Listing of Opamps for EE Minimax DAC Plus

Phil from Cimmaron Technology sent me a list of approved Opamps for
respective positions on the board of the EE Minimax DAC Plus; prices
include the Brown Dog Adapters provided by Cimmaron. I have been using
in the U1/U2 position the OPA2604 and in the U6/U7 position the OPA827.
I have not Opamp rolled this unit much, as I have been busied with other
components for review. I attest that the DAC Plus in SS output with the
tube removed and these opamps is sensational.

(NOTE CAREFULLY the warning at the bottom NOT to use the AD 8620 in the U1/U2 positions!) Also note that the positioning of the opamps/adapter is always with the small square solder point on the topside of the Opamp at the upper right hand when the unit is facing the installer. Finally, it is recommended that an opamp extraction tool and an anti-static device be used when removing/installing Opamps.

Is it "worth it"? YES! YES! YES! :)

For U1/U2
Single-channel op-amps mounted on the 020302 SO8-to-DIP8 single-to-dual
channel adapter:
qty 2 each required

020302-OPA627 $48.00 x 2 = $96.00
020302-OPA827 $38.00 x 2 = $76.00
020302-AD797B $48.00 x 2 = $96.00

. . . also for U1/U2
Dual-channel op-amps mounted on the 970601A SO8-to-DIP8 adapter
qty 2 each required

970601A-AD8620 $23.00 x 2 = $46.00
970601A-OPA2604 $13.00 x 2 = $26.00
970601A-OPA2134 $10.00 x 2 = $20.00

For U6/U7
Single-channel op-amps mounted on the 970601A SO8-to-DIP8 adapter
qty 2 each required

970601A-OPA627 $28.00 x 2 = $56.00
970601A-OPA827 $23.00 x 2 = $46.00
970601A-AD797B $23.00 x 2 = $46.00

The AD 8620 should not be used in the DAC PLUS.
"On some forum there was a suggestion to use the AD8620. for positions U1
and U2. While this is a dual op-amp, it is only rated to use up to
plus/minus 13 volts. The circuit in the EE Mini Max DAC and DAC Plus is
plus/minus 15 volts."
Those prices for opamps are crazy high. Opamps are a commodity device and are typically sold (exaggeration alert) in bushell basket quantities.

The last 2134s I bought were about 2.50$ each.
I believe these are with the op-amps soldered into the Brown Dog adaptors.Well worth it IMHO .
Thanks for the list. Hopefully my friend buy a minimax plus version. opamp rolling will be fun.
Looked at the BrownDog site and they are fine with 2134 pricing.
The adaptor? Solder in, from the look of it, so I don't know what that buys you. Plug in would be fine for swapping opamps. I guess I'm not current on what people are doing. I guess I don't know what the advantage is of soldering in an adaptor in which the part has to also be soldered in. The CMOY I built has a plug-in header so if I ever get the urge, I can swap opamps in seconds.
The single to dual adaptor makes sense.
Thanks for the info Doug. Just placed my order. I have an Ah!Tjoeb CD player in a second system and can attest that opamp rolling has made a difference over stock unit. For roughly $75 - $150 I think this is worth trying.

For now I have ordered the 2604's and 827's. Would be interested in feedback from folks who have tried and liked other combinations.

Love the fact that the EE DAC + allows swappable opamps. It greatly adds to its versatility. Agree 100% with Doug that the unit in SS mode with tube removed is the way to go.
I believe some of the op-amps are to small to just plug into the EE DAC PLUS, that is why the need for the Brown Dog adaptors.So you do not have to solder the smaller op-amps into the MiniMax.

No, you then do NOT have to solder the BD adaptors into the sockets. You should never put your soldering in any of the components in the DAC PLUS. Very sensitive inside the DAC.
That is the reason for the BD adaptors so you don't have to solder.

Chips are built to case standards.
8pin is a dual opamp while 4pin is a single, usually 1/2 a dual.
Putting a replaceable module in a socket is probably good for the opamp rollers, of which there are many...and more coming.

SMT? I'd not try to manually solder one on a bet.

I'm sure, one day, NOS OPA2134s will be 100$ each and unavailable except if you 'know somebody'.

I'm stocking up now, and waiting for the crash.
Right you are.

My bad.

Here is an example of a 5 pin case, SOT-23

Other dual inline cases go up in pincount.
I see references to Quad Opamps....14 or 16 pin?

Now, where did I see a 4 pin case?
Quick follow up. I swapped out stock opamps with 2604 and 827's. My impression is that there is more detail with a tightening up of the soundstage. Between SS mode, tube removal and the opamp changes, the DAC is indeed a step up from the stock unit. Grand total was $80 for opamps and extraction tool. Took me all of 10 minutes to perform the opamp "operation". Highly recommended for EE DAC plus owners. Note that this voids your warranty. However, it really is plug and play if you get the opamps pre-mounted on the brown dog adapters.

Have some National Semi Opamps coming for some additional experimenting. Fun stuff.
I also took shipment today of the 2604's and 827's on the Brown Dog adaptors.
A truly significant upgrade to the stock op-amps in sound. Very organic,more meat on the bone kind of tone. Punchier bottom end with a wonderful midrange.
I'll probably be offering the DAC PLUS with these pre-installed by me as it won't void the warranty that way.

Don't ask me why it took me so long to try.
Thanks to all that have contributed.
Warmest Regards,
Bill. When do you think you'll be offering the DAC PLUS with pre-installed, upgraded op-amps? I've been sitting on the fence about a DAC PLUS purchase for a couple of months now. Personally have never done any op-amp rolling. Just following along on forums about tube-in, tube-out, roll op-amps, etc. Very interesting evolution of this unit since it's into. Thanks, Dave.
Well, I went off the deep end and ordered some Dexa Discrete Opamps as well to try in the U1/U2 position. They are a lot more expensive ($170 plus shipping) but I'm very curious to see if the discrete opamps are as good as people say they are. Will report back...

The EE DAC Plus is a wonderful way to upgrade your digital experience without breaking the bank. Great value and versatility for the $.
I bought some extra 2604's and 827's and I Have the DAC's in stock so give me a call.
Several of the above op-amps are available in 8-DIP configuration so that they will drop directly into the EE DAC without the need for Brown Dog adapters, as follows-
(check with Digikey)
OPA627 (single) can drop right into U6/7
OPA2134 and OPA2604 can drop into U1/2.

And remember that if you use the tube out only, the U6/7 op-amps aren't used so don't bother to upgrade them (pretty sure about that).

I have been using the 49990s for a while now in SS mode (original DAC) and still like them very much, but all this talk is getting me itchy again...
Absolutely loving the OPA2604 duals with the OPA827 singles on the Brown Dog adaptors. Really fleshed out the midrange and added punch to the bottom end.
I am happy user of EE DAC plus for 1 month. Using the DAC without tube( great tweak). I have good expirience with audio-gd discete opa for my Asus ST + H6 board and I ordered( probably stupid before chacking first) pair od burson dual and single HD opa maunted on proper adapter.Now my concern is do this opa can be used in DAC plus .

There specification is
Working voltage: +/-12-25v DC
Current Draw: 19mA (each module)
I will be very thankful for Bill's opinion.
Thank you
EE DAC plus and Burson opamp
I am happy user of EE DAC plus for 1 month. Using the DAC without tube( great tweak). I have good expirience with audio-gd discete opa for my Asus ST + H6 board and I ordered( probably stupid before chacking first) pair od burson dual and single HD opa maunted on proper adapter.Now my concern is do this opa can be used in DAC plus .

There specification is
Working voltage: +/-12-25v DC
Current Draw: 19mA (each module)
I will be very thankful for Bill's opinion.
Thank you
I wrote Alex a week or so ago regarding the use of the Burson's.
Here is his reply.

Hi Bill,

Sorry for my tardy reply, I was away. I checked the Burson web site, it said clearly
that their dual one can replace the NE 5532 and the single one can replace the NE
5534. So they will work just fine with the DAC and The Plus.


Best regards,

Thank you Bill
I will report my findings when I got the opamp. I was concern regarding the voltage compatibility.
although, indirect;y related to tyhis thread, there have been commemnts regarding the superiority of listening to the minimax, bypassing the tube stage and removing the tube.

considering that there are some "good" 12au7s available, in what way does the removal of the tube improve the sound ??
I've not heard anything definitive from EE, but one theory is that the power supply would see less of an overall load and perhaps lower noise level on power rails to opamp.

Whatever the reason, I've tried the tweak and do find it an improvement.
Same* result here, SS output is much improved with tube removed...however, with the right tube (system compatibility) I prefer the 'fleshier' output of the tube stage.
I found no real measurable (by ear)improvement to the tube output with the removal of the SS opamps. My guess would be that the tube stage draws more juice from the p/s vs the SS output opamps.

I was concerned also and wrote Alex again just to double check. His reply;

Hi Bill,

The DAC Plus has enough current supply for four Burson opamps.

Hope the above helps.


Best regards,

I've been experimenting some more with opamps and have to say that the only combination I like a tad bit better than what Doug recommended (2604 in U1/U2 and 827 in U6/U7 with tube removed in SS mode)is to replace the 827's with Dexa discrete opamps. I'm finding the discrete opamp seems to add a bit more air around the instruments while making things a tiny bit warmer. However, the cost of the discrete opamps is rather high and the difference is not night and day. I think the 2604/827 combo is probably the best mod for the $.

I'm going to try two more experiments. The first is to go back to tube mode with a NOS mullard 12AU7. The second is to add Dexa discrete opamps in U1/U2 and see how an all Dexa system works.

More to come ...
Here's an update on some of my tinkering.

As I mentioned before, the setup I've settled in to this point is 2604 opamps in U1/U2, Dexa Discret opamps in U6/U7 (just a smidge better than the 827s) in SS mode with tube removed.

I'm on record as stating I did not like the Dac+ in tube mode with the stock EH tube. I felt the sound was veiled and muddied. However, I have read where several people liked tube mode with a better tube. So in the spirit of giving tube mode one more shot, I ordered a mullard NOS 12au7. Well, after some more extended listening I need to ammend my original statement. While the SS mode still has more detail, the mullard tube is much less veiled than the EH tube and scored points by smoothing out rough patches in bright recordings.

At this point, which mode is better really becomes a function of the recording in my system. If a recording is bright or hard, I prefer the mullard tube mode. In exceptionally well recorded music, I find I enjoy the additional detail of SS mode. I guess the take away is don't ignore tube mode until you first try it with a better tube.

My next experiment will be to replace 2604's in U1/U2 with Dexa Discrete opamps. Will see how an all Dexa opamp unit sounds.

The good news is that regardless of your personal views, the Dac + allows for tremendous flexibility and experimentation. I'm sure almost everyone can find a setting which will be optimal in your system.
hi sibelius:

what do you gain by replacing the stock op amps ?

my take on the stock 12au7 is the opposite of yours, namely, bright, thin and lean.

which mullard did you use, the long or short plate ?

Hi Mr. Tennis:

Moving from the stock opamps to 2604's and 827's gave me a sharper and larger soundstage. It was very noticeable. Not a subtle change. Since then I have swapped out the 827's with Dexa Discrete opamps. This move was more subtle. A little bit more air around the instruments but not as dramatic a move as changing out the stock parts.

My tube is a standard plate mullard rebranded as Daystrom from the early 1960's I believe. Now that I know that NOS tubes makes a difference, I will probably try some additional NOS tubes. Pricing is pretty good when you only need a single.

Changing out opamps is not that expensive. With Brown Dog adapters (which makes installation a snap) I believe I spent about $85 or so including shipping. Well worth the effort IMO.
I have been using the Mullard CV4003 Milspec 12AU7 for the last 2 months.
I could not listen to the MiniMax 2 without this.
I have a 10 year old Marantz CD4000, which I had modified to use two 12AU7s in a new analog output stage.
It has external power supply and tube rectification.
It is extremely musical and preferable to most of the DACs I have heard.
Bill just modded my Minimax 2 and I hope I get it back in time to be able to listen to it this weekend.
His service was awesome.....instant turnaround!
Hi Sibelius,

I noticed you have the Atma-Sphere S-30.
How do you like yours with the Mini-Max2?
I also have one.
Trying to tweak the most out of my system but still prefer Vinyl.
Where did you purchase the Dexa Discrete opamps?

Hi Mike:

Dexa can be purchased from Partsconnexion in Canada or directly from the Mfg in Denmark (NewClassD). There may be other places out there but these are the ones that came up with a quick google search.

I really like the S30. I also have a bunch of SET's but the S30 is the least colored of anything I have. I tend to switch things up a bit but can't envision a situation where I would not have an OTL. It's like having the accuracy of a top notch SS amp with the liquidity of tubes.

I agree with you on vinyl. While the Minimax has greatly improved my digital experience I still prefer analog. The convenience of digital is nice, though. I've been dipping my toes into computer audio and can appreciate the reasons why many shy away from analog.
Update time. Have spent time with an all Dexa Discrete opamp system in both U1/U2 and U6/U7. Impression is that the sound is softer and rounder than the 2604/827 combo. It does a good job of taking the edge off harsh or bright recordings but does not have the same degree of detail or resolution of the 2604/827 combo.

If you want the most detail and resolution I would go with the original recommendation - swap out stock opamps with 2604/827 and remove the tube. It will cost you about $80 and is a noticeable difference.

If you want to tame some digital harshness, replace the stock EH tube with a good NOS tube like Mullard, Amperex or Brimar. If you want some more resolution, you can then swap out the stock U1/U2 opamps with 2604's.

I'm of two minds on the Dexa's. On one hand they are probably the most analog sounding opamps I've tried in the DAC but at about $250-$300 they are not great value.
Only been playing them for a day, but immediately noticed going thru the SS output with tube removed and the dual OPA2604's still in the U1/U2 dual position with the single Dexa's in the U6/U7. Lovely smooth presentation, totally agree with Sibelius on the analog tone to this combo.
This morning installed the dual Dexa's in U1/U2 position and running that at the moment with a Siemens silver-plate thru the tube output.Really haven't had time to critical listen as now just doing some background music to burn in a bit.
Thanks to all of you who recommended these.
Yep, the smooth presentation of the Dexa's along with a NOS tube has won me over and I'm keeping this as my default set-up for now. It does not have the last degree of detail as the 2604/827 combo but it has enough detail and resolution for me while helping to reduce any digital harshness. Cost is only downside. It's $250-$300 for a full complement of Dexa's which may be a lot for people to invest on a $1100 unit. Never the less, I just love the flexibility of the EE unit.
From the context of all the posts here, I have to assume that an opamp is the same thing as a tube or a valve. Is that correct?
No, an opamp is an electronic part on the circuit board of the DAC. Many DAC's have the opamps soldered to the board which makes it extremely difficult to swap out. The EE opamps are not soldered so swapping them out is very easy. Many people (I'm one) find that changing opamps (like changing tubes) can influence the sound. What's very nice about the EE is that between tubes and opamps you can fiddle to your heart's content and tailor the sound to what you like. The only caveat on swapping opamps is that this usually violates the manufacturers warranty if anything goes wrong.
Do the Dexa's fit under the factory lid without having to make jumpers? Meaning, they plug right into the opamp socket and stand upright without hitting anything?
Yes, they do fit under the cover.
You have to make sure just to put them in correctly with the half moon circle cut out on the base of the Dexa'a always on the right hand side while looking at the front of the DAC PLUS.
if you put the dexa op amps in the original minimax, not the plus, what is the difference in sound between the minimax, and the plus, assuming both have the dexa op amps ?

i am assuming that part of the cost of the plus is the replacement of the stock opamps from the original dac.
I can't explain it any better then what I told you over the phone yesterday.
Is there a difference between the Dexa opamps and the burson's? if much?
Does this opamp rolling make the EE any more musical, or engaging
I just Don't feel drawn into the music with this Dac

The Burson's do not fit under the top cover of the DAC. I do not recommend using as they also draw a lot of current.

Very much so the op-amps make a difference. I still like the OPA2604 duals and the OPA827 singles.
@Morningstaraudio, you're right the DIP versions do not fit with the lid on. However, the flylead version fits but you need to bend the legs.
I think the sound difference is worth it :)
Having lived with the DEXA Discrete op-amps for about 3 weeks now, they really do seem to be the one's to beat. I highly recommend for the tube output the Philips E80CC pinched waist D getter version as a substitute for the 12au7. Although this tubes is twice the length and you won't be able to put the tube shield in place anymore , and being that this isn't a direct substitute for the 12AU7 as it draws twice as much heater current, Alex Yeung the designer says it is ok to use. This tube with the Dexa's is fantastic!
Can you describe the sound with the Dexa's in, on another site the user said it gave body to instruments, something that may be lacking with stock op amps

I have been enjoying my minimax plus with dual Burson's in U1\U2 and the Dexa's in U6\U7 for a few months now and couldn't be happier. I find the sound to be stunning. Although with some recordings I like the sound of the Burson's with a Amperex orange NOS tube from pearl cryo better. You sacrifice some of the vivid resolution with the tube as well as output level, but you get a nicer, softer sound when listening to harsher recordings. I bought the flying lead version of the Burson's and trimmed them down to about 3\16" and carefully lined them up to the socket holes and wiggled them in. It was a delicate procedure, but they are in firmly now, and they clear the lid. I later thought of a better way of doing it which I'll cut and paste from another forum to save the typing.

for those who wish to roll with the Burson opamps without the hassle of having to buy the flying lead version, and deal with the shady process of trimming and worrying about the leads bending and potentially snapping off. The original reason I didn't go with the much sturdier dip lead version was because of the clearance issues with the lid. I've thought of a solution. All you need to do is buy some sheets of a product such as:

to use as a spacer\gasket. Stick it to the inside of the lid (not sure how many layers it will take, could just be 1 but buy 4 they are cheap enough), cut a little square out where the bursons line up with the lid, and also a square where the vent holes for the tube cooling are. You will also need to find some longer machine screws to attach the lid and make some little holes in the material where they need to go through. This method will effectively allow enough clearance for the dip version, plus you will reap the benefits of a sound deadened lid! Why didn't I think of this before?
Can you guys list the p/n's of the Dexa and Burson opmps and sources? Are some of you using single and dual dexa's and single and dual Bursons? nd some of you are using singles of one and duals of the other?