Hi folks .....i was experimenting with torriod transformers as i had bought a box of 6 for 50 bucks
i was wondering how they could be utillised for tube service ..... output and power , there are two 115v primaries which can be connected for 230/240 vac service and the seconds are 2 x 14.5vac and 2 x 36.5vac
So by using voltage multipliers one can get a number of different voltages ....which was great as they are rated at 160 va
None of which were useful for filament though .....i know some folk break into them and simply unwind some of the windings to get the voltages they desire as the seconds are generally wound over the primaries...
But i didnt do that , i just wound on some varnished copper , nice and thick, about 1.2mm i beleive so as to accomodate high loads and "presto" it worked a treat exactly 6.3vac supplied
and yes i realise it will add extra load to the primaries .....but at 160va i hade room to move ......
so that was good .....so moving onto the same transformer as a output audio transformer ..... how will it sound ? ....well i done the maths and wound on 16 turns by hand of course (nothing complicated here )
it worked out at 7.9k into 4 ohms and the demo amp was a el84 push pull
I was stunned !!!! It sounded as good as the proper one already fitted into the unit
well there seemed to be no loss of gain when i A/B 'ed the two transformers and the toroid seemed to exhibit a fraction more bass
I attached some short vids so you can see that there is indeed limitless possibillities for these things ...cheap too !!!
I thought it might be usefull to put this thread in as i recently couldnt find much useful stuff in regards to this ... but this encourages me to go further
i was wondering how they could be utillised for tube service ..... output and power , there are two 115v primaries which can be connected for 230/240 vac service and the seconds are 2 x 14.5vac and 2 x 36.5vac
So by using voltage multipliers one can get a number of different voltages ....which was great as they are rated at 160 va
None of which were useful for filament though .....i know some folk break into them and simply unwind some of the windings to get the voltages they desire as the seconds are generally wound over the primaries...
But i didnt do that , i just wound on some varnished copper , nice and thick, about 1.2mm i beleive so as to accomodate high loads and "presto" it worked a treat exactly 6.3vac supplied
and yes i realise it will add extra load to the primaries .....but at 160va i hade room to move ......
so that was good .....so moving onto the same transformer as a output audio transformer ..... how will it sound ? ....well i done the maths and wound on 16 turns by hand of course (nothing complicated here )
it worked out at 7.9k into 4 ohms and the demo amp was a el84 push pull
I was stunned !!!! It sounded as good as the proper one already fitted into the unit
well there seemed to be no loss of gain when i A/B 'ed the two transformers and the toroid seemed to exhibit a fraction more bass
I attached some short vids so you can see that there is indeed limitless possibillities for these things ...cheap too !!!
I thought it might be usefull to put this thread in as i recently couldnt find much useful stuff in regards to this ... but this encourages me to go further
The biggest worry is DC imbalance in the two primary halves. Toroid cores saturate much quicker than equivalent EI cores.
Btw, how do we best estimate power handling in OPT use? 160VA at 50Hz should indicate it can handle 160watts > 50Hz...? (Half that power at half the frequency etc). But that seams too optimistic when looking at typical OPT. ?
Btw, how do we best estimate power handling in OPT use? 160VA at 50Hz should indicate it can handle 160watts > 50Hz...? (Half that power at half the frequency etc). But that seams too optimistic when looking at typical OPT. ?
I spoke to a chap called Stan Kelly (Decca Kelly Ribbon) several decades ago and he told me that he had experimented with toroids as output transformers, but his designs had segmented winding around the toroid to reduce capacitive effects, etc. This made them quite expensive. I've used Farnell mains toroids but have had difficulty getting any significant open loop bandwidth (~7kHz). Good luck.
toroids ....
It really depends on how tech savy you are and how much time you have to sift through all the speculation that appears on some threads and the amount of deviation that occurs on threads
As a simple minded enthusiast most things are trial and error and i guess what i was looking for was simple practical examples of how to utilise stuff that could be considered as junk and with good results
The toroids i used were not built for audio or for tube amps and yet so simply utillised through simple means , and any who see this thread will see this
I dont have workshop gadgets and benches and arrays of test equipment ....just ears ,some knowledge , a soldering iron and a respect for high voltage
I do love tinkering with tubes though .....
this was my objective....
It really depends on how tech savy you are and how much time you have to sift through all the speculation that appears on some threads and the amount of deviation that occurs on threads
As a simple minded enthusiast most things are trial and error and i guess what i was looking for was simple practical examples of how to utilise stuff that could be considered as junk and with good results
The toroids i used were not built for audio or for tube amps and yet so simply utillised through simple means , and any who see this thread will see this
I dont have workshop gadgets and benches and arrays of test equipment ....just ears ,some knowledge , a soldering iron and a respect for high voltage
I do love tinkering with tubes though .....
this was my objective....
toroids
This is what i mean by "speculation" ......
all i did was try it ....and it sounded GOOD!!!!
if it saturated then so be it .....but it didnt
perhaps a smaller unit might , but this impressed me enough to seriously consider using them totally .....no more buying expensive EI's !!!
This is what i mean by "speculation" ......
all i did was try it ....and it sounded GOOD!!!!
if it saturated then so be it .....but it didnt
perhaps a smaller unit might , but this impressed me enough to seriously consider using them totally .....no more buying expensive EI's !!!
If toroid OPTs were so simple and so wonderful then everyone would use them.
DC balance is an issue. Get that wrong (or simply ignore it, as you may have done) and you lose inductance and so lose low frequencies.
A power transformer will not have been wound for good HF performance, so you will get HF problems especially if feedback is used.
I am sure this has already been pointed out in other threads by other people. Power transformers are OK for OPT use provided you are not too fussy about audio.
DC balance is an issue. Get that wrong (or simply ignore it, as you may have done) and you lose inductance and so lose low frequencies.
A power transformer will not have been wound for good HF performance, so you will get HF problems especially if feedback is used.
I am sure this has already been pointed out in other threads by other people. Power transformers are OK for OPT use provided you are not too fussy about audio.
toroids...
its plain that there will always be an element of doubt when one weighs up if it should be attemped or discouraged for whatever purpose .....all the technical information will tell us its a bad idea or marginal at best .....
The thing is , what i did took a mere 5 mins of application to prove beyond doubt that something can be utilised effectively.....it may not be perfect but seldom are guitar amps made to be perfect
As for loss of output over conventional tube transformer ....this seemed negligible to my ears , when A/B'd there really wasnt much in it ....certianly enough to make me consider using it again
would you be temped for just $10 a shot ?
listen to the samples supplied , they were recorded by a phone
i can understand that when we build we try to build it as best we can ,and i have made a dozen amps now including 2 hifi amps ......just because i enjoy making them always using conventional transformers for the task ...this whole thread is about pushing theory aside and just giving it a go, and being pleasantly surprised by it
I know the purist will not agree with me ......but sometimes what does not look great on an oscilloscope may sound great to your ears !!!!
And it works....
its plain that there will always be an element of doubt when one weighs up if it should be attemped or discouraged for whatever purpose .....all the technical information will tell us its a bad idea or marginal at best .....
The thing is , what i did took a mere 5 mins of application to prove beyond doubt that something can be utilised effectively.....it may not be perfect but seldom are guitar amps made to be perfect
As for loss of output over conventional tube transformer ....this seemed negligible to my ears , when A/B'd there really wasnt much in it ....certianly enough to make me consider using it again
would you be temped for just $10 a shot ?
listen to the samples supplied , they were recorded by a phone
i can understand that when we build we try to build it as best we can ,and i have made a dozen amps now including 2 hifi amps ......just because i enjoy making them always using conventional transformers for the task ...this whole thread is about pushing theory aside and just giving it a go, and being pleasantly surprised by it
I know the purist will not agree with me ......but sometimes what does not look great on an oscilloscope may sound great to your ears !!!!
And it works....
You should say that you're talking about guitar amps, thats what I hear in your video.
This is different field compared to exellent audio amps. With guitar amps, the standards are almost very poor in regards of sound quality. They should make some sort of sound, they should be capable to overdrive etc. With them, its not about the most purest signal transmission. You can see this when studying all the most famous brands schematics.
In general terms: NO toroid output transformer can be of the highest quality possible because for pure signal transmission there are techniques applied, that could not be done with a toroid core because of its dimensions and the shape. ALL exellent designs are non toroid transformers. That doesn't mean that it doesn't deliver some sound on the output, but its always of mediocre quality. And thats a fact because thats physics.
This is different field compared to exellent audio amps. With guitar amps, the standards are almost very poor in regards of sound quality. They should make some sort of sound, they should be capable to overdrive etc. With them, its not about the most purest signal transmission. You can see this when studying all the most famous brands schematics.
In general terms: NO toroid output transformer can be of the highest quality possible because for pure signal transmission there are techniques applied, that could not be done with a toroid core because of its dimensions and the shape. ALL exellent designs are non toroid transformers. That doesn't mean that it doesn't deliver some sound on the output, but its always of mediocre quality. And thats a fact because thats physics.
A transformer is thermally limited so you'll get short term power well above 160VA at freqs well above 50Hz. I use 30VA toroids for my audio but then I'm not pushing too many watts - the 30VA size is determined by my target for series resistance, not power handling. Given the typical crest factors for the majority of music you'll find 160VA rather overkill unless you're into kW territory or you're feeding a subwoofer.
Moved to Instruments & Amps.
Here's an extreme case that might be interesting.
I have used those Toroid Transformer for audio: Output ~12V/1A; In ~100/110/115/120/220/230/240V | eBay as OPTs in a small fun project. I had to remove some turns from the secondary to get the impedance ratio I needed so the final result was far from even spaced winding. On top of that, because the design is a push pull with self bias and separate cathode resistors for each tube, there is a DC imbalance of 3 mA.
I found that it could stand a moderate amount of NFB but no more than that. I can't tell if DC imbalance is causing any saturation but it's clear that it does not do any permanent damage and once signal is applied I think DC imbalance has no meaning anymore. Being new to measurements, I post a FFT delivering 2W@8ohm for you to evaluate.
I have used those Toroid Transformer for audio: Output ~12V/1A; In ~100/110/115/120/220/230/240V | eBay as OPTs in a small fun project. I had to remove some turns from the secondary to get the impedance ratio I needed so the final result was far from even spaced winding. On top of that, because the design is a push pull with self bias and separate cathode resistors for each tube, there is a DC imbalance of 3 mA.
I found that it could stand a moderate amount of NFB but no more than that. I can't tell if DC imbalance is causing any saturation but it's clear that it does not do any permanent damage and once signal is applied I think DC imbalance has no meaning anymore. Being new to measurements, I post a FFT delivering 2W@8ohm for you to evaluate.
Attachments
Sorry, I forgot that this is the Instruments and Amps forum. I was going to say that a cheap OPT may be OK for a guitar amp but not good for hi-fi.rifraf50 said:
"Pushing theory aside" is rarely a good idea, unless what is called theory is actually hopelessly simplified or approximated theory which happens to be inapplicable.
Oops: just noticed that this has just been moved to I&A forum, so I guess it was originally in Valves or Parts.
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There are already many tube amps with toridal OPTs.
It is not important if the transformer is toroid or EI or xxx (well yes it is but that is another discussion), the important part is the material in the core.
The material in a transformer for the full audio spectrum (20-20.000 Hz) must be of much higher quality, that a transformer only for 50/60 Hz mains current.
Transformers for mains may appearantly transfer all frequencies, but the distortion and loss will be higher than for a transformer built for audio.
...and then there is the missing DC-gap, which is never added in mains transformers but is needed if it carries DC.
It is not important if the transformer is toroid or EI or xxx (well yes it is but that is another discussion), the important part is the material in the core.
The material in a transformer for the full audio spectrum (20-20.000 Hz) must be of much higher quality, that a transformer only for 50/60 Hz mains current.
Transformers for mains may appearantly transfer all frequencies, but the distortion and loss will be higher than for a transformer built for audio.
...and then there is the missing DC-gap, which is never added in mains transformers but is needed if it carries DC.
One should consider why toroids are much smaller and lighter than usual EI or whatsoever transformers. The answer is the core! All toroid cores are made from GOSS bands of about 0.1 to 0.2 mm thickness. In other words, you have very high core material even in standard power toroids!
The reasons why power toroids arent's that useful for HiFi audio are their rather small primary inductance and their simple winding scheme. One can improve that by increasing the number of turns and by interleaqing thje Primary and secondary parts.
Guitar amp OPT's completely are another world, though, as the OP has been showing to us.
Best regards!
The biggest problem with using off the shelf toroids for output trafos is the limited voltage. You can have any turns ratio you want, but they are pretty much limited to a 170 volt (340 V p-p) swing on the 240 volt “primary”. More for frequencies higher than 50 Hz, but still there is a limit before magenrtization current eats your lunch. Fine for small amps where you can shove enough current into it to make 15 watts of power. But try to fully utilize a 160 VA, forget about it with standard audio tubes. Now if you had one with a 480VCT primary, you’d be getting somewhere. But that’s no longer in the realm of off the shelf cheap from Antek.
One possibility would be to start with a standard tube power trafo that’s more than 240V, and just ignore the 120/240 winding (perhaps use it for feedback) and add an 8 ohm secondary using the number of turns needed to make it work. It would probably have worse frequency response, but hey, at least you could make power.
One possibility would be to start with a standard tube power trafo that’s more than 240V, and just ignore the 120/240 winding (perhaps use it for feedback) and add an 8 ohm secondary using the number of turns needed to make it work. It would probably have worse frequency response, but hey, at least you could make power.
torroids why not ?
I think we have gone off track here ....i have no intention of trying to re invent the wheel , or trying to convince you that this the way to go...etc
what this is about is utilising these seemingly useless trannys whether salvaged or surplus into something useful that those on very tight budgets can afford
I knew that i was gonna get a fair slapping for entertaining the thought that these can actually sound quite good in guitar amp service.....but it did !!!
What i did was a very quick and rude application to prove whether it was worth evaluating even further ......and my ears told me it was
As i stated , there was a mere 16 turns on this unit and it covered about one third of the diameter ......and needless to say it can definitely be improved upon ....perhaps more windings on the primary and in turn on the seconds....and as for interleaving why bother.... but it would seem one would try to go at least the full 360 degrees for the seconds but would it be needed if it performed quite well as it was ...another factor is i used a large tranny for this where a smaller may well saturate
but how would you know if you dont go there ?
I did run 360VDC into it and played at full volume for half an hour at around 18 watts as a guestimate and no saturation occured and temperature was mild... bass was punchy and highs were clear and bright ,18 watts into a quad box gets quite loud after a while ..... so it appears to be successful....
Another usefull thing is that with limited skills one can apply any combination of impedance to these things quite simply...to both primary and secondary to match whatever tubes one wishes to use....
This is the sort of info that i would like to see ......and i would encourage folk to give it a shot .....in previous threads i heard pretty well much the same comments that are appearing on this one and i guess thats why it took me so long to give it a go....i thought it was going to be piontless...
I think these are better than the M20 line transformers that have been mentioned in other budget amp threads and thats speaking as one who has used the m20 successfully in both SE and P/P aplications
Perhaps the trannies are like a box of chocolates .....you never know what your gonna get .... but worth the effort in my opinion...
I think we have gone off track here ....i have no intention of trying to re invent the wheel , or trying to convince you that this the way to go...etc
what this is about is utilising these seemingly useless trannys whether salvaged or surplus into something useful that those on very tight budgets can afford
I knew that i was gonna get a fair slapping for entertaining the thought that these can actually sound quite good in guitar amp service.....but it did !!!
What i did was a very quick and rude application to prove whether it was worth evaluating even further ......and my ears told me it was
As i stated , there was a mere 16 turns on this unit and it covered about one third of the diameter ......and needless to say it can definitely be improved upon ....perhaps more windings on the primary and in turn on the seconds....and as for interleaving why bother.... but it would seem one would try to go at least the full 360 degrees for the seconds but would it be needed if it performed quite well as it was ...another factor is i used a large tranny for this where a smaller may well saturate
but how would you know if you dont go there ?
I did run 360VDC into it and played at full volume for half an hour at around 18 watts as a guestimate and no saturation occured and temperature was mild... bass was punchy and highs were clear and bright ,18 watts into a quad box gets quite loud after a while ..... so it appears to be successful....
Another usefull thing is that with limited skills one can apply any combination of impedance to these things quite simply...to both primary and secondary to match whatever tubes one wishes to use....
This is the sort of info that i would like to see ......and i would encourage folk to give it a shot .....in previous threads i heard pretty well much the same comments that are appearing on this one and i guess thats why it took me so long to give it a go....i thought it was going to be piontless...
I think these are better than the M20 line transformers that have been mentioned in other budget amp threads and thats speaking as one who has used the m20 successfully in both SE and P/P aplications
Perhaps the trannies are like a box of chocolates .....you never know what your gonna get .... but worth the effort in my opinion...
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