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Old 23rd April 2010, 12:54 AM   #141
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engel,
sir if i'd be constructing this amp, how much would it cost me only for the parts on the main pcb with the power transistors on it???...
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Old 23rd April 2010, 03:42 AM   #142
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around 1k mono board only no psu
the psu cost higher
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Old 23rd April 2010, 05:47 AM   #143
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Originally Posted by apexaudio View Post
If you like sound of B500, but is to much powerfull for Hi-Fi, consider about this 50W amp.
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how about 100w hi fi
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Old 23rd April 2010, 06:02 AM   #144
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I hope this forum help you to learn more English, and more about electronic,
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Thank you very much and God bless you
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Old 23rd April 2010, 08:49 AM   #145
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Quote:
Originally Posted by engel dela pena View Post
how about 100w hi fi
For about 120W/200W, 8R/4R use B500 pcb with two pair outputs on +/-60V rail voltage.

Last edited by apexaudio; 23rd April 2010 at 09:19 AM.
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Old 23rd April 2010, 09:43 AM   #146
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by engel dela pena View Post
bulb is very bright during first power
after the in rush current
bulb start to dimmed
with the power still on and the bulb dimmed, start checking that the circuits are operating correctly.
What is the voltage on the supply rails?
What is the voltage across the output, both DC and AC.
What are the currents flowing in the LTP pair, are they matched?
ETC........
When you are sure all is operating correctly and that nothing is overheating, then it's time to plug straight to mains power.
It will probably blow the mains fuse and maybe the supply rail fuses as well.
Go build a timed relay bypassed soft start circuit to save fuses.
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Old 23rd April 2010, 11:53 AM   #147
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Originally Posted by AndrewT View Post
with the power still on and the bulb dimmed, start checking that the circuits are operating correctly.
What is the voltage on the supply rails?
What is the voltage across the output, both DC and AC.
What are the currents flowing in the LTP pair, are they matched?
ETC........
When you are sure all is operating correctly and that nothing is overheating, then it's time to plug straight to mains power.
It will probably blow the mains fuse and maybe the supply rail fuses as well.
Go build a timed relay bypassed soft start circuit to save fuses.
I hope that some basic measurement was already done.

Last edited by apexaudio; 23rd April 2010 at 11:59 AM.
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Old 23rd April 2010, 12:30 PM   #148
wg_ski is offline wg_ski  United States
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Originally Posted by AndrewT View Post
When you are sure all is operating correctly and that nothing is overheating, then it's time to plug straight to mains power.
It will probably blow the mains fuse and maybe the supply rail fuses as well.
Go build a timed relay bypassed soft start circuit to save fuses.
It takes more than one short plug in on the light bulb before I'm confident enough to throw the switch on it. Initially set the bias so the output stage is barely cracked open and make sure music plays. And that you get graceful dropping of the mains and graceful clipping as the bulb gets brighter. Then set the bias high (maybe 100mA in the output stage) and let it idle for an hour. make sure it doesn't run away. Then go back and re-check everything, re-set the bias to a milliamp or two - and then run it without the limiter.

And when you first fire it up, the first thing you do is check bias stability. Set it to target, and see where it goes after the first hour. If all is well, hook up a dummy load. Parallel the dummy load with a speaker in series with 1k ohms (so you can hear what's going on but not at ear splitting level). Then clip the snot out of it with test tones and music. This is a good time to measure power at 20 Hz, 20KHz if you desire, and hear what it sounds like when you drive it hard. If it takes *this*, then it's ready for serious listening tests.
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Old 23rd April 2010, 12:48 PM   #149
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Originally Posted by wg_ski View Post
It takes more than one short plug in on the light bulb before I'm confident enough to throw the switch on it. Initially set the bias so the output stage is barely cracked open and make sure music plays. And that you get graceful dropping of the mains and graceful clipping as the bulb gets brighter. Then set the bias high (maybe 100mA in the output stage) and let it idle for an hour. make sure it doesn't run away. Then go back and re-check everything, re-set the bias to a milliamp or two - and then run it without the limiter.

And when you first fire it up, the first thing you do is check bias stability. Set it to target, and see where it goes after the first hour. If all is well, hook up a dummy load. Parallel the dummy load with a speaker in series with 1k ohms (so you can hear what's going on but not at ear splitting level). Then clip the snot out of it with test tones and music. This is a good time to measure power at 20 Hz, 20KHz if you desire, and hear what it sounds like when you drive it hard. If it takes *this*, then it's ready for serious listening tests.
There is no bias adjust on this circuit.
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Old 23rd April 2010, 01:08 PM   #150
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by wg_ski View Post
It takes more than one short plug in on the light bulb before I'm confident enough to throw the switch on it. Initially set the bias so the output stage is barely cracked open and make sure music plays.
that's where we fundamentally disagree.
I will not plug in speakers to an untested amplifier.
I will not remove the input shorting link until I know that all the operating quiescent currents are as expected.
I will not set the quiescent output stage current (bias) with the output loaded nor with the input shorting link removed nor when the PSU voltage is below the normal operating voltage, i.e no bulb tester in the primary feed.
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