[leeperry]

I got the adapter on ebay: http://www.ebay.com/sch/sorch_audio/m.html?_trkparms=65%253A12%257C66%253A2%257C39%253A6%257C72%253A5698&rt=nc&_dmd=2&_trksid=p3911.c0.m14&_vc=1&_sop=15&_sc=1
 
I've tried a few of his adapters, they're all 2oz, they have a very thick PCB and pins that provide an excellent contact within DIP8 sockets and all around they sound far better than those 1oz and very thin browndogs to my ears. This guy knows how to design adapters

 
About the AD797BNZ, I got them off a chinese broker....these are hard to source, and I believe he ran out but I could ask him if you needed a few.

 

[.Sup]

Quote:

I got the adapter on ebay: http://www.ebay.com/sch/sorch_audio/m.html?_trkparms=65%253A12%257C66%253A2%257C39%253A6%257C72%253A5698&rt=nc&_dmd=2&_trksid=p3911.c0.m14&_vc=1&_sop=15&_sc=1
 
I've tried a few of his adapters, they're all 2oz, they have a very thick PCB and pins that provide an excellent contact within DIP8 sockets and all around they sound far better than those 1oz and very thin browndogs to my ears. This guy knows how to design adapters

 
About the AD797BNZ, I got them off a chinese broker....these are hard to source, and I believe he ran out but I could ask him if you needed a few.

Thanks leeperry for all the info. If you could that would be great as I trust you they are good but if you can't that is fine too and I will seek elsewhere. 

 

[leeperry]

 

If you could that would be great

 
YGPM

 

I got the adapter on ebay: http://www.ebay.com/sch/sorch_audio/m.html?_trkparms=65%253A12%257C66%253A2%257C39%253A6%257C72%253A5698&rt=nc&_dmd=2&_trksid=p3911.c0.m14&_vc=1&_sop=15&_sc=1

Hah, he makes them w/ white PCB now, they look so deliciiiious

 

[leeperry]

Another great chip is OPA1641, it doesn't try to impress you like 797B...it just sounds very musical and detailed, and those thick 2oz thai adapters manage to extract the best out of it:
 
The pins are so thick that I'm always afraid to break my DAC board, talk about good contact! The SQ improvement over 1oz browndogs is dead obvious, they sound shrill and bright in comparison..I even had to reduce my ears resonances EQ

 

[mikael83]

I'm kind of noob when it comes to opas so I need some advices. I ordered  this Dual Opamp Adaptor little too hastily without knowing what kind of AD797BRZ I should order for it. So I found this single AD797BRZ from ebay and I would need to buy 2 of those for the adaptor, right? Then there is this dual AD797BRZ that do not need any adapter? So should I get 2 single opas for the adapter  and are there any differences with those two AD797BRZs? Lastly I do not have any extra power source for my Audio-gd FUN and I read somewhere that opas get better with extra power, so can I drive dual AD797BRZ without the extra power source?

 

[kiteki]

This is a very extensive review in the first post.
 
 
I haven't read all 26 pages but has anyone blind tested any of these op-amps?

 

[AmarokCZ]

Three days ago I recieved ZERO DAC with Audio-GD MOON in it for upgradind to version "Amarok". After upgrading it I quickly "blind-compared" OPA MOON to my 2xOPA627 and the difference between them was impossible for me to tell when listening to AKG K270 or K300. But the difference was obvious when listening to STAX SR-3N because with MOON there was something wrong with highs.

 

[kiteki]

Three days ago I recieved ZERO DAC with Audio-GD MOON in it for upgradind to version "Amarok". After upgrading it I quickly "blind-compared" OPA MOON to my 2xOPA627 and the difference between them was impossible for me to tell when listening to AKG K270 or K300. But the difference was obvious when listening to STAX SR-3N because with MOON there was something wrong with highs.

 
The source is only as transparent as the transducer.  You can't watch blu-ray on a DVD.  I have no idea how transparent STAX really are in reality or if their amplifier section just filters out the signal or the transducers instill stax-ness all over the place.
 

---

 
It seems like AD797BRZ is popular in this thread, is it much different from the AR which I already have?

 

[ryanjun]

Quote:

Category 4 – like a completely arranged room, not quite tidy yet
I'd say, the fight with the Audio-gd op-amps starts making sense here.

Did you ever know that the op-amp grade matters for audio? Yes, it does, at least for OPA2134, OPA2132, LT1028, AD797 and OPA627 which I can confirm. So, let's continue:
2x OPA627BP – welcome to Category 4! Unlike the AP or AU series, this one is not lacking proper attack. Sure, it's not lightning fast but at least this one can keep the rhythm, it's actually pretty similar to the AD797ANZ with the advantage of JFET inputs. Lack of the last refinement and oomph makes it less than perfect. I'll get back to this later.
2x AD797ANZ – this one I regarded for a long time as a piece of wire equivalent when used as a buffer. It lacked some level of the lowest detail but added pleasant tube-like timbre, in a delicate form of course. This one is a bit better than the AD8599, with less accentuated sonic signature.
2x LT1028ACN8 – the better LT1028 grade. Sure it's audible. Instead of the slight dryness you get a bit longer sustain in the mids, with a slightly higher midrange coloration, hardly perceivable when your ears get used to it. The soundstage is correct, the imaging is correct, tha PraT is correct, and what I would like from it to be perfect is a bit more independence of the events in the furthest background plans. It's sounds like it's a bit hazy there, however you can like it.
2x OP27GP – no kidding! Just see the prices of the OP27E from Texas.

There is a trick – this one, I mean the one from Burr-Brown I own, requires class A biasing. Otherwise it's not worth considering. I remember I liked it even more than the 2x LT1028ACN8 combo. As a side note I can write that the OPA627 was designed to have this op-amp offering JFET inputs. Same with the OP37 vs. OPA637.
2x OPA211 – the king of the space, I guess it's even exaggerated. In terms of overall order, clarity, timbre transparency and rhythm, this one is a direct upgrade from the OPA2228. Slight but worth it. The increased shape detail and huge soundstage is probably the result of something I'd call sound disassembling. It's like losing spatial coherence of each sound, having the tone in one place, and the harmonics just aside, not surrounding the right tone. Strange but true.

 
 
Hello, majkel
 
I have a question regarding the review : you categorized OP27GP as "category 4" under one condition that they have to be class-A biased. 
 
Do you remember how much mA did you biased those OP27GPs? (I am planning to use a constant current source for biasing - lm317 current regulator or BJT with a voltage reference perhaps.)
 
I am tweaking my DIY DAC for its I-V & filter stage by trying different op amps in different ways.
 
Pls check out the link below for the DAC. It is a collaboration project by South Korean DIYers, a.k.a. "HAS", and we used asynchronous DDC module with XMOS, ground isolator between DDC and DDC's I2S output, separate linear power supplies to DDC, digital part of DAC, analog part of DAC, and I-V & Filter stages :
 

http://www.headphoneamp.co.kr/337673
 
I happen to have 5 of OPA27GPs from 8 years ago and never used these, but just realized the potential they have thanks to your review.
 
I would very much appreciate it if you can share some data you had from your past experience. Otherwise, I will simply bias them 12mA each at +-15Vdc with sufficient heatsinking.

 

[majkel]

My memory tells me it was 5mA but you can try the rule that you need just a bit less than a half of output short to ground current - see data sheet.

 

[ryanjun]

Quote:

My memory tells me it was 5mA but you can try the rule that you need just a bit less than a half of output short to ground current - see data sheet.

 
Thank you majkel,
 
http://www.ti.com/lit/ds/symlink/op27.pdf
I checked Figure 22 on page 13 in the datasheet.
 
A half of output short to ground current is 15mA, and 12mA seems good number.

 

[kiteki]

Three days ago I recieved ZERO DAC with Audio-GD MOON in it for upgradind to version "Amarok". After upgrading it I quickly "blind-compared" OPA MOON to my 2xOPA627 and the difference between them was impossible for me to tell when listening to AKG K270 or K300. But the difference was obvious when listening to STAX SR-3N because with MOON there was something wrong with highs.

 
So they both sound nice and analog?  Like silky?  Stuff like JRC4556AD sounds a bit more thin and digital to me, even the MUSES ...
 
Perhaps my DAC is "thin and digital" and the MUSES is more transparent, the OPA627 / MOON have the colouration of liquid water?  Difficult to know for sure right ...

 

[AmarokCZ]

It was just quick listen, but both were quite neutral, not thin, with the STAXes the highs of MOON was odd - less realistic (especially cymbals and acoustic guitar), maybe little harsh and little rolled off. Also MOON has high IMD and THD at higher frequencies.

 

[kiteki]

2x AD797BRZ – this is the op-amp truly deserving the name of the Analog Device. This one is a smoother and fuller sounding version of the AD797. Switching from the ANZ to the BRZ series is like going vinyl instead of digital. Everything is smooth to the moment your music craves for the harsh texture like aggressive violin passages, distorted guitars, or stronger double bass phrases. The readability of the furthest plans is great, without going into image sharpening effect which makes you see the details more but lose the feeling of perspective at the same time. Roughly, it's like the AD79ANZ with all advantages of the OPA627BP added.

 
I just noticed this, thanks, now I will definitely have to try the BRZ...

 

[kiteki]

It was just quick listen, but both were quite neutral, not thin, with the STAXes the highs of MOON was odd - less realistic (especially cymbals and acoustic guitar), maybe little harsh and little rolled off. Also MOON has high IMD and THD at higher frequencies.

 
Thanks, EARTH seems like the safest choice right...