Success Rolling Opamps in EE Minimax DAC

I would like to know how it compares to the wyred4sound dac.

Tim

Most interesting, Doug... which characteristics of the EE DAC's sound do you feel were changed by the swap of the opamps?

Makes me wonder how much the parts cost on a $1000 DAC. I know there is the expensive casework, labor and overhead and a necessary profit.
Also it does make you think that if better op amps are $8 why don't they use them in the first place? How much is the difference between the worlds highest regarded DAC chip is VS the ones in most DACs?

Cheap amps like NE5532 (in my Benchmark DAC1) are so much worse than current best amps like LM4562 or OPA1612 but only if you include DC spects. For AC NE5532 is simply amazing in spite of its age.

Njs, the change in sound is fundamental, sweeping, an improvement in every parameter you wish to judge it, imo. When I first put them in and fired up the system I was expecting a marginal change. The difference was SO radical that in the first few seconds the disconnect between what I expected and heard had me thinking, "There's something wrong!" But after a few more seconds I became aware that my expectations had been dramatically surpassed, and realized that the performance parameters had been improved beyond my expectations. I have been highly motivated to have long listening sessions with this change, and have found no area which I would consider the difference to be worse than the original Opamp.

I am sure there will be some systems where this Opamp change will not be to the liking of the owner. I believe that will be rare since the improvements are to my ear across the board.

Mechans, I'm sure there are dozens to hundreds of variables involved in making such a design as a DAC or amp. A designer, and even a design team, has limited intellectual resources. They make a model of what sounds good, finalize it and sell it. The community has forever and vastly more resources to futz with the unit afterwards. I would not discount the work of designers because of those realities.

One can always determine at what quality level they feel the work of a designer/manufacturer is worth spending the money on. This experience opens my eyes to the fact that if Opamps were not soldered into most components likely a great number of them could be improved similarly. You and I both know there's a whole lot more going on that an $8 switch in a component. I recall buying the upsampler board for the Ah! Njoe Tjoeb 4000 and installing it. However, I believe the Opamp rolling of the EE DAC yields a proportionately larger change in sound. What was really shocking to me was the influence of the Opamps on the performance. That in no way discounts or diminishes the rest of the design. But it certainly does make me wonder if a different component might be a lot better if it had socketed Opamps to experiment!

Kijanki, "Amazing" is certainly a word that comes to mind in thinking about the influence of Opamps. I simply had no clue how sweeping their influence could be.

An aside regarding the tendency of people to dump more expensive upgrades for cheaper ones:
I'm certain people will be effusive in praise for the upgraded Maggie 3.7, the Kingsound King III (and many other marvelous new designs appearing at CES/T.H.E. Show), which I'm sure are lovely improvements over the previous designs. Here is a change which yields a profound difference for under $20. The great joy is that it's cheap, potent and marvelous sounding, imo - one of the most impressive tweaks I have ever experienced. But I'm not saying that it's a means of avoiding other upgrades in the system. It's economical thinking to say, "I'll do the Opamp thing instead of the speaker upgrade..." But that's not the way to build one's best system, nor to obtain the best listening experience. To obtain optimum results I would do efficacious tweaks as well as major upgrades.

I have found that one must pursue changes to every element of the system and thriftiness will ultimately not be paramount in every decision to upgrade if one's goal is building the ultimate system to one's taste. Even the most proportionately economical products rise in price substantially when they are an assault on the best sound attainable. In my experience at some point serious dollars (in the tens of thousands) must be spent to obtain a system that has any chance of being in the realm of SOTA. So, a person can do this tweak and call it quits, but I'm not saying here that it will nullify the need to pursue other changes/upgrades.

Mechans,

If SOTA means chips like the ESS Technology 9018, I believe the DAC chip alone is over $50 if you buy in quantity. For instance: The ESS Technology ( I believe the number is 9003 Dac chip) is about $5 in comparison.

We tried to bring the best and many pro audio components use the op-amps we chose in the DAC as it is very reliable and sounds great.I've had other customers use other op-amps in the MiniMax DAC and a couple reported feedback that we chose wisely, as other op-amps they tried might have improved in one area but degraded sound quality in other areas.
I believe Chris from Clarity Cables had great success and recommended to Doug to try the op-amps that Doug used with similar great sonic results across the board.
I haven't tried the op-amps yet but will order some shortly for sure because I trust Doug's ears.

Douglas_schroeder, Audio was ignored for a long time in op-amp design NE5532 being the first designed specifically for the audio. I'd like to try the newest OPA1612 that according to technology progress supposed to be light years ahead but I already read post claiming that in comparison its sound is too sweet and too laid back. My Benchmark DAC1 opamps are SMT but it is OK - I can replace them quickly but Benchmark's 5 years warranty speaks against it.

Doug, firstly thanks for your article. Indeed that is an inexpensive upgrade. However, I am confused. The eastern Electric Minimax DAC I recent purchased (and love) has a tubed output. The pictured DAC is also tubed. Have you bypassed the tubed output in favor of the opamps and their upgrades? If so, how does the upgraded opamp compare to the tubed output. Am I missing something here?

Douglas_Schroeder, just out of curiosity...why were 2 different opamps (LME49720 and LME49710) used instead of just one type?

Tgrisham, yup, that's the EE DAC, with the tubed output. Chris at Clarity Cable said he prefers the SS output with the opamp change, and with the volume control full tilt i agree. But I like the tubed output better under specific conditions delineated just below. You can use either with the opamp change.

I have been varying the EE DAC's output as it very subtly influences the interplay between it and the VAC Signature MkII Preamplifier. I have been working with the DAC's volume control anywhere between 1 O'Clock and 5 O'Clock on the dial. I find the use of an additional quality preamp exhilirating, and experimentation has to my ears shown that interplay between the two volume control settings can yield a preferable result to simply taking the DAC full tilt into the preamp.

Regarding the efficacy of the Opamp rolling compared to the stock unit, the upgraded opamps easily outperform both the SS and tubed function of the stock unit, imo.

Jdec, I'm not sure of the reason precisely for the difference in the two opamps for the upgrade. I believe it has to do with the different circuits for the tubed and SS operation. I would not want to speculate further than that; Chris at Clarity Cable told me precisely which Opamps and which locations to place them. He did say that one set of Opamps runs with the tube and the other SS.

I did not try reversing them, and would not advise it unless Chris or another expert gave the ok. I certainly do not want to lead people astray on the tweak. As Bill from Morningstar Audio said, if you mess with the unit you void the warranty. So, I certainly would not stray from the explicit instructions given by a pro like Chris.

My friend George and I had the great pleasure of meeting Melissa and Chris of Clarity Cable at THE Show 2011 fantastic Raven speakers). We stayed late one night comparing my CDP to the Eastern Electric DAC w/ Chris's mods.

In the estimated eight-nine years I've owned my CDP I preferred it to every other CDP and/or DAC sampled up to about ten x what I have into the CDP. Myself and the owner of a $20k EMM 2-box both preferred my CDP. I preferred it over a $10k Wadia 27ix. Maybe the $30k dCS and/or Meridian were preferred. The point is my CDP soundly trounced every Red Book playback priced anywhere near affordable.

Till that night described above. Best I could tell I preferred the Clarity EE DAC over my CDP throughout, in every way I could detect. The EE gave up nothing in any way, including pure musicality and pure listening pleasure, lack of fatigue, etc. I tried hard to imagine weakness in these areas because that's where my CDP is tops, but no, the EE gave up nothing in that regard.

Chris and Melissa and extremely wonderful and pleasant people with which to share time. It was a great visit. Their cables seem top notch. Chris is really easy to talk to, a nice treat for a specialty company.

I know this is a bit off topic but could anyone help me out a bit. I just got a used Minimax dac and when i use the tube output it has some hum/noise in the background. It only goes away then using SS output. The hum is more pronounce when the volume dial is from 0-75. From 76-100 the hum is till there but less. I tried with a Brimar tube and same, Pangea power cord still hum. Thanks in advance.

I finally replaced opamps in Benchmark DAC1 with OPA1612 and after initial brighter performance sounded a little mushy. There was a LOT of energy (slam) in the bass and extra extension but midrange became muddy.

Today I replaced them again with LME49860 (+/-22V version of LM4562) and sound went from mushy and bassy to detailed and clean. Voices are still free of sibilants but midrange is very transparent, soundstage expanded and cymbals sound pronounced and clean.

Both amplifiers are in 40-50MHz bandwidth range, both have THD in order of 0.00003% plus extremely low noise (OPA1612 has 1nV/SQRTHz) but sound is very different. Original amplifier NE5532 was very close to LME49860 (slightly less dynamic, clear and extended). If I could only cut them in half and attach bass portion of OPA1612 to LME49860 - well, my neighbors might disagree.

My hour of darkness is finally over. I have finished my modification of the EE Minimax DAC.

Welcome to the sunny side of the street? Come now, you're being MODest; please share. :)

I started to post earlier, realized I didn't have time, so I will finish now (can I finish? can I finish? can I finish?)

The following is a klutz’s description of modding the Eastern Electric Minimax DAC via Doug’s recommended op-amp rolling:

I had been enjoying this DAC so much in its stock form that I was more than a little reluctant to monkey with it in the name of what? Futzing around? Flirting with audiophilia? Refusing to leave well enough alone? I had to ask myself – am I dissatisfied with the Minimax? Is there some aspect of its performance that I feel needs improving? The answer to both of these questions was ‘no’ so I tried to just shove the thought of a mod out of my head altogether. But I couldn’t do it. The seed had been planted: the mod was said to be cheap, simple to perform and effective so I picked up the phone and called Digi-Key.

Let me say that you will need more than the parts numbers given by Doug in his article. When I gave the phone person those numbers his computer came up with semiconductors costing over $100.00. I told him that couldn’t possibly be. The ones I wanted were only a couple of dollars. He had to get a tech guy on the line who was able to figure out what I was looking for. The complete parts number they are looking for is LME49710NA/NOPB and LME49720NA/NOPB.

I started to skip the op-amp extraction tool figuring I could use a pair of tweezers or something, thereby saving a couple of dollars, but that would have been a big mistake. You’ll need the extraction tool if you don’t already have one, so don’t cheap out here.

The parts came quickly but I didn’t move to perform the mod quickly. I continued to enjoy the DAC in its stock configuration. The old adage, “If it ain’t broke don’t fix it” kept coming to mind. But finally, last Tuesday night, I decided to go ahead and do what I knew I would inevitably do, but I definitely had qualms about what I was attempting.

I admit to being a klutz. I’m not a hobbyist or a mod person – at all. I’m a dilettante, an aficionado who just wants to listen to and enjoy the music. I’m gladly willing to pay someone else to do my killing for me. But Doug said that this was about a 1.5 on the difficulty scale so I decided, ‘what the hey, let’s open this sucker up’.

I took the Minimax to the dining room table armed with a powerful magnifier and a Phillips head screw driver to remove the cover of the DAC. This was the first moment of consternation when I discovered that the cover isn’t held in place by Phillips head screws. In fact, I’d never seen the type screw used here, but I finally found a mini screw driver that would remove the screws. This was already taking longer than expected. Upon looking at the circuit board through the magnifying glass, I looked and looked but could not find U1 & 2 or U6 & 7. After 10 or 15 minutes of looking I had just about decided that the circuit board designations between Doug’s and my unit were completely different. I thought the project would have to be postponed and I would post about this discrepancy.

Then, I finally saw the designated numbers. I admit that my workstation left a lot to be desired – a dining room table with a chandelier overhead. I was using a bright penlight along with the powerful magnifying glass, but a proper, well lit work station would be a definite plus.

I used the extraction tool to pull the first op-amp out. This was fairly easy and straight forward. I then tried to put the first replacement op-amp in. This turned out to be much more difficult than I had expected. With four straight legs on each side it seemed as if it would be a simple proposition to push it down into its new home. But nooooo. Nothing is simple and easy for me. Shining the penlight and using the magnifying glass I lined up the legs on one side and got them started going in. I thought I had them lined up on the other side and pushed. Ahhhh, that great feeling of sinking in up to the hilt. But then I noticed that the legs on one side had not gone in but were splayed out over the side! I pulled the op-amp out and tried again with the same result. Now I noticed that one of the four legs on the left side was bent a little. This is when I started to despair. I knew that if I couldn’t get the legs to go in while straight, I would never get them in with one bent. I imagined the leg breaking off if I tried to straighten it, and further imagined being without my DAC for awhile waiting for replacement parts to ship in. I thought that even if I tried to put the old op-amp back in, I probably wouldn’t be able to get it back in without bending and breaking it too.

But the gods smiled on me at this point. I was able to straighten the bent leg on the new op-amp and finally managed to push all eight legs in successfully. Wiping my brow I followed suite on the next 3. All of them presented some difficulty to me. When I would line up and begin to push the 4 legs on one side in, the 4 legs on the other side would want to splay out over the side. But I finally was able to seat the other op-amps without bending. Finally it was done! I’d have to say that if you are a klutz like me this will be more like a 5 on the 10 point scale of difficulty, but if you’re the normal audio enthusiast, Doug’s 1.5 is about right.

So, was it worth it? YES, YES and again YES!!! All I can say is WOW! This is indeed one cost effective and VERY worthwhile modification of the Minimax DAC. The openness and spaciousness of the soundstage is unreal: top to bottom, left to right, forward to back. There is now so much more depth to the soundstage. There is also more detail with a greater incisiveness than was there before.

On acoustic, small scale music, it’s like the ensemble is in the room with you. On large scale classical music, the broadened,deepened soundstage and heightened resolution are the best I’ve ever heard a symphony orchestra sound on a home stereo system via Redbook CD. A soundstage has to be big to accomodate a full symphony orchestra! There wasn't the congestion that you so often get when listening to orchestral music on Redbook CD.

I was worried that a modification might somehow take something away from the Minimax’s presentation of rock music. Its rhythmic drive and bass do wonders with rock music and since this is my “go to” music and the area where I had been enjoying the Minimax most, I didn’t want anything to change that aspect. I needn’t have worried. None of these traits are lessened; you just get the bigger soundstage and greater resolution.

What a great upgrade! Many thanks to Doug for making owners of the EE Minimax DAC aware of this modification. For me there’s no going back. I can’t stop listening and am enjoying Redbook CDs like never before. I would say, if you own the Minimax and haven’t done the mod yet, go for it. But if you’re a klutz like me, just be prepared for a little more time and effort into the equation. Definitely worth it. Thanks again Doug!

I too tried the op-amp upgrade you suggested Doug and it sounds quite phenomenal in my (all tube) set up. I still wonder, though, about the new "Custom National Semiconductor op-amps" you refer to in the Audio Blast update of 01/18, which you would move directly to. Can you give us more specifics?
Cheers
Ernst

Thanks for the feedback, gentlemen. Glad you are enjoying the upgrade.

But there's more to come; watch for another Audio Blast article. It gets better, much better.

In its stock form the Minimax has been well received, including one Product of the Year award. Yet, even reviewers do not know the potential of this DAC. I've been able to take it far past the normal operation and will share my experiences.

This DAC is very special. :)

Doug, you have my nomination for the audiophile "tease of the year" award for 2011 (so far).

Have you ever considered writing for Stereophile?

;)

Njs, Wow, I'm in the lead early on! But don't worry, someone will post/write a hyperbolic, way over the top declaration which will far surpass mine. I'm glad some people are finding I'm not overstating the cause for excitement.

Part of the "teaser" issue is that this project stretched out over time more than I thought it would. Initially I thought it would be one article, one experience. However, it's been developing into a more comprehensive study of the effects of Opamps, so I'm keeping interest alive until all the parts of the Audio Blast are in place. It would be a shame to have what I consider a breakthrough and have it sit unnoticed.

I haven't thought much about writing for an audiophile print magazine. Perhaps I should start one. ;)

Thanks for all you time and effort. Cant wait to hear the news considering I just placed an order for one (very first DAC for my new jolida tube int. amp). For the meantime, I will be enjoying it when I do get it.

Doug, what tube are you using with you DAC?

At the moment I'm not using anything exotic, just the stock 12AU7 tube. The reason is that for testing Opamps I felt it would be far more beneficial to use the stock unit's tube as opposed to an alternative. If I use the stock unit in testing Opamps the results are applicable universally, versus for a subset of those who roll tubes.

I've got a couple others but no time now to work with them post-Opamp rolling.

i own the minimax dac. i have several nos tubes. i believe that if you use the tube gain stage, you bypass the opamp. is this correct ?

if this is correct, it may be more productive of your time to tunr the dac with a tube rather than try to find a suitable opamp.

also, if i am correct isn't the absence of an opamp preferable to the presence of an op amp ??

Mrtennis, to my ear the influence of the Opamps supercedes that of the tube rolling.

I'm checking on the SS/tube output question.

Doug, As you know there are two pairs of opamps in the EE DAC: Two NE5532 dual opamps for I/V (current to voltage) for tube and solid state; and two NE5534 single opamps for solid state output only.

Operating the EE DAC with the tube stage engaged bypasses the single opamps' circuit.

I generally prefer operating the DAC in solid state mode and found that rolling a variety of quality (read "expensive") tubes didn't have nearly the beneficial effect as did switching to your LME497X0 opamps.

Njs, you are right on the money with your answer. I received the reply from Alex Yeung, designer of the Minimax DAC, and you have it right.

One set of Opamps are always used regardless of output SS/tube. The other set of Opamps is only used with SS output. In my testing I heard what I felt were clear distinctions with different Opamps using the tube output but I did not want to comment definitively until the question was answered, providing verification.

Yes, it is certainly an acceptable choice to run the unit in SS output and with the upgraded Opamps it is quite refined.

Anyone care to comment on the influence of the power supply on performance. There are competing DAC designs claiming the importance of power supply chokes or elaborate regulation and transformers to serve as important elements.

I suppose this is the sum of all the parts concession I can make but wonder too why the smaller parts are not given more respect or attention.

Kudos to Doug for shifting the direction.

La45- Your point is well taken about smaller or "simple" parts. The speed and Efficiency of Capacitors in the Power Supply and elsewhere cannot be overstated. The impedance or ESR of these devices has a stranglehold over the sonic merits of any audio device. A slow response Cap yields a lethargic and unenthusiastic presentation with lack luster dynamics. However, it also screws with pitch accuracy and intonation. There is no doubt that each component imparts a sonic fingerprint on the signal, but none come close to the musically destructive affects of slow caps IMO.

The biggest problems is that electrolytic caps are constantly aging and losing performance as the electrolyte dries out inside, a process that is unavoidable due to heat cycling and use. Sure they will work for years but not a peak efficiency. They must be tested and changed routinely as surely as a vacuum tube. They are not unlike a rechargeable battery, where the chemistry inside begins to age and perform underpar. I plan on purchasing a ESR meter soon to test capacitors for performance. From what I've seen, it's a far more revealing tool than a capacitance meter.

Many thanks to Doug for all the info on OpAmp rolling.

Be careful with ESR. If we talking DAC then we have most likely volatge regulators. Many voltage regulators don't tolerate low ESR very well. They tend to oscillate when ESR is too low or too high. Also supply current is more even going mostly to cover op-amps bias currents. Momentary currents are very small because of high impedances and easily covered from ceramic decoupling caps. I can see bigger problem in interaction between these ceramic caps and inductance of power supply electrolytic caps - creating parallel resonant circuit that tends to ring.

Kijanki- All valid points that need to be considered in the big picture. My hope is to have a measurement record of the ESR when the equipment is new and monitor the capacitor health as time goes on.

hi doug:

there are many opamps available.

i don't want to listen to too many for obvious reasons.

if i were to replace the single opamp feeding the tube, i would to select one which "slows" things down, is less transparent and has more of a classic tube sound.

anotherwords a bit of veiling or hf roll off wouldn't hurt.

since you have experience with opamps, could you suggest one or two.

i am not looking for greater soundstage or resolution, but rather to get more of a euphonic (classic-tube) sound from the dac.

Mrtennis, yes, there are many Opamps for this unit; I tested approx. ten custom Opamps in multiple configurations. There are literally dozens of configurations possible.

I'm afraid I can't recommend any of the pairings which do what you are seeking. If I understand you correctly, you want the unit to be less transparent, a bit rolled off, and more "syrupy" for better lack of words; as you say more tube-like. Perhaps your ideal would be for it to sound more like Van Alstine had made it.

None of the upgrade Opamps do that. They all increase detail and transparency, some quite dramatically. Some are more tube-like, but if your goal is to veil the DAC more then I'd stick with the stock unit. The upgraded Opamps will open up the soundstage, increase detail and clarity, etc.
So, in your situation you may want to stick with tube rolling and try different digital cables as they also will lend an important influence on how mellow the DAC sounds.

I have sumitted a chart of all the Opamps and my findings with the article. I do discuss the pairings which I find of special interest.

I'll say a word here so that people who may be interested in the Opamp upgrade will be able to determine if it's something they will want to seek. I'm sure there are others who will share the musical taste held by Mrtennis, and it's possible that if they do the upgrade and hear an increased detail/transparency they might be disappointed. Therefore, I'll share a bit about my views regarding this subject, not to be contraditory to Mrtennis, but so that people can deternmine if it is an upgrade they would like.

My experience and development of personal biases regarding sound is to never limit detail, transparency, soundstage depth/width and resolution. I have found that when I sense a problem with these areas of sound reproduction the problem is not them - it's usually tonality, likely in the form of shrillness or etched treble. I will not accept a trade off between proper warmth to the system and extremely high detail/definition. I find that systems without a high degree of detail/definition are not very convincing as reproducers of live music. With higher detail I find that the music is smoother, more refined as opposed to more "choppy" or rough.

Consequently, I will always seek a higher level of the aforementioned characteristics in sound, as well as not sacrifice what is to my ear appropriate warmth/richness tonally. I feel the Opamp upgrades allow for both objectives to be met. I do not feel that there needs to be a trade off ultimately in terms of tonality vs. detail. Perhaps this will help persons determine if the upgrade is something they want to pursue. :)

Mrtennis - OPA1612 (variation of OPA211) is what you looking for (was too warm and bassy for me) but it comes only in SMT (SO8). There are adapters and soldering of SO8 is quite easy.

National Semi amps like LM49720 or one I used LM49860 are more detailed and open/brighter sounding than NE5532. LM49720 is the same amp as LM4562 named differently for marketing. LM49860, I use, is again the same LM4562 with extended supply range to +/-22V. Some reported better sound (possibly die change) but it might be only perception.

NE5532 used to be thinner sounding until 2000/2001 when Signetics factory burned down and they stopped making it. Texas Instr. bought license from Signetics redesigned die (larger) and produced fuller sounding amps. If you have NE5532 check the logo on them. NE5532 are cheap ($.70) while OPA1612 are quite expensive ($8.50). National runs at about $4.

Mr T.

I tried the OPA2107 (dual) in the position that feeds the tubes and think that this might be up your ally. Much greater bass extension with a less in your face sound vs. stock chip and esp. vs. the 49720 which I also tried. They also come in DIP8 so you can pop them into the DAC in minutes, no soldering. Pricey at ~$16 a piece but cheap relative to some tubes and to the dramatic improvement in SQ you get.

But don't stop there, no no, get some upgraded chips (singles) for the SS output as well. I currently have OPA627 in mine and it does some things (the things that you say you like) very very well but lack air and sparkle relative to the 49710.

Doug - looking forward to your article.

-Mike

If so, would you care to comment on the sound of it?

I assumed the power cord provided with the EE DAC I received about a week ago was included just so they could say; "We gave you one." I didn't bother trying it and immediately plugged in a Wire World Aurora Cord, which I have been satisfied with using on a Cambridge 840C CDP.

This afternoon, I was about to put away the EE DAC packing materials and the stock power cord for storage. I decided to give the supplied power cord a quick listen as I might not have an opportunity to do so again. To my surprise it sounded much better than the WW cord, despite its lack of markings or pedigree. There was no need to A/B the cords, as the stock cord was notably better, even with no break in time. I tried a couple of other power cords I had on hand (WireWorld Electra & the Kimber PK10 Palladian) and found the stock cord still sounded best. Maybe I'm deaf or have some problems elsewhere but I would encourage people to give the stock cord a try before casting it aside. It would be interesting to know if this is a fluke or intentional on the part of the manufacturer.

My other transmission was garbled. I was wondering if anyone had tried the OPA2134 and any opinions regarding it.

The EE DAC's stock power cord is not as open sounding as the others I have on hand but controls sibilance much better that the others.

I'm with Mfsoa on the OPA2107 opamps for the dual slots on the EE DAC. They get along really well with the LME49710 single opamps described in Doug's review. Perhaps even a tad better than the LME49720 dual described in the same review.

BTW, Doug, how long until you disclose the identities of the custom opamps with which you were so enamored?

Will these be available through commercial sources?

Njs, et. al., I'm not trying to hold up the process; the article has been submitted for publication but has to go through a process which takes some time. Yes, these will be available to all and I provide the info to obtain them. :)

Don't know if this is possible due to height limitations but has anyone tried rolling the Burson HD op-amps? They sell a DIP version which I'm guessing would be plug and play? I might have this wrong, but seems like it could be a good combo in theory?

Any update with the article?

There is. It's an update to an update. Here's the link: http://www.dagogo.com/View-Article.asp?hArticle=864