Hi all,
I've been winding a few custom output transformers using M6, Z11 (and some unknown laminates in the junkbox) for guitar amps with surprisingly good results. I once got this advice from Sensei Ingo:
I have tried to found out what Ingo referred to but failed so far. Does anyone know what "semi processed steel 660-50" is and where to source it, or perhaps something that is similar?
My next project is an EL84 based 18W "Plexi". I would like to use this laminate and find out if it's the unicorn blood I've been looking for so long...
Thanks in advance!
/Mike
I've been winding a few custom output transformers using M6, Z11 (and some unknown laminates in the junkbox) for guitar amps with surprisingly good results. I once got this advice from Sensei Ingo:
I have tried to found out what Ingo referred to but failed so far. Does anyone know what "semi processed steel 660-50" is and where to source it, or perhaps something that is similar?
My next project is an EL84 based 18W "Plexi". I would like to use this laminate and find out if it's the unicorn blood I've been looking for so long...
Thanks in advance!
/Mike
Here it is. It's all well explained why it can be better than standard steel.
Problem you could have is the ability to order just the small amount you would need for your project. You'd need to find out what the MOQ for that is (Minimum Order Quantity).
I would be interested in buying some laminations in case that were possible.
I suppose sourcing small quantities will make it difficult, and/or way too expensive. Any suggestions where to look for smaller quantities?
I recently purchased a lot of M6 EI76 lams for a project, minimum buy was 10Kg - enough to make 9 transformers.
If you look into the history of Marshal amps it's easy to form the impression that the choice of components was greatly influenced by cost and availability, the same could be said for most amp makers at the time - so a certain OT was used not because it was made with specific laminations but because it was cheap and plentiful - lower cost equates to cheaper laminations, the cheapest lamination would have been 'ordinary' iron as used in power transformers. I've rewound a few Dagnal OT's from Marshal and Laney amps and the laminations weren't the 0.35mm thick lams you'd expect to find in a HiFi OT but 0.5mm thick just like you'd expect to find in power Tx.
If you look into the history of Marshal amps it's easy to form the impression that the choice of components was greatly influenced by cost and availability, the same could be said for most amp makers at the time - so a certain OT was used not because it was made with specific laminations but because it was cheap and plentiful - lower cost equates to cheaper laminations, the cheapest lamination would have been 'ordinary' iron as used in power transformers. I've rewound a few Dagnal OT's from Marshal and Laney amps and the laminations weren't the 0.35mm thick lams you'd expect to find in a HiFi OT but 0.5mm thick just like you'd expect to find in power Tx.
I made an OPT using chinese GOSS 130 x 195mm EI's
Its sounds totally amazing , nothing short of pure unicorn blood - however there are other (other than the iron) factors that IMO affect the sound...eg don't use plastic. I used a cardboard bobbin, craft paper insulation, and candle wax .
Its sounds totally amazing , nothing short of pure unicorn blood - however there are other (other than the iron) factors that IMO affect the sound...eg don't use plastic. I used a cardboard bobbin, craft paper insulation, and candle wax .
Good point. I find that the materials used to build the bobbin can overwhelm the sound of the iron itself. The way the transformer is built is more important than the core choice, IMHO, if we're looking at the subjective sound signature.
I found the same 0.5mm on a Music Man OT I rewound a few years ago. It sounded great as well!
This is interesting! How would you describe the difference between plastic and cardboard bobbin sonic-wise?
I'm not convinced that the bobbin and insulation material have any effect on the 'sound' - a few years back I built a Fender Deluxe Reverb copy for my son, all of the Tx's were wound by me using reclaimed laminations from old power transformers, I wound 2 OT's one with cardboard winding tube and paper insulation and a second with plastic bobbin and polyester insulation, my son auditioned both OT's, he decided if there was a difference he couldn't hear it, he finally settled on the paper insulation simply because that was the last one installed.
Bear in mind he had to wait 30 or 40 min between listening tests while a transformer swap was done, maybe if we'd done a proper A/B test he might have discerned a difference between them.
link to the build log https://www.vintage-radio.net/forum/showthread.php?t=159474
You could probably debate until the cows come home on the 'sound' imparted to OT's by the insulation or bobbin material - at the end of the day if someone says it sounds better with paper insulation then for me that's fine, I believe that for them it sounds better.
Bear in mind he had to wait 30 or 40 min between listening tests while a transformer swap was done, maybe if we'd done a proper A/B test he might have discerned a difference between them.
link to the build log https://www.vintage-radio.net/forum/showthread.php?t=159474
You could probably debate until the cows come home on the 'sound' imparted to OT's by the insulation or bobbin material - at the end of the day if someone says it sounds better with paper insulation then for me that's fine, I believe that for them it sounds better.
It really depends on the type of plastic it is, the type of paper, impregnated or not, dielectrics used, hardness and gauge of the copper wire used, etc. But you can treat the construction of the bobbin as a musical instrument on its own. Then come the impregnating agents, the amount of curing, different types of waxes, potting compounds, etc.
I've developed a fondness for Metglass amorphous cores and virgin Teflon insulation since building my 833C amps. Incredibly detailed without being harsh, at least in the case of the Monolith OPTs I used. Picture is of one if my OPTs under construction with an ECC83 for perspective.
Attachments
Belief often determines sound quality for some listeners, regardless of what comes out of the speaker. Double-blind testing is the only way to separate the wheat from the chaff in that situation.
Read the datasheet, to me it looks like plain vanilla PT grade iron, nothing to write home about.
Not bad, not special,in any case Guitar OTs are LoFi anyway.
No unicorn blood anywhere to be found, if anything winding geometry and interleaving which do affect parasitic inductance, coupling, parasitic capacitance, resonant peaks, are WAY more important.
Jim Marshall was as cheap as any successful large scale manufacturer or he would have failed.
Orange and Hiwatt did.
Both used expensive HiFi rated Partridge Transformers (and expensive Fane speakers).
They hade rich and famous customers ... that alone is not enough.
Marshall catered to the masses.
Don't obsess over iron, that one looks good enough and then some.
Just guessing: 660 might mean the steel type and 50 might be lam thickness.
2.4W/kg loss at 50 Hz? Wow!
Cheapest available here in Argentina is 2.2W/kg, premium is thin lamination grain oriented 1.8W/kg, go figure.
That steel is not grain oriented, they mention "average of transversal and longitudinal" which is clear enough.
They also present as a special feature that it is "semi treated" , then explain that after punching EIs you can retreat them again in an oven, because punching which is a violent mechanical action changes magnetic properties for the worse.
True enough .... only you can also do the same with any other lamination 😄
I bet your currently available lamination will do fine, and OTs will sound GOOD.
Just wind and mount them, and post results. 👍🏻
I'm sorry, I can't tell - I've never made an OPT with a plastic bobbin.
However, as the OPT is a giant capacitor (as well as other things) , if you like the sound of plastic capacitors, use plastic.
That's sounding more like Magick than electronic engineering : ) The problem with cardboard bobbins is that they don't have structural integrity. The few I've made have ended in disaster, the sides giving way and all the turns spilling out as well as other failures. I can understand the thickness or dielectric of insulation having an effect of interwinding capacitance but how does the difference between beeswax & wax X effect the "sound"? And how would you quantify that, or test the difference?
Forgive my skepticism, but if we are not careful we'll go down the cosmic rabbit hole that guitarists have fallen down -
Andy.
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Check out this video, fast fwd to the 6.55 min mark - is there some truth in the comments on wax potting or is this creative marketing to give the impression that only Audio Note transformers have magic wax that improves sound.
Wax does work. It's not magic, it's dampening. However, not everyone likes the signature of waxes and various ones sound different.
They apparently save no cost on transformers, but use plastic bobbins in the video. I suppose i can live with plastic bobbins then 🙂
It's possible that any sort of winding impregnating material will slightly increase interwinding and inter-layer capacitance, since the dielectric constant for any material at all will be higher than that of air. I have wound output transformers for tube amps and experimented with that, measuring a pair of identical transformers the same in every way except that one has no impregnant while the other does. First major resonance occurred at a much higher frequency for the transformer NOT using the filler.