[xtreme4099]

don't know why these opamps dont get much more publicity ...it blows away the ad8620 i had in meta42. I ordered some samples with help from ppl(who recommended them) from the analog devices website, i got them this morning.

i opened up my meta and took out the board, my meta has a brown dog adapter. i didnt have any spare ones so i sodered off the ad8620 from off the brown dog and sodered on the 8066(dual version of 8065), turned on the meta ...a humm oh no, the brown dog wasn't sitting all the way ...doh ..hurray sound. All in all it sounds so damn clean, the detail is there sounds good ....listened to Eric Clapton unplugged - layla...and then Pink Floyds - Delicate Sounds of Thunder Live album ...track 3 ...Wish you were here ... you feel the reverb and twack on every string way better than the 8620, the one thing 8620 does do better, is it oscillates highs better.

I had a chance auditioned the ppa again yesterday with phil in maple valley, and had the chance to hear the ppa with several op amp configurations, we tried the burr brown opa627...the detail just wasnt there .... then the opa637's ...good op amp way detailed ...but then slapped on a pair of ad8065's and wow way more detail...unforgiving ....this was a kimber kcag cable hooked up to my m-audio revolution with foobar2k /kernel stream enabled and outsrced to 96000khz, so pretty damn good source, so yeah could definitely tell the difference.

i remember phil telling me 8065/66 are rated 145mhz bandwith ...making them darn quick and detailed, which is why he opted for 637 for his ppa, personal taste i guess, he also recommended i try some el2002 to keep up the 8066's, the el2001's i currently have are rated 70mhz, the 2002's at 180mhz, got to hand it to phil he does know what he's talking about when it comes to sound, the ppa is coming along great and sounding equally amazing.

 

[Squalish]

Punctuation is your friend. You don't need to be commited to Lady Ellipsis, plenty of fish in the sea, like Period and Comma.

 

[guzzler]

its all subjective, but the 8620 is considered by most to be a good choice of high end op-amp, but if you prefer the 8066 its yours! might give it a try myself as well, seeing what a great recommendation you gave it!

g

edit: spelling

 

[jeffreyj]

Quote:

Originally posted by xtreme4099 ... i opened up my meta and took out the board, my meta has a brown dog adapter. i didnt have any spare ones so i sodered off the ad8620 from off the brown dog and sodered on the 8066(dual version of 8065)...

So you did not A/B test the two units side-by-side, then? You are relying only on your memory to generate your comparison?

Quote:

i remember phil telling me 8065/66 are rated 145mhz bandwith ...making them darn quick and detailed, ...

If you need to amplify an FM radio station then the extra bandwidth comes in handy, otherwise it is a liability.

I have a META42 board and I think it's very nicely laid out. Well, that ground track running around the perimeter is a little iffy, but other than that it's a stable board for use below 100kHz or so. Asking it to deal with a gain stage of such high bandwidth is not fair nor right. Proper board layout techniques for RF are a world apart from audio, and if those layout techniques aren't employed then how can any benefit be derived? None can, and in fact, I'd bet an AD8620 that you've got a screaming oscillation going on way up in the tens of MHz.

It's analogous to putting some family sedan-sized Goodyears on a Dodge Viper - good tires, wrong car.

 

[xtreme4099]

i think ill keep simple and just say that i like the 8066 better...

 

[jamont]

Quote:

Originally posted by jeffreyj I have a META42 board and I think it's very nicely laid out. Well, that ground track running around the perimeter is a little iffy, but other than that it's a stable board for use below 100kHz or so. Asking it to deal with a gain stage of such high bandwidth is not fair nor right. Proper board layout techniques for RF are a world apart from audio, and if those layout techniques aren't employed then how can any benefit be derived? None can, and in fact, I'd bet an AD8620 that you've got a screaming oscillation going on way up in the tens of MHz. It's analogous to putting some family sedan-sized Goodyears on a Dodge Viper - good tires, wrong car.

I have a META42 with an 8620, how can I tell if I have high frequency oscillation? I don't hear anything obviously wrong, but if it's happening at MHz frequencies how would I know?

 

[xtreme4099]

jeff is right ...the 8620 does better in the highs ...but the 8066 sounds pretty clean ...im gonna order some extra brown dogs from tangent or something and do a more in depth comparison...

 

[binary_digit]

xtreme4099> I think that jeffreyj is refering to self oscilation (Generation of a waveform all on it's own) rather than your use of the term to denote the Decay in music to a Black background.

I The AD-8066 is plenty stable in the PPA and i belive it also should be in the Meta as well. this is using closed loop gains of 11 or more. this is what both the PPA and xtreme4099's META is set at.

http://home.earthlink.net/~goodclose/joann.html
the AD-8065's Designers homepage.

hope you find this of intrest

 

[jeffreyj]

Quote:

Originally posted by binary_digit xtreme4099> I think that jeffreyj is refering to self oscilation (Generation of a waveform all on it's own) rather than your use of the term to denote the Decay in music to a Black background.

Indeed I was; thanks for the clarification, as I wasn't quite sure what xtreme4099 meant!?!

Quote:

I The AD-8066 is plenty stable in the PPA and i belive it also should be in the Meta as well. this is using closed loop gains of 11 or more. this is what both the PPA and xtreme4099's META is set at.

The loop gain is an important factor for ensuring stability, but not the only one.
I just measured the C and L characteristics of the detachable cord on my Senn's and got 470pF and 5.5uH per channel. Most high-speed op-amps will become great oscillators with so much capacitance and so little inductance in the line. Of course, this is on the verge of re-opening a fairly recent can of worms so I'll not post more, but I think you know where I'm going with this.

edited: enjoyed the web page link you provided!

 

[morsel]

Your conclusion is surprising. Maybe your AD8620 is damaged or defective. The AD8066 is a lesser opamp by spec and listening test. You might want to try another IC just to double check.

 

[binary_digit]

specs from data sheet indicate the 8066 has higher slew rate , higher bandwidth, with slightly higher noise.
http://www.analog.com/UploadedFiles/...AD8065_6_c.pdf
http://www.analog.com/UploadedFiles/...D8610_20_c.pdf

 

[ppl]

My favorite opamp for the ppa is the opa637's in the gain channels and the opa627 in the ground channel. This combination gives a well rounded, buttery soft, input friendly configuration. The highs are vivid and spacious, the mids clear and friendly, the lows strong and fast. It is important to me that I have the configuration that allows me to go from source to source with the same listening comfort. The 8065 in all channels of the PPA sound marvelous with the HD580's and up sampled 24 bit 192k(?) with the M audio revolution card. The highs were extremely well delineated and crystal clear. The opa combination sounds noticeably distant in mids and highs by comparison. The bass was similar on the opa and the 8065's. When listening to less than perfect recordings from this same setup the highly analytical 8065 revealed every flaw in it. I found this to be uncomfortable and preferring the opa combination instead.

the bright representation of my sony MDRv6 and the similar mdr7506 made this even more insulting. None the less when returning to high quality I found this alleviated and replaced with a more delightful although slightly brighter than the 580's. Since I don't have the 580's yet, and some of my portable sources may be less than ideal (line out portable cd player) I prefer a more forgiving configuration like that of the opa637/627.

The AD-8610 like the opa637/627 is forgiving with my less than perfect sources and recordings. The AD-8610 can obtain a more black background than any of the opamps thus far mentioned. It is also one of the most light and airy. The opa 637/627 in comparison has a far superior sound stage. The PPA by virtue of its ground channel topology also provides a wider sound stage in comparison to similarly equipped conventional amps. Combining these two results in a seemingly neverendingpanoramic3dspacialization.

(My new word).

So that is why I prefer the opa 637/627 in my personal PPA but your results may vary. A quick probe on the oscilloscope revealed no ring or oscillation.

Addendum: If the AD-8065 is used in the PPA I strongly recommend that the higher bandwidth HA-5033 buffers be used. This is a drop in replacement for the presently installed HA-5002 buffers. This would require heat sinking them because the HA-5033 draws over 20mA each. The amp will now consume 300mA from the DC power supply at idle .

Not much of a portable anymore. Back to the OPA's.

 

[xtreme4099]

8620 is good ..but on the meta it seems as if adds a concert hall almost dsp effect to the music almost synthasized ...the ad8066 seems to decay the music quicker ...while the 8620 fades with every note .....ill have to try the 637's on the meta perhaps, aren't they single channel, i have one of those brown doggs with surface mounts.


Quote:

yeah. Combining these two results in a seemingly neverendingpanoramic3dspacialization. (My new word). -ppl

 

[ppl]

xtreme4099> The reason i recomended the 8066 in your case is the fact that you are using your meta as a home unit on your PC and since you like detail the 8066 is ideal in your situation. To evaluate the OPA-637 in the META42 you can get a BD adaptor from tangent to adapt two singel op amps to a dual socket.

Also since you are using your meta at home I recomend you get some EL-2002's from tangent ( If he still has any) Regardless of what op amp you use. the 2002 IMHO sounds alot better than the EL-2001. the Bottom line is for you to like the sound of your amp and remember that mine or anyone elces choice is not nessasarly right for you.

 

[ppl]

Quote:

Originally posted by jeffreyj Indeed I was; thanks for the clarification, as I wasn't quite sure what xtreme4099 meant!?! The loop gain is an important factor for ensuring stability, but not the only one. I just measured the C and L characteristics of the detachable cord on my Senn's and got 470pF and 5.5uH per channel. Most high-speed op-amps will become great oscillators with so much capacitance and so little inductance in the line. Of course, this is on the verge of re-opening a fairly recent can of worms so I'll not post more, but I think you know where I'm going with this. edited: enjoyed the web page link you provided!

This would be true if the op amp is directly connected to the Headphones however in the instant cases the cans are connected to the Buffers. Glad you liked the Link.