Hi,
For a new amp project I am planning to use Plytron/Aplimo 4070-CFB output transformers driven by a pair of KT88’s. These transformers are quite expensive compared with UL transformers without cathode feedback windings. So I am wondering if these transformers are worth the extra expense.
Does have someone used these transformers in a DIY project? Curious about the results and if these transformers with the use of cathode feedback really are an improvement concerning the sound.
Cheers
For a new amp project I am planning to use Plytron/Aplimo 4070-CFB output transformers driven by a pair of KT88’s. These transformers are quite expensive compared with UL transformers without cathode feedback windings. So I am wondering if these transformers are worth the extra expense.
Does have someone used these transformers in a DIY project? Curious about the results and if these transformers with the use of cathode feedback really are an improvement concerning the sound.
Cheers
According to the datasheets those OPTs from Plitron should be fantastic, also I have considered to use those transformers myself, but unfortunately I found them too expensive.
But I have found a cheaper OPT which will be nice foran a EL84 amp, PAT 4000.
I would also like to hear if there are any here who have experience about the output transformers from Plitron.
But I have found a cheaper OPT which will be nice foran a EL84 amp, PAT 4000.
I would also like to hear if there are any here who have experience about the output transformers from Plitron.
Hey-Hey!!!,
I have no experience with the Plitron output transformers at all. However, for the cathode feedback arangement, I have ( and am now listening to
) amps built around the ancient Dynaco A441. 15% tertiary winding and no taps in the main anode winding. The feedback level is enough to run pentodes without any other NFB to absolutely fantastic sound. I am building some more OPT with this winding config, and a seperate similar winding for offering additional screen feedback( Ultra-Linear style) and seperate voltage supply
.
The only trouble you may have with the torroid core is lack of DC imbalance tolerance, causing saturation at level that make the less permeable cores of E-I constructed tx's yawn and ask if they should be excited. Perfect idle current and tube characteristic match will be very important I suspect.
regards,
Douglas
I have no experience with the Plitron output transformers at all. However, for the cathode feedback arangement, I have ( and am now listening to


The only trouble you may have with the torroid core is lack of DC imbalance tolerance, causing saturation at level that make the less permeable cores of E-I constructed tx's yawn and ask if they should be excited. Perfect idle current and tube characteristic match will be very important I suspect.
regards,
Douglas
I listen to an amp using transformers with a 10% tertiary winding made as replacements for a Mcintosh MA230. The sound quality is excellent and the output stage can be driven with "normal" circuitry.
Dynaco A441
I would like to get a pair of these. Any suggestions on a source? MagneQuest?
Dynaco A441
I would like to get a pair of these. Any suggestions on a source? MagneQuest?
Hey-Hey!!!,
Mike at Magnaquest is not planning a run of that TX anytime soon. Anticipated pricing on that TX is about $600 too, which is fairly reasonable. I have been pestering Mike for more than a year to wind some of them. Somebody quoted me a minimum run of 30 pairs and that is more than I can buy at once( by about 29 pairs ). So I am making my own, with improvements too. This source is a bit more reasonable and the primary z is lower impedance for a different output valve. BUT, it is available and without too much delay and has more Iron in it too.
regards,
Douglas
Mike at Magnaquest is not planning a run of that TX anytime soon. Anticipated pricing on that TX is about $600 too, which is fairly reasonable. I have been pestering Mike for more than a year to wind some of them. Somebody quoted me a minimum run of 30 pairs and that is more than I can buy at once( by about 29 pairs ). So I am making my own, with improvements too. This source is a bit more reasonable and the primary z is lower impedance for a different output valve. BUT, it is available and without too much delay and has more Iron in it too.
regards,
Douglas
Bandersnatch said:
The only trouble you may have with the torroid core is lack of DC imbalance tolerance
I have heard it before, but I'm just wondering....
Plitron does also make some toroid chokes for use in tube power supplies, how have they solved the problem with DC current in these chokes?
Gunderz said:
I have heard it before, but I'm just wondering....
Plitron does also make some toroid chokes for use in tube power supplies, how have they solved the problem with DC current in these chokes?
Don't they also do SE OPT's too? Wouldn't they simply cut the core and gap it?
Hi,
Thanks for input so far. Looks promising. Yes sensitivity for imbalance is also something I am worrying about. But that holds for any PP transformer isn’t it? I am working on a servo for the grid bias to solve this and to keep idle currents balanced automatically. Toriods have a very tight closed magnetic circuit, which has its own disadvantages. But on the other hand it is the configuration with the lowest leakage inductance and hence widest bandwidth. I do not know what steel they are using. Normally some “leakage” also relaxes the influence of the large non-linearity of the permeability of the steel.
Have found a specialised transformer maker here in the Netherlands, Automatic Electric Europe. They use special ultra thin laminated C-cores and amorphous cores for audio transformers also. They are on holiday till July 28. I will contact them when they are back. see what they can do. But it seems Menno v.d. Veen has patented the CCF topology combined with UL, called "Super Triode". Don’t know if this only holds for toroidal transformers.
dshortt9,
Sowter in Britain makes replacement transformers for the Quad II with a tertiary cathode winding. Maybe this is of help.
With 10% tertiary cathode winding I need roughly 70V_pp to 80V_pp extra driving voltage. You are using a “normal” driving stage you told. What driving tube are you using for it? And at what HV?
Cheers.
Thanks for input so far. Looks promising. Yes sensitivity for imbalance is also something I am worrying about. But that holds for any PP transformer isn’t it? I am working on a servo for the grid bias to solve this and to keep idle currents balanced automatically. Toriods have a very tight closed magnetic circuit, which has its own disadvantages. But on the other hand it is the configuration with the lowest leakage inductance and hence widest bandwidth. I do not know what steel they are using. Normally some “leakage” also relaxes the influence of the large non-linearity of the permeability of the steel.
Have found a specialised transformer maker here in the Netherlands, Automatic Electric Europe. They use special ultra thin laminated C-cores and amorphous cores for audio transformers also. They are on holiday till July 28. I will contact them when they are back. see what they can do. But it seems Menno v.d. Veen has patented the CCF topology combined with UL, called "Super Triode". Don’t know if this only holds for toroidal transformers.
dshortt9,
Sowter in Britain makes replacement transformers for the Quad II with a tertiary cathode winding. Maybe this is of help.
With 10% tertiary cathode winding I need roughly 70V_pp to 80V_pp extra driving voltage. You are using a “normal” driving stage you told. What driving tube are you using for it? And at what HV?
Cheers.
Pjotr said:But it seems Menno v.d. Veen has patented the CCF topology combined with UL, called "Super Triode". Don’t know if this only holds for toroidal transformers.
Patents only hold for production runs, and only if they can be enforced. If you spec the Tx and take that to a winder, there's nothing stopping them making one for you.
Thanks for the info on the Quad II but I'm looking to build a higher power amp.
My amp is built around a vintage Eico HF-89 chassis bought without the output transformers on e-bay. Here is the schematic:
http://sanacacio.net/hifi/hf89schematic.jpg
I used 6L6GC's instead of the EL34's that were originally used as they matched my CFB transformers better. I use a 1.8k feedback resistor instead of the network shown on this schematic. With 475V B+ and fixed 450V on the screen grids (no UL) I get about 55 wpc. The 6SN7 works well for this but I would use the newer JJ ECC99 in a future design. I love the sound of this amp on my ProAc 2.5 clones.
If anyone is interested in a group purchase of Dynaco A441's please post here.
My amp is built around a vintage Eico HF-89 chassis bought without the output transformers on e-bay. Here is the schematic:
http://sanacacio.net/hifi/hf89schematic.jpg
I used 6L6GC's instead of the EL34's that were originally used as they matched my CFB transformers better. I use a 1.8k feedback resistor instead of the network shown on this schematic. With 475V B+ and fixed 450V on the screen grids (no UL) I get about 55 wpc. The 6SN7 works well for this but I would use the newer JJ ECC99 in a future design. I love the sound of this amp on my ProAc 2.5 clones.
If anyone is interested in a group purchase of Dynaco A441's please post here.
Hi,
Very highly recommended. Wil Blauw is a passionate xformer winder who has already wound countless xformers.
He's also wound the iron for Bas Horneman, D'haen and probably a few other members I'm not aware of.
I haven't heard but good news about them, so maybe you should give them a try.
Cheers,😉
Have found a specialised transformer maker here in the Netherlands, Automatic Electric Europe. They use special ultra thin laminated C-cores and amorphous cores for audio transformers also.
Very highly recommended. Wil Blauw is a passionate xformer winder who has already wound countless xformers.
He's also wound the iron for Bas Horneman, D'haen and probably a few other members I'm not aware of.
I haven't heard but good news about them, so maybe you should give them a try.
Cheers,😉
Thanks Frank,
Triode Dick is also very pleased with them. For sure I will contact them. For some unknown reason I have an uneasy feeling about using toriods for audio output transformers. Usually my intuition do not lie.
Cheers 🙂
Triode Dick is also very pleased with them. For sure I will contact them. For some unknown reason I have an uneasy feeling about using toriods for audio output transformers. Usually my intuition do not lie.
Cheers 🙂
Here is a link to a description of an amp with bias servo using Plitron OPT.
http://www.normankoren.com/Audio/TENA.html
Further, Dave, I cannot reach you by the email provided with your note to me. please try again.
Third, there is no way Meno is going to be able to enforce a patent on the use of cathode feedback windings, regardless of turns ratio. Frank Mcintosh and Gordon Gow came closest to patenting that sort of thing, and Dynaco with its A441 is slightly different( slight understatement ). I have no fear of any patent infringement issues with the use fo cathode feedback, even if I wound it on a torroid. My design is like nothing available( or I'd be buying some, instead of having them created ).
regards,
Douglas
http://www.normankoren.com/Audio/TENA.html
Further, Dave, I cannot reach you by the email provided with your note to me. please try again.
Third, there is no way Meno is going to be able to enforce a patent on the use of cathode feedback windings, regardless of turns ratio. Frank Mcintosh and Gordon Gow came closest to patenting that sort of thing, and Dynaco with its A441 is slightly different( slight understatement ). I have no fear of any patent infringement issues with the use fo cathode feedback, even if I wound it on a torroid. My design is like nothing available( or I'd be buying some, instead of having them created ).
regards,
Douglas
Hi,
Thanks for that link Douglas, I found it already some time ago. I am up to use a servo with a transconductance amp driving an integrating capacitor. It is build rather simple with discrete transistors. Also the bias supply will be stabilised with a shunt regulator, build with discrete transistors.
I have also my eyes on the JJ ECC99 Dave, looks promising. But I am a bit reserved to use parts that are not commonly available and wear out after time. E.g. the higher anode dissipation has certainly its attraction. Biased moderately it will last very long IMO (over 10K hours).
Yesterday I got Menno’s book “Modern High-end Valve Amplifiers” from the library. Although focussed entirely on his own toroidal transformers there is a load of really good information and theoretical background in it.
Concerning the patent, I have searched http://patents.uspto.gov/ and could not find anything. The only thing I can find is this article http://www.plitron.com/PDF/PB/Article/Atcl_4.pdf from which I quote:
The names Super-Pentode and Super-Triode
are registered by the author and subject to
European Union and international copyright
laws. Licensing inquiries concerning
reproduction of and manufacture for trade sale
should be directed to Menno van der Veen:
So not much to worry about.
Cheers 🙂
Thanks for that link Douglas, I found it already some time ago. I am up to use a servo with a transconductance amp driving an integrating capacitor. It is build rather simple with discrete transistors. Also the bias supply will be stabilised with a shunt regulator, build with discrete transistors.
I have also my eyes on the JJ ECC99 Dave, looks promising. But I am a bit reserved to use parts that are not commonly available and wear out after time. E.g. the higher anode dissipation has certainly its attraction. Biased moderately it will last very long IMO (over 10K hours).
Yesterday I got Menno’s book “Modern High-end Valve Amplifiers” from the library. Although focussed entirely on his own toroidal transformers there is a load of really good information and theoretical background in it.
Concerning the patent, I have searched http://patents.uspto.gov/ and could not find anything. The only thing I can find is this article http://www.plitron.com/PDF/PB/Article/Atcl_4.pdf from which I quote:
The names Super-Pentode and Super-Triode
are registered by the author and subject to
European Union and international copyright
laws. Licensing inquiries concerning
reproduction of and manufacture for trade sale
should be directed to Menno van der Veen:
So not much to worry about.
Cheers 🙂
Patents only hold for production runs
Though it may be irrelevant here, this is not true. Under patent law, you are allowed to build the patented object for experimental purposes only. If you build a pair and use them in your living room, you are infringing the paptent. And the transformer winder is guilty of contributory infringement. As a practical matter, it's unlikely that lawyer-sharks will descend on you for building something for your own use, but stranger things have happened. In fact, if I were a nasty shark, I'd maintain that just by having built a pair, rather than a single unit, you've demonstrated that it's NOT just for experimental use.
there is no way Meno is going to be able to enforce a patent on the use of cathode feedback windings,
It depends on the scope of the claims. The problem is that patent examination procedure can be somewhat lax out here on the fringes of profitability, and the courts presume issued patents to be valid. You may well prevail at trial if the prior art clearly anticipates the claims or if you can conclusively demonstrate that what you built doesn't infringe (literally or doctrine of equivalents), but getting to that point will run you more money than a nice house in Petaluma. Here in the US, it's over $200K in legal bills just to get to the Markman hearing. If I had to guess, vdV grants a royalty-free license if you buy the transformers from him.
Again, this is all probably moot here, but people should know that there IS legal exposure to deliberately infringing a patent.
SY,
Different countries, different laws. What you posted I'm fairly sure doesnt apply here, but that certainly wouldn't stop someone who was monied up from trying.
You would also be unlikely to successfully prosecute, or even get a magistrate to hear it, a winder who simply took a written specification I supplied to him and asked him to make an item.
As for your point about building two, as they are used in pairs, it wouldn't be hard to argue that two are required to test and experiment with them in the manner in which they are designed to be used. Bit hard to test for stereo (ie 3D) in mono.
When I'm interstate next month, I'll see a friend who is a patent lawyer and ask.
Different countries, different laws. What you posted I'm fairly sure doesnt apply here, but that certainly wouldn't stop someone who was monied up from trying.
You would also be unlikely to successfully prosecute, or even get a magistrate to hear it, a winder who simply took a written specification I supplied to him and asked him to make an item.
As for your point about building two, as they are used in pairs, it wouldn't be hard to argue that two are required to test and experiment with them in the manner in which they are designed to be used. Bit hard to test for stereo (ie 3D) in mono.
When I'm interstate next month, I'll see a friend who is a patent lawyer and ask.
Different countries, different laws.
I understand that. I'm pretty familiar with patent law in Europe and Australia. The question is not usually what is defensible or arguable- it's what will keep you out of the courts in the first place.
Hey-Hey!!!,
So Meno owns the names, I am not going to go using them, that's for sure. I would as I said buy from him if he offered what I want. But he does not and I am quite capable of doing( heck it's done already )the needed research on transofrmer winding and testing.
Patent law provides for building to experiment. Stereo takes two and the scope of the experiment is not limited by any statute. So build, listen, listen some more. Listen in likely use environment. See where I am going with this?
Besides if he patented the design, included with it would be some very detailed instructions for creating the device in question.
I am not trying to throw mud at Meno, his accomplishments speak for themselves. Only at the claim that he has some sort of control over the use of cathode feedback. The Acro-TO-350 is another one that was wired like this, and I think it had U-L taps on the anode winding too.
regards,
Douglas
So Meno owns the names, I am not going to go using them, that's for sure. I would as I said buy from him if he offered what I want. But he does not and I am quite capable of doing( heck it's done already )the needed research on transofrmer winding and testing.
Patent law provides for building to experiment. Stereo takes two and the scope of the experiment is not limited by any statute. So build, listen, listen some more. Listen in likely use environment. See where I am going with this?
Besides if he patented the design, included with it would be some very detailed instructions for creating the device in question.
I am not trying to throw mud at Meno, his accomplishments speak for themselves. Only at the claim that he has some sort of control over the use of cathode feedback. The Acro-TO-350 is another one that was wired like this, and I think it had U-L taps on the anode winding too.
regards,
Douglas
STC...
Hi,
Yep...been there already.
Pretty controversial stuff.
Cheers,😉
Hi,
Type in "super triode" at Google and have fun.
Yep...been there already.
Pretty controversial stuff.
Cheers,😉
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