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Old 10th July 2014, 05:28 PM   #1
Letcon is offline Letcon  Argentina
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Default The leach amp 200w

Hello. This is my first post on this forum.
We built two modules leach amplifier, 200W at 4ohm. The Leach amp 200W amplifier
I am happy, but I want to upgrade to two things.
Let's implement a clipping indicator and limiter and protection similar to ODEP, the Crown.
I mean if air routes are blocked, when it reaches a certain temperature the radiator, it reduce the power delivered to the speaker, to a low level, in any case not to interrupt. That clear up the radiator temperature reaches back to a value considered safe.
I noticed that it would be more easily obtained with a microcontroller, but I know almost all the microcontrollers.
Can you help me with a limiter scheme and a scheme for ODEP adapted to leach?
Thank you dear colleagues.
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Old 11th July 2014, 02:15 AM   #2
dangus is offline dangus  Canada
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Elector published plans for a good clipping indicator back in the '90s. It should be in the audio collection CD-ROM.

Adding limiting will compromise audio quality since you'll need a VCA or something. Better to just not put coats over the amp rack.
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Old 11th July 2014, 05:10 AM   #3
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Want to improve the sound of the amp...

Gajanan Phadte
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Old 11th July 2014, 07:15 AM   #4
Letcon is offline Letcon  Argentina
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So the limiter quit.
I was looking in elector this clip indicator.
With my little ODEP system can someone help me, please?
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Old 11th July 2014, 09:07 AM   #5
Letcon is offline Letcon  Argentina
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You may not relay something that at a certain temperature to pass amplifier input through some resistant ... or what?
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Old 11th July 2014, 11:06 AM   #6
AndrewT is offline AndrewT  Scotland
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I built the Leach Clone using a three pair output stage.
It gave maxima of 170W into 8r0 and >300W into 4r0 using a 40-0-40Vac transformer.

It was rated at 170W into 8ohms.
It did not meet my SOAR criteria to be rated for 300W into 4ohms, But it does meet my criteria for 6ohms loading. Can't recall the number since I don't have any speaker rated at less than 8ohms.

If I were to reduce the transformer from 40-0-40Vac to 35-0-35Vac, it would become 4ohms capable and easily meet a 200W into 4ohms rating.

The only additional protection required would be DC detect and speaker isolation. Heatsink overtemperature shut down. Maybe supply rail fuses that blow more quickly than the close rated mains fuse.

Oh and add in the missing resistor to the protection circuit to convert the current limit protection to IV protection. The Clone has this extra resistor.
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Last edited by AndrewT; 11th July 2014 at 11:12 AM.
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Old 11th July 2014, 02:55 PM   #7
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Rod Elliot published a useful clipping indicator. Power Amp Clipping Indicator

A simple thermostat switch in the mains supply will protect the amp from high temperatures. Look at the bottom of the page http://www.mouser.com/catalog/catalogusd/647/2290.pdf
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Old 11th July 2014, 07:22 PM   #8
Letcon is offline Letcon  Argentina
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Yes, but I want to work as protection.
When the heater reaches a certain temperature, to reduce the signal, up to 10-15% until the radiator cools again at a temperature considered safe.
Can you help me with such a scheme?
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Old 11th July 2014, 08:33 PM   #9
CBS240 is offline CBS240  United States
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Use a fan. Have the fan come on at a higher temperature, then turn off at a lower temperature. Theory is that the fan does not normally run but if the amp is playing loud enough to heat the radiator that much, then you won't hear the fan. Use a couple of comparators and a thermistor/voltage divider to set the limits for turn on, turn off. There is a circuit diagram on Rod's site somewhere.
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Old 11th July 2014, 09:35 PM   #10
Letcon is offline Letcon  Argentina
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So what I want from this protection?
When you turn on the amp, turn vetilatoarele about 5 seconds at maximum speed.
Then return to the control function of temperature, speed increases proportionally with temperature.
If it comes with all the fans at a high temperature, say 95 degrees Celsius, the protection limit signal from the amplifier to the power drop, about 10-15% of maximum power.
After the final floor fans cool up to a certain temperature, what we consider safe to return again depending on temperature control, speed proportional to the temperature increase.
Now I hope I did better understood.
Excuse the English, I'm not good pric.
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