possible, as opposed to triode operation. I don't know how much Class A power I have, but I bet I'm in it most of the time.

"Tubes and designs have come along way since 1951" I don't understand how someone with your knowledge can make that statement. I don't agree at all. Reinventing the wheel cannot be equated with "coming a long way". Consider the first triode amp was built in 1907, and that the Ultra Linear circuit that came about 45 years later, was at the time -- considered quite a leap in fidelity. So, what has happened since then, except the regurgitation and tweaking of circuits that have been around for 75 years or more. I would argue that any improvements in any of these designs are mostly due to better tolerances in manufacture, superior parts, etc, applies equally to all the old circuit designs -- including Ultra Linear designs. I can't tell a hill of beans difference between the AE-35 DJH I had and the Quicksilvers. How can that be? Is my hearing THAT bad? The "Author" of the .PDF document I gave the link for was David Hafler. It is a copy of the original paper appearing in the 1951 November issue of 'Audio Engineering'. The following is from a small book put out by Sonic Frontiers called 'A Taste of Tubes'. In 1934, W. T. Cockings seminal article on "quality amplification" appeared in the British DIY publication, Wireless World. In it, Cocking suggested that 5% distortion was too high for quality amplification. He went on to state that "the aim being to reproduce in the listeners own home exactly what he would hear if he were in the studio." This statement marks the conceptual origin of the era of high fidelity, insofar as we are able to trace it. Cocking is recognized as the harbinger of high fidelity not only because he was influential and authoritative, but because his amplifier was to evolve, by deliberate steps, into the famous Williamson amplifier. After explaining his approach, Cocking compared triodes to pentodes and found triodes preferable for their ability to damp a moving-coil loudspeaker at resonance. He next compared push-pull to single-ended operation and concluded that the latter produced objection-able 2nd harmonic distortion. Cockings amplifier soon became known as "The Wireless World Push-Pull Quality Amplifier". This seed-pod or germinal amplifier was destined to become the touchstone of tube design for nearly twenty years. Williamson Stirs the Pot In April, 1947, D. T. N. Williamsons article "Design for a High Quality Amplifier" appeared in Wireless World. Williamson echoed Cockings words when he summed up his analysis of the require-ments for high quality amplification: "It appears then that the design of an amplifier for sound reproduction to give the highest possible fidelity should centre round a push-pull triode output stage and should incorporate negative feedback." Thus, the evolution of Cockings "Wireless World Push-Pull Quality Amplifier," (as begun in 1934), ultimately culminated in the famous Williamson amplifier of 1947. The distinguishing feature of each incarnation of this amplifier was the use of triode tubes (actually, KT66s wired for triode operation) in push-pull configuration. In spite of their reduced power output, triodes were preferred over pentodes because their distortion products were found to be less objectionable. This meant that, to obtain a given power output, more money had to be spent. Thus the identification of high fidelity with higher cost began to take root in the public mind. In 1946, Avery Fisher introduced the first commercial high fidelity system. It included a 50-watt triode amplifier, Jensen co-axial speak-ers, AM/FM tuner, preamp and phonograph. The $1,200 price, however, put this model out of the reach of most music lovers. Other companies like Altec-Lansing, Brook, Bogen, Bell, and RadioCraftsmen also joined in the fray. T o s ave money, audio enthusiasts could buy hi-fi components in kit form from companies such as Heathkit, Eico, and, later, Dynaco. The kit-building craze was fueled by the large numbers of post-WWII military-trained electronics technicians. The Pentodes Revenge By 1949, Williamsons triode amplifier had become the prototype for high quality amplifiers the world over. In the face of this enormous interest, there arose a new generation of pentode amplifiers to chal-lenge the long-standing triode tradition. The pentode movement consigned to public address systems early on by engineers and audio-philes alike was reinvigorated when new techniques were discov-ered that caused pentodes to sound/perform more like triodes. Quads Potent Pentode Recipe Three companies in particular stand out for their achieve-ments in pentode amplifier design. In 1945, Peter Walker of Quad found a way to dramatically reduce the high-order pen-tode distortion products. Taking a clue from Blumlein, Walker found a way to turn the high pentode gain into local feedback. To obtain this feedback, Walker incorporated a tertiary cathode winding within his output transformer. This technique produced local feedback in accordance with the AC impedance of the cathode winding. This more sophisticated form of feedback provided a greater benefit than loop feedback alone, since there was only one high-frequency pole to create phase shift. Unlike loop feedback, the cathode feedback remained effective at the fre-quency extremes, thereby reducing the high-order distortion products associated with pentodes at no expense to power output! McIntoshs Pentode Pie`ce de Resistance In 1949, Frank McIntosh and Gordon Gow took Walkers technique a couple of steps further in their 50W-1 amplifier. First, they increased the number of turns in the cathode winding (Fig. 7) to obtain correspondingly more local feedback. Second, the plate and cathode coils were wound adjacent (bifilar) to one another to create a "unity coupling" between the two windings. This reduced transformer leakage reactance by a factor of 3-to-1, thereby extending transformer bandwidth and reducing phase shift. The reduced phase shift translated into more effective loop feedback at the frequency extremes, enabling McIntosh to claim the lowest dis-tortion across the widest spectrum of any known power amp. The editors of Audio Engineering hailed the McIntosh as "the first major change in years in amplifier coupling circuit principles." No mention, however, was made of the Quad amp. Hafler and Keroes Go Ultra In 1951, David Hafler and Herbert Keroes approached the pentode from a different angle. They returned a portion of the plate volt-age to the screen-grid (Fig. 8). This local feedback loop became known as the "ultra-linear" connection. It soon formed the basis of the Acro Ultra-Linear amplifier. Keroes, a transformer expert, knew that the screen-grid was a non-linear input terminal where feedback is concerned. Nonetheless, he found that the tapping point could be adjusted to enable linear feedback action. This nar-row window of operation was claimed to provide "ultra linearity." In their own words: "We have achieved a new tube type without designing a new tube. This tube is neither triode nor tetrode, but its improved linearity over either of those types justifies the designation ultra-linear." In reality, this statement applies as much to the Quad and McIntosh amps as it does to the Ultra-Linear amp. Nonetheless, because the Quad amp was little known in the US, the ultra-linear technique became widely adopted. During the Golden Era alone, more than twenty different manufacturers adopted the technique including Marantz, Harmon-Kardon, Fisher, Scott, Eico, and Dynaco. Indeed, the very name, "Ultra-Linear", was to become generic; in that it ultimately came to refer to the technique itself, rather than to the amplifier that inspired the name.

I haven't said much about the Quicksilvers. I know I have this propensity for singing praises for something, and then as I spend more time with a piece -- I begin to zero in on it's deficiencies. The Quicksilvers sound so good with the RF-7's -- I just don't want to mess with them. I only asked Dale if the Dynaco's were in triode or not because I was curious how much power he was running. Regarding the SS rectification bit -- I mentioned to you before that Saul Marantz used it in the 8B. Anything done right -- sounds good. I appreciate the speed and drive it gives me. http://www.aikenamps.com/UL.pdf

If you don't mind -- where did you find that information on the site? Thanks.

Yeah, I know the rules, but man, it sure is a drag moving 100 pound speakers a half inch at a time. I was REALLY hoping someone would say something like, "One and a half times the total area of the ports". Maybe I'll just move my chair a half inch at a time.

Craig put these in triode? How much power are you running now? Watch your ears with those Scalas. If you're not careful, you'll end up like Craig -- calling your kid in to ask, "how does it sound"?

I bring this up every couple of months when I think about it. Does anyone know the optimum distance from the wall with rear ported speakers? I know it relates to port size, but I can't remember the dag gone formula. RF-7 has two 4" ports.

Dave, You gotta fill us in. Equipment Room Size Placement Etc.

Sure is nice seeing some of the top brains of the outfit handling a slight difference of opinion in such an intelligent and calm manner. Of course, a technical slug fest between you two would have been pure bliss. Well, from the day I received the Quicksilvers, I've had them on the 4 ohm taps of the transformer because of the known dips in the RF-7's impedance. I had the RF-7's wired this way with the Apollos, and didn't see any reason to change this on the Quicksilvers. A little of topic here, but not really I guess -- the literature with the amps say they put out 60 watts whether on the 4 ohm or 8 ohm taps. I don't really understand how this can be possible. Just think, going to 4 ohms halves my power. If I wire them in triode I halve them again. Before I know it, I'll have 8 EL-34 tubes giving me less than 20 watts. Yeesh. I actually like the Ultralinear sound with my music quite a bit, so I'll be leaving them this way for a time. As far as adding the resistor goes, I think I'll give it a try. As far as non-flat response goes -- ain't many of us getting that anyway. Between room acoustics, and running tube amps on speakers with less than ideal impedance curves -- who knows what the real response looks like. Hey, if it sounds good -- who cares? One thing Leo. If you look at the impedance curve of the RF-7, and average the whole thing out -- it's really a 6 ohm nominal speaker. Based on this, what do you think about me trying 12 ohm resistors instead? The idea is to get a 4 ohm load at the amps outputs, correct?

So Kelly recommends the Rega. This is good. EVERYONE recommends the Rega Planet. I've never read a bad word about it. I would only hesitate to buy one because they are getting along in years somewhat, and CD players are prone to early failures if not treated with some care over time. Personally, I stay here because of the somewhat relaxed atmosphere, and I can say what I want without having to worry about being flamed. I used to post at the Asylum -- but any post has the potential for igniting a war. It gets old. I consider Kelly somewhat eccentric and rather unique. Though I think he is out of his mind sometimes, I have stepped into waters I normally would not have, and have come out with an understanding of his perceptions -- and am the better for it. I bought the Scott because of Kelly's love for vintage sound, I bought the Superamp because of his preference for low power, I bought the Apollos because of his kinship with SET, and I waddled into cable hell -- and in all this -- finding that most of what he said is true. In the end, I go in a different direction, trading some transparency for more control and authority in my music -- but this does discount any of his opinions. At any rate, I'm enjoying my music at an unprecedented level because of him. I'm also prone to multiple revisions of my posts. I read them once posted, and realize the verbiage I employed didn't really get my meaning across -- so I change it. Then I notice a letter missing from a word, and then a grammatical mistake. I care enough to fix the post. I consider Kelly a friend, and I can only say that if some of you cannot contribute something positive to the forum in the form of suggestions to advance listening pleasure -- you might consider going somewhere else. Please.