[Monago]

Hello!
 
Just a quick question about stereo SOIC-8 sockets...
 
I have a sound card in my computer which currently sports an AD8620BR opamp that I wanted replaced with the LME49990. My only problem is this: the LME49990 (as you probably know) is a mono opamp as opposed to the stereo output of an AD8620, which means I'd need 2 49990's to fit in the aforementioned socket where the AD8620BR currently resides.
 
So my question; is there any way to fit the LME49990 into a single stereo channel SOIC-8 socket by using some sort of adapter?
 
My only thought is using a dual SOIC to DIP8 adapter, requiring a bit of creative mounting on my part (assuming this would work). If not, is there some other dual mono to stereo SOIC-8 adapter I'm unaware of which would do the job?
 
Thanks!

 

[shake]

edit: herp

 

[kiteki]

You need this -
 

 
 
Why LME49990?
 
Pick up several, see what you think
 
- http://www.ebay.com/itm/1set-Dual-Mono-Op-amp-OPA627AP-OPA627-replace-NE5532-/350563724981
 
- http://www.ebay.com/itm/IC-2x-LT1028ACN8-DIP-single-Op-amp-Ultralow-Noise-/350529800392
 
 
Happy listening.

 

[PurpleAngel]

Quote:

Hello!
 
Just a quick question about stereo SOIC-8 sockets...
 
I have a sound card in my computer which currently sports an AD8620BR opamp that I wanted replaced with the LME49990. My only problem is this: the LME49990 (as you probably know) is a mono opamp as opposed to the stereo output of an AD8620, which means I'd need 2 49990's to fit in the aforementioned socket where the AD8620BR currently resides.
 
So my question; is there any way to fit the LME49990 into a single stereo channel SOIC-8 socket by using some sort of adapter?
 
My only thought is using a dual SOIC to DIP8 adapter, requiring a bit of creative mounting on my part (assuming this would work). If not, is there some other dual mono to stereo SOIC-8 adapter I'm unaware of which would do the job?
 
Thanks!

Just order the pre-soldered (2 LME49990) dual SOIC to DIP-8 adapter on eBay for $20.
The seller Frugalphile has a good rep.

 

[shake]

Quote:

- http://www.ebay.com/itm/1set-Dual-Mono-Op-amp-OPA627AP-OPA627-replace-NE5532-/350563724981
 

Are those fake OPA627s?
The ones I have from digikey look different
 

 

[jcx]

only replace JFET input op amps with other JFET or CMOS input op amps
 
the question is why would anyone want to to replace a really good recent FET input op amp suited to >> kOhm circuit impedance with a nV BJT input op amp  suited for <300 Ohm source/feedback Z - almost certainly the circuit designed for AD will be noisier with the LME due to the LME input's current noise
 
another point is that FET inputs of the AD8620 are expected to be much more resistant to EMI/RF/out of band delta-sigma noise than the LME49990 - very important in a sound card
 
the AD8620 is plenty fast @25 MHz GBW, the LME 4x higher bandwidth will complicate proper bypassing, capacitive load isolation for stability - particularly on a adapter it is hard to good 100 MHz bypassing, low inductance connection to gnd plane
 
if you worry about slew rate the JFET AD8620 is more than 2x better than the LME49990 despite the latter's 110 MHz GBW
 
 
the 2nd post shows the LME49600 buffer pkg

 

[Avro_Arrow]

I would listen to jcx above...but if you choose not to, this adapter will fit two SOIC single op amps into a DIP dual op amp spot.
 
Edit:
 
Brain Fart...this would be the correct adapter.

 

[kiteki]

- http://www.ebay.com/itm/1set-Dual-Mono-Op-amp-OPA627AP-OPA627-replace-NE5532-/350563724981
 

Are those fake OPA627s?
The ones I have from digikey look different
 

 
Hmm, they're made in different countries right?
 
jcx - you seem to be very technical, could you explain how the LT1028 could result in very clear distortion when driving a headphone or IEM directly, however sounds perfect when connected to my stereo?

 

[jcx]

as a class the "1nv/rt(Hz)" BJT input op amps only really advantageous use in consumer audio is in moving coil phono preamp circuits - everywhere else the V_noise performance is overcome by the high bias BJT input current noise reacting with kOhm source, feedback resistors, Z - just maybe the ESS 9018 DAC in parallel mode could fit the input V,I noise the noise of these op amps
 
for lower published distortion numbers the OPA164x is the current JFET input op amp series to compare to - despite the low cost
 
for some circuits the input capacitance modulation of JFET input with common mode voltage is a limitation - the OPA627 is to my knowledge still the best for high source Z, the V_noise, 1/f corner is still lower than most modern op amps clearly aimed at replacing it: AD8610/20, ADA4627, OPA826
 
for moving magnet phono preamps use OPA626/7
 
 
for driving headphones your headphone's  Z, sensitivity has to  be considered - how loud do you consider dynamic headroom peaks reach in your favored music genera, do you listen at "background" level all day long or do you want to "rock out" at live performance levels for < 1hr a day?
 
http://gilmore2.chem.northwestern.edu/articles/hearing_art.htm
 
 
datasheet output short circuit current limit is a poor estimate of op amp practical max drive capability - I have seen 10x increase in distortion from a op amp at ~1/2 of the short circuit current limit
 
the AD8610/20 fares pretty good on the output current
 
 
note that the above was written while consuming a Samuel Adams Stony Brook Red 1 pt 9.4 oz 9%  alcohol content - spell check rulze

 

[kiteki]

jcx that's very interesting can you continue your answer in this thread?  http://www.head-fi.org/t/612062/help-with-lt1028
 
I'd like to isolate the differences I can hear in op-amp's and lack your technical insight.

 

[PurpleAngel]

Quote:

Are those fake OPA627s?
The ones I have from digikey look different
 

audjade_chn is the seller who sold me my AD797BRs (10 pre-soldered adapters) and they work fine.
audjade_chn seems to have a good rep on Head-Fi.
I believe the same op-amp can have "difference" styles of markings.

 

[kiteki]

I recommend OPA2111KP from aud_jade, sounds very nice with particular IEM's!  Very interesting op-amp, unlike OPA827 for examle, it's just errrr... neutral? - which I bought from someone in Thailand...
 
AD8620 is err, not netural, a little clinical, impressive at first then I insert OPA2111KP.
 
I had no prior knowledge on any of these prior to listening to them, they all look the same and they're all just random numbers and I buy them randomly, I don't know what could influence my perception of them other than numerology and price.

 

[wakibaki]

Quote:

note that the above was written while consuming a Samuel Adams Stony Brook Red 1 pt 9.4 oz 9%  alcohol content - spell check rulze

 
Hmm. What's your excuse for the missing capitalization that most of the rest of us manage to achieve? It's inconsiderate to force your readers to accommodate your idiosyncratic punctuation, lacking Cormac McCarthy's facility for prose poecy. Pull your socks up.
 
w