The Opamp thread

[majkel]

@leeperry - AD797BN is not produced any more because it's not RoHS compliant. European vendors don't sell it and it's obsoleted.

The statement that Moon = Burson v.2 is in the Opamp Distortion document from SGacoustics.com Just read it. The guy compared the schematics of both.

I am sorry for people having equipment in which artifacts and colorations from Audio-GD OPA's bring improvements. See the Opamp Distortion document for their distortion numbers. It's bigger than of typical tube stages and not of the tube kind. I still admit the OPA's are amongst the best sonic choices but I will never agree they set a new level of quality.

Regarding the trim pins trick - we know nothing about the OPA228 and the AD797 schematic how it is done. For the LT1028 - I can agree it does not change the bias currents but decreases the input stage amplification a bit and increases the B-C junction headroom a bit. I also think that the change is a disputable improvement. For the OPA228 I like what I hear and I can make a quick comparison with an unmodded pair. So I'm sure of my impressions. The sound is more open and free of a slight nasal coloration which my friend also heard in my rig.

 

[SpudHarris]

Quote:

Originally Posted by ecclesand /img/forum/go_quote.gif Got the ADA4627s earlier today and soldered them on some adapters. Anymore it takes longer for the iron to heat up than to actually solder them. I'm liking them so far...very clean sound with a black background. I'm using them in conjunction with some Hi-C BUF634s as a headphone amp driver.

Hey Doug, getting mine today via DHL (fingers crossed).

ROBSCIX - Yes the 228's. Hmmm, not quite sure how to describe the changes in sound. Probably cleaner and punchier, not as laid back if you like. Not sure if I like it more or less, it's just different.

 

[leeperry]

Quote:

Originally Posted by majkel /img/forum/go_quote.gif The statement that Moon = Burson v.2 is in the Opamp Distortion document from SGacoustics.com Just read it. The guy compared the schematics of both. I am sorry for people having equipment in which artifacts and colorations from Audio-GD OPA's bring improvements. See the Opamp Distortion document for their distortion numbers. It's bigger than of typical tube stages and not of the tube kind. I still admit the OPA's are amongst the best sonic choices but I will never agree they set a new level of quality.

well, IC's(like 1028ACN8 or so) bring a boring L/R SS...Earth provides you w/ a *stunning* 3D-ish SS(on my cd1k at least, same drivers/construction as cd3k), some casualties are meant to be expected!

in "District 9", the helicopters were literally turning around my head...no IC *whatsoever* will ever provide you w/ this kind of SS, same goes for the barbershop demo when he's at the back of your head w/ the trimmer

And Andrea already pointed me to this PDF, it says that the burson "mk2"(now what's "mk2"?) has identical distortion figures to earth(not moon)...that's something we've been very well aware of.

anyway, I'm getting a new burson this week, if it's even better than Earth as final buffer, it'll be a keeper for sure..I'll feed it w/ some 1028ACN8/OPA228P or AD797BN

 

[12Bass]

Did a bit more listening to OPA827, OPA211, and OPA1611 in the preamp of my (modified) Eden bass amplifier. Although I've preferred the sound of the OPA827 in other applications, I thought that the OPA211 had a more clear and direct sound in the part of the circuit where I was testing. In contrast, the OPA827 sounded somewhat soft, a bit midrangey, and slightly less detailed. When I popped the OPA211 back in, it sounded better to me. Once again I compared the OPA1611 to OPA211 and thought that OPA211 sounded a little better - more transparent somehow. Perhaps it is worth noting that I'm seeking a mix of both transparency and pleasing coloration in reproducing the sound of my instruments.

 

[12Bass]

A pair of OPA827s on a BrownDog adapter, with a 0.01 µF capacitor across the power rails.

 

[ecclesand]

Quote:

Originally Posted by comic /img/forum/go_quote.gif I'd be eager to try the ADA4627-1, but there's no way to buy it yet. It's the only opamp left that could challenge my favorite LT1028CS8.

I bought the ARZ versions direct from AD.

You seem to make a few statements as fact. The LT1028 is NOT perfect sounding. It may be to your ears and in your circuit but I'm sure others will disagree with you...myself included.

He's baaaack!

 

[qusp]

so i've got some LME49720HA on the way for something interesting. got the 20 rather than the 10, although I usually prefer to get 2 singles, as it makes for easier modding, but I get more for my postage dollar with dual samples

interesting to note they only allow samples of a single device rather than Ti and AD's open house for prototyping. anyone know whether they will operate under the stated minimum current of 2.5+-?? some opamps will work quite nicely and be stable under their st6ated minimum supply voltage, but others are rather cranky

also, looking for a quality low voltage differential input and output opamp for a DIY balanced DAC based on the PCM1794A or more likely 1798 due to being more efficient. have some OPA1632 on the way as soon as they catch up on orders, but that wont be for a month or so, any alternatives in the same class you guys know about?? plenty of opamps with differential inputs, but many have SE output only

 

[ROBSCIX]

I find out of those units the 10HA as favorable over the 20HA's...but I fine many single are preferable over duals.
I am unsure about the current requirments.

 

[ecclesand]

To my ears, the ADA4627 is the real deal. The music flows so effortlessly with them as both line driver for a CS4398 DAC and paired with HI-C BUF634s as a headphone amp. All my testing has been with the ARZ version as the BRZ were more expensive. I think I may need to pick up a couple BRZ versions for comparison.

In my Lite DAC-AH, I switched back to the opa627 from the opa827. To my ears, the opa627 bests the 827 in every category. However, I need to pick up a few more ADA4627s and mount them on single adapters to try in the Lite. These may just beat the opa627 in this circuit.

 

[ROBSCIX]

..another added to my list. I am going to need another opamp case soon

..Ah OPA637SM...ever try those?

 

[diditmyself]

Quote:

Originally Posted by majkel /img/forum/go_quote.gif Regarding the trim pins trick - we know nothing about the OPA228 and the AD797 schematic how it is done.

I have what I think is the real AD797 schematic. I don't know why it was removed. I can put it up again. I can see no other way of trimming the DC offset by connecting 10k resistors to V-. It has to be on the CM emitters.

 

[qusp]

Quote:

Originally Posted by ROBSCIX /img/forum/go_quote.gif I find out of those units the 10HA as favorable over the 20HA's...but I fine many single are preferable over duals. I am unsure about the current requirments.

like I said, so do I, but for ease of use and current requirements I got duals this time; got the metal cans, never used them before actually, other than shielding what advantage do they have over DIp and soic?? also if you guys could have another glance at my post ^^ I had edioted it but forgot to finish; wondering if you guys have much info on differential in/out opamps in the same class as OPA1632 for a possible portable balanced DAC project using discrete buffers?? seems the only way i'm gonna get balanced output on the go is to do it myself

OPA1632 sound great in my buffalo32, but are a bit higher current than I would like and also Ti wlont catch up with production for a month or so when mine will ship

 

[Pluto2]

Quote:

Originally Posted by 12Bass /img/forum/go_quote.gif A pair of OPA827s on a BrownDog adapter, with a 0.01 µF capacitor across the power rails.

Hi 12bass, did you also put in a bypass cap at the bottom chip? neceesary?

 

[SpudHarris]

Quote:

Originally Posted by ecclesand /img/forum/go_quote.gif To my ears, the ADA4627 is the real deal. The music flows so effortlessly with them as both line driver for a CS4398 DAC and paired with HI-C BUF634s as a headphone amp. All my testing has been with the ARZ version as the BRZ were more expensive. I think I may need to pick up a couple BRZ versions for comparison.

Doug I'm with you there buddy, man these are something else. It's not very often that an opamp has so much immediate appeal but these are just awesom. In the same set up as the OPA827's (Hi-C Buf634's and LME49710HA's in ground) these just excel with electronica/trance. Got a feeling tonight is gonna be a late one............

These are expensive and a pain to get as samples but you guys have to try them.

 

[12Bass]

Quote:

Originally Posted by Pluto2 /img/forum/go_quote.gif Hi 12bass, did you also put in a bypass cap at the bottom chip? neceesary?

Not sure the bypass across the rails is actually necessary at all.... mostly there right on the chip just in case of possible instability. I've usually already put bypasses on each rail in the circuit. And, to answer your question, no, I just use a capacitor across the rails on the top chip. Too much hassle to do the bottom one with BrownDogs. However, sometimes I'll put a capacitor beneath the socket if I solder an SOIC part to a DIP socket.