Hi all, I'm new to this site, although I have browsed threads in the past.
I'm a hobbyist with guitar amps and pedals and audio gear. I wanted to jump in on this if I may because I have a Sansei AU Alpha 607 MRX which I love. After lots of other amps including Naim, AudioNote and Unison Research gear, I find this amplifier so natural and enjoyable listen to. All that said I just recently got tempted to tinker; Thinking the bass was probably softer than it should be I changed /uprated the main reservoir caps to 15000uf nichicon super through (the originals being type 2 12000uf caps). I had not read
@czubsi 's comments about setting the amp up first and not changing the reservoir caps unfortunately. I agree that maybe the biasing would have fixed this, but whilst at first it sounded like crap, after a day or so of run in its starting to sound significantly tighter, bigger in the bass, and the upper end its starting to smooth.
My amp came with mainly unicon electrolytic caps and a few chemicon. Because of this I also changed all the supply board electrolytics to Elna Silmic ll. I did this because other pictures of the AU alpha 607 MR/MRX had Elna Silmic and the spacing on the boards fits these caps better than the unicon in some places. I'm waiting to see how these sound after running in before I change the signal path electrolytic from unicons to Elna.
What I loved about the amp was its naturalness especially in high end and midrange detail. I wonder if some of this was due to it being biased cooler due to drift in values, although the union/chemicon power board caps (which I've kept) were all pretty much spot on.
The amp is coming round and starting to sound nice again with much more bass weight, but my question
@czubsi, if he might be so kind, would be, how do I set this up? Had I read your comments before I would have asked this first. I have built and biassed plenty of valve amps. I see there is a bias trim pot on each power board along with two hot/cold trim pots. Where would i meter to read and adjust these and where would i find the correct readings? Would these be milli volt or milli amp measurements?
Any help from
@czubsi or anyone else who knows would be very much appreciated.
Thanks in advance,
Carson