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Old 5th June 2004, 04:19 PM   #1
malan is offline malan  Zimbabwe
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Question superamp with +127 0 -127

can I use leach superamp with +127 0 -127 volts for getting more power at 8 and 4 ohms.like only increasing the r13-14 and 82 ohm pairs.
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Old 5th June 2004, 06:48 PM   #2
jaycee is offline jaycee  United Kingdom
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No. You would roast pretty much all of the transistors by exceeding their Vceo ratings by doing so.
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Old 5th June 2004, 08:41 PM   #3
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If you absolutely need more power and absolutely wants to use the Leach super amp, the best (and most save) way to get doubble power is to make two more Leach's and bridge them
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Old 5th June 2004, 08:48 PM   #4
sss is offline sss  Israel
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u mean one more leach
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Old 5th June 2004, 10:45 PM   #5
djk is offline djk
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"can I use leach superamp with +127 0 -127 volts for getting more power at 8 and 4 ohms.like only increasing the r13-14 and 82 ohm pairs."

Essentially correct.

Q5 and Q6 would need to be changed to 2N540X and 2N550X types. Q16 and Q17 will have to go to a different part too, and lots, and lots, and lots more (high voltage) outputs.

Far better would be to build the Super Leach.

http://users.ece.gatech.edu/~mleach/superamp/

Similar changes will need to be made here too, but the series connection really reduces the SOA burden on the drivers and outputs.

What you really should do is order a service manual for a Crest 8000, one of the best pro sound amps that has been around for a long time. The schematic looks just like the Super Leach with some extras, inrush current limiting, relay and DC sense, things of that nature.

http://www.crestaudio.com/products/p...es/pro8001.cfm

ACDs idea has merit too. My Leach amplifiers run on ±63V and do 600W/8R bridged. I have three pair of MJ15011/12 for outputs, for a new build I would use the MJ21193/94.
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Old 20th June 2004, 02:33 PM   #6
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djk

I'm interested in your leach bridge. can you share me your
bridge phase inverter schematic & pcb.?

ric
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Old 20th June 2004, 03:26 PM   #7
Electrons are yellow and more is better!
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I'm closing this thread. 256 volts and a huge transformer is dangerous and also something only for experts in amplifier design. If you don't know so much about the difficulties I think you should try other solutions.

Reconsider your need for power.127 volts can give you 2000 watts. Do you need that?

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Old 20th June 2004, 04:43 PM   #8
Electrons are yellow and more is better!
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Ok, I'll open this thread (due to some pressure) again BUT don't try this at home.

Only for very experienced designers.



A bridge connected +-127 Volts is technically madness. It's like Glenn something from New Zeeland who thought about a 20 kW amp... but it did never leave the computer.
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Old 20th June 2004, 04:55 PM   #9
Electrons are yellow and more is better!
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Quote:
Originally posted by Ricdelros
I'm interested in your leach bridge. can you share me your
bridge phase inverter schematic & pcb.?
djk uses only +- 63 volts so is it about this voltage it's OK.

Bridge connected +-127 volts gives you 2 x 4 kW and 2-4 kW heat and need a 8-16 kVA transformer..... and three phase connection....and a huge case.
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Old 20th June 2004, 05:42 PM   #10
Eva is offline Eva  Spain
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I'm just curious :

What speakers are you planing to drive?

Most drivers [even the big ones with 4" or 5" voice coils] start to 'sweat' when driven with 600W just before clipping and in my experience 1200W is the practical limit for 18" or 21" drivers

To get 1200W into 8 ohms +-150V rails would be required but with so high rails also class G or H operation [ie: +-50V +-100V +-150V] is required in order to mantain dissipation and power consumption in reasonable numbers and to keep under control the costs and the number of output devices required [look for QSC schematics, 'EX4000' model may be a reference]

In my oppinion, if you want more SPL and have reached 500W, the best solution is not to add more power but to add more drivers and more amplifier channels. Increasing the number of drivers also increases efficiency so theoretically dual drivers with 500W + 500W produce as much SPL as a single driver with 2000W

Proper horn loading may also boost the SPL by 10dB, and this is a serious thing since it means that 100W of input in a horn loaded system may produce as much SPL as 1000W of input in a direct radiating system

If you want to produce some SPL outdoors, the absolute minimum number of bass drivers or bass horns to place toghether is four [mono bass or four at each side] due to spatial loading issues. Groups of less units will suffer from very poor efficiency
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