Does anyone has experience with toroidal SE transformer. I heard that Plitron transformer are great and much better than anything else on the market. I tried to find some text about that, but there is nothing. There is a book available with explanation: "Modern High-End Valve Amplifiers: Based on Toroidal Output Transformers" by Menno van der Veen (all plitron audio transformer are based on his knowledge), maybe someone has it and is ready to share experience? I'm willing to buy this book, but it is not available in my country what means that it will cost me about 200$ because of our laws, too much. Toroidal transformers are ideal for diyers because there is no air gap which is impossible to build correct with amateur tools, and quality is always the same. So guys please help!!!
Regards, Zogu
Regards, Zogu
...as you said:
"Toroidal transformers are ideal for diyers because there is no air gap....."
so this excludes them absolutely for conventional SE output stages - only Parafeed with a conventional air-gapped plate choke would still be an alternative. Their comparably small cores don't tolerate any DC-magnetisation.
Toroidal OPTs are good fpr PP-amps. If you need a low prim./sec. ratio only, you might even try simple and cheap mains transformers, generously oversized in their power handling capabilitiy. I useed such transformers (115:30V, 160 VA) as OPTs in my Circlotron amp (about 60 W rms) - with very satisfying results.
"Toroidal transformers are ideal for diyers because there is no air gap....."
so this excludes them absolutely for conventional SE output stages - only Parafeed with a conventional air-gapped plate choke would still be an alternative. Their comparably small cores don't tolerate any DC-magnetisation.
Toroidal OPTs are good fpr PP-amps. If you need a low prim./sec. ratio only, you might even try simple and cheap mains transformers, generously oversized in their power handling capabilitiy. I useed such transformers (115:30V, 160 VA) as OPTs in my Circlotron amp (about 60 W rms) - with very satisfying results.
Hi ulibub,
yes, i thought that too, but there is a way to eliminate D.C. Look at hxxp://www.plitron.com/audio_se.asp. This transformer works great, it is expensive but square signal on 50hz looks almost like square which is very rare, much better than Tango U-808, my friend has both and we tested. And this transformer is toroidal SE transformer!!! How they eliminate D.C.? This is maybe written in book which i mentioned in previous post, or maybe someone else nows that. Only way which looks logical to me is low primary D.C. impedance with huge core for big impedance, for example 50ohms and 70H, if i use ohm law 50ohms * 0.070a = 3,5v D.C and big impedance is always good for eliminating D.C. Maybe core can tolerate this amount of D.C. I'm not transformer expert and I now very little about it, that is why I'm looking for help and maybe is way to completely eliminate D.C. with wiring methods....
yes, i thought that too, but there is a way to eliminate D.C. Look at hxxp://www.plitron.com/audio_se.asp. This transformer works great, it is expensive but square signal on 50hz looks almost like square which is very rare, much better than Tango U-808, my friend has both and we tested. And this transformer is toroidal SE transformer!!! How they eliminate D.C.? This is maybe written in book which i mentioned in previous post, or maybe someone else nows that. Only way which looks logical to me is low primary D.C. impedance with huge core for big impedance, for example 50ohms and 70H, if i use ohm law 50ohms * 0.070a = 3,5v D.C and big impedance is always good for eliminating D.C. Maybe core can tolerate this amount of D.C. I'm not transformer expert and I now very little about it, that is why I'm looking for help and maybe is way to completely eliminate D.C. with wiring methods....
Hi Zogu!
Ok, if you give up with toroidal's main advantages (saving space and weight, thus reducing stray capacities and inductances), but using large cores and air-gaps (which indeed should also be possible with toroidals - double C-cores are nothing else than with iron band toroidally wound cores in rectangular form stabilized with resin and cut into two halves), you also could realize any transformer you'd like in toroidal style.
To achieve some tolerance of pre-magnetization, a big amount of iron is the only thing that matters (if you dont want to use such things like DC-compensation windings....), the more if you don't have an air gap - the shape of the core being secondary. So certainly using for instance a 500 VA-core (without air-gap) to transfer finally 13 Watts of power certainly would allow for a fair amount of pre-magnetization.... Looking at the mechanical dimensions of these Plitron transformers I would assume something like that. But then I'm asking if I still have the advantages typical for a toroidal - or if a conventional xfmr then wouldn't be equally as good.
But that's just our advantage of being amateurs - trying everything imaginable!
I haven't used Plitron (van der Veen) toroidals so far, but I've heard only good things about them. I also have an older book of Menno van der Veen, and I certainly can say that I got the impression looking at the physical backgrounds he presents there that this man knows what he's talking about...
I also used a generously oversized toroidals in my amp to allow for some (always present) DC-imbalance of the output tubes.
All the best
Uli
Ok, if you give up with toroidal's main advantages (saving space and weight, thus reducing stray capacities and inductances), but using large cores and air-gaps (which indeed should also be possible with toroidals - double C-cores are nothing else than with iron band toroidally wound cores in rectangular form stabilized with resin and cut into two halves), you also could realize any transformer you'd like in toroidal style.
To achieve some tolerance of pre-magnetization, a big amount of iron is the only thing that matters (if you dont want to use such things like DC-compensation windings....), the more if you don't have an air gap - the shape of the core being secondary. So certainly using for instance a 500 VA-core (without air-gap) to transfer finally 13 Watts of power certainly would allow for a fair amount of pre-magnetization.... Looking at the mechanical dimensions of these Plitron transformers I would assume something like that. But then I'm asking if I still have the advantages typical for a toroidal - or if a conventional xfmr then wouldn't be equally as good.
But that's just our advantage of being amateurs - trying everything imaginable!
I haven't used Plitron (van der Veen) toroidals so far, but I've heard only good things about them. I also have an older book of Menno van der Veen, and I certainly can say that I got the impression looking at the physical backgrounds he presents there that this man knows what he's talking about...
I also used a generously oversized toroidals in my amp to allow for some (always present) DC-imbalance of the output tubes.
All the best
Uli
Their equivalent push-pull transformers have primary inductances of ~500 Henries. The primary inductance of the 5K SE OPT is only 28 Henries, which would indicate the core is gapped. I have seen the Plitron single-ended output transformers used in conventional SE amplifiers. They wouldn't work in those situations without a gap.
John
zogu said:
That's most probably a production secret, not of any importance at all to know for amp builders. Such a low prim. inductance, just with such a big xfmr at the given impedance can only be reached with an air gap - and quite a large one.
Or do they use some kind of ferritic core material?
physics is as it is....
Uli
I've found someting:
"distributed air gaps"
See the last posting at the bottom of the page......
That explains how they build these SE-toroidals...
Uli
"distributed air gaps"
See the last posting at the bottom of the page......
That explains how they build these SE-toroidals...
Uli
I found much better explanation on other site which is using menno designs: hxxp://www.amplimo.nl/index.html?lang=en-uk&target=d21.html.
I don't now can I quote some text from their site, so I will not, but please look at text which explains their transformers and look datasheet for some of se transformers. In short they are using special huge core and selected core material for very small power and transformers are based on this calculation: hxxp://www.plitron.com/PDF/Atcl_5_2.pdf, but as I can see this is only for push-pull transformers.
Maybe someone from plitron or amplimo can help us, after all this thread will be here for a very long time and this is is best commercial for them?
Regards, Zogu.
I don't now can I quote some text from their site, so I will not, but please look at text which explains their transformers and look datasheet for some of se transformers. In short they are using special huge core and selected core material for very small power and transformers are based on this calculation: hxxp://www.plitron.com/PDF/Atcl_5_2.pdf, but as I can see this is only for push-pull transformers.
Maybe someone from plitron or amplimo can help us, after all this thread will be here for a very long time and this is is best commercial for them?
Regards, Zogu.
zogu said:
Hi zogu,
as I can remember Menno in his great book don't elaborate the question of "toroid SE secret".
Since I'm interestiing on this question too I purchased two toroids
230V/8V-0-8V, 50 W (you know why ...) ... but until now I haven't enough time to experiment.
If you like to hear more, please post your e-mail here (I'm new on forum so I can't open your e-mail address).
Regards,
You can expect good results if you keep the DC balance to less than a few mA. To achieve this a simple LM317 CCS in the cathode of each of the output valves works. An adjustment pot will also work, but is more fiddly and will need re-adjustment over time.
I have used main toroidals in a few parafeed output stages. The first time I used a pentode CCS as the plate load. The second time I used a MOT as the plate load. Both worked very well.
Shoog
Hi ma_coule,
My email address is not hidden and I think that you can see it in my user profile, if you can't it is zoguaudio(at)gmail.com.
There is some explanation about SE transformers in Menno's book , it is on few pages and I don't know how detailed is explained. Here is table of contents of Menno's book: hxxp://www.evatco.com.au/modhend.htm
My email address is not hidden and I think that you can see it in my user profile, if you can't it is zoguaudio(at)gmail.com.
There is some explanation about SE transformers in Menno's book , it is on few pages and I don't know how detailed is explained. Here is table of contents of Menno's book: hxxp://www.evatco.com.au/modhend.htm
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