Hi Susan, impressive result (the carefull winding and the bandwidth). The 'dropping a spool method'!
About the winding effort, have you ever heard of using a Hula Hoop, a tube one on which the outer side has a slit or slot. With a loop of maybe about 1 m circumference, the outside is opened somehow; and the toroid is placed trough the loop that is subsequently closed into a circle. Then the full length of the wire is wound along the hulahoop. (enough for, means 10-15 layers?).
Next the coil is wound and somehow the mathematical magic is supposed to work such out that the wire is wound on the coil.
[You might well envision this, I can't] I never did this myself, always used a long stick (say 50 cm). And my results never were mediocre.
About the winding effort, have you ever heard of using a Hula Hoop, a tube one on which the outer side has a slit or slot. With a loop of maybe about 1 m circumference, the outside is opened somehow; and the toroid is placed trough the loop that is subsequently closed into a circle. Then the full length of the wire is wound along the hulahoop. (enough for, means 10-15 layers?).
Next the coil is wound and somehow the mathematical magic is supposed to work such out that the wire is wound on the coil.
[You might well envision this, I can't] I never did this myself, always used a long stick (say 50 cm). And my results never were mediocre.
Amorphous cores do not yield higher bandwidth; they have different magnetic properties, but HF bandwidth is a winding thing (capacities).
Quite a few: Titan2000, AlephX, F5, and many commercial amps (I repaired) but none as good as the ones I build myself. 
Titan had a lot of massive power but was not musical.
AlephX plays very good but consumed a lot of power.
F5 is charming and enough power to drive my speakers.
I believe the Zeus has most detail.
I was ones very impressed by a very old solid state McIntosh. Forgot which one...
Also a MC225. Not bad at all but not really impressed.
One of course has to consider the speakers amps are mated with.
@daanve : Don't know, I'm not at all a transformer expert. Perhaps one needs less 'iron' or copper to get the same results?
Hugo
Titan had a lot of massive power but was not musical.
AlephX plays very good but consumed a lot of power.
F5 is charming and enough power to drive my speakers.
I believe the Zeus has most detail.
I was ones very impressed by a very old solid state McIntosh. Forgot which one...
Also a MC225. Not bad at all but not really impressed.
One of course has to consider the speakers amps are mated with.
@daanve : Don't know, I'm not at all a transformer expert. Perhaps one needs less 'iron' or copper to get the same results?
Hugo
Many thanks for all the comments 
One point to make is that I am winding bifilar i.e. two wires at once; I am also "perfect winding" so the two wires do not cross over at any point.
This is very difficult to achieve when machine winding, especially for toroids with the circular-shuttle winding technique.
I do have some ideas as to speed things up a bit, but it will still take time. This first toroid was in effect a pathfinder mission!
I have made myself some winding spindles, but they are not necessarily easier to use in this case when I am trying to get the best layering of the wires.
Commercial machines are generally for power-transformer winding, and my core at 150mm when wound is already in the large size specification!
See WH-300 - digitally controlled toroid winding machine as an example of what is needed!
One point to make is that I am winding bifilar i.e. two wires at once; I am also "perfect winding" so the two wires do not cross over at any point.
This is very difficult to achieve when machine winding, especially for toroids with the circular-shuttle winding technique.
I do have some ideas as to speed things up a bit, but it will still take time. This first toroid was in effect a pathfinder mission!
I have made myself some winding spindles, but they are not necessarily easier to use in this case when I am trying to get the best layering of the wires.
Commercial machines are generally for power-transformer winding, and my core at 150mm when wound is already in the large size specification!
See WH-300 - digitally controlled toroid winding machine as an example of what is needed!
Very impressive, many thanks for sharing.
For each heatsink, if you set up a 12V fan with it up against the fins, but running off a lower voltage so it is only turning slowly (but not stalling), to actively move the air it will disperse a surprising amount of heat. Helps with testing and enables a higher bias to be used with these small heatsinks
Thanks for the tip, Susan.
Nice 'forks' you made. Without them it would be impossible to tame those wires I guess.
And such a winding machine will probably cost an arm and a leg, as they say..
I will soon build the mosfets on the big heatsinks for the final assembly and I hope they will disperse enough heat. If not, I'll lower the bias for I don't need all that massive Quad Fillar Powered Iron and Steel Juice
Hugo
Nice 'forks' you made. Without them it would be impossible to tame those wires I guess.
And such a winding machine will probably cost an arm and a leg, as they say..
I will soon build the mosfets on the big heatsinks for the final assembly and I hope they will disperse enough heat. If not, I'll lower the bias for I don't need all that massive Quad Fillar Powered Iron and Steel Juice
Hugo
Yes - six wires in, six wires out.
The 1st and 3rd layers are the primaries, with one of each per side in series...
The 3rd layer is the cold-side i.e. the earth centre-tap is formed from the end of one and the start of the other winding on that layer.
The middle 2nd layer is connected in parallel, thus making the step-down ratio between the MOSFETs and the speaker load.
The wires start and stop in the same place as it will make for tidier connections between 1st and 3rd layers.
Also I have the idea that the transformer is to be mounted vertically in front of the heatsink on a small plinth - think like a Stargate - so all the wires want to be together.
I didn't use the spindle for this toroid - I literally had the two 500g spools of 0.80mm wire in my lap and flipped the core over and over and at every turn dropping the two spools through the hole in the middle.
I kept track of which spool was nearest to me and which further, untangling as I went, and hand forming the wire onto the core.
I also wound a layer of Kapton tape onto the finished layer to hold it in place and make the next layer more easy to see as I was winding - otherwise all the wires tend to blur into each other.
It's quite demanding work, even sitting on the sofa listening to music, so I did each layer on successive days.
DIY digitally controlled toroid winding machine:Many thanks for all the comments
One point to make is that I am winding bifilar i.e. two wires at once; I am also "perfect winding" so the two wires do not cross over at any point.
This is very difficult to achieve when machine winding, especially for toroids with the circular-shuttle winding technique.
I do have some ideas as to speed things up a bit, but it will still take time. This first toroid was in effect a pathfinder mission!
I have made myself some winding spindles, but they are not necessarily easier to use in this case when I am trying to get the best layering of the wires.
View attachment 1214194
View attachment 1214195
Commercial machines are generally for power-transformer winding, and my core at 150mm when wound is already in the large size specification!
See WH-300 - digitally controlled toroid winding machine as an example of what is needed!
The windings aren't exactly precisely wound on the toroid.
But,-making it heavier, more solid and sturdy and with carefully machined parts it would surely give better results.
Also, looking at the magnet wire spool arrangement it's easy to see why the windings have problems with ending up closely side by side.
Forget bifilar or even trifilar winding with such a flimsy machine.
The large main "wheel" could be made much larger to allow for some kind of wire guiding arrangement.
With regular E-I transformer winding machines the windings can be made very even and nice, so it must be possible to do the same with a toroidal winding machine.
You would need a metal lathe and a milling machine though . . .
Thanks
Sure. In essence it's similar to the EI transformers, I am aiming for a certain number of turns and DC wire resistance.
BUT here with the toroid the windings are spread out along the whole circumference of the core, whereas in the EI it is less than 40% which is actually used.
I am hoping that with the amorphous core I will get better FFT results - I would use the amorphous cut C-cores but they are horrendously expensive in the larger sizes although I have smaller ones to use for TVCs and the input transformer - when I get round to that!
These I bought a while back (a decade maybe, or more) as a set of four, and they were not cheepies but they were affordable from a NOS trader on eBay.
Thanks.
The machine size qoes up rapidly with the size of core and weight of wire one wants to wind.
If I can't wind bifilar it isn't any good as my transformers need the same lengths of wire to be balanced and matched.
I may do something - but it is a lot of work to make something like this - and I do have access to a lathe and a milling machine!