Not Yet Another 1731 Discrete Op Amp

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owel

Well-known member
Joined
Jun 3, 2004
Messages
1,088
Location
Nashville, USA
Yup, another 1731 DOA... my version  ;D ;D ;D

Very low-profile.
0.37" component height. 0.74" overall height (including mill-max pins)
Measured Specs:
THD+N less than 0.0021%, +4dB, f=1Khz, Unity gain, 30K BW
97.8dB S/N Ratio

5625282514_ab853d7410_z.jpg

Component placement almost perfectly symmetrical.
Component names AND part values printed on silkscreen for easy assembly (if you can read that small!)

5625282448_55e820b2e4_z.jpg

Looks like a guy with John Lennon glasses and a mustache.

5625282416_8f8acb20ef_z.jpg

Undergoing testing... using my OpAmp Test Jig. (See Black Market if interested to order my OpAmp Test Jig PCBs/Partial Kits)

I'll measure it again once I have the right resistor values... had to do a lot of substitutions as I don't have some of the values on hand.

I'm offering this one as READY-MADE and as a KIT as well... more info to come. I just got this working this morning.
 
Not ANOTHER  1731 ...............
kidding , for someone with diminishing eyesight
i appreciate the black on white scheme
and the symetrical john lennon reference , nice !
 
Got the chance to re-test my 1731 clone (calling it my DOA-17).

My 1st prototype had some resistor and capacitor substitutions since I didn't have the exact part values on hand.  So it was exhibiting a sudden increase in THD+N at Vout > 12dBm (goes up to 0.0274% THD+N). Now, using the appropriate resistor and capacitor values, the numbers look even better.

THD+N less than 0.0034%, Vout=0dBm, f=1Khz, BW=30Khz, Unity gain, 600R load, +/-18VDC
THD+N less than 0.0021%, Vout=+4dBm, f=1Khz, BW=30Khz, Unity gain, 600R load, +/-18VDC
THD+N less than 0.0016%, Vout=+17dBm, f=1khz, BW=30Khz, Unity gain, 600R load, +/-18VDC

I'll post the 1731 KITS and ready-made DOAs on my website asap. Hope you guys will check it out.

5651825003_b20bb763c7_b.jpg
 
owel said:
I'll post the 1731 KITS and ready-made DOAs on my website asap. Hope you guys will check it out.
I just checked and they're not there  :mad:

;D

Nice layout. You take very nice pictures, btw.
 
Yes, could be used as a sub. It's just like any other 1731/2520 opamp around here.

The +/-18V is my test condition. Of course, it will also run at +/-15V or +/-16V. 

-2.4mVDC at outputs, unity-gain  (about +/-1mV compared to other 2520/1731 clones)
Max. output: @+/- 18V supply = +23.06 dBm (loaded 600-ohms)
 
owel said:
Yes, could be used as a sub. It's just like any other 1731/2520 opamp around here.

The +/-18V is my test condition. Of course, it will also run at +/-15V or +/-16V. 

-2.4mVDC at outputs, unity-gain  (about +/-1mV compared to other 2520/1731 clones)
Max. output: @+/- 18V supply = +23.06 dBm (loaded 600-ohms)

Cool, so I could use it as a summing amp in my console without DC blocking caps, replacing the 5532 (or rather OPA1611 that currently reside in there). Hm... sounds good. :)
 
I'll start posting a more extensive assembly guide in the next few days.

In the meantime, here are some close-up shots.
5663653396_822cd64aff_o.jpg


Someone asked me how the specs compare to a real 2520, I was curious too so I ran the same tests and found some interesting results.
NOTE: These numbers may not be absolute, but since I'm using the same PSU, Test Jig, cables and equipment, I think the tests readings are valid relative to each other.

+4dBm output, +/-18VDC, f=1Khz, BW=30K
Both opamps have the same  THD+N .... it's a TIE. Woot!
SINAD and SNR differences are 0.13dB and 0.1dB respectively. (DOA have the higher numbers, but very small difference.)

But at +17dBm output is where things got interesting.
Loaded with 600R resistor
DOA-17 is 0.0018% THD+N
2520 is 0.0032% THD+N
...
but if I remove the 600R load
DOA-17 goes up to 0.0025% THD+N
2520 goes down to 0.0017% THD+N
...
anyway, this is splitting hairs. The differences above are very small. I just found it interesting how the 600R load affected both differently.

But if you want to know which one has the better SINAD and SN ratio, PM me  ;D
So there you go.
 

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