by Kevin OBrien on 04/21/2012
EE MINIMAX DAC PLUS: OP AMP ROLLING!!!
I decided to give my Eastern Electric Minimax DAC Plus an anabolic shot in the keyster a couple days ago. One quick and easy tweak you can apply to this DAC is changing out the operational amplifiers (op amps) to get a different sound. This is an option because Alex Yeung used sockets for the op amps instead of soldering them in like most other designers do. THANKS Alex!
A VERY helpful company based out of Oklahoma, Cimarron Technology, helped make this possible. They offer very handy adapters that allow you to drop in replacement op amps without the need to solder them onto the adapters yourself! I am specifically referring to the "SO8 to 8-pin DIP Adapter" that they offer for $3. They give the user several options for pre-mounted op amps such as the LME49990, OPA627AU, OPA2604, OPA827AI, AD8397, and the OPA2134 to name a few.
Alex, the designer of the Minimax DAC and DAC Plus, has approved these for use with both the DAC and DAC Plus. This voids the warranty but I'm not too worried about that. I've played the unit for over 8 months with absolutely no issues so I figured I'd just go for it and I'm glad I did.
According to Bill O'Connell of Morningstar Audio, the op amp rolling can make a nice improvement. He offers the combination that I have tried pre-installed for an extra $100 over the retail price of the DAC Plus. This way you can retain the warranty if that is important to you. You can save $20 by doing it yourself. I obviously opted to do it myself. The op amps are plug and play so there's really not much you can do wrong as long as you're careful.
I ended up going with the OPA2604 in the U1 and U2 positions. If the user is only interested in the tube output, he can choose to replace only the U1 and U2 op amps as the U6 and U7 op amps are used for the solid state output. I also ordered the OPA827 for positions U6 and U7. One quick note here: If you plan on ordering the above mentioned combination you have to order (2) of each op amp pre-soldered onto the "SO8 to 8-pin Adapter".
Do NOT order any other adapter board combination. There are a couple more options such as the Burson Audio HD Op Amps as well as the NewclassD Dexa Dual 73728 and Dexa Single 73729. Both sets of op amps can be had from Parts Connexion. Folks have reported that a combination of Dexa's and Burson's can really take the DAC Plus to a new level but the price tag is a little steep. The Dexa combo (4 op amps) will run you $280 and the Burson combo (4 op amps) comes to $295!!! OUCH! Most users agree that the 2604/ 827 combo is the way to go for $80. If you're on a budget like I am, it's DEFINITELY the way to go. One caveat here: If you are using the latter op amp combo (Dexas or Bursons), the cover of the DAC Plus will not fit on top of the unit. You most likely will have to space the cover from the chassis with spacers and longer screws or something to that effect.
I figured it would be nice to try the solid state output of the DAC Plus with the tube removed just for fun. I'm glad I tried this. There seemed to be a bit more detail in the SS mode so I chose to keep the DAC Plus in that mode. I can alter the presentation of the music by switching my preamp tubes to GE 12AX7's from my current Siemens 12AX7's if things get a little too bright so I wasn't worried.
The op amp rolling results were pretty interesting. I noticed more detail/ separation and more punch in the low end. This was just what Bill had reported during his op amp rolling sessions. VERY COOL! I could definitely hear more detail and the instruments seemed that much easier to identify as they felt like they were in their own space.
I ran the op amps in for 100 hours just to make sure before I did any critical listening. There seems to be some debate on whether "burn-in" is real or just a phenomenon. I am definitely a believer in burn-in. That is an entirely different discussion for another time.
I hope I've shed some light on what your options are for rolling op amps in the Minimax DAC and DAC Plus. It's as easy as popping off the cover, removing the original equipment, and then placing the new op amps in their place. Make sure you place them in the sockets facing the correct way and you're good to go. That's about the only thing you need to pay close attention to as well as not discharging any static electricity into your DAC's internal components. Again, if you're not comfortable with this process, Bill will pre-install the 2604's and 827's for a $20 charge over the cost of the parts. THANKS Bill!
Until next time...
-KOB
Associated Equipment For This Review:
- HD Reference-2 Computer Music Server
- Quicksilver 12AX7 Tube Preamp
- McIntosh MC275 Tube Power Amp
- Von Schweikert VR5 HSE Speakers
- YFS Custom Litz Speaker Cables
- YFS USB Reference V1 Custom USB 2.0 Cable Prototype
- YFS Custom Room Treatment
- YFS Custom Interconnects
- YFS Custom Power Cables