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Old 11th May 2004, 11:08 AM   #11
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Quote:
Using chipamp as opamp hasn't any sense. IMHO.
Its quite true. Opamps are designed for its uses, chipamps also designed for certain purpose.
But very curious what will be the sound, if we use chipamps in the place of opamps. Will it result in something drastic in sound reproduction?

People in audio are known to use strange things. Some tube that are not inteded for audio use, can produce very good audio power amp. Nelson Pass uses Lateral mosfet, which the factory said is not suitable at all for audio. Gammut amp uses single gigantic mosfet (industrial mosfet) for its output. Mr.Pass himself has conducted strange experiment with opamps, using tons of it (I forget, is this lead to power amp, or just very powerful preamp), and experimented to put 10K resistor from opamp's output to negative rail, to force the opamp to work in class A.

Just wondering. Has anyone tried chipamp for opamp?
Is chipamp has stability like opamp, so it can be treated like opamp purpose (like make buffer with chipamp, gain=1)?
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Old 11th May 2004, 11:10 AM   #12
matjans is offline matjans  Netherlands
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Default why would you use a chipamp as an opamp?

(power) chip amps are designed to be output devices (hence the "power"). They are in most cases beefed up opamps anyway.

So why not just use some voltage regulators and a normal opamp?
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Old 11th May 2004, 11:48 AM   #13
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"Is chipamp has stability like opamp, so it can be treated like opamp purpose (like make buffer with chipamp, gain=1)?"

I believe the chipamp is not stable with a gain of 1.
Minimum gain is 10.
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Old 11th May 2004, 04:48 PM   #14
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The OPAs (541, 548, 549...) are stable at gains of 1.
But using them for a pre?
Have you though of the PSU requirements of doubling the number of chips?
Much less work and much cheaper, and much better to use a good signal op-amp.
Or no op-amp at all, adjust the gain on the chiamp.
But I tend to prefer the GainClone with a pre, or at least with a good input (op-amp) buffer.
Sounds just that little better to me, believe it or not.
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Old 11th May 2004, 05:35 PM   #15
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http://focus.ti.com/docs/prod/folders/print/opa445.html
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Old 11th May 2004, 06:14 PM   #16
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What do you all think of FET input op-amps for pre-amp use?

Something like Texas Instruments TL072, or On-semi's MC33078, or Nationals LF412 or LMC662?
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Old 12th May 2004, 01:22 PM   #17
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Quote:
Originally posted by lumanauw
No, no, I do not intended to use opamp at all. Infact I wanted to use chipamp for opamp use. Why? In another thread (MOX thread) , someone built active Xover using diyopamp, the supply is more than +/-30V (opamp uses +/-15V). I think why dont we use chipamp as opamp?
Three reasons

1. Cost The chip amp will cost more that a good low level opamp.

2. Distortion Almost a any low level opamp will have better distortion performance that a chip amp in that application.

3. Noise Good high performance opamps have a much lower noise floor than a chip amp.

Just because an ideas goofy doesn't make it bad, but it doesn't make it good eather.

Later BZ
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Old 12th May 2004, 02:00 PM   #18
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Quote:
Originally posted by officeboy
What do you all think of FET input op-amps for pre-amp use?

Something like Texas Instruments TL072, or On-semi's MC33078, or Nationals LF412 or LMC662?
FET input amps are OK, but those types you mention are old, should work OK but not outstandigly.

More modern FET types, like the OPA2604 or AD825, should do better.


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Old 12th May 2004, 02:02 PM   #19
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Ok, lets make it reverse. Does anyone has built series-parrarel opamps as chipamps? It should be better than chipamps, if the arguments are like that.
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Old 12th May 2004, 02:21 PM   #20
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No, not really. I have done the parallel opamp thing for headphone amps but more that that and the size of the circuit board starts to become a problem. To get 1 watt out of TLO72s for example would require about 25 chips or 50 opamps in parallel per channel.

Its best to use a part for it's intended purpose and range of operation. The designers made the part that way for a reason.

The trick is to choose the best part you can find and then use it in the most suitable way for that part. That's the secret.

Later BZ
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