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Old 17th April 2003, 12:06 PM   #1
Electrons are yellow and more is better!
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Default AD8610, OPA134, OPA627, BUF634 SMD headphone amp

Today I have both tested and listened to OPA627, OPA134 and AD8610 (at +- 15V, didn't die!). Electrically AD8610 is outstanding, can handle too large signals excellent, offset at the out 0.046 mV cold and 0.079 mV warm!!! The OPA627 can't handle large signals at high frequencies very well. It may be better if the signal is DC connected.

OPA134 is also excellent but have slightly higher offset, 2.5 mV at the output. I have also tested the buffer at medium speed mode and high speed mode, no visible or audioable change. Soundwise all opamps do their work very good. I (my ears) can't hear any major difference.

I notice also that groundplane pcb cools rather good. BUF634 in high speed mode gets rather hot. Also the regulators are rather well cooled.

Some guy here (forget the name right now) has elevated AD8610 to the skies and must admit, it's a good opamp!
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Old 17th April 2003, 12:33 PM   #2
ALW is offline ALW  United Kingdom
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Default Ad8610

Quote:
Some guy here (forget the name right now) has elevated AD8610 to the skies and must admit, it's a good opamp!
Might have been me - it's the best I've heard, bar none.

The AD8065 is worthy of investigation too - it has even better capacitance driving capabilities than the AD8610, and lower distortion at HF.

Try them, I'd be interested to know your views (I've not compared in detail).

Wouldn't run it for long @ 15V though, the XFCB process really is restrictive, the 8065, IIRC, is +/-12 - lower than the +/-13 of the 8610.

Andy.

P.S. Are you selling those boards?

P.P.S. can I be so bold as to suggest there's something wrong if you can't hear the difference between the two bandwidth modes, BTW, it's obvious to me, the WB mode being better. Maybe it's the yellow electron clouds, clouding judgement
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Old 17th April 2003, 12:50 PM   #3
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Per-Anders,

did you assemble three PCBs using different op amps, or how
did you compare them since you use SMD?
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Old 17th April 2003, 01:34 PM   #4
dimitri is offline dimitri  United States
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Dear Per- Anders,
Have you tried to listen/measure your QRV-04 amp without the feedback around the BUF634 (feedback resistor switched from BUF634 output to BUF634 input), like in Ben Dunkan headphone amp?
Thank you
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Old 17th April 2003, 05:19 PM   #5
Electrons are yellow and more is better!
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Quote:
Originally posted by dimitri
Dear Per- Anders,
Have you tried to listen/measure your QRV-04 amp without the feedback around the BUF634 (feedback resistor switched from BUF634 output to BUF634 input), like in Ben Dunkan headphone amp?
Thank you
Not sure what you mean
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Old 17th April 2003, 05:24 PM   #6
Electrons are yellow and more is better!
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Quote:
Originally posted by Christer
Per-Anders, did you assemble three PCBs using different op amps, or how did you compare them since you use SMD?
I have only one prototype and I switched (slowly!) between opamps. With this method you will forget how it exactly sounded, I know, but still, every opamp sounded splendid. Electrically I liked AD8610 the most. "Klockrent" performance!

Can anyone give me an english word for klockrent?, Bull eye maybe? :bulleye:
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Old 17th April 2003, 05:31 PM   #7
Electrons are yellow and more is better!
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Default Re: Ad8610

Quote:
Originally posted by ALW
Wouldn't run it for long @ 15V though, the XFCB process really is restrictive, the 8065, IIRC, is +/-12 - lower than the +/-13 of the 8610.
I used 15 volts only because I don't feel like fiddleling with the voltage. Off course should you use max +-13 volts if you don't want to risk anything.

Quote:
Originally posted by ALW
P.S. Are you selling those boards?
Yes.
Quote:
Originally posted by ALW
P.P.S. can I be so bold as to suggest there's something wrong if you can't hear the difference between the two bandwidth modes, BTW, it's obvious to me, the WB mode being better. Maybe it's the yellow electron clouds, clouding judgement
Note that I NOT have used low speed mode, only medium and high speed.
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Old 17th April 2003, 09:15 PM   #8
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Default a question

How do you prototype with the SMD parts? Especially those that need the ground plane to act as a heatsink?
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Old 17th April 2003, 09:33 PM   #9
Electrons are yellow and more is better!
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I prototype with the "real thing" when it comes to SMD but if I am unsure about something I use regular parts.
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Old 17th April 2003, 09:46 PM   #10
PMA is offline PMA  Europe
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Hi peranders,

this is my PCB for Audio Buffer (OA+BUF634T):
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