[Wayne1]

I believe the AD8620 as a proper single opamp must be a misprint, with the author actually using the AD8610, a single opamp with the appropriate pin-out, as opposed to the dual AD8620, which would, in technical parlance, go all hinkey, and possibly, let the smoke out.
[Wayne - are the rails on the EE within the AD8610 +-13 volt rail limits?]

The rails for the op-amps on the EE MiniMax DAC are +- 15 volts. They are limited to about 200 ma.

Scotty,
The signal from the I/V op-amp is driving the tube and the second op-amp all the time. Perhaps removing the single op-amp might cause some change in the sound of the tube stage by changing the overall load on the circuit. That would be better to experiment with than plugging in an incompatible op-amp that could cause damage.

I've been thinking about this most of yesterday and over night. I've tried to calm down about this. What Doug published was very irresponsible journalism, at best. It does not appear that he ever bothered to check with anyone with more knowledge of electronics that he possesses. Peer review of DIY articles be people with small amounts electronics knowledge should be mandatory.

In the Dagogo article, it appears he communicated with Alex, but a couple of posts ago, Alex (bravophase) distinctly says DO NOT swap singles for dual op-amps and the other way around.

Hi Guys, the NE5532 and its sub(dual) and NE5534 and its sub (single) are not compatible to each other. If you plug in the dual opamp to the sigle opamp place, and vice versa, it may damage your DAC.

Cheers !

Alex

So Doug published suggestions that were against the advice of the designer of the DAC. He also goes on to say the sound of a single op-amp in the dual position sounds better. It is only receiving HALF of the signal from the DAC chip and then passing it through a filter circuit to the the tube.

For me, it certainly calls into question the validity of any article or review he has ever written.

There is more to say but I just get angry all over again. All I will comment on is be careful about what you read on the internet, Miss Information is everywhere.

[Occam]

I'll post here, rather than in that group therapy session over on AA.
Kudos to Doug for updating his article, but apparently he still doesn't feel it necessary to find proper nerd to proof his copy for technical issues -

1. The suggestion of the AD8620 for the I/V chip is (still) inappropriate, given the 15 volt bipolar rails in the EE dac. The AD8620 is rated for a maximum of 13 volt bipolar rails. I'm not surprised that this hasn't blown up his EE dac, yet. Give it time.... it might well continue to function in his unit, but given enough folks following that recommendation, some will inevitably be sorry. Given the plethora of available chips that are rated for the rails, with appropriate specifications, the risk is silly.

2.

*U1/U2   OPA827 (dual) and   U6/U7   OPA2604 (single)

It would be proper to recon this as one of the better combinations.  My notes simply indicated, “Gorious! Perfect!” as it was a finalist. *The OPA2604 is not currently offered by Cimmaron. I believe it is an older Opamp; if sourced elsewhere Cimarron can use the Brown Dog adapter to make the Opamp for your Minimax.

*U1/U2   OPA2604 (dual) and   U6/U7   AD797B (single)

This was the big winner in my system, offering scrumptious sound for both the Legacy Audio Whisper DSW and Kingsound King speaker systems. I find precious little to nitpick about this pairing; it yields a mature, “full bodied” sound with plenty of crispness and detail but without a trace of stridency. *Again, one may have to search for the OPA2604.

In the former, the OPA2604 is a dual opamp, not a single. Its use in the position for a single is still inappropriate. Throwing shit up against a wall to see what sticks is a wonderful personal learning technique, but not when making recommendations to others.

Regarding the later, why would Cimmaron or anyone want to take a smt dual (unless adding ps decoupling on the adapter) and mount it on a dip adapter when the chip is readily, inexpensively available already in dip8 form?
Shopping for OPA2604ap

FWIW

[*Scotty*]

As of today 3/26/2011, Doug has sort of printed a retraction in the form of a re-submission of his article in which the appallingly bad advice regarding installing op-amps backwards into the circuit have been removed.   
 Unless he has read Paul's post however, he may still be ignorant of the potential to let the smoke out of his DAC due to the rail voltage miss-match between the AD 8620's maximum design voltage of 13volts and EE 15volt IV rail voltage.
  In hindsight it's obvious that he got into this mess via a lack research and the failure to vet his list of substitute op-amps with Bill O'Connell before he started the chip rolling adventure.   
  I imagine his first thoughts at the beginning of this project were,"how hard could it be?" and "what could possibly go wrong?".   He closes his introduction to the revised article with the acknowledgment that the details do matter and more than was first apparent to him.
Here is a link to his Mea culpa and Volte-face. 
http://dagogo.com/View-Article.asp?hArticle=864
 Still, it is clear from the content of his introduction that he does not appear to understand that he got damned lucky that the DAC didn't die and/or that the op-amps didn't crap out when powered by only by the negative rail of the power supply when he installed the chips backward.
Scotty

[bunky]

Doug started his original article on op amp rolling in the Eastern Electric MniMax DAC using recommendations from Chris Owen who is a electrical engineer who also happens to own and operate Clarity Cable. I talked with Mr Owen at length over the phone and he said that he had tried many variations of opamps in the EE DAC and that he prefered the LME49990 surface mount op amp using the brown dog adaptors to install them in the DAC. Chris also said that he prefered using the tube side with a Seimens 12AU7 Nickel plate installed in the DAC. Mr Owen directed me to the www.cimarrontechnology.com website so i could purchase 2 pcs of ( P/N 970601A ) which is a brown dog adaptor with a single LME49990 presoldered to it and 2 pcs (P/N 020302A ) which is a brown dog adaptor using two LME49990 pre soldered to it with one on top and one on the bottom in a dual op amp configuration. i believe Doug's intentions were to show that a average Joe or Jane whatever the case may be could DIY install opamps in the EE DAC to improve the sound of the stock unit in a plug and play fashion just like we do with tubes but he took it upon himself to experiment without consulting with professionals and got in it way over his head. i guess he is very lucky that his DAC did not go up in flames      thanks.....WCW III

[mfsoa]

My post from Audiogon:

Hi Doug,
I urged you via email to correct a fatal flaw in your article, yet you chose not to address it in the least in your revision.

As far as I understand, when the tube output is selected, you are listening ONLY to the op-amps in  the U1/2 positions. You are NOT listening to the op-amps in the U6/7 position. When the SS output is used, you are listening to ALL 4 op-amps. Obviously this distinction must be made very clearly for each description of the sound coming from the unit.

Therefore, unless you tell the reader whether each and every evaluation was performed with either the tube or SS outputs, the reader does not know which op-amps you were actually using. Obviously, since the reader does not know which op-amps are being used, any description of the sound quality obtained is completely meaningless.

You say that "Because of what is to my ear a more pleasing tonality I have tended to use the tube output the most" If this is the case, why do you then go on to desribe the sound of sets of ALL 4 op-amps, two of which are  not even being used? Or, maybe you were referring to the SS output, in which case you actually were using all of the op-amps you mention.

The reader doesn't know, because you don't say

Again, this renders any discussion of sound quality meaningless since we don't know what op-amps you were actually listening to.

It is just as meaningful as saying that you have two preamps and three amps in for review and then describing the sound quality without telling the reader which pieces are being used!

I don't know how to be any clearer that the current article says absolutely nothing about about how particular op-amps sound unless you tell us which op-amps were in use! 

You can fix this easily, by making two tables - One that lists the op-amps in U1/2, which were evaluated by the tube output. The second table will list the op-amps in both the U1/2 positions and the U6/7 positions, which were evaluated via the SS output.

I think as a reviewer you would like the reader to know what is being reviewed. Such is currently not the case.

Best of luck to you. I hope that the article can be revised once again so that you let can the reader know which op-amps were being used in your listening tests.

-Mike

Maybe it's just me, but when read a review I'd like to know what piece of gear is being reviewed. Kinda gives the review a little more meaning.

And maybe it'd be good if he let people know that his top choice for the tube output, the OPA2604, is available for $5 each (two needed) in the format needed for direct drop-in into the DAC (no adapters needed), instead of saying that it'll take $140, but that Cimarron can't currently provide the 2604!  Google, man, Google. 60 seconds.

I do have 6 49990s on the way. Will be interesting...

-Mike

[Occam]

.......
I do have 6 49990s on the way. Will be interesting...

-Mike

Mike,

It should sound quite nice.... if you happen to be driving an original VAC Renaissance 30/30 pushpull 300B amp. 

FWIW,
Paul

[mfsoa]

Well, I have a VAC preamp at least!

I'm afraid that the 49990s might be too lean 'n clean for my taste (and w/ the Cherry amp), esp. relative to the OPA2107 but we'll see.

But I've taken the SS output too far in the rich, creamy direction (with some source material - with others it's oooh so nice) with the OPA627s. So I'd like to inject a lttle more air into things w/ the 49990s.

If the 49990s don't pan out, I'm eyeballing the OPA827.

[bunky]

i just ordered a wrist ground strap from Amazon.com so i can safely install the LME49990 op amps in my MiniMax DAC. i may also order two of the OP2604 to try in the U1/2 position as a alternative to the LME49990. any suggestions  from anyone for a tool to extract the op amps with would be most welcome. thanks....WCW III

[balja]

 

[srb]

The simplest and cheapest is the one-piece spring steel type similar to the OK Industries EX-1 available for a few dollars.  You have to be careful that the chip doesn't release violently all at once and mangle pins.  I try to place a finger on top of the chip to carefully control extraction with a very slight rocking action.
 

 
A more precise and controllable tool is the slide-action type similar to the OK Industries EX-2 available for around 20 dollars.  However, you may not be able to use it in very tight locations.
 

 
They are available at most electronics parts and tool vendors, including Digi-Key.
 
Steve

[mfsoa]

As Doug S. warned, make sure you are pulling up on the op-amp only, and not the socket that is attached to the board.

I often see the OPA2107 being mentioned as upgrade to the 2604, but it's pricey as far as op-amps go.

Or try the OPA627, which Doug says isn't supposed to sound very good (which is really funny because it is kinda revered as being the best replacement op-amp you can get, save for maybe some of the new ones) and that it is supposed to be inexpensive (which is also really funny since it is one of the most expensive op-amps you can buy). Oh, if only Doug had access to this thing called Google and 30 minutes of time, it would have saved him so much trouble.

[Occam]

Well, I have a VAC preamp at least!

I'm afraid that the 49990s might be too lean 'n clean for my taste (and w/ the Cherry amp), esp. relative to the OPA2107 but we'll see.

But I've taken the SS output too far in the rich, creamy direction (with some source material - with others it's oooh so nice) with the OPA627s. So I'd like to inject a lttle more air into things w/ the 49990s.

If the 49990s don't pan out, I'm eyeballing the OPA827.

I'll hazard to guess you'll end up with the current chip as your I/Vs and the LME49990 as the SS output chips.  The 827s would be slightly less warm than the 627s. Along the same lines of FET input, single SS output chips, you might also consider the ADA4627-1 from Analog Devices. I've not personally heard it in that role.

[MarkM]

Last night I dropped in the OPA1612 after not listening to them for a couple of months.  I had been sticking with the LME49720 & (10) in their respective positions while doing some mods to my dac to keep a baseline on the sound as I did the mods in stages over the past month.

The 1612 and 1611 are very clean and dynamically extended op amps.  I really like this op amp while listening to the tube output.   Also listened to the 2604 and many others early on and will have to spend the next week reevaluating the impact of the changes in my system.  Not sure where this will end up, definitely not a single in a dual position. 

So many options to suit each taste.

Will start a new thread next week on the mods I did to the power suppy, caps and the all important +-15v regulators that were upgraded to take those opamps and the dac to the next level for those interested and daring.

[grodri02]

Any more updates regarding the LME49990?

[bunky]

I installed my LME49990's the other night configured on Brown Dog adaptors as duals in the U1 and U2 positions and as single op amps on Brown Dog adaptors in the U6 and U7 positions. they are very smooth, clear and hyper detailed. mine have been running for 30+ hours. do these things have a break in period   

[PeteG]

I installed my LME49990's the other night configured on Brown Dog adaptors as duals in the U1 and U2 positions and as single op amps on Brown Dog adaptors in the U6 and U7 positions. they are very smooth, clear and hyper detailed. mine have been running for 30+ hours. do these things have a break in period   

I would say close to 50hrs mine settled down, than I was able to go back and try my different tubes again.

[Noseyears]

My friend just upgraded his Oppo 83 dvd player with Burson hd opamps, and the result was good. I noticed a huge improvement on details and soundstage.

They could work well on the Minimax dac.

[Levi]

Hey Bunky,

How did you mount your LME49990. Pictures please!!!

I installed my LME49990's the other night configured on Brown Dog adaptors as duals in the U1 and U2 positions and as single op amps on Brown Dog adaptors in the U6 and U7 positions. they are very smooth, clear and hyper detailed. mine have been running for 30+ hours. do these things have a break in period   

[Levi]

I am trying some discrete OPA from Audio-GD.  It's operating voltage is +-9-25Volts and 50mA each x2.  Stay tuned!

[Levi]

Just to update.  Here is a picture of the OPA Audio-GD EARTH.  As it's description, the sound is more analog and natural.