Jump to content


Flavors of Audio Op-Amps


58 replies to this topic

#1 bpribadi

    Realistic Hobbyist

  • Senior Member
  • 819 posts

Posted 03 September 2004 - 11:50 AM

I would like to try different flavors of sound for 'My Modified Pimeta Clone' headamp (it is not Pimeta, just like Pimeta circuit diagram with PPA jfet cascode). So I bought some Burr Browns to be compared with the Analog Devices.

I can’t rely on Tangent’s Notes on Audio Op-Amps too much, because he tested those Op-Amps in CMoy circuit. They might sound differently in my headamp, because of the Jung’s multiloop configuration (like in Pimeta) and jfet cascode class A biasing (like in PPA). Another thing, I might have different taste than him biggrin.gif
http://www.tangentsoft.net/audio/opamps.html

The power supply for the headamp is regulated using LM2941 and LM2991 set at precisely +7.2 and -7.2 volts (14.4 volts rail to rail).
user posted image

I will try more Op-Amps as times and budget permits wink.gif

Amplifier : 'My Modified Pimeta Clone' DIY HeadAmp
Source and Headphone : Panasonic PCDP SL-CT810 and Grado RS-1
CDs : Ultimate Demonstration Disc from Chesky Records, Women of Song from Chesky, Best of Audiophile Voices, Jennifer Warnes – The Hunter, and some other CDs.

So, I tested them with bright, lively sounding, and very revealing headphone. And for my taste of music, vocal is very important. I like thick and warmth midrange.

There is no exact measurement to describe how audio equipments sound. All measurements are subject to personal taste, so this Op-Amp comparison is only sharing of my experience with those Op-Amps, with hope there will be readers benefit from it.

The Result:

AD8620
Very bright and lively sounding Op-Amp. The treble sounds a bit too dominant. Very good detail and imaging. I love the transient and impact of the AD8620. My only complain with this Op-Amp is the treble, a little bit too sharp, and the color tends to the metallic sound.

The good : Bright, very good detail, lively sounding, the most transparent sounding so far.
The bad : Treble can be sharp and harsh with bright headphones.

Application: Not to be paired with bright headphones. You might get ears fatigue. Probably good for Senns, but not for Grado. I still can enjoy it with my RS-1 though, but only for certain recordings. Very good detail and resolution will reveal recordings flaw. So, this Op-Amp is only for good recordings.

OPA2604
Sweet, but veiled sounding Op-Amp. It’s sounds the other way of AD8610. Not bright, veiled, with poor detail. There is no way you will get ears fatigue with this Op-Amp, but you might get bored. It is not a lively sounding Op-Amp. It is not bad, it has a nice color of sound, just a bit mellow with strong Burr Brown’s laid back signature. Some people might like it.

The good : Sweet, warm, never sound offensive, good for long hour easy listening.
The bad : Poor detail, veiled, mellow, far from lively.

Application:
To be paired with very bright and lively sound headphones. For those who like long hour easy listening, this Op-Amp might be the choice. As it will hide many details, it might be good to listen poor recording with this Op-Amp.

OPA2228
Very nice natural sounding Op-Amp. I like its treble. Not too bright, just nice. It has the laid back Burr Brown sound, but light not as strong as the OPA2604. It is not very bright and lively, but not heavily veiled either. For Senns it might sounds analytical, but for the lively sounding Grado, it makes the Grado sounds well controlled. I can use this Op-Amp for a long hour listening with Grado without getting ears fatigue. Good detail, but not as good as the AD8620. The midrange and bass are slightly thicker than the AD8620 which are nice. Overall, I like this Op-Amp in my headamp paired with Grado, it sounds natural and really ears friendly. I can feel a lot of 'air', like listening to the singer in open air. When you listen to my amp with this Op-Amp, it is not a WOW, but its sweet, and you might wear the headphone longer. I just miss the lively sounding and transparancy of the AD8620 a little bit.

The good : Natural and sweet. Very nice treble, good midrange and bass.
The bad : Not as detailed as the AD8620, and slightly slow in transient and impact.

Application:
To be paired with bright and lively sound headphones. Very nice for long hour listening, better than the OPA2604. As it is not highly revealing amp, it forgives flaw in recordings. I might put this OPA2228 permanently in my ‘Pimeta like headamp’, it is very nice to be used for listening my ‘non audiophile’ CD collections.

OPA2134
Putting this Op-Amp in Pimeta doesn't change it's sound characteristic a lot. Just a tad more transparent (only a tad) compare to CMoy. I would say that this Op-Amp has the worse imaging than others that I have tested. Very narrow, narrower than my PCDP output. Very narrow space between the singer and the musical instruments, sometime feel like putting my head in a bucket. It only good in bass, nothing else. So for some music from MIDI, which doesn't need imaging at all, this Op-Amp is fine. It has big bass and thick midrange, which is good. The treble is a bit 'short', means bell's sound will sound shorter than the AD8620 or OPA2228. Ok, I have no intention to make it sounds like a bad Op-Amp. OPA2134 is a good Op-Amp, very DIYer friendly, and they have nice sound color of which I like. My complaint is only the narrow imaging, that's all.

The good : Big bass and thick midrange. Nice color of sound.
The bad : Poor imaging.

Application:
I think this Op-Amp need bright, transparent, and wide imaging headphone to balance it's narrow imaging characteristic. This Op-Amp is a NO NO for people who demand good imaging, probably another good alternative for those who like music from MIDI / electronica, and like BIG bass.

AD8066
This Op-Amp dethrone the OPA2228. It sounds much better than the OPA2228. It has the AD signature, bright and fast. What I like most from AD8066 is the BASS. It has excellent bass, bigger than the OPA2228 and AD8620, and it goes lower. It has very good low bass. For comparison, OPA2134 also has good bass, but more to the mid bass, while AD8066 has better overall bass. My headamp is DC coupled, so it takes all frequency from DC. If yours is AC coupled, you might not be able to hear or feel the excellent low bass from the AD8066. Try 'The Hunter' from Jennifer Warnes to test the bass.

If OPA2134 'KICKS' then the AD8066 'KICKS' and 'SHAKES' party.gif

This AD8066 is not only good in bass. It also has excellent imaging, about the same as the AD8620. I love the treble which is a tad smoother, more 'airy' than the AD8620 which I often feel a bit sharp. So the conclusion is, excellent Op-Amp, very neutral, excellent bass, crystalline clear mid and treble (very good transparancy), excellent imaging, fast and detailed.

The good : Excellent BASS, fast, detailed, good imaging, with a pleasant 'airy' feeling. This Op-Amp really brings music to life.
The bad : Depend on personal taste, might be too bright for some people.

Application:
Eventhough I think this Op-Amp is an excellent general all-purpose audio Op-Amp for any headphone, but it tends to sound bright. With good recordings (non-metallic treble recording), this Op-Amp sounds very good with my RS-1. AD8066 is very revealing, you will hear any flaw of poor recording. For poor recording, OPA2228 might still preferable.

OPA637
I agree with most of the DIYers that said that this OPA637 (and OPA627) is one of the best Audio Op-Amp. It is the most expensive as well dry.gif . I didn't have enough time to listen to it, just a few tracks of Chesky Demo Disc, so my comment here will be based on mine and my brother comment (I bought the OPA637 for him). I use this Op-Amp in the amp I made for my brother, which in theory has the same circuits as my headamp.
http://img.photobucket.com/albums/v294/bpr...mp/IMG_6693.jpg

It sounds Very Very Very natural. Almost no coloration, very musical with high listening pleasure. It has thick bass and midrange, with just the right level of treble for my Grado RS-1. The imaging is excellent. Comparing with AD8066, the AD8066 is a tad brighter, and slightly has more space in between the singers and the musicians, but the different is subtle. The OPA637 has the laid back Burr Brown sound which I like, but it is very minimum comparing with other OPAs.

The good : Very neutral and musical. Thick bass and midrange with transparant treble. One of the best Audio Op-Amp.
The bad : Probably a little dark for dark Headphone, slightly laid back sound which might not suit some people.

Application:
The best general Audio Op-Amp. Highly recommended for Grado users, or other bright sounding headphones. For Senns users, please audition before you spend the money for this Op-Amp.

OPA2107
If you like Burr Brown sound but OPA627/637 is way out of your budget, try OPA2107. It has the color of the expensive OPA637. So far amongs the other OPAs I tested, this is the one that is close to the OPA637, but it doesn't have the superb detail and the good imaging of the OPA637. It has a natural-dark sound, with very good bass and midrange, the treble is fine, but not as transparant as the ADs. It also has the BB laid back signature, more laid back than the OPA637 and OPA2228. I rolled back and forth with OPA2228 (which I like for being very warm and sweet), OPA2107 sounds more natural, faster, with more accurate and better imaging. But it is a bit darker than OPA2228. So for it's price, between the OPAs, it sounds right. More natural & faster than OPA2134, OPA2604 & OPA2228. Compare to the AD8066, I prefer the AD8066 for having better imaging and more transparant treble.

The good : One of the best Burr Brown Audio Op-Amp for the price. Natural-dark sound good for bright headphone such as Grado. Excellence Bass and Low Mid, very tight and thick. It sounds musical and enjoyable, good for long hour listening headphone.gif
The bad : Dark sound not good for dark Headphone. Laid back sound which might not suit some people. The imaging is narrower than the AD8066 (but wider than the OPA2134, OPA2604 & OPA2228). The treble is a bit too dark for me, not as transparant as the AD8066.

Application:
Good general Audio Op-Amp for it's price, recommended especially for those who like the dark and laid back Burr Brown sound. Recommended for Grado users, or other bright sounding headphones.

Now I'm still using the AD8066 in my Amp, so far it is the best sounding Op-Amp for me.

Thanks for reading this long post yawn.gif
Happy listening! headphone.gif
Bram
-------------------------------------------------
Flavors of Audio Op-Amps

Edited by bpribadi, 05 October 2005 - 01:35 PM.


#2 mukegile

    Junior Member

  • Senior Member
  • 54 posts

Posted 03 September 2004 - 02:03 PM

w00t.gif .......2228.....good pick Bram ...probably we should try it on 4D...,
who knows biggrin.gif ... it can finance for more projects... whistling.gif
I’m only a man in a silly red sheet
Digging for kryptonite on this one way street

#3 huangyong

    musician that doesn't play instrument

  • Banned
  • 930 posts

Posted 03 September 2004 - 06:43 PM

hey hey good reviews on opamps, can fight tangent liao..lolz...
btw, have you tried opa627 and opa637??

may be we can arrange a small DIY meet when I got adapters from digi01. will let you try my opa627BP and modded cdp. how?

#4 bpribadi

    Realistic Hobbyist

  • Senior Member
  • 819 posts

Posted 04 September 2004 - 07:32 PM

QUOTE
may be we can arrange a small DIY meet when I got adapters from digi01. will let you try my opa627BP and modded cdp. how?


Sure! that's cool yes.gif

I don't have the OPA627 or OPA637 yet, because they are expensive dry.gif

But since I'm going to make Mini PPA for my brother, I have somebody to finance for the OPA637 happy.gif I probably will buy them once my Mini PPA board done. My plan is to finish it by end of October or around November.

But I would love to try in my Pimeta before I buy though wink.gif Thanks a lot for the offer !

#5 bpribadi

    Realistic Hobbyist

  • Senior Member
  • 819 posts

Posted 05 September 2004 - 04:27 PM

Just update my small review with OPA2134 wink.gif

Thanks for your interest!
Bram

#6 Q00

    Clumsy Goondu

  • Senior Member
  • 1,332 posts

Posted 05 September 2004 - 07:56 PM

Just a question though, have u given each op amp enough time to burn in yet? Some might improve over time?
Home: Aiwa XP-7 vintage pcdp ->Digital out ->Harman Kardon AVR 2500 ->DT-150

Portable: NJB3 ->Sony MDR-7506

#7 av98m

    Senior Junkie

  • Senior Member
  • 749 posts

Posted 05 September 2004 - 08:33 PM

Your findings pretty much match mine. I compared the opa2604, 2134, and 2227 in the output section of my cdp. The 2227 came up tops, much to my suprise because I had the same misconception regarding slew rate. They stayed in my cdp until I tried the opa627. tongue.gif The 627 is however much more expensive and requires use of browndogs.

Edited by av98m, 05 September 2004 - 08:37 PM.

goodbye

#8 Sipher

    Newbie

  • Senior Member
  • 985 posts

Posted 05 September 2004 - 09:30 PM

av98m,

how does the 2227 sound like in your cdp? similar to what bpribadi said about 2228?
Marantz CD-63mkII KI Signature -> PPA -> Beyerdynamic DT880
user posted image

#9 av98m

    Senior Junkie

  • Senior Member
  • 749 posts

Posted 05 September 2004 - 09:33 PM

QUOTE (Sipher @ Sep 5 2004, 09:30 PM)
av98m,

how does the 2227 sound like in your cdp? similar to what bpribadi said about 2228?

It sounded....dare I say it...tubey. It definitely made my harsher recordings easier to listen to.
The opa2227 has an even slower slew rate than the 2228 fyi. Can't remember the exact figures.

Edited by av98m, 05 September 2004 - 09:34 PM.

goodbye

#10 Sipher

    Newbie

  • Senior Member
  • 985 posts

Posted 05 September 2004 - 09:42 PM

2227 is 2.3 while 2228 is 10. i think.
2228 is used when the gain is 5 or greater. for cdp application, use which one??

did u listened to the 2227 with the setup in your sig?
Marantz CD-63mkII KI Signature -> PPA -> Beyerdynamic DT880
user posted image

#11 av98m

    Senior Junkie

  • Senior Member
  • 749 posts

Posted 05 September 2004 - 10:35 PM

2227 is unity gain stable so I used it. Had no idea how to adjust for the 2228's gain requirements.

Yes.
goodbye

#12 bpribadi

    Realistic Hobbyist

  • Senior Member
  • 819 posts

Posted 06 September 2004 - 09:43 AM

QUOTE
Just a question though, have u given each op amp enough time to burn in yet? Some might improve over time?


Nope, only the AD8620 had been 'burnt-in' for more than 24 hours. The rest are fresh from Farnell Warehouse happy.gif

I got no time to have them all burnt in properly no.gif But according to experts, Op-Amp doesn't sound much different with burning in, but the rest of the components in the amp that will give significant change with burn in.

QUOTE
Your findings pretty much match mine. I compared the opa2604, 2134, and 2227 in the output section of my cdp. The 2227 came up tops, much to my suprise because I had the same misconception regarding slew rate...


I'm glad I got friend in my findings tongue.gif Yeap, the OPA2228 is the most tube like sounded compare to the rest that I have tried. I haven't tried OPA627 or 637. I guess the OPA2227 and OPA2228 will have the same sound characteristic, since they are in one family. I didn't buy the OPA2227 because of the slow slew rate, and my amp gain is 6.6, so just nice for OPA2228. For CDP tweak, since we don't know the gain, I think it is wise to use OPA2227 for the affordable solution. For the expensive solution porbably the OPA627 is the best.

Av98m, do you mind to share how's the OPA627 sounds compare with the OPA2227? Thanks!

I'm waiting for AD8065 (single) and AD8066 (dual) from AD, will update this thread once I've tried them headphone.gif

Edited by bpribadi, 06 September 2004 - 10:07 AM.


#13 av98m

    Senior Junkie

  • Senior Member
  • 749 posts

Posted 06 September 2004 - 11:07 AM

The opa627 does sound better, very musical. However, the huge difference in price between the 2227 and the 627 means that for NAD cdps, at least, I will only recommend the 2227s for opamp upgrade.
goodbye

#14 bpribadi

    Realistic Hobbyist

  • Senior Member
  • 819 posts

Posted 07 September 2004 - 09:55 AM

I read that Tropicalrips also found that this OPA2228 sounds good:
http://www.sgheadphones.net/index.php?showtopic=2400&st=90


#15 Absolute0

    Nobody

  • Moderator
  • 1,061 posts

Posted 07 September 2004 - 03:19 PM

How much does the OPA627 cost? I was thinking of getting one if someone can help me fit it on a browndog adapter so that it can be socketed in my amp (I can't do any DIY... sleep.gif ) . I am currently using the AD8620, and largely agree with bpribadi's impressions. It pairs really well with the HD650, which isn't bright fortunately and in fact benefits from the slight brightness and detail of the op-amp. But I remember liking the OPA627 more when I had my PIMETA, for the rich, warm and very musical sound signature.

Really nice amp, bpribadi, btw. happy.gif
Period.