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Old 27th July 2007, 04:38 PM   #1
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Default BPA200 without DC-servo

Hi
How much sounding BPA200 without DC-servo is worse?
How to adjust offset voltage without servo?
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Old 28th July 2007, 12:53 PM   #2
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Hi,
The output offset is a factor times the input offset current times the difference between the two input source resistances.

One can adjust the resistors attached to the non-inverted input pin. Trial and measure the error. Or add a trimming pot across the [standard resistor+20%]. The resistor may have to be increased rather than decreased.

The slight disadvantage of the integrated circuit power amp is the range of temperature that the front end amplifier has to withstand during normal (and abnormal) operation. This causes more drift than in a similar non integrated (discrete) amplifier.
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Old 28th July 2007, 09:05 PM   #3
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Quote:
Originally posted by AndrewT
Hi,
The output offset is a factor times the input offset current times the difference between the two input source resistances.

One can adjust the resistors attached to the non-inverted input pin. Trial and measure the error. Or add a trimming pot across the [standard resistor+20%]. The resistor may have to be increased rather than decreased.

The slight disadvantage of the integrated circuit power amp is the range of temperature that the front end amplifier has to withstand during normal (and abnormal) operation. This causes more drift than in a similar non integrated (discrete) amplifier.
Thanks for an explanation, now I understand why in AN-1192 use 0.1 % tolerance resistors
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Old 28th July 2007, 09:20 PM   #4
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I have one more question
An input buffer is required because of the low input impedance from paralleling of the inputs. If I am going to use the preliminary amplifier (Velleman-kit K8020) is necessary input buffer?
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Old 4th August 2007, 09:26 PM   #5
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Nobody can answer ?
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Old 4th August 2007, 10:01 PM   #6
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I would say yes, If the input resistors are less than 22K (I’m assuming you are using inverted amps).


22K/2=11k

Specifications

"Output load impedance: 10K or higher”
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Old 5th August 2007, 07:27 PM   #7
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Quote:
Originally posted by jaudio
I would say yes, If the input resistors are less than 22K (I’m assuming you are using inverted amps).


22K/2=11k

Specifications

"Output load impedance: 10K or higher”
Thanks!
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Old 5th August 2007, 07:36 PM   #8
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Quote:
Originally posted by jaudio
I would say yes, If the input resistors are less than 22K (I’m assuming you are using inverted amps).


22K/2=11k

Specifications

"Output load impedance: 10K or higher”
I'm going to use the 20.5K 0.1% resistors, input resistance turns out 10.25K.
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Old 6th August 2007, 01:27 AM   #9
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Quote:
Originally posted by jaudio
I would say yes, If the input resistors are less than 22K (I’m assuming you are using inverted amps).


22K/2=11k

Specifications

"Output load impedance: 10K or higher”

If you use a chip like the DRV134, you can do away with the buffer. If you are going totally inverted (To trim away dc offset), you have to use a single end to differential chip or you could try something like http://sound.westhost.com/project51.htm

Can you post your schematic?
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Old 6th August 2007, 06:14 AM   #10
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Quote:
Originally posted by jaudio



If you use a chip like the DRV134, you can do away with the buffer. If you are going totally inverted (To trim away dc offset), you have to use a single end to differential chip or you could try something like http://sound.westhost.com/project51.htm

Can you post your schematic?
I use AN-1192 schematic BPA200
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