TDSS Upgrade of Legacy NuForce Amplifiers

Reference Series 9, 18 & 20 Power Amplifiers

"The best kept secret in High-End Audio today!!!"

 NuForce Ref-9 "Flat Face"

NuForce Ref-9 "Flat Face"

 NuForce Ref-9V3 "Stealth"

NuForce Ref-9V3 "Stealth"


Units with Voided TDSS Warranties


Latest Warranty Policy

 NuForce Ref-18

NuForce Ref-18

 NuForce Ref-20

NuForce Ref-20

Ref-9 Internal.jpg

Stock Ref-9V3
Power Specifications
175Wrms @ 8-ohms
335Wrms @ 4-ohms

Ref-18-20 Internal.jpg

Stock Ref-18/20
Power Specifications:
200Wrms @ 8-ohms
400Wrms @ 4-ohms


About the amps. Wow! They sound fantastic!!! It is like the “old” NuForce Ref9 SE’s after steroid treatments.           Everything I loved about the amps has been amplified (no pun intended).  The base is deeper, sound field is wider, midrange is warmer and the dynamics more pronounced.  It is like I purchased a brand new pair of mono blocks - not just having “upgraded” some old ones.

Moreover, the modified amps produce a sense of more amplifier power with even darker backgrounds...                  As the circuits break in, the sound keeps improving...                                      WOW!!! Nothing but non-stop TRUTH and BEAUTY !!!

Jim D.                            (on Level-3 Upgrade)



Level-1 Upgrade

(D.R.R.T. Upgrade Only)

MSRP $500.00 each


Level-2 Upgrade

D.R.R.T. Upgrade +
5VDC Power Supply Upgrade

MSRP $750.00 each


Level-3 Upgrade

D.R.R.T. Upgrade +
5VDC Power Supply Upgrade +
High Voltage DC Power Supply Upgrade


500-Wrms "No Fan"

Audio Power Output =
360-Wrms @ 8-ohms
480-Wrms @ 4-0hms

--- OR ---

500-Wrms "With Fan"

(Required for Ref-18/20)

Audio Power Output =
360-Wrms @ 8-ohms
480-Wrms @ 4-0hms

MSRP $1,250.00 each

!!! - - - Special Offer - - - !!!
quantity Discount PRICE
--- 2 OR MORE UNITS ---

= $1,200.00 EACH
(w/ shipping included!!!)


With the new power supplies, the amps have taken quite a bit of break-in... I want to give you some initial observations.

First, the amp has so much more dynamic range... The amount of bass drive is amazing. It is as if a sub-woofer has been installed into the system! Not just more bass but clean, defined and more realistic toe tapping sound.

I also detect a bit less sibilance in the midrange, ever so slight but really in a good way. Sound-stage is a bit more forward, but a tad wider than before.

Absolute non fatiguing sound.

The music really draws you in and gives me the desire to listen for long periods at a time. 

Chris K.                        (on Level-3 Upgrade)


If you happen to have a pair of Ref-9s, 18s or 20s that either aren't working and/or you are looking to make a move up to better performance, rather than delegate them to a landfill or sell them at a significant loss you might consider letting us "transform" them for you into an amplifier capable of such improved performance that you might not even recognize them for what they once were.

If you don't own a pair, hurry up and go get a couple of used ones before the word gets out and their price starts going back up. Trust us... it's GONNA HAPPEN because word travels fast when you're talking deals like this. Oh... and speaking of "deals," unless you are quite "well to do" you probably won't be able to afford what it would otherwise cost to replace them with anything else as good either... let alone better.

(PS. We have a few empty chassis here in stock, which would probably be cheaper than buying a used pair elsewhere. We only have a few though, so when they’re gone…)

OK, we have now warned you. Don't blame us if a used pair of NuForce Reference Series amps start becoming rarer than hens' teeth and/or their prices start going through the roof. we're gonna keep "do'n R thang," and if that drives up their price... oh well - you had your chance.


 NuForce Ref-9V3 "Stealth" Copper

NuForce Ref-9V3 "Stealth" Copper



First, there is D.R.R.T. If you take the time to read all about it you'll likely need a short vacation, but at least you'll also understand just how significant it really is when it comes to improving the sound of your beloved Ref-9, 18 or 20. At first we simply called it our TDSS "Custom Upgrade" - mainly because we hadn't developed any other upgrades yet and, being pretty "down to earth"-type folks, we weren't real concerned about getting very savvy with our marketing. When you come from an engineering background, your primary concern is reliability and overall performance, not so much marketing hype and being trendy.

In any case, it was the NuForce Reference Series amplifiers and correcting their somewhat high failure rate that became the primary motivation for what has since become the TDSS Upgrade service. Once having worked though all of the issues and witnessed for ourselves the impressive results thereof, it was obvious that the complex distortion artifacts that D.R.R.T. was intended to address, along with the passive techniques we developed for remedying them, would also apply to virtually any other audio component... regardless of make or model. Hence, the TDSS Custom Upgrade (now D.R.R.T.) - and onward.


Improved Amplifier Reliability & The Origins of D.R.R.T:

With NuForce Reference Series power amplifiers being in widespread use from about 2007 onward, they became the driving force behind the development of the first TDSS Custom Upgrades. As had been the case for several years, enthusiasts found their award-winning sound quality and overall value to have few equals. Although, they weren't so enamored with the frequent failures many were experiencing with them.

Fast-forward to early 2014, NuForce’s repair facility in California had ceased operations and TDSS was solicited by them to became what is now the only authorized NuPrime and Legacy NuForce service center in North America. That being the case, now it would be our reputation that would be on the line if a recently repaired amp were to subsequently fail again in a short period of time. You see, many folks aren’t that interested in the technical aspects of a product, so they will often be a bit skeptical when you try to tell them that their amplifier has an inherent design flaw that is causing the repeat failures. Rather, they are just as likely to suspect that the service center lacks sufficient competency to perform the necessary repairs correctly, and interpret such comments as more a matter of CYA and excuse making instead.

That said, the primary goal of our first upgrade effort was more about trying to correct the underlying design flows so as to make the amps more reliable, than anything else. At the time we just wanted to give NuForce Reference Series owners another option beyond having to deal with the need for repeated repairs and a bunch of “lame” excuses from us.

As "serendipity" would have it though, almost as much to our own amazement as anybody else’s we found that not only did our modifications result in much improved amplifier stability & reliability, but they also ended up having a secondary, "not fully anticipated" effect. To our surprise and great pleasure we discovered that the amplifiers' slight static background noise levels had essentially vanished to "zero," and their dynamic speed, resolving power and ability to more fully and naturally render subtle harmonic detail had been greatly improved as well - in fact, amazingly so. . "Not bad" when your original goal was to simply “fix” the darn things so they quit blowing up! :-)

At that point we determined to do all that we reasonably could to enhance and optimize these improvements to their furthest practical limits by including a few additional performance-enhancing modifications. From there onward, the TDSS "Custom Upgrade" (now D.R.R.T.) had been born... and the rest is fast becoming history.


Ref-20 Bkack Pair.jpg

— NuForce Ref-20 Pair —



If you already happen to own a pair of NuForce Reference Series amps (or even a recent NuPrime version of the Ref-20) and you're in the market for a SERIOUS step up in performance and reliability, you really owe it to yourself to to take a serious look at our new Power Supply upgrades. In fact, you can easily pick up a used pair of Ref-9s these days for $1.5K and often less. Then get the Power Supply Upgrade (D.R.R.T. included) installed for another $2.4K and end up with a pair of amps that sound like they should easily cost over $20K... for less than $4K!!! That's nearly the price of a single stock NuPrime Evolution One alone! As far as sonic performance goes, (in our opinion) there isn't an amp out there that can even come close to competing with that combination for less than $10K, so we're talking about one of the "best kept secrets" in high-end audio today.

You can rest assured that if you do decide to "go for it," it will likely be a long time (if ever) before you're in the market to replace them. In fact, as is often the case with any truly exceptional piece of audio gear, they may very well be the last amplifiers you'll ever own.

The Power Supply Back-Story:

So it was that TDSS began offering our Custom Upgrades (D.R.R.T.). They were fast becoming a great "hit" with nothing but rave reviews following, so realizing their potential we began offering them for all of the NuPrime products as well. Along the way though we ran into a bit of a "snag," at least with respect to the older legacy NuForce Reference Series amps.

You see, not realizing the Custom Upgrade (D.R.R.T.) was even available, a large percentage of NuForce Reference Series customers were simply coming to us to have their defective amplifier repaired.  After informing these customers about the Upgrades and that they were successful in improving amplifier reliability AND sonic performance, many opted to go ahead and have the upgrade installed along with the basic repair. In most such cases only the Amp Module had failed, so it was a matter of replacing it and then installing the Upgrade components. Once in a while though it would be the switching power supply inside the units that had failed, and that was fast becoming a problem.

As things were, the power supply used in the Reference Series amps were not originally manufactured by NuForce, but were an "off the shelf" switching supply made by "Skynet," a company in Taiwan. Well, by late 2015 the existing stock of Skynet supplies at the NuPrime factory (the former NuForce factory) began getting low, and as it turned out Skynet had discontinued the thing a couple of years prior and with no "drop in" replacement having been made available. Finally, the NuPrime factory had no alternative but to start shipping defective supplies back to Skynet for repair.

OK, so now TDSS and our customers here in the USA are being forced to wait long turn-around times in order for us to get repaired power supplies back from Taiwan just to finish the repair on their amps. Even then, we're talking power supplies that were overly expensive in the first place. Add to that, they had already been in service for years, had always generated more heat than one would expect/prefer, were older designs and therefore generally less reliable... and now they had already failed at least once and are being “refurbished”??? Oh, man - that just didn't sit well with us so we set out upon a quest to find a substitute power supply that was readily available here in the USA from a few of the major electronic part vendors. As good fortune would have it, we found some that were much more modern and "clean" looking AND exceeded the required power rating by an additional 200-Watts! Not only that, but they easily fit within the space that was available inside the amp chassis. Bingo!

The next step was to acquire a sample pair and give them a try. We took an existing pair of Ref-9s that had already received our Custom Upgrade/D.R.R.T. treatments and installed the new supplies in them. Then we took them "out for a test drive" by connecting the amps to a pair of 4-ohm NuForce S-9 loudspeakers. THEN... "we let 'er rip." What we had thought was going to be a simple "joy-ride down memory lane" turned into the equivalent of an Indianapolis 500 race, and those Ref-9s were leading the pack!!!

Once again a simple "repair" turns into a major revelation, and NOW another major upgrade. Sure, the new power supplies were rated at 500-Watts as compared to the old Skynet supplies at 300-Watts), so we were expecting a good bit of sonic improvement as a little bonus. Nevertheless, we were in no-way prepared for yet another total transformation of these amplifiers, and we don't use that term lightly either. By "transformation" we mean that the improvements were so blatantly obvious such that we could LITERALLY hear the difference within 3 or 4 seconds of hitting “play” on the CD Player.

For testing purposes, one of the selections we played was the classic Sheffield "Track & Drum" recording. To our amazement the drums became what almost sounded like miniature "explosions," while at the same time subtle harmonic textures like brushed cymbals sounded as though the drummer was right next to us in the same room. Now, you have to keep in mind that this pair of Ref-9s had already received our D.R.R.T. upgrade, so most of the above other than the far greater dynamics had already been greatly improved. That said, we couldn't have imagined that it was even possible that many of those same qualities could be improved further yet - but they were. On top of that though, now the peak dynamics into the somewhat difficult-to-drive 4-ohm load of the S-9s became something nobody would have ever thought possible.  Never before had we ever heard the Ref-9s sound so "real" and incredibly dynamic. At the same time we had never heard the S-9s sound anywhere near that good either. Eureka!!!

Previous to this little "experiment," when using a pair of stock Ref-9s in the same setup, the highest gain setting on our preamp that we could ever achieve before audible "clipping" distortion would set in was about an "88" on the preamp's digital readout. Now we had the preamp cranked all the way to its maximum output with a reading of "99" and could go no further. Yet, this pair of Ref-9s wasn't even breaking a sweat, with no hint of clipping whatsoever.

In fact, we haven't had a chance to go back and try pushing things any further, as we've been too busy ever since to find the time. Besides, during that first listening test the volume was so loud that we literally had to scream at each other to communicate, even though our whole team was standing right beside each other. That said, at this point we'd rather not risk blowing up the S-9s right now... just to see how far these puppies will go. The reason we're a bit "leery" of going there is because the aluminum cones of the woofers in the S-9s were almost hot to the touch after we were done listening, so the odds are we'd just blow them up if we tried that again and pushed the combination even further. Besides, as it is with the new power supplies installed, the Ref-9s now have more dynamic headroom than most any sane person would ever need - and we’re the type of listeners that like to crank things up LOUD once in a while!!!.

Actually, from our "guess-timation" and based on the peak dynamics that we achieved that day, from a "headroom" standpoint that pair of Ref-9s sounded as though they were AT LEAST 500-watt amplifiers - EACH. That makes a certain amount of sense too because if you do the math, it turns out that "IF" the 52VDC power supply output were to be a theoretically "perfect" Voltage Source (no such thing exists in reality) and powering a 4-ohm load, it would output 676-watts (52^2 / 4 = 676).

Furthermore, when you factor-in the energy storage of the capacitor bank that follows after the power supply and the fact that the output voltage of these new power supplies is obviously much better regulated allowing them to output more current without the voltage beginning to "sag" (drop), the upshot is that the short-term peak power is being increased quite dramatically. In other words, the Ref-9s after having been upgraded with the new power supplies now "sound like" they have the "dynamic headroom" that you might otherwise expect to hear coming from a conventional 1,000-Wrms "linear" (i.e., non-switching) amplifier.

In full disclosure, we have yet to actually undertake the process of testing to get exact numbers, but for the most part it's pretty much academic because a pair of any Reference Series amps upgraded with these new power supplies become something NOBODY has ever heard before, and that's including the engineers that originally designed them! Let's just put it this way... over our 40+ years in high-end audio we have NEVER heard a better sounding amplifier at ANY price... and we've been around the block quite a few times along the way!!!