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24.15.35.211
In Reply to: RE: HK Citation 2 rebuild questions posted by Ping on April 16, 2015 at 18:47:48
"These were highly engineered and they didn't throw in random size capacitors willie nillie."
That a pretty strong assertion - you're saying that is what I do in my Citation kits? No way that's the case, no way. Back in the early 1960s Citation designer Stu Hegeman would have KILLED to have access to the parts I do now. He was limited by (among other things) cost factors, by diode durability issues, and by the parts he had access to. If he were alive today he'd be VERY pleased at how we treat his masterpiece amp.
BTW - define for me what you mean by "speed" and "flow" of the power supply.
And where in the world did you get the idea that modern parts are less "music-friendly"? Nonsense! For instance, you mean to say the fast/soft power supply diodes we now use that can handle 3 amps of continuous current and 600 volts PIV while generating near zero noise are not as good as the old "top-hat" diodes - the ones that were expensive as all get out and failed often if they pushed at all? One PRIMARY reason for the smaller cap sizes on older gear with solid state diode power supplies was that the rectifier diodes couldn't handle the currents! With today's far superior diodes capable of handling surges of 100s of amps (if need be) we are free to use cap values and caps with so much lower ESR than Hegeman could have even dreamed of.
I'm sorry, but IMHO you simply don't know what you are talking about. My comrade Don and I have redone HUNDREDS of Citations, how many have you done? How many have you heard? If you do a search and look for reactions to the performance of the "McShaned" Citations what do they say?
The preponderance of evidence is STRONGLY against you.
This post is not meant to be contentious either. But is IS meant to challenge the erroneous beliefs you are passing on and describing as indisputable facts.
Follow Ups:
My apologies to most of you on this site. I thought this was an open forum to have discussions. Clearly you only want to hear things that jive with your already established opinions. I've done a little bit of research since my original post and the responses here just to see what else is out there. There are so many other sites and forums that have similar philosophies to mine. I've found a lot! Surely this can't be the first time you've heard this! It appears to be an ongoing debate. Many many professionals believe that gutting vintage amps is the wrong thing to do.
My advice to any owners of these amps is to experiment for yourself. Try some vintage tone capacitors at key spots. Its easy to do. Maybe take some cues from what is found in vintage guitars and guitar amps. If you don't hear a difference throw in whatever industrial parts you can find from panasonic and be done with it.
And as for how many amps I've restored I pose this question to you. How many amps have you designed? IMHO the people who designed these fantastic amps that are still being used today are a bit more knowledgeable than someone who restores them.
Ping
I hope we didn't come off as condescending but many are very passionate about their Macs and Citations. Several of the caps that Jim puts in the kits are vintage paper in oil caps that are new old stock.They are sonically very similar to the 160p and I agree that the 160p caps are fantastic but when they have been in use 50 plus years,you have to realize that they may not be up to spec anymore and leak DC and this causes many problems for tubes and output transformers..The bumblebees were also a nice sounding cap when they worked but their reliability is horrible because they were made in a humid plant and that's why so many of them are cracked.If you could find a source for NOS 160P capacitors in a plentiful supply, let Jim know because I'm sure he would be more than happy to stock them. The problem is they no longer exist and the K40y pio caps sound almost identical to them in their sonic patterns only they are more reliable.
There's something else going on that nobody mentioned and it's this.Citation amps ran extremely hot and it wasn't just because of the tubes being biased at 90ma and 100ma each.That was part of it but the truth is the power supply filter bank was too small and underrated for energy storage and delivery for a class A type amp of that higher power rating.Think about this.When is a power transformer working its hardest? When it's charging the capacitors and being the filter caps were small by comparison,extra current is constantly being pulled thru the power transformer causing it to heat up more because it has to constantly refill those undersized caps much more than it would if you used modern filter caps of a higher capacitance value. OTOH when Jim designed a stout power supply to fit the Citations and the Mac amps,they could loaf a lot more because the transformer wasn't working as hard as it was when you try and play the amps at higher volume levels.The Citations run much cooler after the McShane rebuild and that way you don't have to risk ruining your power transformer from excessive heat.. How is that a bad thing?
The other problem is that the old coupling caps leaked DC overtime and this would cause output transformer failures..A good example was the Heathkit W5m. Many would say it was because the 16309 output transformer was too small but there was more to it than that.Every failed output transformer I have found in those amps had the original black cat 1uf coupling caps in them and that was mainly what caused the output transformer to fail..The caps would leak DC going to the grids of the KT66s and they would draw excessive grid current putting a huge load on either side of the output transformer causing the primary winding that feeds that one tube to open up.Many of these output transformer failures could have been avoided if people would have changed the output couplers to the KT66s.While the 16309 output transformer was smaller,having the output tubes drawing so much extra current took them beyond their power rating causing most of the failures.There is also the issue with power transformers failing in the W5ms and this was because people never changed filter caps nor the rectifier tube socket that would develop leakage between the pins. This was due to poor layout and design and if you put in a new high quality rectifier tube socket and get all those resistors off the tube socket that are hanging from it,this will greatly improve your chances of saving your power transformer and make your amps perform much better..How is this a bad thing?One more thing I want to address...Jim and I do not modify or redesign vintage amplifiers and preamps.We may address a weakness in design but that is an upgrade and not a circuit redesign..There are those that do butcher vintage gear for the iron or change the circuit to something else.
The Citation 2 was born with six 12BY7a and that's the way we leave it.
Some try to redesign the original by changing the circuit to dual triodes and when you do that,it's no longer a Citation 2..
There is nothing wrong with vintage circuitry.I have said many times before that a tube conducts the same way in 1956 as it does in 2015.
Nobody ever went broke underestimating the intelligence of the American public
H. L. Mencken
Edits: 04/18/15 04/18/15
No, you've been civil, not at all. I think the 160 and dry( non-oil) bumblebees are pretty similar. Sure sure I am well aware of capacitors leaking d.c. So you check them of course.
Again the stout ps supply causing the power transformer to run cooler is not bad in itself, of course not. I'd be more interested in how it sounds though. But I think we can rest assured that the transformer is being safely operated with the original power supply in place. The fact that it still works after 50 yrs and potentially tens of thousands of hours of use is a pretty good indication.
I am going to go listen some tunes now.
Ping
The bumblebees did have a similar sonic nature to the 160p but being there were so many issues with them,I just replace them to be safe..The 160P caps are fine if they measure ok.
Again the stout ps supply causing the power transformer to run cooler is not bad in itself, of course not. I'd be more interested in how it sounds though.
It sounds like a Mac or a Citation 2 with a bit more refinement. Try it,I think you will love it.. But I think we can rest assured that the transformer is being safely operated with the original power supply in place.
` That would be true if we were listening to records from the 1950s and 1960s because they didn't have super dynamics in the 95 plus db range that would constantly drain the undersized power supply on peak transients. That is basically the whole argument for beefing up the power supply so we don't drain it and it keeps us from hitting the DC rail which is distortion at its worst.
Just try building one the way Jim says and if you don't like it,you can always put it back to original values.The manufacturers used smaller value electrolytics because that's all they had in those days. It was adequate for the time tho with what we listened to..You could say it's like trying to use Pentium 2 computer today.At the time they were made,they were plenty fast but since the dynamics of web browsing and internet speeds have changed,they no longer work well in today's market.
Nobody ever went broke underestimating the intelligence of the American public
H. L. Mencken
Edits: 04/20/15
I'm surprised to see such hostility on this topic, and I don't know why you're getting so much crap for what you've said. I'm not in agreement with all of it either, but there are certainly some gray areas in this. Besides, your opinions seem pretty tame compared to most of the rotten advice that masquerades as fact on this forum. Guess you struck a nerve... :)
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Buy Chinese. Bury freedom.
T/K,
Ping is very much entitled to his opinion. What raised the hackles were statements of opinion as if it was Biblical Truth. Did you see IMO or I think?
Far too much nonsense has been "floated" on this forum, of late. :> (( It has to be opposed, less the "big lie" gain traction and people start believing it.
Eli D.
"Did you see IMO or I think?"
Eli, you can believe that I understand how you feel about this. I've been through it myself with a few other members. Still, I have to wonder if it's really necessary to always state that it's the author's opinion when discussing something other than formulated science like Kirchoff's Law or the Pythagorean Theorem. Opinion constitutes so much of what's written in forums like these, I always assume it's necessary to search out or ask for an authoritative source if it's a topic of interest to me. In this case, however, it's evident Ping is coming from a place that is not black and white, and that there will be no authoritative source. His perspective seems to be based on an opinion that the equipment should be restored, that the original performance is not only good enough, but that it consists of a sacrosanct product of its designer that should not be tampered with. I personally don't agree with that, but there's room for it in the audio community. Just as some people prefer to restore a Model T while others install a V8, it's simply different strokes. More to the point, I don't think he deserves to be vilified for this opinion. He's not preaching a deranged pie-in-the-sky philosophy like some of the Asylum inhabitants, and at the very least, his approach won't make the amplifier worse. I know you guys are passionate about this, but I think intelligent Cit II owners will understand your perspective and will appreciate Jim's wealth of knowledge and experience on this subject without the need to insult the other side. Just my $.02. :)
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Buy Chinese. Bury freedom.
"There are those that do butcher vintage gear for the iron or change the circuit to something else."
I don't see anything wrong with that. Not one bit. These are engineered machines, not carrier pigeons. :)
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Buy Chinese. Bury freedom.
Jack
If you are going to butcher a nice clean vintage unit for the iron that is factory built,I couldn't go along with that.If it's an old POS that's on its last leg,that wouldn't be a big deal.
There has been an evolving trend going on with vintage gear following that of the vintage car market.For example,you have the crowd that loves an all original 51 Merc with the flathead and the three speed manual overdrive,just the way it came out of the factory at Ford.
You then have the crowd that wants to chop,channel,and lower the car and put in a modern crate engine and auto trans out of newer Mustang,or maybe a chromed out small block Chevy or Ford engine.Is one group right and the other one wrong? It depends on whom to talk to.I like both.
Nobody ever went broke underestimating the intelligence of the American public
H. L. Mencken
"If you are going to butcher a nice clean vintage unit... I couldn't go along with that."
That's your choice. It's my opinion that stripping the iron off a '60s amplifier and rebuilding it in a modern chassis isn't butchery. Didn't I read somewhere that Jim McShane used to do that with the Cit II amps? Correct me if I'm wrong.
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Buy Chinese. Bury freedom.
" Didn't I read somewhere that Jim McShane used to do that with the Cit II amps?"No, ABSOLUTELY NOT!! I would never do that, period. If you did read it it was either totally mistaken or a complete fabrication. IIRC a guy by the name of Mike Moffat - who was later of Theta fame - did that though.
Edited - I stand corrected, it was Bruce Moore. The mixup came about because I am currently considering purchase of a basket case Cit II that was indeed reworked by Mike Moffat - I got the names confused. Thanks for the correction.
Edits: 04/19/15
OK, I'm corrected too. :) It was a long time ago that I read that piece, must have mixed up the names.
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Buy Chinese. Bury freedom.
IIRC, Bruce Moore made a 120 monoblocks that used Citation II output iron.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
Jack
Depending on the amp,that would be your choice but would you butcher a mint condition Mac Mc275 just to get the iron?
Nobody ever went broke underestimating the intelligence of the American public
H. L. Mencken
Well, if your position is going to be based on a MacIntosh, using words like "mint" and "butcher", there's nothing to discuss.
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Buy Chinese. Bury freedom.
How about a clean factory built Citation 2? I don't think you would butcher that either.
Nobody ever went broke underestimating the intelligence of the American public
H. L. Mencken
I've seen some that the only thing worth salvaging on them is the output iron. The power transformers on the Citation II are not the best to begin with. Many of those amps ran so hot the potting material literally melted out.
I kind of wished the Citation II was allowed to be designed with a pentode output. I think that wold have made a very good amp even better.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
" The power transformers on the Citation II are not the best to begin with."
I don't agree at all, IMHO those transformers were top shelf stuff. What about them was substandard?
"Many of those amps ran so hot the potting material literally melted out."
Often the heating was due to the trafo being on an amp that needed work. And early on H-K got crazy with the bias spec of 100 ma. per tube. So the transformers were worked VERY hard in many cases. But even many of those trafos that were not well treated are still running just fine today, 50+ years later.
IMHO those trafos may have been assassinated by other amp issues but they very rarely failed on their own. We've seen some issues with the bias winding in the last few years, but that's it.
If I were to get another HK Citation II, I would have to seriously consider a newly made power transformer with more reserve (overkill) to help out performance. I'm sure the original quality of the power transformer is fine. It's more the fact that it was run HARD near its limits for a lot of years, so many of them are stressed.I also wonder if a pentode output would have been better in the long run.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
Edits: 04/19/15
and they don't generate a lot of heat unless people leave old leaky caps in the unit that stress the power trafo..The Heath W6m also uses a doubler and as far as the Citation 2 running hot,that was true back in the day when they were biased at a 100ma per tube..With the McShane mods and the reduced bias on the tubes,they run much cooler than before.
I wasn't a fan of doublers either until I realized their wonderful attributes..Do you realize the power transformer in a doubler has fewer turns of wire that is thicker and heavier and therefore has a lower impedance secondary.
The biggest reason for doublers back in the day was the price and availability of higher voltage and higher current silicon diodes.I wish they would use them again.
Nobody ever went broke underestimating the intelligence of the American public
H. L. Mencken
Edits: 04/22/15 04/22/15
Always good when you provide some good insight, Mikey. Valid points to consider.
Having said that, I still prefer not to use a voltage doubler. I'm also not a fan of cathode bias. To me, fixed bias is a better technical solution, especially in the DIY world.
I never cared much for the sound of the Mac's you mentioned. Always thought the Citation II sounded better. I have always wondered what the Citation II would sound like as a all pentode design.
Give me fixed bias pentode output any day.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
Interesting: Marantz 8 and 9's also used voltage doublers. Doublers were quite common in the old days. For modern designs, Quicksilver has almost totally ( i haven't see all his designs) gone over to a doubler system.What is interesting is Mike has used the doubler for B+ supply for the front end tubes ( 600 volt B+ = 300 volt at the half way point) or for the screen 2 taps. This, in effect, enables him to run a non ultralinear output and also enables his amps to be stable running anything from a 6L6 to a KT 120
Edits: 04/19/15
All the smaller HKs I'm rebuilding have doublers. They work very well, and I wouldn't hesitate to design one into new gear. That's a useful trick regarding the 1/2 B+ tap. Of course, it can also be done with a FWB if the PT has a center tap.
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Buy Chinese. Bury freedom.
It's just economics, in the old days, it may be fine to "butcher" an amp for its irons, but these days, an original un-molested amp of certain makes is worth a lot more than the irons. So in most cases, it does not make sense to do so anymore. Anyone continue with the practice of "salvaging" is either got more money than sense or just "out of the loop".
"Anyone continue with the practice of "salvaging" is either got more money than sense or just "out of the loop"."
Really? How about 40- or 50-year-old integrated amps with worn out pots and switches that can't be replaced, faceplates faded and scratched, and virtually every part needing replacement, including NLA capacitor cans, riveted-in tube sockets and banks of rear-panel jacks? Then there are those awful tone control PECs, sub-optimal bias designs and phono preamps that by modern standards bordered on "defective" even when they were in new working condition. Gimme a break. Anyone who strips this iron and uses it to create a modern, high performance system has done the audio world a favor.
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Buy Chinese. Bury freedom.
+1
You make many good points, however, we are not talking about beater units of pedestrian origins... Citation II, like most of Hegeman's designs are collector items, unless they are completely beyond repair, why would you want to strip them for parts? With some exceptions, these units could be brought back to life with some TLC, they are a part of electronics and American history, I think they should be perserved and appreciated as they are.
Unless you have a rare factory built that is in clean or mint condition,I let those alone.OTOH,a Dynaco ST70 turns my stomach in stock electrical condition.They are so anemic in every way they pretty much have to be modded to get real performance out of them.This is why there are so many aftermarket parts available for them,sort of like the small block Chevy.
The early ones had undersized power transformers and then you have that single GZ34 that struggled because it is being run close to its limit in that amp under dynamic conditions..The Knight KB85 used two GZ34s which made much more sense.They also used much more filtering than the Dyna ST70 which was a measly 90uf total.
Nobody ever went broke underestimating the intelligence of the American public
H. L. Mencken
Of course, I'm referring to amps in the condition I described. MOST are now in that condition or worse, due to age. I have no qualms about converting any of them into modern tube amplifiers, and I have a dozen or so in storage just waiting their turn. :)
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Buy Chinese. Bury freedom.
I've designed at least 3 from scratch, and done complete redesigns to a number of others. But that's really not relevant.
" I thought this was an open forum to have discussions."
It is. It appears however that discussions that don't fall into line with your thinking disturb you.
"There are so many other sites and forums that have similar philosophies to mine."
You are definitely entitled to your own opinions/philosophies. You are NOT entitled to your own facts.
" Maybe take some cues from what is found in vintage guitars and guitar amps."
Guitar amps are completly different beasts. They are not music reproducers, NOR ARE THEY DESIGNED FOR FIDELITY! But even in that field there are great opportunities to utilize better improved parts and so on. I am right now in the midst of rebuilding a classic early 70's Ampeg V4B for my friend and Grammy winning jazz bassist Phil Palombi. A few years back I did an Ampeg B-15N for him that he now uses in the studio and at home. He told me the B-15N "kicks the ass" of the high dollar amps he's played through. And that's why he sent me the Ampeg. The bad news for you? I used quite a few modern parts in the B-15, and I'm doing it again in the V4B. I also built him a Citation II amp 2 years ago. He and (so far) all his fellow musicians that have listened to it say it's the best they've ever heard. To be fair, these guys haven't heard every amp ever made (who has?), but they hear VERY well.
I have a TON of respect for the great designers of days passed - Stu Hegeman was one of them. I would never violate the intangible bond I feel with him and his work. Sadly, he was gone before I could ever meet him in person, but I feel very comfortable saying that he'd find what we do with his design would meet his approval.
I can't even believe I need to respond to a post like this. The number of logical fallacies in your post is astounding. You harp on the notion that I may not have my own FACTS. Well...You have stated so many opinions that YOU are trying to pass off as fact. I have never said in any of my posts that I think you should drive an audio system with a guitar amp. I was only talking about the tone caps. Using vintage guitar amps as a reference was merely an example of where one might find good sounding caps. You sound to me like you approach amps an electrical engineer and select parts that fit the bill according to engineering standards. Unfortunately, this does not always mean the "right" cap selection SOUNDS the best. I think it's great that a Grammy winning bass player likes your rebuild. However, that does not give you the authority to suggest that a legendary designer like Stu Hegeman, would love your design rebuild or think it's an improvement. That, to me, sounds incredibly bold and arrogant. I think there's an equally likely chance that he might think your rebuild killed the music. We will never know. Again he could very easily have used larger supply capacitors. Nothing stopped him; they were available. But, he didn't. And don't give me the mess that those top hat diodes couldn't handle it. They could with ease. And you talk about how good the diodes are today but many prefer the sound of the old diodes because they sound more like a tube rectifier. I think people can draw their own conclusions. You are a restorer of old amps that thinks he knows better than the original designer.
In response to your thoughts on why I felt attacked, I would like to say that your statement "It appears however that discussions that don't fall in line with your thinking disturb you" is completely ridiculous! Let me remind you that after one post stating my opinion I was the one who was attacked, called a troll and called stupid; not the other way around. One last thought...you said it's not relevant that you designed 3 amps from scratch and have redesigned a number of others. If it's not relevant then why did you ask me how many I've done?
I'm bowing out after this - think what you like.On guitar amps - I supply tubes to some of the smaller "boutique" amp makers out there. A LOT of them use TONE CAPS such the very popular Sozos that were not even around in the old days. And besides, they are not seeking fidelity; they are seeking a tone that is often based on deliberately induced distortion.
Why did I say I designed 3 amps (actually one was a preamp)? Because you asked and though I don't consider it relevant I wanted to answer your inquiry.
Why do I say what I say about Stu Hegeman? Because I HAVE communicated with a couple of today's designers who DID speak personally with Stu before he died and who HAVE told me that what we do with the Citation gear is terrific and in keeping with the original design intent he had. Now if they are lying to me then I'm off base, but I don't think they are.
BTW, he WAS limited in some of what he could do. There was a very low frequency oscillation in his prototypes that he struggled with, and he wasn't able to do exactly what he wanted to "fix" it because he had to have a design ready for production in short order. Also, I'm told by people who knew Stu that he felt that an ultralinear configuration may not have been the best choice for the amp, he preferred pentode mode. He was pushed by the sales guys to get the amp to produce very low distortion while putting out as much power as possible. The specs of the amp were a key part of the advertising pitch. Stu was a recording engineer, he wasn't a "specs" guy, so some design conflict was probably inevitable.
A quick thought about power supply capacitors - they and the semiconductor diodes were two of the most expensive small components in the amp. I'm not even sure they could be had in the day, but with the heat under the hood of the Cit II chassis I cannot imagine that Stu would not have used 105 C rated electrolytics if they were available at an affordable price. Nor would he have failed to utilize the other attributes of modern capacitors such as compact size, long life, low ESR and DF, and the myriad of other highly desirable characteristics offered today. FYI, MANY of the developments in these capacitors (and diodes) came about as the result of the switched-mode power supply and the constant demand for improved performance at less cost in less space. None of that development was present when the Deuce was deigned.
The diodes and capacitors? Please search out and read Rick Miller's 1990 (IIRC) design-changing Audio Amateur article regarding diode noise performance and the early 80s Walt Jung and Richard Marsh article "Picking Capacitors". You'll see how products not available to Hegeman made/make improved performance possible. Rick's article demonstrates using sound science that diodes like the top hats and even later pieces such as the 1N4007 sounded NOTHING like a tube rectifier due to the presence of relatively large amounts of PN burst noise generated by the minority carriers (holes) moving across the junction. That noise is completely absent from vacuum diodes (and Schottky diodes) as there is no mechanism to generate it. And it is only present at greatly reduced levels in modern fast/soft recovery diodes.
As far as mentioning what I did about the amp I sent to Phil Palombi... it is only relevant because I find that he and his comrades in the world of jazz (Phil was a classically trained bassist BTW, so he brings a lot to the table) have the ability to hear music far better than I do. So I value his opinion more than mine for that reason, and because he has no bias towards it like I may have. I did not mention that based on my reputation a number of other very well respected listeners have sought "McShaned" Citations. Dick Olsher (formerly of Stereophile and other respected publications, now writing for The Absolute Sound) sent me a Citation II amp to do for him. Sadly the core amp he sent was totally destroyed by UPS during shipping, and that project never came to fruition. My friend Dr. Norm Thagard, CNN expert correspondent, space shuttle astronaut, and audio design associate of Nelson Pass uses EIGHT "McShaned" Citation IIs in his home system. You can read about the special preamp Norm designed to drive all the amps in a back issue of AudioXpress.
At CES a few years ago a cable maker used his "McShane/Citation" at the show, and he got some amazing comments - here's just one:
""... a cable competitor, (name removed to protect the innocent and guilty), came by on a scouting mission. His interconnects start at about 6 times what our line tops out at, but he was very interested in our design and wanted a good listen. We played "freedom in the groove" for him and he said "this sounds very nice" and I started talking about the bang-for-the-buck factor with the $2k (McShane/Citation II) amp and $1k speakers and he stopped me mid sentence. "It sounds very nice at any price" he interrupted."
There's more, but no kidding - doesn't it seem like maybe there is SOMETHING worthwhile going on with these amps??
Finally, I never "attacked" you, but if you took it as an attack because as I stated before THE PREPONDERANCE OF EVIDENCE points in a different direction than your thinking it is certainly regrettable. I am sorry you took it that way, but only you can decide how to react to what I posted. Maybe I should not have said "facts", I should have just said "the preponderance or weight of empirical evidence". So my apologies for not defining my position more clearly and less controversially.
Edits: 04/19/15
I don't take measurements or base my likes and dislikes on theories or specs just listening. I have listened to probable close to 100 different brands and series of electrolytics and many many other film caps over a period of 10-15yrs. I have seen where caps that measure well sound really good and where caps that measure really well sound bad. Diodes that are supposed to be really good sound OK and generic run of the mill ones sound excellent. All of my opinions are based only on listening no measurement devices and no theory. From my experience, there are subjective qualities present in parts that aren't measured but experienced by some listeners and maybe not others. I have never listened to your products but I would guess that I would prefer the stock version with certain parts changes over the rebuild with parts with good data sheets. The main problem that is introduced by the wrong parts is an electronic sound however subtle that kills naturalness. When I listen I am comparing to the way I think live music should sound. Specs and theory are not part of the equation and are not enough to built great music makers. More capacitance is sometimes better but sometimes not. It must be judged by listening. For example, the noise you say is present in the old diodes. It may not bother the human ear such as seen with second order distortion. It actually sounds good to some but alas its a distortion so should be bad right? Not all distortion or "noise" causes problems for the listener you have to listen to find out what's what. After your post its clearer to me where the disconnect is. Different philosophies.
"he felt that an ultralinear configuration may not have been the best choice for the amp, he preferred pentode mode. He was pushed by the sales guys to get the amp to produce very low distortion while putting out as much power as possible."
I've always wondered why the Cit II and V were UL, while all the smaller amps and receivers were pentode. This also says something for the greater level of GNFB in the Citation series, something I would have thought less necessary due to UL operation. It's too bad these designs came at a time when specs ruled the day. It must have been quite stressful to design VT products under those conditions.
Thanks for the info!
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Buy Chinese. Bury freedom.
There is actually very little global NFB in the Cit II. Most of the 31 db of NFB is either the unbypassed V1/V4 voltage amp cathode resistors or one of the multiple NFB "short" loops used in the driver/PI and from the plates of the output tubes back to the drivers.
For some reason (senior moment?) I can't recall the exact number - but it's single digits, like 5 db IIRC.
BTW, the Cit V is not U/L, it's pentode. As a result, improving the screen supply regulation is a positive step. Also, unlike the Cit II most of the Cit V NFB IS global.
"There is actually very little global NFB in the Cit II. Most of the 31 db of NFB is either the unbypassed V1/V4 voltage amp cathode resistors or one of the multiple NFB "short" loops"
I shouldn't have referred to it as global. The point I was making is that the Cit II employs UL *plus* tons of NFB, much more than the smaller amps. I recently measured my A500, and it was less than 15 dB. That's enough to produce distortion numbers that are more than acceptable, but nothing like solid state. That would be quite a challenge, designing a large tube amp that could compete in a market guided only by numbers.
Thanks for the info on the Cit V. I think I knew that at one time... :)
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Buy Chinese. Bury freedom.
Some great information, Jim. Thanks for the update.
"What this country needs is a good 5 watt amplifier!" (Paul Klipsch)
I would rather Citation II monoblocks...that power iron is just too heavily loaded. That, and space for film caps( at equal capacitance to the upgrade values). While I am 'in there', adjust some values so as to take advantage of a current regulator in place of the tail load.
Rest assured, if I didn't settle on W6m, there would be a distributed 'Deuce running my bass horns instead.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
It is a conundrum. If you challenge the rank bullsh_t the troll produces, feeding occurs. OTOH, failing to challenge allows untruth to gain traction. :> ((
Eli D.
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