Fireblade
Seasoned Member
  

Knowledge comes, but wisdom lingers. A.L.Tennyson
Posts: 1046
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Not to answer your question, but relevant nevertheless. I just finished a long tube-rolling stage on the Mini Torii, and found quite a different setup to the stock complement to be much better.
The curious thing is, I have not tried that many alternatives (will continue on stage two, with a 2nd tube stash), but the changes are already very significant.
Driver: Brimar 12AT7 (white letters label, made in England). Replaces stock RCA (USA) 5963.
Output tube: Reflektor plant, black glass, Russian 6V6. Replaces stock JJ 6V6 S
Rectifier: RFT EZ-80. Replaces stock JJ EZ-81
Output VR: Sylvania OA3 (stock)
Input VR: OC2 (stock)
Excellent detail retrieval, amidst a warmth only special driver/output tube combinations manage to provide (a marriage made in heaven). Great bass throughout the relevant frequency spectrum.
I used to have a dark, non-transparent, semi-booming sound overall, that worked fine with excellent recordings but was just ok with most selections.
Today, the described combination has beaten everything else I've tried so far, and I sincerely doubt major improvements over this are possible from tube-rolling alone (but you really never know.)
The reason why this took so long to test is the Mini really does not 'cook' the tubes as with other more powerful amps, and so, normally the burning-in takes much longer.
In addition, both the Brimar driver and the Russian 6V6 are tough cookies to bake, sounding awful during most of the long burning-in expected time horizon.
In the end, the results are more than worth it, and I can report great satisfaction from this tube set. The reason I intend to continue for a 2nd stage, is to see if more driver choices can open up new fine-tuning avenues in the Mini, mostly because I have not tried any more drivers than those two.
I found current production Tung-Sol 6V6GT a close second to the Black Glass tube, but with a tendency to go overboard on high pitch passages (brightish under high frequency demands), which excludes it from classical music, although still a good choice for jazz and rock.
The stock JJ 6V6 S seems to lack pace and power compared to the other two, and decidedly laid back and very uninteresting.
The stock RCA 5963 is definitely not working in my system, it does not matter what other tubes go with it, it is terrible. The Sylvania OA3, which works wonders now, used to overcome this driver to the point of rendering the sound heavy bass-diffused and dark. The only remedy came in the form of OD3 VR's, but these would flatten the sound,rendering it two-dimensional.
All in all, a great experience and a nice and relatively cheap way to significantly improve the sound. Of course, this result is entirely my own conclusion, under my own system conditions (see signature), and it may not work like this in different settings, preferences, etc.
My quest right now is to find a couple more good driver candidates to see if I can still improve upon this.
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