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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

LF03 discrete opamp
LF03 discrete opamp
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Old 5th June 2012, 07:43 AM   #11
Brett is offline Brett
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Are you going to offer boards for this? I have an interest for a specific application.
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Old 5th June 2012, 09:42 AM   #12
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Quote:
Originally Posted by Brett View Post
Are you going to offer boards for this? I have an interest for a specific application.
Bare board sets (2 + 1 PCBs) and kits (PCBs + parts) are available. Please PM me or email me at siva dot chander at gmail dot com.

(Note that there are changes to the schematic that require a track cut, one additional reference diode per channel, and some changes to component values. These changes allow operation over a wider range of rail voltages (+/- 3V to +/- 18V) than the original circuit, and a consequent reduction in GBW product at low rail voltages.)
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Old 4th September 2012, 04:10 PM   #13
Ryssen is offline Ryssen  Sweden
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Hello,hows it going with my order?Been a while now..


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Old 6th September 2012, 09:31 PM   #14
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I got an e-mail telling that my order is ready for delivery.


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Old 9th September 2012, 07:40 PM   #15
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A couple of pics of the current LF03 Rev C module as well as a Rev C assembled on the original board with track cuts:
Attached Images
File Type: jpg lf03c1_12x9.jpg (146.3 KB, 1186 views)
File Type: jpg lf03ac2_12x9.jpg (166.3 KB, 1144 views)
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Old 26th December 2012, 09:57 PM   #16
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You got an email
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Old 25th September 2013, 05:46 AM   #17
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Update: SMD LF03 versions have been prototyped and are fully functional - I'm evaluating the audible sonics, which seem to be similar to the previous through-hole version, the LF03c. The SMD single, the LF03s has been tested working in a MyRef Rev C in place of the LM318 monolithic opamp.

Pics of the different versions of the LF03, including the latest SMD version(s) - from left: the LF03c (through-hole dual), LF03d (SMD dual, derived from the LF03c topology) and LF03s (SMD single, which is the same as one channel of the LF03d and shares the same PCB):
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File Type: jpg lf03x3_12x9.jpg (210.9 KB, 927 views)
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Old 25th September 2013, 06:50 AM   #18
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Link to posting on the vendor's forum offering the LF03s (DIP8 single) and LF03d (DIP8 dual):

http://www.diyaudio.com/forums/vendo...ml#post3644382

(These are general-purpose bipolar-input opamp upgrades, and have been widely used in I/V, line amplification and other small-signal and line-level applications, in addition to the LM318 upgrade in the MyRef Rev C mentioned in the posting. The most common application for the dual version is CDP/DVP/DAC line-amp upgrades.)
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Old 28th September 2013, 07:34 PM   #19
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It would be interesting to see some Samuel Groner style tests of these. The last time I was playing with discrete folded cascode topologies in simulation, results were rather disappointing.
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Old 29th September 2013, 08:41 AM   #20
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Quote:
Originally Posted by sgrossklass View Post
It would be interesting to see some Samuel Groner style tests of these. The last time I was playing with discrete folded cascode topologies in simulation, results were rather disappointing.
The LF03 is not a folded cascode, though I've built another DIP8 single (LF05) using a folded cascode - which sounds OK but not as detailed and well-defined as the LF03, which uses a base-driven differential VAS with a floating current-mirror - a bit like a bipolar-input Kaneda on steroids.

For Class-A discrete opamps, the measured distortion can be misleading - they often sound better than the numbers may indicate. Conversely, Class-AB monolithics often sound much worse than the distortion numbers indicate - the LM4562 being the poster child.
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