I've probably listened to a lot, I don't remember to be honest... I would prefer the MC240 quality and sound profile...
I assume since the only thing different between the old Macs and the new one's and other amps with lesser specs is the transformer that it must be the transformer that allows for such good tolerances. Process of elimination.
I assume since the only thing different between the old Macs and the new one's and other amps with lesser specs is the transformer that it must be the transformer that allows for such good tolerances. Process of elimination.
Just goes to show you how tastes can vary - friend of mine has owned all of the vintage Mac amps and the MC240 was his _least_ favorite! Back when I used to own a MC250, their first solid-state design, he said it was better than the MC240.
Anyways - there have been different changes to the Conrad Johnson line. I've only heard the old MV75 which is their version of the classic Mullard 5-20 circuit. The Mullard is an easy to build circuit, has a lot of available mods like current sinking the phase splitter. It was also used in some of my favorite vintage amplifiers, the Eico HF-50 and HF-60. Both had excellent output iron.
Anyways - there have been different changes to the Conrad Johnson line. I've only heard the old MV75 which is their version of the classic Mullard 5-20 circuit. The Mullard is an easy to build circuit, has a lot of available mods like current sinking the phase splitter. It was also used in some of my favorite vintage amplifiers, the Eico HF-50 and HF-60. Both had excellent output iron.
Of course you need a trifilarly (at least, see MC-3500) OT with tubes that operate at low screen voltages. Or you go for source followers as screen supplies. But this amplifier still is Unity Coupled, and these tubes also operate as true pentodes.
Best regards!
Good, practical advice, Eli, as usual. Thanks for the 6922 cascode alternative to 12BY7. Do you perhaps have any comparative performance test numbers?
I don't really care about which design is used... I like the round and strong sound from the MC240. If the MC275 sounds the same I'd probably want that instead... if the MC3500 sounds the same then I'd probably want that...
When you say iron do you mean the core of the transformer? Or does iron mean the copper or silver wire used to wrap the transformer?
"Iron" is slang for magnetics: transformers and chokes.
The "Big 3" of "Golden Age" amps are the Harman/Kardon Citation II, the McIntosh MC275, and the Marantz 8B. Due to the non-availability of specialized O/P "iron", "cloning" any of the 3 is, for all practical purposes, impossible. If your pockets are deep, a worthwhile DIY project is acquiring an old "Big 3" amp and doing a stem to stern refurbishment.
The H/K Cit. 5 is not very far behind the Cit. 2 and it is amenable to "cloning". Maximum results will obtained by using high quality O/P "iron". There are several winders you can go to to get something suitable. For instance, Electra-Print. Unlike most 6L6 family amplifiers, the Cit. 5. employs 4 Kohm primary O/P transformers. Designs that incorporate a global negative feed back (NFB) loop require "iron" whose power handling capability is greater than the max. that can be delivered to the speakers. That headroom is needed to cope with the error correction signal NFB triggers. 75 or 80 W. of full power bandwidth seem about right.
thanks for the info... and just to clarify, the reason they can't be cloned is because of the transformers, nobody knows the wiring design, or the wire isn't available, or the cores aren't available, or all of the previous, or some other reason?
The core lamination's of the exact alloy and size may not be available plus if the particular winding technique isn't known than it can't be wound as a faithful reproduction.
Most times when a replacement transformer is needed for something rare a specialty winding shop will unwind the failed transformer and take careful notes so they can replicate it. If that shop goes out of business that info is gone until someone else repeats the process. I don't think a transformer shop is likely to share that info with anyone else either.
All this information is readily available if you do a little searching. You have been given a lot of good advice by some of the pretty smart folks here on this thread and the one you started on Mac transformers. You still seem to be dumbfounded as to why you can't just buy the magic from Wallmart or RadioShack. Do a little research on your own and maybe you will understand why some output transformers cost as much as a whole amplifier or why some vintage ones can cost multiples of that.
Why does a set of tiny little plug in Altec microphone transformers cost what they do? It's only a few ounces of copper wire and another few ounces of core material but a set can easily sell for well over a thousand dollars.
BillWojo
Most times when a replacement transformer is needed for something rare a specialty winding shop will unwind the failed transformer and take careful notes so they can replicate it. If that shop goes out of business that info is gone until someone else repeats the process. I don't think a transformer shop is likely to share that info with anyone else either.
All this information is readily available if you do a little searching. You have been given a lot of good advice by some of the pretty smart folks here on this thread and the one you started on Mac transformers. You still seem to be dumbfounded as to why you can't just buy the magic from Wallmart or RadioShack. Do a little research on your own and maybe you will understand why some output transformers cost as much as a whole amplifier or why some vintage ones can cost multiples of that.
Why does a set of tiny little plug in Altec microphone transformers cost what they do? It's only a few ounces of copper wire and another few ounces of core material but a set can easily sell for well over a thousand dollars.
BillWojo
Just trying to nail down the reasons why people think that a transformer is so unobtainable. I can't say I agree with you or them. To me it's just wire and I already know a shop that can do most of the Mac transformers. I just want to nail down the reasons why everyone here thinks it can't be done when I've got a guy waiting on the line ready to do it. I also don't really know much about amps and the little details like you guys claim to know.
How does the CJ transformers differ from the vintage mac240 transformers?
is it also true that this patent doesn't contain the needed info to create a unity coupled transformer mac clone?
US2654058A - Wide band transformer
- Google Patents
How does the CJ transformers differ from the vintage mac240 transformers?
is it also true that this patent doesn't contain the needed info to create a unity coupled transformer mac clone?
US2654058A - Wide band transformer
- Google Patents
I'd also want to own a pair of MC3550's or MI350's. But reportedly there were only a few hundreds made, and noboy knows how much of them have survived. Hence nowadays they are sold at really vertiginous prices, if ever 
.
Were they also made with 240 V power transformers?
Yes, the »iron« is the transformer's core, als the magnet wire usually consists of Copper.
Best regards!
.Were they also made with 240 V power transformers?
Yes, the »iron« is the transformer's core, als the magnet wire usually consists of Copper.
Best regards!
I have been down this rabbit hole and missed my opportunity when I didn't buy certain components for a close enough 8b clone.
You can make a Marantz 8b (there is a close "copy" in a back issue of AudioExpress July 2002 staring right at me... there are on-line pdfs of the article using google to locate). The author based his on another Marantz 8b replica that used LUX Audio OPTs with a mixture of, "several phase compensating capacitors and resistors are installed to optimize frequency response" in lieu of Marantz OPTs. However, the AudioExpress author admits, that it is a close enough copy because of the transformer winding in the 8b is special and how he got around all that.
The 8b feedback signal for each channel is taken not from the secondary tied to the loudspeaker outputs, but from an extra pair of secondary windings that were intended specifically for the job. The 8b featured a NFB resistor and compensation capacitor combination to obtain a flat frequency response above 100 kHz and below 50 Hz.
On top of all that, each of the 8B's output transformers had an extra primary where each was isolated from the other and dedicated to a single EL34 tube and these were adjusted with a trim pot from the factory. The Japanese replica came close with a mix of NFB components and the use of LUX OPTs.
The AE author wanted to do away with that in his copy of the replica of the 8b. Rabbit hole. But to get closer to or surpass the Marantz 8b sound, the AE clone design used Plitron output toridal transformers (and as George from Tubelab has pointed out, these are no longer made). Throw in a Tango transformer for power and you get a close copy (all these made better frequency response and power on tap than the original 8b).
The AudioExpress article gets around all the 8b NFB resistor and compensating capacitors through the use of those Plitron modern output transformers. There are capacitors further upstream, but nothing like the 8b or the replica design he based his AE article on.
So, those original 8b transformers were so special that the first design replica came close replicating the 8b sound with a different set of NFB resistors and capacitors. The AE author then took that design and furthered it by using Plitron transformers and getting BETTER frequency response and for a final surprise... he added in the NFB selector switch just so you could change the flavour characteristics and as a pseudo volume control. You know, just as an experiment you can switch on and off.
He ends it off by saying, that his modernized 8b based amplifier far exceeds the overall performance of the original Marantz 8b.
What I see is the Plitron output transformers are now near impossible to find (there is one on everyone's favourite auction site lists at $399 USD but there is no other to make a pair) and a used Tango power transformer can be found for approximately $138 USD from Japan (not including shipping). The price to performance is not very efficient.
I thought of re-making some of the epic amplifiers and I am sure everyone here has at one time or another. I thought about it, did the math, and recalled that a wise man here messaged me with respect to speakers when I was considering buying a vintage pair of Klipsch Cornwalls or just building my own with modern components. He said, "...yesterday's gold is today's silver."
Damn. I still have the PM to remind me and keep some perspective.
So I applied that to my DIY'ing. I went with a proven designs that can be found here in the forums. And the modern amplifiers work in both the design, output, and price.
If more power is something you want, there are variants that will do that for you. There are members here that sell boards ready to use and there is the GB section. There are some brilliant contributors here and it is a friendly place.
The great thing is that with these designs, you can do it as outlined with all the listed parts and pretty much go toe to toe with the Conrad Johnsons, Marantz 8b, ST-70s, and Quad tube amplifiers. You can approach their numbers for a fraction of the cost, be able to shop the wider marketplace, have choice in components from power to signal paths, and build something that tested and proven that you can make and fix yourself.
You can make a Marantz 8b (there is a close "copy" in a back issue of AudioExpress July 2002 staring right at me... there are on-line pdfs of the article using google to locate). The author based his on another Marantz 8b replica that used LUX Audio OPTs with a mixture of, "several phase compensating capacitors and resistors are installed to optimize frequency response" in lieu of Marantz OPTs. However, the AudioExpress author admits, that it is a close enough copy because of the transformer winding in the 8b is special and how he got around all that.
The 8b feedback signal for each channel is taken not from the secondary tied to the loudspeaker outputs, but from an extra pair of secondary windings that were intended specifically for the job. The 8b featured a NFB resistor and compensation capacitor combination to obtain a flat frequency response above 100 kHz and below 50 Hz.
On top of all that, each of the 8B's output transformers had an extra primary where each was isolated from the other and dedicated to a single EL34 tube and these were adjusted with a trim pot from the factory. The Japanese replica came close with a mix of NFB components and the use of LUX OPTs.
The AE author wanted to do away with that in his copy of the replica of the 8b. Rabbit hole. But to get closer to or surpass the Marantz 8b sound, the AE clone design used Plitron output toridal transformers (and as George from Tubelab has pointed out, these are no longer made). Throw in a Tango transformer for power and you get a close copy (all these made better frequency response and power on tap than the original 8b).
The AudioExpress article gets around all the 8b NFB resistor and compensating capacitors through the use of those Plitron modern output transformers. There are capacitors further upstream, but nothing like the 8b or the replica design he based his AE article on.
So, those original 8b transformers were so special that the first design replica came close replicating the 8b sound with a different set of NFB resistors and capacitors. The AE author then took that design and furthered it by using Plitron transformers and getting BETTER frequency response and for a final surprise... he added in the NFB selector switch just so you could change the flavour characteristics and as a pseudo volume control. You know, just as an experiment you can switch on and off.
He ends it off by saying, that his modernized 8b based amplifier far exceeds the overall performance of the original Marantz 8b.
What I see is the Plitron output transformers are now near impossible to find (there is one on everyone's favourite auction site lists at $399 USD but there is no other to make a pair) and a used Tango power transformer can be found for approximately $138 USD from Japan (not including shipping). The price to performance is not very efficient.
I thought of re-making some of the epic amplifiers and I am sure everyone here has at one time or another. I thought about it, did the math, and recalled that a wise man here messaged me with respect to speakers when I was considering buying a vintage pair of Klipsch Cornwalls or just building my own with modern components. He said, "...yesterday's gold is today's silver."
Damn. I still have the PM to remind me and keep some perspective.
So I applied that to my DIY'ing. I went with a proven designs that can be found here in the forums. And the modern amplifiers work in both the design, output, and price.
If more power is something you want, there are variants that will do that for you. There are members here that sell boards ready to use and there is the GB section. There are some brilliant contributors here and it is a friendly place.
The great thing is that with these designs, you can do it as outlined with all the listed parts and pretty much go toe to toe with the Conrad Johnsons, Marantz 8b, ST-70s, and Quad tube amplifiers. You can approach their numbers for a fraction of the cost, be able to shop the wider marketplace, have choice in components from power to signal paths, and build something that tested and proven that you can make and fix yourself.
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I'd also want to own a pair of MC3550's or MI350's. But reportedly there were only a few hundreds made, and noboy knows how much of them have survived. Hence nowadays they are sold at really vertiginous prices, if ever
Were they also made with 240 V power transformers?
Yes, the »iron« is the transformer's core, als the magnet wire usually consists of Copper.
Best regards!
I read a post about a guy who made one on this website, did you see it? Seems doable.
What is it exactly about the MC240 and 8b transformers that can't be replicated?
Is it the core material or size or shape? (I think it can be done.) What was the core made of originally?
Is it the wire coating, chemical makeup of the wire, thickness? (I think it can be done.) What was the original wire exactly?
Is it the winding design and turns? (There are people out there who claim to sell winding services for the classic McIntosh amps, I emailed one 2 days ago. There are also a lot of patents and documentation about these transformers. My next step is just to call McIntosh directly and see what they say.)
Something else?
All or a combination of the above?
How many watts did the 8b clone make?
What's the best push pull output transformer than can be DIYed? I think that's the main question here since everyone is afraid of trying to clone the proven classics.
Is it the core material or size or shape? (I think it can be done.) What was the core made of originally?
Is it the wire coating, chemical makeup of the wire, thickness? (I think it can be done.) What was the original wire exactly?
Is it the winding design and turns? (There are people out there who claim to sell winding services for the classic McIntosh amps, I emailed one 2 days ago. There are also a lot of patents and documentation about these transformers. My next step is just to call McIntosh directly and see what they say.)
Something else?
All or a combination of the above?
How many watts did the 8b clone make?
What's the best push pull output transformer than can be DIYed? I think that's the main question here since everyone is afraid of trying to clone the proven classics.
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