jacco vermeulen said:
Actually, what you wrote was:
I'm glad that you now admit this "realistic" strategy will get people in trouble. Let me repeat it once again, for newbies' sake, connecting 220V to 110V primaries WILL get you in trouble, BURN the transformer and even DAMAGE YOUR HEALTH. The "reverse" strategy, on the other hand, works just fine in theory as well as in practice and has not hurt anyone so far.
Unwinding secondaries is not a highly recommended procedure for newbies. It takes a lot of patience, some additional tools and equipment and good knowledge of transformer design. In this particular case, I suspect it may be necessary to fully unwind 2x15V (and thus loose that voltage) before unwinding any part of the main secondary winding. Not to mention the hassle of putting back on the plastic isolation, which is well over any newbie's head.
Manufacturers have to choose the most suitable wire diameter for a particular design. Their choice is dependent on the transformer's load schedule, operating temperature, mechanical and electromagnetic core characteristics, copper purity and so on. Thus, for example, there are transformers manufactured to work under constant nominal load as in halogen lamps. They usually have overdimensioned wire diameters but underdimensioned saturated cores because the core-parameter is of no particular importance for the operation of halogen lamps. On the other hand, there are transformers manufactured for "audio" purposes, which have underdimensioned wire diameters (because there is no constant nominal load) and overdimensioned cores that are never saturated in order to avoid THD and EMI-RF noise. It is quite rare to find toroidal transformers with overdimensioned wires and cores and an electrostatic shield between the primary and secondary windings. In fact, this is why I usually do advise local transformer manufacturers on how to wire transformers for me.
Nominal current is determined by the wire diameter and vice versa, and in this case it is 7.6A. Nominal current has nothing to do with the number of secondary windings. I would really like to know how you came up with a current increase of 18 percent.
Again, I do not get your calculations. This is how they should be done:
For secondary voltage 40Vx2, nominal power is 80x7.6A=600VA.
For secondary voltage 28Vx2, nominal power is 56x7.6A=425VA.
P=k x Vsec.
It follows that the percentage nominal power reduction equals percentage nominal voltage reduction.
Speaking of Alephs, Aleph4 needs about 3A per channel. So, for 2 (stereo) channels this is 6A, which is below the transformer's nominal current of 7.6A. Obviously, in case of the Aleph4 the transformer will work WITHIN ITS CURRENT LIMITS and with NO overload risk. This goes for the Aleph 2 as well.
Terry, if you would like to use your transformer as is, consider the Leach Superamp, also known as the double barreled version at http://users.ece.gatech.edu/~mleach/superamp/ .
Regards,
Milan
Christmas Caroll
Joe had a spot of luck, from a newspaper add he bought himself a brandnew small block V8 Chevy crate engine.
As he wanted a car to put it in he went to the nearest car dealer.
The car salesman told him he had just what the engine needed: a top of the line 2 seater Pontiac sportscar.
The only thing he had to do was take 4 sparkplugs out of the engine and drop it in: the car's chassis could easilly handle the torque of the V8 but the power output was too much for it.
Joe asked the salesman how much torque he would get out of it with only 4 cylinders running.
No problem, the salesman said, with only 4 cylinders running the engine can be boosted to deliver more torque without any danger of overheating, i promise you !!
Anyway, you only need 3 cylinders to do 60 mph, 4 is more than enough, this engine is just the thing this car needs.
Another customer had been listening, he budged in and told them he had seen a brandnew Vette for sale, just around the corner, the owner told him it only needed a V8 to run.
Hold on, the salesman said : why didnt you say you wanted the engine with all 8 cylinders running !!!
Look here, i have this great Camaro for sale !
The car just came out of the factory, because it is not the latest model is has prooven itself over the years.
That engine is only a bit undersized but it slides in like butter, i promise you !!
Joe had a spot of luck, from a newspaper add he bought himself a brandnew small block V8 Chevy crate engine.
As he wanted a car to put it in he went to the nearest car dealer.
The car salesman told him he had just what the engine needed: a top of the line 2 seater Pontiac sportscar.
The only thing he had to do was take 4 sparkplugs out of the engine and drop it in: the car's chassis could easilly handle the torque of the V8 but the power output was too much for it.
Joe asked the salesman how much torque he would get out of it with only 4 cylinders running.
No problem, the salesman said, with only 4 cylinders running the engine can be boosted to deliver more torque without any danger of overheating, i promise you !!
Anyway, you only need 3 cylinders to do 60 mph, 4 is more than enough, this engine is just the thing this car needs.
Another customer had been listening, he budged in and told them he had seen a brandnew Vette for sale, just around the corner, the owner told him it only needed a V8 to run.
Hold on, the salesman said : why didnt you say you wanted the engine with all 8 cylinders running !!!
Look here, i have this great Camaro for sale !
The car just came out of the factory, because it is not the latest model is has prooven itself over the years.
That engine is only a bit undersized but it slides in like butter, i promise you !!
Mornin Terry,
There are no PCB's for the SuperAmp available from Prof. Leach's web site. Got to make your own. Your power supply is going to put out about 75 V +/- which is OK for the amp, but you will not get 300W/channel with this value. According to Prof. L. you will need more than 90V to achieve this output. Bummer.
On the plus side, this is one sweet sounding amp. Working on making my 4th one as a gift for my son. Not really more difficult than making the low TIM Leach amp. Just more parts and bigger heat sinks. And 100V caps are not cheap.
Prosit
There are no PCB's for the SuperAmp available from Prof. Leach's web site. Got to make your own. Your power supply is going to put out about 75 V +/- which is OK for the amp, but you will not get 300W/channel with this value. According to Prof. L. you will need more than 90V to achieve this output. Bummer.
On the plus side, this is one sweet sounding amp. Working on making my 4th one as a gift for my son. Not really more difficult than making the low TIM Leach amp. Just more parts and bigger heat sinks. And 100V caps are not cheap.
Prosit
Kristijan did a pcb design on the Leach amp, why not ask him.
In 2002 someone did an ExpressPCB design for the SuperLeach, you can find him with a search and email him.
BrianGT made one for TO247 devices, you may contact him on his GainClone page.
Otherwise JPG's of the PCB's made can be printed, ExpressPCB software downloaded, the file remodelled according to the JPG print and ordered from ExpressPCB.
Maybe someone is interested both in designing the PCB and getting in on a group buy, i am game for a couple of boards.
In 2002 someone did an ExpressPCB design for the SuperLeach, you can find him with a search and email him.
BrianGT made one for TO247 devices, you may contact him on his GainClone page.
Otherwise JPG's of the PCB's made can be printed, ExpressPCB software downloaded, the file remodelled according to the JPG print and ordered from ExpressPCB.
Maybe someone is interested both in designing the PCB and getting in on a group buy, i am game for a couple of boards.
Hi Prosit,
Wow, 90V.
Mine should be around 77V if I did the math right. Good thing about it, is that I have a bunch of new 80V 15000uf caps that I would like to use for the PSU. 90V would be too high anyway.
I'd be surprized if I could hear the difference from the other 13V, but maybe. I guess I need to learn how to make a PCB sometime. Might as well be sooner than later, I suppose.
Hi jacco,
That was great!
I know, starting with the transformer is a little weird but we all need some sort of inspiration.
The funny thing is, when I asked about which amp to build for my first amp, (in another thread), the Leach amp was suggested. Somewhere along the line I ended up buying ESP boards, thinking they were for a Leach amp.
It wasn't until I started building it that I realized how mistaken I was. Oh well, the P101 is supposed to be a great sounding amp too. I should know in about a week when my heatsinks arrive.
Blessings, Terry
Wow, 90V.
Mine should be around 77V if I did the math right. Good thing about it, is that I have a bunch of new 80V 15000uf caps that I would like to use for the PSU. 90V would be too high anyway.
I'd be surprized if I could hear the difference from the other 13V, but maybe. I guess I need to learn how to make a PCB sometime. Might as well be sooner than later, I suppose.
Hi jacco,
That was great!
I know, starting with the transformer is a little weird but we all need some sort of inspiration.
The funny thing is, when I asked about which amp to build for my first amp, (in another thread), the Leach amp was suggested. Somewhere along the line I ended up buying ESP boards, thinking they were for a Leach amp.
It wasn't until I started building it that I realized how mistaken I was. Oh well, the P101 is supposed to be a great sounding amp too. I should know in about a week when my heatsinks arrive.
Blessings, Terry
Overhere the minimal margin is 15% over Vdc, for 77 Vdc the caps need to be at least 90 Volt types.
The power company in Holland is allowed to have a margin of
+10 % on the nominal 230 Volt.
5 % is added for the increase in voltage of the transformer without a load.
That is the absolute bare minimum, taking in account that simultaneous power surge and zero load is unlikely and caps have a safety margin.
The data of your transformer states 63.5 Vdc at zero load, that is already nearly 90 Vdc.
If the voltage wandwidth of your local power company is 10 % too the minimum you will need for that transformer are 100 Volt capacitors.
Often enough power companies accidentally go beyond the 10 percent margin, so many would go for even higher than 100 Volt types.
The power company in Holland is allowed to have a margin of
+10 % on the nominal 230 Volt.
5 % is added for the increase in voltage of the transformer without a load.
That is the absolute bare minimum, taking in account that simultaneous power surge and zero load is unlikely and caps have a safety margin.
The data of your transformer states 63.5 Vdc at zero load, that is already nearly 90 Vdc.
If the voltage wandwidth of your local power company is 10 % too the minimum you will need for that transformer are 100 Volt capacitors.
Often enough power companies accidentally go beyond the 10 percent margin, so many would go for even higher than 100 Volt types.
acenovelty said:Terry,
80V caps are just a bit skinny for a 77V PS. Take a look at the surge rating. Can't be too careful. Caps make a loud noise when they blow. You don't get to see the magic smoke, just lots of white stuff all over everything.
Prosit
Not to mention that the smell of boiling capacitor juice doesn't go well with other holiday scents.
Bob
/who got to watch hot electrolyte squirt all over his kitchen table/
quick q: 2 transformers, with the primaries connected to each other in series will equal half the effective voltage across each transformer yes? but will derate each transformer to half the maximum loading on the primary side? eg, 2x 500va transformers in series will only be capable of safely delivering 500va?
jacco vermeulen said:
Maybe I'm not looking properly but I couldn't find any PCB's for the Leach on his sight.
Seems like most folks are making their own. Is there any good literature around on how best to make your own PCB's?
I sure wouldn't mind learning how to make them myself.
Thanks, Terry
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