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Old 8th March 2002, 09:51 PM   #1
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Default Reducing Super Leach amp power

How could I reduce the power from original 270W to about 200W per channel. I would like to keep all 8 transistors per side.

I was thinkinkg of reducing the rail voltages down( but I am afraid of earlier clipping) , so am I on the right way?

Thanks
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Old 8th March 2002, 11:19 PM   #2
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Let me see if I understand this... you wish to reduce output power, but you don't want to limit the rail voltages because you're concerned about clipping, and you don't want to reduce the number of output transistors?

May I ask why you want to reduce the power output in the first place? I'm not being snide, just trying to figure out what are your constraints.
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Old 8th March 2002, 11:42 PM   #3
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I want to reduce power output to about 200W to protect my speaker from transients. I know if i put down the rail voltages, the output power would decrease. But if I go to low with voltages, amp would clip at some voltage.

So should I reduce the voltages down and observe the output of amp on osciloscope?

Or what if I reduce the gain?

Thanks!
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Old 9th March 2002, 03:43 AM   #4
bawang is offline bawang  Malaysia
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Talking Leach amp option?

Why not build the Leach amp at 120W/channel into 8 ohms? Remember that doubling or reducing the power by half only gives a difference of 3dB in SPL given the same loudspeakers. And at 4 trannies per channel, it's a hell of a lot cheaper too......
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Old 9th March 2002, 12:10 PM   #5
djdan is offline djdan  Romania
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You can reduce rail voltage to +/- 68V (no load) for 200w/8ohm.
If you don't like clipping your speakers run happily for long time .
For example : If you have high end speakers rated at 100w/8ohm, rms power , it can work without problems at 250w rms with normal musical program if you do not run in clipping.

For more info about this subject take a look to JBL site:

www.jblpro.com/pub/technote/spkpwfaq.pdf

Best regards ,
Dan
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Old 9th March 2002, 01:03 PM   #6
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Why not clip the input? Calculate the input peak amplitude that will give 200W average into your speakers. Then use diodes to clip the input signal. This way you can easily remove the limiter if you get more powerful speakers. You can apply the limiter in the amp or in the pre-amp.
BAM
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Old 9th March 2002, 04:34 PM   #7
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I can confirm this - a previous system I had was 4 cabinets each nice hifi 12" 3way, hanging off 500+500 rms/4 ohms pro audio amp.
Each cabinet was rated 100w, but I ran this system for 1 1/2 years without any burnt drivers.( or burnt ears)
CD player wired direct into amp caused intermittent clip lamps on some tracks.
I often ran this at full power for extended period.
I think you are best to build the amp as specified and if you are worried turn down the volume a bit.
You will be surprised how much CLEAN over drive that you can get away with, without damage.
Choice of music is a little critical when way over driving - huge bass tracks may need to turn down a bit.
Let your ears be the judge.
A big amp always sounds better than a smaller one.

Regards, Eric.
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Old 10th March 2002, 11:33 AM   #8
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Tkanks for some advices!

I am using B&W 602 S2 speakerswhich have recommended amplifier power 50 - 120W 8Ohm.

Would It be OK to put 270W Leach amp to work with my speakers?
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Old 10th March 2002, 01:07 PM   #9
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Hi Supernet, I have been and had a look at reviews of your B&W speakers.
Unfortunately 270 rms is probably a little over enthusiastic for a 7" 2 way cabinet.
I used to have much modified Yamaha NS-20 8" 2 way, rated 40w rms, 80w program hanging off 150 rms/ch fed directly from cdp, using power amp input level controls.
Attenuators at max gave brief intermittent clip, but not really sonically noticeable.
Sound was bloody great, but speakers were sensitive to loading -ie all the house doors and windows, and internal doors and drawers etc needed to be closed when running at full power.
If you are running at these powers, signal MUST be perfectly clean or else damage will happen.
In this experience I ran this system for 2 years without damage, but I advise not to go much power beyond this.(150 rms clean)
Add another pair of cabinets and you'll get the sound and power handling that you want.
If you can discipline youself to hear damaging overload and just avoid it, such an amplifier I am sure would make a wonderful system.
Regards, Eric.
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Old 10th March 2002, 09:16 PM   #10
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Thanks Mrfeedback.

Now I am using a Leach amp. It is powered with Musical Fidelity X PRE tube amp. The sound is wonderful, but preamp has only 6dB gain.So when I listen from CD player got my volume knob (normaly) at "12.00" position. I could almost turn it to the max and sound become a little hard, so I got some power in reserve.
So If a powered my speakers with Super Leach amp I would have plenty of headroom and higher damping factor and of course much better bass control. (although, I have never seen yet any power amp with such bass control.

Am I right?
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