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Old 22nd March 2005, 02:15 AM   #1
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Default My first pre-amp for my LM3886GC

I built this very simple preamp using a circuit very similar to the CMOY headphone amp.

The input impedance is 100K and the input caps are 1uf giveing a very low corner frequency for input, and I cannot here any distortion.

I have the gain set at 6.

There is a rat shack 100K pot for volume control that works surprisingly well.

I have tried a couple of opamps so far and here is what I thought of them:

1) OPA228 very good! A little cold sounding with some of the classical music I listened to, maybe a touch edgy.

2) RC4560 WOW!!! I love this opamp, much warmer,fuller, but still highly detailed. I would choose this over the OPA228 right now.

Has anyone else used the RC4560? I just got the samples last week. It looks like a newer opamp. The specs are good. The only down side over the OPA228 is slightly higher THD.

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Old 22nd March 2005, 03:36 AM   #2
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Interesting...
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Old 22nd March 2005, 04:19 AM   #3
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U need to solder the IC.
RCA phono connectors are prefered choice.

Else u will have problems later.

Gajanan Phadte
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Old 22nd March 2005, 12:34 PM   #4
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Quote:
U need to solder the IC.
Maybe I will will after I test the dozen or so opamps I have on my desk. I am not sure why it would make a difference with a good socket.


Quote:
RCA phono connectors are prefered choice.
RCA jacks are going in tonight. I set it up for headphone first to give the opamps a test.
Cheers!
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Old 22nd March 2005, 07:37 PM   #5
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The OPA228/2228 is a great opamp in gains greater than five with low current draw (read: battery powered). However, I don't believe it's a FET input amp. You might get better performance out of a number of other chips (AD8065, AD8610/20, OPA2132/627/637, etc.).

Without knowing more about your feedback and resistor values, I can't really make any more suggestions, other than to check the datasheets to make sure these guys are stable at whatever gain setting you're using.

Mike
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Old 23rd March 2005, 04:05 AM   #6
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Quote:
Russ White wrote
I am not sure why it would make a difference with a good socket.
The contacts, whatever they are made from, will tarnish due to climatic effects like humidity. This may be one of the reasons why audiophiles reconnect their connectors which improves sound due to contact cleaning by rubbing. Moreover the IC when soldered, the pcb copper acts like a small heatsink although in this case it may not be necessary.

Gajanan Phadte
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Old 23rd March 2005, 04:29 AM   #7
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Quote:
The contacts, whatever they are made from, will tarnish due to climatic effects like humidity.
Yep, good thinking. When I settle on an opamp I really like I will solder it to the board. Thanks.
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Old 23rd March 2005, 09:47 AM   #8
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Could you post the schematics?
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