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Old 23rd March 2013, 11:57 PM   #1
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Default Good chip amp for driver measurements.

I need a chip amp, for general purpose, that would be used while testing new speakers or measuring frequency response of new drivers or for the breakin of drivers.

So I am expecting power rating of 10W @8E or more.

Good THD rating, flat response between 10Hz to 30KHz.

At first thought I had LM3886 in my mind but not sure if its worth. Also suggest any other that can be used.


EDIT: I just saw LM1875, Is it good enough? would you suggest it ?
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Last edited by Aucosticraft; 24th March 2013 at 12:14 AM.
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Old 24th March 2013, 08:50 AM   #2
JMFahey is offline JMFahey  Argentina
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In a rising power scale: TDA2030 LM1875/TDA2050 LM3886 TDA7294

They are all very good and meet or exceed your specification, I'd use LM3886

Chip cost is nil, compared to PCB/PSU/transformer/cabinet/hardware .
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Old 24th March 2013, 12:30 PM   #3
PetruV is offline PetruV  Romania
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tda2003 if you use single supply
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Old 24th March 2013, 01:58 PM   #4
johnr66 is offline johnr66  United States
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Quote:
Originally Posted by PetruV View Post
tda2003 if you use single supply
Poor advice. You would have to use two TDA2003 ICs in a bridge design and operate near the max Vs. to get the 10 clean watts of output into an 8 ohm load.

TDA2050/LM1875 is the better suggestion. You may need to adjust some values of components to be sure you are getting the full response range you need.
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Old 26th March 2013, 05:57 PM   #5
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Personally I would use the LM3875 over the 3886 unless you want high current delivery. It doesn't have a ground on the chip and that makes for fewer mistakes and an easier layout.
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Old 27th March 2013, 04:49 PM   #6
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Thanks friends,

After reading you all I think I should go for LM3875. as this amp should serve my purpose.

Higher rating amp would add cost of powersupply too. I am still not sure if I can get flat response from this chip in frequencyband of 10Hz to 30Khz. ( not about the input filters)

If any body has a idea, please share.
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Old 27th March 2013, 04:56 PM   #7
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Quote:
Originally Posted by Aucosticraft View Post
Thanks friends,

After reading you all I think I should go for LM3875. as this amp should serve my purpose.

Higher rating amp would add cost of powersupply too. I am still not sure if I can get flat response from this chip in frequencyband of 10Hz to 30Khz. ( not about the input filters)

If any body has a idea, please share.

"if I had to build a chip amp" I would build an LM3875. but, Why don't you try a discrete amp class A or class A/B!
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Old 27th March 2013, 09:17 PM   #8
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Quote:
Originally Posted by Aucosticraft View Post
Thanks friends,

After reading you all I think I should go for LM3875. as this amp should serve my purpose.

I am still not sure if I can get flat response from this chip in frequencyband of 10Hz to 30Khz. ( not about the input filters)

If any body has a idea, please share.
30kHz - in its stride! In your application I would probably put a second order low pass Butterworth at a frequency above this so you know it's flat in your band of interest, rather than have it degrade by itself. Say at 80k. That is, if -0.2dB at 20kHz is too much off flat for your purposes - which is probably what you would get with a single pole. It would be a good microphone though, to make this important.

Last edited by ChristianThomas; 27th March 2013 at 09:21 PM.
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Old 28th March 2013, 07:15 PM   #9
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Originally Posted by lanchile View Post
"if I had to build a chip amp" I would build an LM3875. but, Why don't you try a discrete amp class A or class A/B!
discrete amp could have been my choice but, I wish to keep it simple and easy to repair ,if in case.

Quote:
Originally Posted by ChristianThomas View Post
30kHz - in its stride! In your application I would probably put a second order low pass Butterworth at a frequency above this so you know it's flat in your band of interest, rather than have it degrade by itself. Say at 80k. That is, if -0.2dB at 20kHz is too much off flat for your purposes - which is probably what you would get with a single pole. It would be a good microphone though, to make this important.
Well, I believe LM3875 don't need compensation if used as shown in reference application. I am not sure about the phase errors. But I hope it would perform flat.
Adding extra RC filter will disturb the phase depending on frequency. And this is not good for measurements.

Correct? So, I thought I would avoid any input filter. And hope it would be stable, and flat in the given frequency response also, would have negligible phase error.
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Old 28th March 2013, 08:13 PM   #10
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Originally Posted by Aucosticraft View Post

Well, I believe LM3875 don't need compensation if used as shown in reference application. I am not sure about the phase errors. But I hope it would perform flat.
Adding extra RC filter will disturb the phase depending on frequency. And this is not good for measurements.

Correct? So, I thought I would avoid any input filter. And hope it would be stable, and flat in the given frequency response also, would have negligible phase error.
No, it doesn't need compensation, though an L//R and a Boucherot cell are a good idea, and can be lightly done.

I did mean having an input filter, which is something I would do largely to define the shape. (It would be a bit risky to trying and do it on the amp itself, I suspect.) But I don't think you see the effects of the amp's own parasitics until beyond 200k, so yes it would be absolutely flat. Certainly flatter than many audio power amps. (And that means phase, too.)

I can't see any reason why you would need (or want) a discrete design. You mostly get distortion of around 0.02% or below and you also have much more open loop gain to play with than you could probably find easily by yourself.
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