Hi all,
I built an active preamp two months ago using a DACT selector and stepped attenuator, a Cascode Power Supply (this power supply unit is of first class!) and, of course, a Buffer Amplifier. The improvement with regards to my 300 pounds Marantz preamp was incredible: the bass, that was missing, suddenly appeared (I use a 2.7uF Mundorf MCap instead of the standard MKTs), the sound scene now has dept!!! so it's three dimensional, and not only like a picture.
I'm sooooo happy with my preamp! The thing is that last week I ordered some coax cable and resistors to Amidata and I needed to order something else to be free of delivery cost, and I remembered about the OPA 627 for the Buffer Amplifier. I should say that I was very sceptical about the improvement that this change could give to the excellent results that I was having with my preamp, but I finally ordered the 627.
Bearing in mind that I was prepared to find no difference between the OPAs I selected some cuts from different albums that I know very well. The last one that the OPA 134 played was “Lil’ Sis” from the album “Family Portrait” of Victor Lewis, recorded by Audioquest. The percussion and, specially, the metal section of this recording is absolutely superb and extremely difficult to reproduce. The result with the OPA 134 was very good (nothing new, I’ve been hearing this piece for more than two months in this preamp). The same piece “Lil’ Sis” was the first one that I auditioned with the brand new OPA 627 placed instead of the 134. Oh my god, I couldn’t believe was I was hearing: the detail was dramatically improved, to a extreme that I’VE NEVER HEARED BEFORE… the cymbals was there, it was almost impossible to think that the sound could come from two loudspeakers…(DIY loudspeaker, with Monacor SPH-165CP woofer and Scan Speak D2905/95 tweeter, 3rd passive filter at 1,7khz). It was like perfectly focussing a picture that was a bit blurred, and the tonality is now close to perfect. I’ve realised that the noise has been reduced more and now It’s almost impossible to hear anything with the ear at 1cm from the tweeter (bear in mind that I’ve used non inductive resistors and the Mundorf MCap Supreme –a non inductive capacitor- for the tweeter’s passive filter!!!).
If you’ve been reading everything until here (sorry!) maybe you are thinking the same as I’m thinking… is it possible to implement those OPAs to the MOS125? And more important, can it be implemented in the Active Crossover?.