Hi Mark,
as there is no plot of transimpedance vs. frequency given in the 49713 datasheet, it seems that (by reconstruction from a set of other plots given and a bit of guesswork and comparison with other CFB parts where this spec is given) the transimpedance corner frequency might be on the order of 10..20kHz -- which would be very nice. Would you mind to comment on that, given your specific insight/knowledge of the part?
- Klaus
as there is no plot of transimpedance vs. frequency given in the 49713 datasheet, it seems that (by reconstruction from a set of other plots given and a bit of guesswork and comparison with other CFB parts where this spec is given) the transimpedance corner frequency might be on the order of 10..20kHz -- which would be very nice. Would you mind to comment on that, given your specific insight/knowledge of the part?
- Klaus
Hi Tolu,
Yes, that combination for your preamp will be the easiest to implement and will work fine. But you might try the 713 for the first stage also. If the low value input resistor is a problem for you then you could try the non-inverting configuration for the LME49713? May or may not be better than an inverting LME49710. If I were still at National I would have done that test for you! Also for a preamp you should use the metal cans! I will be building a Phono preamp sometime soon so maybe I can get a chance to try a few different combinations but without an AP2 Cascade at home I can only listen and I prefer to measure first to make sure I am not "fooling myself" with unknown non-linearities! Listening is more time consuming than measuring so I like to start with a known condition before spending the extra time in my sound room "working-listening" instead of using that extra time for "fun-listening!"
Anyone have an AP2 for sale or trade?
And...
Klaus,
I will check up on that transimpedance graph question with my "Sources" for you. I know we did not measure that and it is a great question!
Mark / Audioman54
Yes, that combination for your preamp will be the easiest to implement and will work fine. But you might try the 713 for the first stage also. If the low value input resistor is a problem for you then you could try the non-inverting configuration for the LME49713? May or may not be better than an inverting LME49710. If I were still at National I would have done that test for you! Also for a preamp you should use the metal cans! I will be building a Phono preamp sometime soon so maybe I can get a chance to try a few different combinations but without an AP2 Cascade at home I can only listen and I prefer to measure first to make sure I am not "fooling myself" with unknown non-linearities! Listening is more time consuming than measuring so I like to start with a known condition before spending the extra time in my sound room "working-listening" instead of using that extra time for "fun-listening!"
Anyone have an AP2 for sale or trade?
And...
Klaus,
I will check up on that transimpedance graph question with my "Sources" for you. I know we did not measure that and it is a great question!
Mark / Audioman54
Hi Ken,
The schematic was never released but it is very simple and very close to identical to the schematic in AN-1490. It uses the same Darlington packages shown in AN-1490. I believe separate devices instead of the darlingtons would be better though. So if you (or anyone else out there) have any suggestions on other driver pairs I would be excited to try them!...after I find a used AP2 so I could measure the results and then listen to it!
Mark / Audioman54
The schematic was never released but it is very simple and very close to identical to the schematic in AN-1490. It uses the same Darlington packages shown in AN-1490. I believe separate devices instead of the darlingtons would be better though. So if you (or anyone else out there) have any suggestions on other driver pairs I would be excited to try them!...after I find a used AP2 so I could measure the results and then listen to it!
Mark / Audioman54
Hi Mark,
Panson is building one with a triple descrite darlington configuration. He're the link: http://www.diyaudio.com/forums/showthread.php?p=1904474#post1904474- Post 136 (I couldn't find a link thing like the old forum, so I hope it works otherwise just cut and paste it into your browser) I doing the same triple idea with a 2sa1381/2sc3503 pre driver, MJE15032/33 driver and NJL4302/NJL4281 output transistor. Using his idea of a seperate VAS board (49811) from the output board I'm also building one with the STD03 darlingtons.
Ken
Panson is building one with a triple descrite darlington configuration. He're the link: http://www.diyaudio.com/forums/showthread.php?p=1904474#post1904474- Post 136 (I couldn't find a link thing like the old forum, so I hope it works otherwise just cut and paste it into your browser) I doing the same triple idea with a 2sa1381/2sc3503 pre driver, MJE15032/33 driver and NJL4302/NJL4281 output transistor. Using his idea of a seperate VAS board (49811) from the output board I'm also building one with the STD03 darlingtons.
Ken
Hi Mark,
No I havent. I'm still waiting for details on my DAC changes, and am looking for a machine shop that will make a bending guide for me for both 8 pin dip spacing, and SOIC pad spacing. I have it designed, just need to find someone with a milling maching to fab it for me.
There's a nice note here at Audio Asylum of positive results of using the TO-99 LME49720:
http://www.audioasylum.com/forums/hirez/messages/26/261252.html
No I havent. I'm still waiting for details on my DAC changes, and am looking for a machine shop that will make a bending guide for me for both 8 pin dip spacing, and SOIC pad spacing. I have it designed, just need to find someone with a milling maching to fab it for me.
There's a nice note here at Audio Asylum of positive results of using the TO-99 LME49720:
http://www.audioasylum.com/forums/hirez/messages/26/261252.html
Hi Mark,
I have - in an inverting preamp - just got my dc-servo working for it as well. I'm driving a LME9811 with a predriver/driver/Thermal trak output - just listened to it this past weekend. It's pretty wonderful. Still some bugs to work out in the setup - a relay based input selector kit that isn't working - I seem to be able to get the complicated electronics to work, but, am ready to throw the selector kit in round file...
Ken
I am using sources -> relays -> RC filter -> pot (10 KOhm log, Bourns conductive plastic) -> LME49720 (aka LM4562, non-inverting, gain 2) -> 51 Ohm series resistor -> output
The RC filter sets a pole at 100KHz. There are no coupling capacitors anywhere. Offset is very low ~1 mV. Without the RC filter the pre-amp provides gain to several MHz.
Yes, gimme a couple of days to put it into a schematic editor.
BTW, its actually 2 of LME49710, not the dual opamp LME49720.
4562=49720
Jackinnj,
The LM4562 and the LME49720 are the exact same part! We added the
LME49720 to the LME series to make the new number sequence make sense. I.e. LMe49710/LME49720/LME49740, single/dual/quad. The slightly different specs are another story...
Mark / Audioman54
PS - Anybody heard of any engineering audio jobs out there? 11 months and no work really stinks!
Jackinnj,
The LM4562 and the LME49720 are the exact same part! We added the
LME49720 to the LME series to make the new number sequence make sense. I.e. LMe49710/LME49720/LME49740, single/dual/quad. The slightly different specs are another story...
Mark / Audioman54
PS - Anybody heard of any engineering audio jobs out there? 11 months and no work really stinks!
What Mark didn't explain is that the the LME49713 is a current feedback op amp. The impedance of the output to negative input must be within a certain range for it to work. One of the benefits of the CFB opamp is much higher bandwidth- on the order of 30 MHz full power bandwidth. And it brings associated challenges like stability etc.
The extra ink on the latter part's silk-screening probably accounts for the few picovolts of lower noise spec'd.
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