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LF03 discrete opamp
LF03 discrete opamp
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Old 9th October 2013, 09:39 AM   #21
linuxguru is offline linuxguru  India
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OK, I managed to squeeze in the dual (LF03d) as an upgrade for the I/V converter of a Kenwood DP-1001 CD player (mostly sold in Asia, I don't know if it was ever exported to the EU or North America). It's a high-quality, mid-priced CDP with a fairly beefy PSU, TDA1547 DAC, and a line output stage consisting of a dual opamp with discrete Class-A output current booster. It sounds pretty good even with the stock opamps (I/V, line amp), but the LF03d as the I/V takes it into fairly high-end territory.

The challenge lies in physically fitting the LF03d on the DAC riser card, which has fairly limited clearance to the transport next to it. The second constraint is the relatively low rail voltage for the I/V converter opamp: ~ +/- 5V or lower, which the LF03d can handle comfortably (but is not optimal for numerous otherwise highly-regarded monolithics like OPA627, which choke below about +/- 9v)

There are a number of upgrades I did to the I/V stage, including Black Gates, styroflex caps, Wima FKP2s, small chokes on the opamp rails for LC filtering, etc., but all of those are optional and contributed relatively small increments to the sonics, compared to the opamp upgrade.

Compared to the LME49722 and the 2x OPA627 which were previously in this player, on a scale of 1 to 10, I'd rate both the monolithics (LME49722 and 2x OPA627) at about 6-7 and the LF03d at about 9 on audible sonics - definition, detail and dynamics are distinctly superior with the LF03d.
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File Type: jpg lf03d_dp1001_iv_10x7.jpg (152.0 KB, 914 views)

Last edited by linuxguru; 9th October 2013 at 09:59 AM. Reason: correction and addendum
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Old 10th October 2013, 04:00 AM   #22
pinnocchio is offline pinnocchio  Canada
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Are you able to compare it to a OPA1642?

Do
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Old 10th October 2013, 06:59 AM   #23
linuxguru is offline linuxguru  India
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Quote:
Originally Posted by pinnocchio View Post
Are you able to compare it to a OPA1642?
No, I don't have a OPA1642 in hand. I did try an OPA1612 long ago (though not A-B with the LF03), and didn't like its sonics (a bit harsh) at line level.
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Old 8th June 2014, 11:38 AM   #24
lduarte1973 is offline lduarte1973  Portugal
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hi , how much do you ask for assembled dual opamp ?
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Old 8th June 2014, 12:23 PM   #25
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Quote:
Originally Posted by lduarte1973 View Post
hi , how much do you ask for assembled dual opamp ?
Thanks for your enquiry, PM sent.
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Old 17th October 2015, 10:32 AM   #26
horizonrays is offline horizonrays  India
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Quote:
Originally Posted by linuxguru View Post
Thanks for your enquiry, PM sent.
same question ,
how much does it costs ?
and what's it's slew rate ?
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Old 17th October 2015, 11:19 AM   #27
linuxguru is offline linuxguru  India
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PM sent. I haven't measured the slew rate of the latest version, but the GBW is ~10 MHz, and it's unity-gain stable.
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Old 10th June 2021, 05:47 PM   #28
donovas is offline donovas  South Korea
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Looking for ad797 clones i found this. Id like to implement this into my preamp for it seems like a very noble and unique design. (Much appreciated, Linuxguru!)

Id like to know if as a non inverting 3x gain config i will have to worry about on/off thumps or not. The output is single ended it seems? Thats why i raise the concern.
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Old 10th June 2021, 08:15 PM   #29
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I didn't encounter on/off thumps, but YMMV - it's a function of rail-sequencing and overall circuit topology, so it can happen with even otherwise well-behaved opamps.
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Old 11th June 2021, 07:08 AM   #30
donovas is offline donovas  South Korea
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Thank you. And how can the dc offset be nulled? Replace r11, r12 with a 2k trimpot?
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