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Hand winding custom output transformer

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One of my local customer request for custom- made 832 PP amplifier. This is the output transformer I made for 832 PP project.
The output are double C core type, with 0.23mm silicon steel. I seldom use Amorphous core because of its slightly thin sounding, I need bigger Amorphous core to get decent lower frequency.
I'm using a hand cranked winder, so that I can layout the winding pattern I wanted. This 50 years old winder had been with me since my very first OPT till now.
I'm not quite satisfy with its square wave ringing, because none of my DIY single ended transformer has ringing problem. I will just try to use it and see how it turn out in actual operation. Please subscribe for my coming DIY 832 amplifier.
audiophilediyer.com

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26 авг 2024

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Комментарии : 72

@hmjeon8609 4 месяца назад

Your winding technique is quite impressive that the eindings rarely overlap.

@ifixmycarmyself2502 4 года назад

Very nice and informative video. I built a 300B amplifier last winter and winded my own OT. I don't have the nice winding machine you have but a very primitive DIY apparatus without gears so I couldn't wind more than one hour at the time. Took me three weeks to finish the transformers. Found a good article by Jim Flowers from 1997 on transformer winding from start to finish with all necessary calculations of reactance, leak inductance, dimensioning and what have you. I really recommend the article for all DIY transformer winders out there. Thanks again for your video. Just wish I had that winder :)

@AudiophileDIYer 4 года назад

Hi，Thanks for comment. Yes, there are many good article about transformer winding and Jim's article are one of them . The simple winder machine i used is an antique winder, but they keep manufacture it till today, not very expensive , you can search on ebay for one. I have several Diy type motor controlled winder and also industrial grade winder machine, but I enjoy hand crank method for all my output transformers.

@garygranato9164 4 года назад

very impressive dedication to diy-HIFI, great vid

@alexandernaydenov7400 4 года назад

Good to see a fellow winder!

@VikasG007 2 года назад

I need winding data for my ecc83, and el84 tube, here in india sound output transformer is not available. So i think to wind a transformer. But due to nill knowledge unable to wind it. I need 5k:8 ohm transformer with 6watt. Can you provid mein me Right Data. So that i wind it with my self. Thanks......

@andrewrexhalina4006 4 года назад

Hi can you give a link of tutorial about output transformer rewinding?im so glad that i will know how..thanks

@mattportnoyTLV 3 года назад

Great video. I wind my own line level and mic input transformers. I use M6 and amorphous cores. Where do you buy your cores from?

@tomng8696 3 года назад

Can you give some Info about: primary impedance, wire gauge, how many turn, secondary wire gauge how many turns...Thanks

@miklee4834 2 года назад

You are a genius.👍🏻

@allanpennington 5 лет назад

Great vid. I am building a replica of an old Vox amp.Its original OT had an 8K input impedance with 8 & 15 Om secondary taps. The amp was originally rated as a 10W amp, but anecdotally owners of originals and its tube compliment mean it probably pushes more like 18W when driven hard. It had 1 x 12AX7 as pre-amp and tremolo, 1 x 12AU7 for second gain stage, (cathode coupled), 1 x 12AU7 for reverb drive and recovery, 1 x 12AU7 for phase inverter, 2 x EL84 output tubes cathode biased in push/pull and 1 x EZ81 rectifier. The PT was 300-0-300V giving a DC output design V of 390V before the first dropping resistor/filter stage. The B+ was around 300V. There are no specs I can find for the original English made Drake OT which had serial nos 352-98 or 352-93. A similar OT available on the market today with similar impedance are only rated for 10 or 15W. Is it possible to wind an OT with 8K in and 8&16Ohm Out that would be rated at say 20W? What is the difference between one rated at say 10W and a higher rating? I assume the winding ratios are the same to achieve the desired input vs output impedance ratio but in a higher wattage rated OT does it mean thicker gauge copper or more turns on each side or a combination of both to get an OT that can take a higher wattage output from an amp?

@AudiophileDIYer 5 лет назад

Hi. I repaired a Vox AC10 Twin last year for my customer and I love it. The EL84 push pull with 300V B+ can put out 18W for sure, just like Marshall 18W . I think Vox rated 10 watts just for clean, non distortion output, and it should be at least 15 ~ 18 watts before clipping. I bet most of 15 Watts OPT on market can do the job without much problem. The Wattage ratings of most OPT on market are a little bit confused actually, For Hi-Fi OPT, the wattage are based on lower frequency than guitar amplifier OPT. Also, you can try to find replacement OPT for Marshall 18W for your Vox project if you want higher rating, choose the one with 8 and 16 ohm output to suit your need. ( classictone.net, for example ) For winding a higher wattage OPT, you need bigger EI laminates, thicker copper, turn ratio remains , but less turn than the lower wattage transformer. You can tell the wattage by its physical size. By using higher wattage OPT, you can get more bass, more clean power , and OPT last longer , but slightly different distortion characteristics because smaller OPT nearly saturated / distorted earlier than vacuum tube clipping, and the bigger OPT is the other way round. Hope this help and enjoy your Vox amp replication.

@allanpennington 5 лет назад

Audiophile DIYer Brilliant, that’s just what I needed to know. There is the Marshall one I could use and I have seen a beefed up Fender one at a 20W rating, which has slightly thicker iron. They are cheap enough to try them both when I get the amp done. Thanks

@allanpennington 5 лет назад

@@AudiophileDIYer Thanks, that is interesting. I am also trying to match the power transformer and have discovered that depending on who made the transformer, stack height varied between 2 or 1.5 inches tall with the same lamination plane area footprint of 3.15 x 3.88 inches. I understand this would effect the overall flux of the transformer. Would it also impact the prim and secondary winding resistance? I assume this would mean different sag characteristics when used in a valve rectified circuit? I think most modern EI laminations available in ready made Tx are 3.125 x 3.75" which I hope is close enough to the original. Or are the bobbin size and the leg size of the laminations more important?

@AudiophileDIYer 5 лет назад

@@allanpennington Hi. If I'm building a guitar amp for my own, I will go for the slightly bigger core power transformer ( compare to original ) . The bigger core has lower DC resistance and less sagging characteristics, more durable and less heat. The B+ may be little bit higher than original because of less sagging characteristics, , and I can adjust it by increase the resistor value ( the one right after the rectifier ) or if you have choke in your circuit, you can fine tune your B+ by reduce the capacitor value which is between the choke / rectifier. Slightly higher B+ can be cure as mentioned as above but if you have lower B+ , then you can't do anything with it. Thats just my 2 cents worth and hope this will help...

@allanpennington 5 лет назад

@@AudiophileDIYer Quick update after further research The OT originally was wound on an EI-075 (35 UK size) lamination with a 1" stack height. This is smaller than the 18W Marshall. Closer to some of the PP Fender types though. 8K Prim into 8 and 16 Ohm Sec @ min of 15W will be the target. The difficulty is in knowing how many Prim-Sec-Prim-Sec interleaves to use. They definitely had interleaved windings. The search continues

@JFGIsko22jr 7 месяцев назад

Nice video bro..can you help me..i need to know the data for 40%ultap 8kohms OPT for my on going tube amplifier..i build one opt but the sounds distorted..i need to know what is the internal connection of the winding..thanks a lot

@TheStudio49 3 года назад

Thank you great video

@lincolnmicrophonellc 5 лет назад

I need to watch this again but the geometry is to reduce leakage inductance? The parallel of all secondaries is to minimize dc resistance on secondary? Why switch from kraft paper to the glassine type paper? You have great winding technique, nice laying layers. Very clean. Thanks for showing the transition and taping of the paper layers, this has always been a mystery to me.

@AudiophileDIYer 5 лет назад

Thanks for your comment. This is one of winding method I used to suit my design. In fact , its just an old school winding method, no secret here. I used thin translucent paper to support every layer of primary so that it can wind tidily and also create small distance in between , to reduce capacitance. The brown kraftpaper is thicker, to isolate between primary and secondary. Paralleled secondary can reduce DC resistance, and also reduce leakage inductance, frequency response can be extended，but drawback is ringing effect when measure using square wave. Most of the time, I use thicker gauge copper for secondary and series them to get more decent square response, but I need to wind more interleave sections of primary / secondary to get the same result as the parallel one. I will upload more videos regarding transformer winding real soon . hope this help.

@IanScottJohnston 3 года назад

Nobody seems to be selling transformer kits anymore....any ideas where I can get some. Am looking for something suitable for 40VA and with 44mm x 55mm mounting centres.

@hadiprayitno8632 4 года назад

good job sir....best regard

@gingercinammon 3 года назад

hi. great work. may i ask what kind of paper are being used for winding separation?

@roz7.62 5 лет назад

Cool video! I’m just getting into winding my own transformers and cant get my hands on enough videos like this to learn from. I’m winding an opt for a 100w guitar amp this weekend (its basically a copy of the Dagnall c2668). Any tips or resources to share with a rookie like me?

@AudiophileDIYer 5 лет назад

Hi. Thanks for your comment , I will post more transformer winding videos in near future. did you get your material yet? ( EI laminates, copper etc ) there're a lot of output transformer calculation page on www. I'm writing an article regarding transformer windings , ( focused on practical wingding, not calculation ) will post to my own webpage real soon. You can email me audiophilediyer at gmail dot com if you have problem during winding process. I will try my best to answer your question.

@roz7.62 5 лет назад

Audiophile DIYer - I really appreciate that. I’ll shoot you an email with some questions. I do have materials. I got some EI150 M6 lams from a company out in California, bobbins from Edcor, magnet wire off eBay (Essex brand), and polyester tape as a wrap from amazon. Not the most cost effective hobby. I actually wound it once already and disassembled it because I felt like I could do it better.

@philipandrew1626 5 лет назад

Josh, enjoyed your discussion on the MacroFab podcast Episode 174. Did you end sharing your transformer spreadsheet as I couldn't see it in their show notes? macrofab.com/blog/mep-ep174-apply-inspiration-here/

@lamnguyen6859 3 года назад

can you share the recipe, sir?

@motogee3796 Год назад

Hi the primary inductance is high (45H) as expected for an iron core transformer. How is it possible to push any meaningful power thru such high resistance XL=282f esp at higher frequencies?

@The-Master-of-None 4 года назад

Does your smaller wire wound like you wind it by hand. What i mean is it one after another or do they overlap?

@AudiophileDIYer 4 года назад

All thin copper wires are wind tidily without any overlap. If it overlap, I need to correct it immediately.

@The-Master-of-None 4 года назад

@@AudiophileDIYer you're amazing sir. You're skills are so great. I can't wind like you did.

@AudiophileDIYer 4 года назад

With some practice, I'm sure you can wind it tidily without much problem.

@uzbekboom05 4 года назад

Best of the best !!!

@AudiophileDIYer 4 года назад

TQ :)

@Torpengpogi 4 года назад

hi audiophilediyer, one of my opt of my dynaco sca-35 with z565 opt passed my dcr test on primary (tube side) and secondary (speaker side), but failed the secondary (speaker side) with inductance testing using my LCR MM, giving me negative measurements on both 8 and 16 ohms vs. common taps. also this channel using this opt, tubes (EI84/6BQ5) are always problematic motorboating and red plating after a few minutes of used, do you think my opt is defective? the other channel with good readings on my LCR MM inductance testing is not giving problems on tubes, thanks.

@AudiophileDIYer 4 года назад

Hi, please disconnect the whole output transformer form the circuit, and measure the primary inductance, the inductance should be more than 20H at it's primary, and by short circuit the secondary and measure inductance of primary again , it should be not higher than 50mH . Please let me know whats your readings . You need to check your tubes bias, and also leaky old electrolytic capacitors as well.

@Torpengpogi 4 года назад

@@AudiophileDIYer hi, i will do it this weekend, and i will post the result measurements, as per your instructions.

@kgsalvage6306 3 года назад

Do you have any links to transformer parts? Cores, ect...

@AudiophileDIYer 3 года назад

Hi, Unfortunately parts for transformers in small quantity seems not really easy to get now. I will try to source some if possible, and put it on my web page for purchase.

@kgsalvage6306 3 года назад

@@AudiophileDIYer That would be much appreciated. I've found the same issue. Can be bought in large quantities. There's a few listings from China, but they are still a bit pricey. I'll keep checking your site. Edcor sells parts, but you might as well have them do it for the cost you pay.

@MOfrhr 4 года назад

Hello. Where to buy the coil skeleton, please ?

@AudiophileDIYer 4 года назад

Hi，I bought the bobbin locally . Maybe you can try to find some in the e-bay? my odd size c core bobbin are all 3D printed .

@MOfrhr 4 года назад

@@AudiophileDIYer thanks

@hadiprayitno8632 5 лет назад

Can you tell me how your tecknik winding with good result sir .... your winding is very good .... thanks sir

@AudiophileDIYer 5 лет назад

Thanks for comment . I will find time to write a long article about output winding . please stay tuned .

@hadiprayitno8632 5 лет назад

@@AudiophileDIYer oke i will be waiting your article thanks you sir.....best regard

@soumikdas5857 4 года назад

Umm whats the exact frequency did you take for the turns calculation

@AudiophileDIYer 4 года назад

Hi. I'm using 25Hz , at around 5000 Gauss .

@soumikdas5857 4 года назад

Isn't 25 hz is too much low I mean if the frequency goes in upper ragne like 300 or 400 Will not it make a high impedance In primary section for huge turns ratio in 25 hz?

@soumikdas5857 4 года назад

N i opend a old output transformer N i calculated the turns ratio N its result is 122 hz

@soumikdas5857 4 года назад

M just a bit confused N i want to make a output transformer

@AudiophileDIYer 4 года назад

Hi, @@soumikdas5857 I'm a little confused with your question now. I used 25Hz as frequency to determine the size of core and wattage, and the turn ratio is not effected by the above mentioned frequency at all , I used 25Hz as standard for all my tube amps which is without any negative feed back , and around 40~50Hz can be used if the design is with negative feedback. Guitar amp even used higher frequency at 50~100Hz , or even higher. I'm an audiophile , so I will not saving my building cost and sacrifice the bandwidth of my output transformer. The calculation is very basic and there're tons of info about audio transformer calculation on internet. for the higher frequency response, it depends on your winding method, the number of interleaved layers, isolation paper material and thickness etc. This output transformer had been used in my 832A projects here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-F2tvsyVNDxE.html and the measured frequency response is 20Hz -0.5dB ~ 63Khz -0.5dB Thats the result I aim for. Hope this help.

@flegstrogs 5 лет назад

whats the frequency you use? 70hz?

@AudiophileDIYer 5 лет назад

Hi, This is an audio output transformer for vacuum tube amplifier, and operating frequency range are expected to be from 20Hz to 20Khz. Thats why I did some simple frequency test from low to high at the end of this video.

@hadikayanuar1367 3 года назад

@@AudiophileDIYer are you use 50Hz? Cause i think that wave like no problem in thats frequency

@AudiophileDIYer 3 года назад

@@hadikayanuar1367 I'm not quite sure about your question. This is an Audio output transformer For vacuum tube amplifier, not power transformer, I did show clearly test frequency of 50Hz, 10Khz, 20Khz, etc.

@hadikayanuar1367 3 года назад

@@AudiophileDIYer oh i see