have finished a set of boards which i am going to supply with +/-55 volt rails. waiting for updates to the bom regarding protection circuit reisistors....any news?
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An externally hosted image should be here but it was not working when we last tested it.
Hi Tony,
did you strip out the drums from front loading washing machines for your PSU? Are those front end voltage regulators? How did you arrange for the increased drive voltage? What voltage did you choose?
The protection circuit values will depend on the (wait for it, it's a long list) Vrail, output transistor, number of outputs, output Tc, output Iq, Re, actual Vbe of protection trs, actual diode voltages, and how close to SOAR YOU want to run. There are probably some I have missed and the relationship between them is mathematically quite complex. I am trying to imagine how a look up table to satisfy some of these variables could be put in the Wiki, but the only solution I had was a spreadsheet. However any mathematical suggestion from me will be put down by others and I have no intention of going down that route again.
One bit of guidance I can give you is that the voltage divider formed by R68 & R28 MUST give a voltage at T10 base less than T10 turn on voltage when in quiescent condition. The output current limit goes up as the voltage at T10 base goes down. Thought of from the opposite end, as the T10 voltage rises to approach the turn on voltage then only a small output current will activate the protection (not what you want).
Your Vrail is similar to original Leach, how about copying his values but remember to check (calculate or measure) the T10 base voltage when not driving the output.
did you strip out the drums from front loading washing machines for your PSU? Are those front end voltage regulators? How did you arrange for the increased drive voltage? What voltage did you choose?
The protection circuit values will depend on the (wait for it, it's a long list) Vrail, output transistor, number of outputs, output Tc, output Iq, Re, actual Vbe of protection trs, actual diode voltages, and how close to SOAR YOU want to run. There are probably some I have missed and the relationship between them is mathematically quite complex. I am trying to imagine how a look up table to satisfy some of these variables could be put in the Wiki, but the only solution I had was a spreadsheet. However any mathematical suggestion from me will be put down by others and I have no intention of going down that route again.
One bit of guidance I can give you is that the voltage divider formed by R68 & R28 MUST give a voltage at T10 base less than T10 turn on voltage when in quiescent condition. The output current limit goes up as the voltage at T10 base goes down. Thought of from the opposite end, as the T10 voltage rises to approach the turn on voltage then only a small output current will activate the protection (not what you want).
Your Vrail is similar to original Leach, how about copying his values but remember to check (calculate or measure) the T10 base voltage when not driving the output.
Can someone please help me with what the input impedence of the leach amp and also the leach super amp are?
Regards
Bowdown
Regards
Bowdown
thanks, i was thinking of copying values from original leach 4.5, the botom pic btw is the power supply i am going to use on the amps, they are nichicon 2 x 22mf/63volts, 2 x 6.8mf/63volts bypassed with 4.7ufd/100volts polyester metalised foil caps.
i will do a regulated front end psu in my next leach diy and will be about 9 to 10 volts higher the the output rails.
thanks for the advise.
bowdown said:
the latest iterations have input impedances at 22k...the original leach super amps had around 50k...
I'm sorry to butt in with a wild question.
What is the minimum voltage rails that I can use with the origeonal Leach amplifier?
I've got a transformer with 32-0-32 rating, would that do?
What is the minimum voltage rails that I can use with the origeonal Leach amplifier?
I've got a transformer with 32-0-32 rating, would that do?
tony: hi, have you bought those boards from Jens?
how much would those cost?
well, pretty interesting
rgds,
hienrich
how much would those cost?
well, pretty interesting
rgds,
hienrich
Jens,
Is the value of R4 in your manual a mistake?
You have it listed as 10R. Should it be 100R?
Leach uses 82R.
Is the value of R4 in your manual a mistake?
You have it listed as 10R. Should it be 100R?
Leach uses 82R.
Anyone of you guys heard of LeClanché capacitors ?
I have a few axial 63volt MKP's of the brand that are small enough to fit the C4-C6-C11 space, wondering how well they are.
I have a few axial 63volt MKP's of the brand that are small enough to fit the C4-C6-C11 space, wondering how well they are.
Thank Jens Rasmussen for his Great design and generosity.
I just placed the order and mailed all the boards out.
The boards were $11 each in the Group Purchase.
I just placed the order and mailed all the boards out.
The boards were $11 each in the Group Purchase.
group buy!
oh, you missed the group buy! it was going on for the last few months....
i got myself 6 boards....
oh, you missed the group buy! it was going on for the last few months....
i got myself 6 boards....
do you mean 550 Pesos for each board?
and are where do we buy heatsinks for these design?
rgds,
hienrich
What are you guys using for inrush limiters for the power supply?
For the last few large amps I had picked up some surplus timer modules from old Xerox ( Looks like a bridge rectifier) but now I have no more. They were great, adjustable timer on delay with just one resistor, input was 120V with a delayed 120V output driving a relay that shorted the current limiter. Alas I have no more.
For the last few large amps I had picked up some surplus timer modules from old Xerox ( Looks like a bridge rectifier) but now I have no more. They were great, adjustable timer on delay with just one resistor, input was 120V with a delayed 120V output driving a relay that shorted the current limiter. Alas I have no more.
hienrich said:
it costs me three times that amount to get the boards to my place!
heatsinks can be purchased from conrad engineering in australia for about A$100 a pair of 350mm x 150mm x 50mm thru fedex.
but i am going to diy using a 300 x 150mm x 6mm using ga16 aluminum plates bent inot L's and attached to 6mm plate.. will cost substantially less..
i use a 10ohm 50 watt resistor then a time delay relay to short it out in about 3 secs, timer is a discrete transistor driving the relay.
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