Hi,
First post!
Is it possible to wind an output transformer for a KT66 valve in single ended?
I have built valve amps before, however I would like to try winding an output transformer. Would a ferrite ring work as a core?
Can any one tell me number of turns and possible size of core.
Regards
M.Gregg
First post!
Is it possible to wind an output transformer for a KT66 valve in single ended?
I have built valve amps before, however I would like to try winding an output transformer. Would a ferrite ring work as a core?
Can any one tell me number of turns and possible size of core.
Regards
M.Gregg
Yes.
No. There are a couple of major problems with that. If it's an OPT for a single-ended final, the DC bias current will saturate the core, unless there is an air gap. Unless you have a gapped toroidal core already, you're gonna have a helluva time trying to cut a ferrite core without breaking it.
Secondly, ferrite won't give decent low frequency performance since its perm and Bsat are a good deal lower than that of a proper silicon steel core, or one that uses more exotic materials, either alone or in combination with Si-steel lams.
Save your ferrite toroids for RF projects.
Wolpert Audio Transformer Design Manual: it looks like this is no longer available over the 'Net. Send me an e-mail, and I can send it back as an attachment.
Keep in mind that OPT design and winding is somewhat of a "black art", and requires empirical design gained mainly through experience. You might have to wind more than a few bad/mediocre OPTs before you get that experience.
Winding bad audio xfmrs is easy. The good ones take some considerable doing, which is why the really good ones are $Pricey ( and why cheap ones sound like:
An externally hosted image should be here but it was not working when we last tested it.
)
Wolpert paper is here:
http://www.dissident-audio.com/Auto...rs/&file=Wolpert_Audio_Xfmr_Design_Manual.pdf
Yves.
http://www.dissident-audio.com/Auto...rs/&file=Wolpert_Audio_Xfmr_Design_Manual.pdf
Yves.
M Gregg,
I like your idea
clearly ferrite is no good, as stated by Miles.
Send me a PM and you can have a pair of M6 c-cores for postage.
I recently scored a whole load of c-core trannys and the cores I had are no longer needed. They are some of the core kit jobs sold on ebay from China. I tested them at 50Hz and for the pair they can handle 300VA, so for one core in single ended with a (or pair of) KT66 etc. they would be ideal.
I have been messing about winding some push pull trannys so you will have to do a lot of reading, winding, wondering, re-reading, winding again etc. but the cores should be a start
The whole subject of winding your own outputs has been neglected slightly on the forums. Possibly because it is hard work, both in maths and the actual winding. After all this the final design is likely to be flawed and a re-jig/re-wind is needed
I dont mean to disuade you in any way because its the most fun I have had in a while just getting the bits together ie ECW, insulation, making bobbins, finding cores.... the list goes on.
The best info I have found is the bible:
http://www.pmillett.com/tubebooks/Books/intro_RDH4.pdf
and Patrick Turners great workdown:
se-output-trans-calc
( If you want the cores, be sure to PM me before Monday morning as I work away four days a week and may not have internet access)
Cheers Matt.
I like your idea
clearly ferrite is no good, as stated by Miles.Send me a PM and you can have a pair of M6 c-cores for postage.
I recently scored a whole load of c-core trannys and the cores I had are no longer needed. They are some of the core kit jobs sold on ebay from China. I tested them at 50Hz and for the pair they can handle 300VA, so for one core in single ended with a (or pair of) KT66 etc. they would be ideal.
I have been messing about winding some push pull trannys so you will have to do a lot of reading, winding, wondering, re-reading, winding again etc. but the cores should be a start
The whole subject of winding your own outputs has been neglected slightly on the forums. Possibly because it is hard work, both in maths and the actual winding. After all this the final design is likely to be flawed and a re-jig/re-wind is needed
I dont mean to disuade you in any way because its the most fun I have had in a while just getting the bits together ie ECW, insulation, making bobbins, finding cores.... the list goes on.
The best info I have found is the bible:
http://www.pmillett.com/tubebooks/Books/intro_RDH4.pdf
and Patrick Turners great workdown:
se-output-trans-calc
( If you want the cores, be sure to PM me before Monday morning as I work away four days a week and may not have internet access)
Cheers Matt.
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ot se kt66
Hello!
Can design and build an output transformer for a SE KT66 tube, but first you must determine what diagram you use, the performance you want to get this project (!?).
Audio applications, can not use a ferrite core, only E + I, C core or toroidal.
If we see a diagram that you use, I think I can help with this project.
Nice weekend!
O.Lazaroiu
Hello!
Can design and build an output transformer for a SE KT66 tube, but first you must determine what diagram you use, the performance you want to get this project (!?).
Audio applications, can not use a ferrite core, only E + I, C core or toroidal.
If we see a diagram that you use, I think I can help with this project.
Nice weekend!
O.Lazaroiu
A KT 66 will work fine in SE mode. With 440 VDC on the plates you can expect to get 5.8 watts. Is this enough power for your needs? It will certainly drive a Lowther of any kind to quite loud levels, but anything under 90 db sensitivity will be starved for dynamics.
If you are serious about learning how to design and build an OPT I can help you move down that road. Designing audio transformers is part of my professional life and I will be glad to help you.
This is not something that can be learned quickly, though it is not particularly complex. It isn't a Black Art either, I don't have to wear a flowing caps with arcane signs stitched on to it nor a pointed cap. Just a few simple formulas, some hard to obtain technical data, and you can design very good transformers, for commercially available materials.
Learning how to make the things, that is a bit more involved, but again, a few simple rules applied in the design portion will help this part tremendously.
So, how serious are you?
Bud
If you are serious about learning how to design and build an OPT I can help you move down that road. Designing audio transformers is part of my professional life and I will be glad to help you.
This is not something that can be learned quickly, though it is not particularly complex. It isn't a Black Art either, I don't have to wear a flowing caps with arcane signs stitched on to it nor a pointed cap. Just a few simple formulas, some hard to obtain technical data, and you can design very good transformers, for commercially available materials.
Learning how to make the things, that is a bit more involved, but again, a few simple rules applied in the design portion will help this part tremendously.
So, how serious are you?
Bud
.... BudP ...... certainly one of Black Art artisans
best thing can be - if you are willing to make short ( not so short - not short at all
) thread or blog - with that theme ......I presume that only already knowledgeable members will contribute , not making noise in so precious theme
I never take my self as complete tube DIY-er , just because I never had enough time to invest in necessary time consuming process of learning little tricks in OPTs calculating and making .
making stage with xformers made by someone else just never looks complete enough to me , so I never said that I made some amp by my self completely
Hello all,
I am surprised at the response from the forum!
I thought a single ended would be an easier transformer to build than PP. I seem to be wrong!
The main point of the post was to try to get arround the Op transformer being such a sticking point.
My thoughts are to build the transformer and then build the amplifier to match. Taking the easy road so to speak!
So for a starting point which is the best option for a first optx SE or PP?
Would it be better to do KT66 PP? Giving more output?
--------------------------------------------------------
In the past I have built 8 EL34's running in PP 4 per channel and wanted to build a small good sounding amp!
Any thoughts?
Regards
M.Gregg
I am surprised at the response from the forum!
I thought a single ended would be an easier transformer to build than PP. I seem to be wrong!
The main point of the post was to try to get arround the Op transformer being such a sticking point.
My thoughts are to build the transformer and then build the amplifier to match. Taking the easy road so to speak!
So for a starting point which is the best option for a first optx SE or PP?
Would it be better to do KT66 PP? Giving more output?
--------------------------------------------------------
In the past I have built 8 EL34's running in PP 4 per channel and wanted to build a small good sounding amp!
Any thoughts?
Regards
M.Gregg
Well well ... search this forum for "Baby Huey"
And if you want to wind, here is how I did the OPT for the original 6GW8 version.
http://www.dissident-audio.com/AutoIndex/index.php?dir=Transfos/Dissident/Fiches/&file=DA17-2a.pdf
Have fun winding and be patient and carefull.
Yves.
And if you want to wind, here is how I did the OPT for the original 6GW8 version.
http://www.dissident-audio.com/AutoIndex/index.php?dir=Transfos/Dissident/Fiches/&file=DA17-2a.pdf
Have fun winding and be patient and carefull.
Yves.
Yvesm,
Regards your transformer diagram. I assume A/B are the speaker terminals. What are X and Y? I assume that the bottom of the winding diagram is the core and you do each layer 5*109T followed by a mylar insulator then 1*32T then the next one on top of the other?
7K anode load output 6Ohms?
Regards
M. Gregg
Regards your transformer diagram. I assume A/B are the speaker terminals. What are X and Y? I assume that the bottom of the winding diagram is the core and you do each layer 5*109T followed by a mylar insulator then 1*32T then the next one on top of the other?
7K anode load output 6Ohms?
Regards
M. Gregg
Hi M. Gregg
You're right !
Apologize for using French and millimeters rather than imperial units: my brain was trained to do so
First and last primary sections have a total of 545 turns, 109 turns per layer (this just fits in the coil former -or bobin) with the specified wire gauge.
Middle one has 1090 turns in 10 layers.
There are no additional insulation between layers.
X and Y terminals have no other use that to allow connecting wires together, nothing else must be connected to.
Note that the thickness of the insulation is different: 0.4mm around the first half secondary and 0.2 mm around the second one
The insulation material is not a mylar foil, but a thing brand named "MylarCelite" wich is a kind of sandwich constitued by a cardboard layer and a Mylar one. It's total thickness is 0.2mm, so you must use 2 turns of it to obtain 0.4mm as noted.
If not available, better use cardboard than plastic which usually have higher dielectric constant.
Be prepared for some deception, irritation and copper vasting before you succeed to neatly roll your first bobin
Yves.
You're right !
Apologize for using French and millimeters rather than imperial units: my brain was trained to do so
First and last primary sections have a total of 545 turns, 109 turns per layer (this just fits in the coil former -or bobin) with the specified wire gauge.
Middle one has 1090 turns in 10 layers.
There are no additional insulation between layers.
X and Y terminals have no other use that to allow connecting wires together, nothing else must be connected to.
Note that the thickness of the insulation is different: 0.4mm around the first half secondary and 0.2 mm around the second one
The insulation material is not a mylar foil, but a thing brand named "MylarCelite" wich is a kind of sandwich constitued by a cardboard layer and a Mylar one. It's total thickness is 0.2mm, so you must use 2 turns of it to obtain 0.4mm as noted.
If not available, better use cardboard than plastic which usually have higher dielectric constant.
Be prepared for some deception, irritation and copper vasting before you succeed to neatly roll your first bobin
Yves.
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Yvesm,
However the insulation is critical to prevent HT getting onto the speaker connections under fault conditions! How do you bring out the start and ends of the windings? Could you just sleeve with PTFE and bring them down he edges of the former?
Also I assume 20% UL taps would be 218T from the start of the HT winding on each side.
Regards
M. Gregg
However the insulation is critical to prevent HT getting onto the speaker connections under fault conditions! How do you bring out the start and ends of the windings? Could you just sleeve with PTFE and bring them down he edges of the former?
Also I assume 20% UL taps would be 218T from the start of the HT winding on each side.
Regards
M. Gregg