owel

Not Yet Another 1731 Discrete Op Amp
« on: April 16, 2011, 03:46:51 PM »
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


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


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


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.


gemini86

Re: Not Yet Another 1731 Discrete Op Amp
« Reply #1 on: April 16, 2011, 03:49:41 PM »
that has to be one of the cleanest layouts I've seen on a doa... very nice.
- Rodney

"...you better call Kenny Loggins, 'cause you're in the danger zone."

okgb

Re: Not Yet Another 1731 Discrete Op Amp
« Reply #2 on: April 17, 2011, 08:41:07 AM »
Not ANOTHER  1731 ...............
kidding , for someone with diminishing eyesight
i appreciate the black on white scheme
and the symetrical john lennon reference , nice !
GKB Audio / Greg Boboski

Re: Not Yet Another 1731 Discrete Op Amp
« Reply #3 on: April 17, 2011, 01:12:16 PM »
indeed, great work, I will certainly have to try a few in the near future.

Pete

leadbreath

Re: Not Yet Another 1731 Discrete Op Amp
« Reply #4 on: April 17, 2011, 06:05:28 PM »
very nice!
f**k marlbro's and weed ill stick to smoking germanium and silicon

owel

Re: Not Yet Another 1731 Discrete Op Amp
« Reply #5 on: April 24, 2011, 11:39:11 PM »
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.


Re: Not Yet Another 1731 Discrete Op Amp
« Reply #6 on: April 25, 2011, 08:28:18 AM »
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  >:(
 
;D

Nice layout. You take very nice pictures, btw.

owel

Re: Not Yet Another 1731 Discrete Op Amp
« Reply #7 on: April 26, 2011, 03:10:31 AM »
Okay, now posted on the site.  ;D
http://www.fivefishstudios.com/diy-kits/doa-17-discrete-opamp

Quote
Nice layout. You take very nice pictures, btw.
Thank you for the compliments.

living sounds

Re: Not Yet Another 1731 Discrete Op Amp
« Reply #8 on: April 26, 2011, 07:46:55 AM »
Since it's running on +/- 18V  - could I use it as a sub for a common monolytic op amp? What amount of DC is present at the outputs?

owel

Re: Not Yet Another 1731 Discrete Op Amp
« Reply #9 on: April 26, 2011, 12:07:34 PM »
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)


living sounds

Re: Not Yet Another 1731 Discrete Op Amp
« Reply #10 on: April 26, 2011, 12:57:24 PM »
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. :-)

owel

Re: Not Yet Another 1731 Discrete Op Amp
« Reply #11 on: April 28, 2011, 01:17:56 AM »
I'll start posting a more extensive assembly guide in the next few days.

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


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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