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The Opamp thread
Mar 2, 2012 at 5:44 AM Post #3,736 of 7,383


Quote:
mad max said:
 

Pads for psu bypass caps is a must.  Since class A biasing is so popular, pads for that should be a must as well - whether biasing with just a resistor or going with the JFET cascode thing.  All the pads ought to at least be a little long like on the iBasso adapters, not just for ease of soldering, but for modifications/tweaks/etc. in general.  Also, a possibility of directly soldering pin 4 to the exposed underside pad that some chips have would be nice, too, or the possibility of connecting the underside pad to a trace that leads to a small hole on the pcb for a wire and thus a connection to ground.
Click to expand...


connection to ground? opamps dont know what ground is, the exposed pad (power pad) is for heatsinking the die generally (thats why its connected to the ground plane, for thermal connection, not due to needing an electrical ground connection) and while sometimes also connected to the rails or a reference voltage to servo the output, there is no benefit to provide a point for a wire to connect as it will not help with heatsinking at all, in fact using a powerpad package on an adapter would be almost certain to involve over-temp death to the device.
 
 
Mar 2, 2012 at 10:40 AM Post #3,737 of 7,383
Will LM7171 work as replacement for MC33078N provided that I will put 2x LM7171 on an adaptor that is popularly sold for BB OPA627. I seek even cleaner crispier sound than LM4562.
 
OP AMP, VOLT FEEDBACK, 7171, DIP8
  1. Op Amp Type:High Speed
  2. No. of Amplifiers:1
  3. Bandwidth:200MHz
  4. Slew Rate:4100V/µs
  5. Supply Voltage Range:5.5V to 36V
  6. Amplifier Case Style:DIP
  7. No. of Pins:8
  8. Operating Temperature Range:-40_C to +85_C
  9. SVHC:No SVHC (20-Jun-2011)
  10. Amplifier Type:Voltage Feedback
  11. Base Number:7171
  12. Gain Bandwidth:140MHz
  13. IC Generic Number:7171
  14. Input Offset Voltage Max:7mV
  15. Logic Function Number:7171
  16. Operating Temperature Max:85_C
  17. Operating Temperature Min:-40_C
  18. Operational Amplifier Features:High Speed
  19. Package / Case:DIP
  20. Slew Rate:4100V/µs
  21. Supply Voltage + Nom:15V
  22. Supply Voltage Max:36V
  23. Supply Voltage Min:5.5V
  24. Termination Type:Through Hole
 
 
IC, OP AMP, DUAL AUDIO, 33078, DIP8
  1. Op Amp Type:Low Noise
  2. No. of Amplifiers:2
  3. Bandwidth:16MHz
  4. Slew Rate:7V/µs
  5. Supply Voltage Range: ± 2.5V to ± 15V
  6. Amplifier Case Style:DIP
  7. No. of Pins:8
  8. Operating Temperature Range:-40_C to +105_C
  9. SVHC:No SVHC (20-Jun-2011)
  10. Amplifier Type:Audio
  11. Base Number:33078
  12. Gain Bandwidth:9MHz
  13. IC Generic Number:33078
  14. Input Offset Voltage Max:3mV
  15. Logic Function Number:33078
  16. Operating Temperature Max:105_C
  17. Operating Temperature Min:-40_C
  18. Package / Case:DIP
  19. Slew Rate:7V/µs
  20. Supply Voltage + Nom:15V
  21. Supply Voltage Max:15V
  22. Supply Voltage Min: 2.5V
  23. Termination Type:Through Hole


 
 
Mar 2, 2012 at 1:27 PM Post #3,739 of 7,383
Quote:
qusp said:
connection to ground? opamps dont know what ground is, the exposed pad (power pad) is for heatsinking the die generally (thats why its connected to the ground plane, for thermal connection, not due to needing an electrical ground connection) and while sometimes also connected to the rails or a reference voltage to servo the output, there is no benefit to provide a point for a wire to connect as it will not help with heatsinking at all, in fact using a powerpad package on an adapter would be almost certain to involve over-temp death to the device.
 
Click to expand...

 
I forgot which ones, but I've seen a few opamps' datsheets specify to not connect the powerpad to the rails, that's why.  But to hell with those chips, you say?
Forget them then.
 
Mar 3, 2012 at 2:45 PM Post #3,740 of 7,383
It seems the AD797BR is better then the AD797AR, is this then general consensus?
 
On eBay seller audjade_chn, who seem to have good feedback, is selling 20pcs of (used) AD797BR soldered on to 10 SOIC to DIP-8 adapters
Price is $79.99 (includes shipping), has anyone here ever dealt with this seller?
 
Mar 4, 2012 at 5:43 PM Post #3,741 of 7,383
I have ordered from Audiojade on a number of occasions and always got a genuine item and great service. Off the top of my head the last chips I bought were used OPA111AM (TO99) and OPA637BM (TO99).
 
I think that the BR version of 797 sounds better but it's not night and day. If you buy them but don't want all 10 modules I'd take a couple off your hands. I have 6 off them but they are all on single adapters which limits some applications (EF-5 for instance)
 
Let us know how that pans out.
 
Mar 4, 2012 at 7:34 PM Post #3,742 of 7,383


Quote:
spudharris said:
I have ordered from Audiojade on a number of occasions and always got a genuine item and great service. Off the top of my head the last chips I bought were used OPA111AM (TO99) and OPA637BM (TO99).
I think that the BR version of 797 sounds better but it's not night and day. If you buy them but don't want all 10 modules I'd take a couple off your hands. I have 6 off them but they are all on single adapters which limits some applications (EF-5 for instance)
Let us know how that pans out.
Click to expand...

Can not find AudioJade
But i did find a seller of the AD797BR, called Audjade_chn
 
 
 
 
Mar 4, 2012 at 8:53 PM Post #3,743 of 7,383


Quote:
mad max said:
 
I forgot which ones, but I've seen a few opamps' datsheets specify to not connect the powerpad to the rails, that's why.  But to hell with those chips, you say?
Forget them then.
Click to expand...



yeah ive only ever personally seen a thermal connection, which is the most common, or a reference voltage for an output servo (VCOM, which might be what youve seen on opa1632dgn), normally thermal and no point having that on an adapter. not worth catering for either way
 
@sssboa: i recommend you stay away from the LM7171 with bandwidth of 200Mhz and gain BW of 140Mhz that'll be a bitch to keep stable in an audio circuit on an adapter
 
Mar 4, 2012 at 9:28 PM Post #3,744 of 7,383
Mar 5, 2012 at 3:18 AM Post #3,745 of 7,383


Quote:
purpleangel said:
Can not find AudioJade
But i did find a seller of the AD797BR, called Audjade_chn
 
Click to expand...


rolleyes.gif

 
 
Mar 11, 2012 at 4:42 PM Post #3,746 of 7,383
I ended up buying 10 pre-soldered adapters (20 AD797BR op-amps), I'm really only going to need three adapters, maybe I'll sell off the extras on head-Fi?
 
Mar 12, 2012 at 2:06 PM Post #3,750 of 7,383
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