Hi Carl this is a nice board, but Im wondering if it would be better with space for large diodes as the bridge you have doesnt look like it will cope with a 1000watt leach amp. Also CRC is a better approach and the Rs can allways be replaced with wire if the user doesnt want to use them.
Im not sure if I will be buying it depends on what the power supply ends up looking like, I have some big cans upto 75V, if I get into 100V territory I may be interested🙂
******* Hell.
A 1kVA 65+65Vac transformer has a maximum secondary AC current into a resistor load of 7.7Aac.
The maximum output from a capacitor input filter is approximately half this, i.e. ~3.8Adc.
Your are overloading the transformer by ~+320%
I can tell from the lack of specify component values that this spreadsheet is not for a VI limiter.
I suspect it is for the standard Leach two slope current limiter.
I generally specify the units to avoid confusion.
I rarely specify Peak Power (Wpk). I much prefer to state Vpk and Apk, (go to post483 to see an example).
If you see me quoting V without the appropriate subscripts then I expect to be pulled up for that carelessness.
A 1kVA transformer is designed and rated to deliver 1000W into a resistive load.
The Peak voltages and Peak currents can be very different dependent on the duty cycle and the load.
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Vpk and Apk is better when discussing design, because they are what is dissipated and real power to deal with.
Dealing with reactive loads is really diffcult and manufacturers specify power into resistive loads.
The original has reference to the components in Jens 6 transistor version so it should be relevant.
Are you certain this is not correct?
this is because power into a resistive load is all that counts......reactive components do not dissipate power, they store energy....
currents and voltages required by reactive components must pass or flow thru copper wires at the same time as that of power into resistive loads......
If one rail is not delivering current then wont the other have twice the current delivery capability?
It can deliver 1KVA, it doesnt matter where or how, that saits only limitation I would expect.
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In the example of a woofer, does the inductor not convert power into movement and there fore consuming power?
Carl,
I like the very neat organized nature of using your power supply board. I had the same comment concerning the diode bridge that Luke offered. What size and specification diodes had you planned on installing? We will need something good for 50 amps instantaneous, this is from experience not calculation, to charge all that capacitance. Of course a low voltage softstart would make everything less harsh. How many you got and what will the damage be for 4 boards?
Luke, I am having problems with this protection circuit. It looks like Jens was planning on building his amps with 58 volt rails. I will be using 2 1kw trannies with approximately 70-74 volt rails and regulated frontend. After rereading Leach's website on this subject it seems there are 6 resistors which are controlling the two transistors which cut off the output signal. However, two of these resistors it looks like are the main feedback control. Increasing the resistance in this area SHOULD delay the protection circuit cuton. Or could we not use the values in the Super Leach for our amps. I have not found a schematic of the exact circuit on the Super Leach just the Low Tim amp.
Dr. Leach provides a nice little graph plot, theoretical he says, for this circuit. The values for cuton seem to be in an area approaching 15 amps at our voltages. I can not see that much current being supplied to my speakers anytime soon.
By the way where is Jens these days? He has four of these boards himself to build.
Tad
I like the very neat organized nature of using your power supply board. I had the same comment concerning the diode bridge that Luke offered. What size and specification diodes had you planned on installing? We will need something good for 50 amps instantaneous, this is from experience not calculation, to charge all that capacitance. Of course a low voltage softstart would make everything less harsh. How many you got and what will the damage be for 4 boards?
Luke, I am having problems with this protection circuit. It looks like Jens was planning on building his amps with 58 volt rails. I will be using 2 1kw trannies with approximately 70-74 volt rails and regulated frontend. After rereading Leach's website on this subject it seems there are 6 resistors which are controlling the two transistors which cut off the output signal. However, two of these resistors it looks like are the main feedback control. Increasing the resistance in this area SHOULD delay the protection circuit cuton. Or could we not use the values in the Super Leach for our amps. I have not found a schematic of the exact circuit on the Super Leach just the Low Tim amp.
Dr. Leach provides a nice little graph plot, theoretical he says, for this circuit. The values for cuton seem to be in an area approaching 15 amps at our voltages. I can not see that much current being supplied to my speakers anytime soon.
By the way where is Jens these days? He has four of these boards himself to build.
Tad
You're skipping that a powersupply is a tag team operation.
The transformer delivers the power to the load and recharges the capacitors under normal circumstances, but both transformer and caps deliver the juice during peak operation.
Somewhat comparable to the drive of a hybrid car.
Yes but these are tested with sine waves continuously. The Tx is delivering real current. But Im not talking just about the power supply. If you look at this type of amp with high rails, its transistors can only deliver a small amount of current because of the SOA curves. Am I missing something?
And the other thing is, with high rails class A, the amp will consume hundreds of watts for just a few watts of class A power.
Im rethinking if I want to do a class A with regulated output now, but it sure is sexy🙂
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Luke,
A little note from Leach: Component Change: R37 through R40 - 680 ohm (changed from 470 on 4/4/2). This change makes the protection circuit less sensitive so that the amplifier can drive more current into lower impedance loads. I made this change after a correspondent told me that he built the amp to use with his home built electrostatic speakers which have a very low impedance. He said the amp sounded distorted. He removed the protection circuit and that solved the problem. He said that he has had no problems with the amp with the protection circuit removed. My original amp had no protection circuit, and I never had any problems with it.
A good place to start.
Tad
A little note from Leach: Component Change: R37 through R40 - 680 ohm (changed from 470 on 4/4/2). This change makes the protection circuit less sensitive so that the amplifier can drive more current into lower impedance loads. I made this change after a correspondent told me that he built the amp to use with his home built electrostatic speakers which have a very low impedance. He said the amp sounded distorted. He removed the protection circuit and that solved the problem. He said that he has had no problems with the amp with the protection circuit removed. My original amp had no protection circuit, and I never had any problems with it.
A good place to start.
Tad
in the case of the woofer. electrical current causes the motor movement of the cone/voice coil assembly.... but most of the power is dissipated in the voice coil due to its dc resistance....power input to the woofer is converted to heat and sound.....
Hi tad,
firstly, I would like someone to confirm if this is ok to use before you do.
Andrew said that Jens uses a different limiter than Leach so his calcs wont work if this is the case. If this calculator is ok, then I have done some calcs for you. I have assumed you are using the mjl3281 and 0.47 ohm emmiter resistors, if you have mjl4281 then change the device wattage to 230.
Also change the emmiter resistors value if your using a different value.
Hope this is clear, otherwise a chat program may help. Does this forum offer chat?
whats the typical resistance of a speaker coil, I would expect it to be very low. If a theoretical speaker were a pure inductor would it not consume power?
Hi Tad, I assume your talking about Dr Leaches schematic in regard to R37 through R40? In Jens 12 output version they are transistors R15,R16, R18, R19, R22, R26 and R66 - R70.
But there are other values you must change, R42 and R36, these are 100 as set by Jens. R12 and R64 set by the spreasheet.
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