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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! :)

RECOMMENDATIONS OF OPAMPS FROM CIMMARON TECHNOLOGY:
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."
douglas_schroeder
sibelius
256 posts
 
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.
rodagon
10 posts
 
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!
rodagon
10 posts
 
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?

Thanks,
Mike
sibelius
256 posts
 
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.
sibelius
256 posts
 
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.
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