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IMPORTANT INFO RE: OPAMP ROLLING MINIMAX DAC

(My apologies for the splayed nature of my posts on the Minimax DAC lately; I used a new thread here to get the most attention as I feel there is important new information that potential buyers/Opamp rollers need to see)

The testing and writing up of the Opamp rolling article was a large project and it has been called to my attention that I made an error in my indications of the U1/U2 and U6/U7 locations by color.

I have revised the article to be corrected and I believe once reworked will be accurate. I appreciate Mfsoa's (Audiogon member's moniker)heads up on this.

I also have been made aware by Bill at Morningstar Audio that a thread on the Audio Circles discusses the potential danger of swapping the positions of the Opamps. I will include the thread below. I would not wish for anyone to encounter issues with the unit. It seems as though the most urgent warning is to those who have already modded Minimax DACs, that they do NOT switch the positions of the Opamps. I performed all Opamp rolling on a stock unit. Given this new information I would urge that this warning be heeded by those with modded units.

With this in mind it is all the more clear that one conducts these experiments at their own risk.

If there is concern over experimenting with reversed placement of the Opamps, it should be kept in mind that the favored pairings can be used in their normal locations successfully. Here are a couple more options in which the Opamps are in the proper locations:

U1/U2 OPA827 (dual) and U6/U7 OPA827 (single)
In my notes I had this as one of my "finalists"
The distinction between the absolute best pairings became very small
at the end. This pairing would likely find wide acceptance in many
rigs.

U/1U2 AD8620ARD (dual) and U6/U7 LME4990 (single)
This Analogue Devices chip may be worth checking out with other Opamps
in the U6/U7 position. If I had not been sent the (unavailable currently from Cimmaron) OPA2604 I might have used this combination as my reference.

My apologies for any confusion and much thanks to those well versed in the use of Opamps to help identify potential issues and ensure the article is clear!
douglas_schroeder

Showing 4 responses by douglas_schroeder

douglas_schroeder OP
3,281 posts
 
Sorry, the link is here - way too much involved in this...

http://www.audiocircle.com/index.php?topic=86504.20
douglas_schroeder OP
3,281 posts
 
The entire affair has become convoluted (in regards to the concept of reversing positions of Opamps in the unit)

I made a mistake with the color indications in the article. Meanwhile, it seems credible concerns over reversing the positions of the Opamps threaten to overshadow the entire venture.

I sense to forge ahead would cause unneeded headaches; I have re-submitted the article removing references to reversed positions.
douglas_schroeder OP
3,281 posts
 
Note: THE REVISED OPAMP ROLLING ARTICLE IS NOW ONLINE, along with an introduction which explains how this all came about.
douglas_schroeder OP
3,281 posts
 
Mike, perhaps it was not clear that I tried to indicate in the article the tube output would be the standard in testing. I felt the tube output was overall preferred and that readers would be most interested in it. I would comment upon SS output when I felt it was meritorious.

I realize that the article does not show a comprehensive analysis of all permutations of the Opamps, prices etc. as I state in the article, "Considering Opamps, tubes, solid state or tube output, and the volume setting dozens upon dozens of variations are possible, and you can appreciate that I’m not paid to run a lab." Considering that this was an unsolicited article, one I pursued on my own initiative as a service to the community to raise awareness of the activity of Opamp rolling, I secured some Opamps and tested them to see if Opamps make a difference - if that was not good enough, my apologies. If it is helpful, I found in general that the distinction between any given set of Opamps operated in SS/Tube output was less dramatic than comparing entirely different sets of Opamps.

I put in between 35-40 hours of communication with suppliers and manufacturer, setting up systems, testing Opamps and writing/editing. The goal was to introduce Opamp rolling and weigh its efficacy, nothing more. I am disappointed that not one individual from the professional or amateur DIY/Mod community contacted me to warn me of the potential danger of suggesting reversed Opamps. The heads up came from Bill O'Connell of Morningstar, the distributor, and I'm grateful for it.

I have learned information about the situation which has left a negative conclusion in my mind about the incident, but I do not wish to discuss it publicly.

I am finished with the topic. People can make of it as they wish.
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