The Opamp thread

[pelopidas]

That is terrible news! You just made me go buy some more 49990s just to have some reserves
I hate panic buying ....
Also, don't buy them off of ebay, the majority of pics look like fakes. The surface is rough, like it was sanded, the print looks different too. They are cheap enough on Mouser and Digikey that you should not risk it on ebay.
 
Here you can see the dimple on pin 1. this is how every single 49990 looked that i have ever used.

 
here is what is flooding ebay. It is ground down and there is no dimple. The type looks wrong and the "squiggle" looks wrong
 

 

[Mad Max]

Perhaps, perhaps not.  Maybe something even better is in the makings to replace it in TI/National's lineup?

 

[Foxer]

Hey everyone!
 
I want to replace the (1x) NJM2114 and the (3x) NJM2068 on my CREATIVE X-Fi Elite Pro sound card.
 
-- I'm looking for a good clean accurate and precise sound (but not boringly flat) --
 
I have in mind the OPA1602AID as i heard very good things about it ..but i also read that AD8599ARZ is a pretty good candidate!
 
 
Around here somewhere there was a post from @majkel, having a top 5 list:
1. LT1028ACN8 mono
2. OPA211ID (issues like in the review) mono
3. AD797BRZ (finally I found slight imaging issues and timbral imbalance) mono
4. LME49720MA stereo / LME49710NA (I guess I like the former a bit more) mono
5. OPA-Sun v.2 (thick, flawless, likeable sound) stereo
 
but as you can see, most of these are mono.. and i need stereo. And i don't know how they fair against the opa1602aid & ad8599
 
Can you guys please help me out with some opinions/suggestions??
Any advice is appreciated!
Thanks!
 
P.S. This sound card delivers +/-12V to the opamps.
 
 
(later edit)
I would be willing to try 2 mono LT1028ACN8 with an adapter, if they're THAT good.. although it would cost me an arm & a leg. 
But still, i don't know how they fair against the (waaaaay more cheaper) OPA1602AID.

 

[Mad Max]

1602 and 8599 are good choices.  I would take OPA1662 or ADA4898-2 over 1602.
I recommend ADA4610-2 as well.
TL5580 is also worth a mention, and OPA2209 is no slouch either.
4562/49720MA (the -NA version is DIP8 and you need the SOIC8 version) is common among the soundcard modders if I'm not mistaken.
OPA Sun v2 must be sourced second-hand, unless Kingwa only makes them on-demand lately.  I have one (not for sale), it has a very fun and energetic sound.
797 is serious business, and finicky (it tends to overheat/malfunction when thrown into a circuit that's not specifically designed for it).
 
Whatever you end up using, be sure to add a WIMA cap across the power pins (pins 4 & 8 on duals, pins 4 & 7 on mono/singles)

 

[Foxer]

@Mad Max
 
Thanks for the imput!
 
Yes, the LM4562 was a popular swap for the X-Fi, but after a while ppl ditched it for better alternatives. The LM4562 was said to be very dynamic/impressive, but not very accurate, and kind of metallic sounding (at least on the x-fi)... plus, very susceptible to EMI.. and LM49720(ma) would be just a better variant of it.. or so i read.
 
Can you somewhat describe the sound or share some impressions on the OPA1662 & ADA4898-2 in relation to the OPA1602AID ? 
I'm planing to order everything from Farnell, and the ADA4894-2YRDZ is the only "ADA4898-2" variant they have (any good?), and sadly no OPA1662's ..so it might be a bit of a hassle to try and find it.
 
Also, is the Wima cap you linked, the exact value i should use?? (250V seems a bit excessive). Coz i was also planning to use a Film PolyPropylene CAP on the OpAmps, of 0.1uF 63V.. (wima's lowest voltage for 0.1uF caps is 100V sadly; and 250V for 0.15uF)
 
(later edit)
Both the 1602 and 8599 were tried on the X-Fi by different ppl, with reported amazing results. Thing is.. not one person tried both 

 .. so i have no actual comparison btwn them.
Also, i don't know if i should venture off the "proven path", as i have read that an OpAmp could sound different depending on what you put it in, and the surrounding circuit.. don't know how much though.. 

 

[Mad Max]

The higher the voltage, the better the dielectric, or so another guy told me.  To me, it does sound a bit better for the cap to be higher in voltage rating.  I go for the 100V or 63V WIMAs when there's not enough physical space for the ones I linked.  Those smaller voltage caps tend to fit into tight spaces, if not, then 100V 0.1uF WIMA MKS4 is nearly as good and uber compact (only 2.5mm thick).
 
I like 1602, but feel that 4898 and 1662 offer a more refined sound, especially 4898.  Who knows, perhaps 1602 will be "happier" in the Creative card than 1662 and give you better sound than 1662 might?  That 4898 version you linked is the right one.  4898 has this naturalness to its sound that just rocks, plus it is quite hi-fi.  Pretty neutral, too, so long as you give it the extra cap as I recommended.  There's no other place for you to source it from?
 
I cannot tell 4562 and 49720 apart, and they're supposed to be the same chip anyway, like OPA1642 vs. OPA2141.  I like LME49860 and 49990 better than 4562/49720, as far as those National Semi chips.

 

[Foxer]

I live in Romania.. so it can be a bit difficult to source electronics that aren't that "mainstream", at a decent price. Farnell delivers here from their stock in the UK and take @ 6$ for shipping .. Mouser delivers from the US and takes @ 32$ for shipping

 
But i will put a ADA4894-2YRDZ on my list 

 I'm thinking of getting one of each & testing them out before ordering 3 more for the surround channels. 
 
Just hope my soldering skills will be up to par.. (argh, i wish Farnell also had some adapters! ..but i'm gonna take the ghetto route & just solder on some wires for testing

 ..and not gonna forget the cap

 )

 

[pelopidas]

I have found that putting a 10uf Silmic II on the power pins makes a more profound improvement than a 0.1 film. The board will already be bypassed with various capacitors to keep the opamp stable but the power might be filtered with "average" capacitors in the first place. Putting a quality capacitor on the chip in essence cradles the opamp in its sonic signature vs the signature of the other capapcitors. If you want really deep and full bass put a 10 uf Silmic II on the chip. It's better than any other capacitor I have tried.

 

[Foxer]

I have found that putting a 10uf Silmic II on the power pins makes a more profound improvement than a 0.1 film. The board will already be bypassed with various capacitors to keep the opamp stable but the power might be filtered with "average" capacitors in the first place. Putting a quality capacitor on the chip in essence cradles the opamp in its sonic signature vs the signature of the other capapcitors. If you want really deep and full bass put a 10 uf Silmic II on the chip. It's better than any other capacitor I have tried.

 
I was actually thinking of changing the card's power rail decoupling caps for the OpAmps. They are 2x G-Luxon of 220uF 25V , and i was wanting to replace them with low ESR Panasonic FM's of the same values. (Farnell doesn't have any ELNA (silmic) caps 

 ).
Some people replaced those caps with even bigger ones, but i don't know... maybe i should too? I know different values caps charge/discharge at different rates.. so a bigger cap would take more time to charge, and suck up more Amps.. 
 
Also, the 10uF cap u recommend; i'm thinking 16v..? (the opamps are fed 12V)
 
I'm really actually thinking of trying both a 10uF Panasonic FM, and a 0.1 WIMA PP Film in parallel.. would that be bad in any way?
 
This card IS actually severely lacking mid-low bass..

 

[Mad Max]

I feel that FMs contribute to a particularly ugly and fatiguing sound.  FCs are okay, but add some midrange dryness.
From impressions I've read around the web, Rubycon ZLS, ZLG, ZLH, and RX30 may be some good stuff, I haven't gotten around to trying them out yet.
I hate the massive size of Silmics.

 

[Foxer]

Damn it... now i have to scrap half of my check-out list on Farnell ) .. I was about to order @ 20 FMs.
TBH i did come across recommendations for FCs (if ELNAs couldn't be sourced) but not for FMs. I just went for the FMs coz of their lower ESR.. and thought they would be better.
 
Looks like Farnell has Rubycon ZLG & ZLH.. I'm gonna do a little research.
 
 
(it pisses me off how hard are ELNAs to find ...impossible actually in RO.  Things would have been so easy if i could have just popped to the store and bought some 

)

 

[pelopidas]

http://m.ebay.de/itm/12-pcs-10uF-25V-ELNA-RFS-SILMIC-II-AUDIO-Capacitor-85-C-br-NEU-Kondensator-/361425093253?nav=SEARCH

That should do it for the opamps. What value do you need for the board?

 

[Foxer]

http://m.ebay.de/itm/12-pcs-10uF-25V-ELNA-RFS-SILMIC-II-AUDIO-Capacitor-85-C-br-NEU-Kondensator-/361425093253?nav=SEARCH

That should do it for the opamps. What value do you need for the board?

 
Thanks @pelopidas, but i was kinda trying to stay away from eBay, and also get everything from one place (for convenience sake) but also to avoid extra shipping bills.. coz i can barely afford the order as it is. 
My entire order on Farnell was about 40eur incl. shipping. If i order from eBay, shipping would cost at least an additional 10 euros... which tbh i'd rather spend on some extra opamps or caps -for testing 

 
As soon as i get the chance, i'll do the research on the Rubycon ZLG & ZLH, cross my fingers and hope that ppl found them to be good ELNA replacements..
(Got some furniture coming in tomorrow, so i need to take care of that 4 the moment..)

 

[pelopidas]

Farnell does carry the Panasonic SEPF line. Much much better than FM. Almost as good as Silmic. Just make sure you don't exceed the rated voltage.

 

[Foxer]

Farnell does carry the Panasonic SEPF line. Much much better than FM. Almost as good as Silmic. Just make sure you don't exceed the rated voltage.

 
Aren't Polymer caps bad for audio?
 
@trodas did some explaining here: 
http://www.techpowerup.com/forums/threads/x-fi-sound-bugs-i-think-i-have-a-solution.23582/page-3#post-887544
 
"Polymer caps is great for high-frequency voltage filtering (just check their frequency response curves, for christ sake!) while using them for anything getting close to audio is UNFORGIVABLE mistake that completely erase any filtering in low-frequency, hence the strong bass line kill the quality effectively.
You can't measure that on the RMAA, to show this problem you need the DAC/opamps output a loud bass line and then the polymers crumble and kill the voltage filtering = the card output get much less that satisfactory.

Just because todays there are some kind of "hype" about polymers does not mean that they are usefull for everything. They have a very strict usability around 200 - 500kHz, and that it is.

The key to understand this problem is thing called ripple rating coeficient. It basicaly says what multiplier has to be applied on the rated ripple for different frequencies. Nothing show this better that this table:

Samxon X-con URL polymers: 120Hz = 0.05; 1kHz = 0.30; 10kHz = 0.70; 100kHz = 1.00
Samxon elyctrolyte GA caps: 120Hz = 0.50; 1kHz = 0.80; 10kHz = 0.90; 100kHz = 1.00

The specs are very much the same as with all other polymers - even spoken - the better polymers, the worser they run at low audio frequency."