Review of TDSS Upgraded
NuForce Ref-20 by Gammajo
(D.R.R.T. / LEVEL-1 Upgrade Only)
"After hearing good things from several audiophiles about TDSS and Bob Smith's mods (which do not void the manufacture warrantee), I sent him my Reference 20 mono amps for enhancement. I did so nervously, because I had enjoyed my 20's in stock form for over a year.
Right out of the box the newly modded units sounded a touch harsh and constrained but within the first 20 hours of break in, they relaxed and opened up. My first criteria was fully met - that the mods preserved the liquidity, hint of warmth, dynamics, clarity, and quiet of the original that I so loved.
As the 20's are already excellent, the improvements were subtle but easy to recognize and taken together launched the 20's into another level of goodness. With the mods there is a touch more high frequency extension and a good bit more air. Images are more solid, defined, and clear within their own space. Initial transient attacks are a good bit punchier and surprisingly sudden without adding any steeliness. This helps percussion, from high bells to bass drums, sound more exciting and real. The mods remove an, unnoticeable until its gone, layer of digitalness. There seems to be less time smear compared to live music so string bass and massed violins are presented more realistically, and fast runs on piano allow each note to be appreciated within its own fraction of a second, and PRAT is enhanced. The last tenth of an ounce of resolution is revealed without any added edginess or harshness.
The summary results of these changes are that orchestral music is thrillingly more alive and dynamic with clearer positioning on the sound stage, and soft passages massage the soul because their sweetness, and nuance is better revealed. Rock music is more involving, voices sound even more real compared to the 20's and soft background voices are particularly enhanced.
If you have the equipment that can reveal this level of quality I think you will be pleased. Why? I think the mods preserve all the original genius circuitry yet remove nearly imperceptible RFI, EMI and vibrational distortion and increase quiet. I personally think that the modded 20's can complete at the $50,000 amp level and perhaps even be preferred by many whose minds and hearts are open to the music being the reason we engage in our quest."
From Link 2:
"For price I would contact TDSS directly as there are different options and I would not want to mislead. From my point of view prices was very reasonable (cheap) for what you got - they also turned the unit around very quickly and a friend of mine who as had similar work there opened his units and found everything very carefully done."