Success Rolling Opamps in EE Minimax DAC

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.