Quicksilver 300B PROTOTYPE Tube Monoblock Amplifiers - One of a Kind!

$8,499 $9,999

We received these amps from a serious collector that had the most amazing equipment, so we suspected they were quite special.

Since we could not find any information or pictures online that matched these amps, we ended up call Quicksilver. Yes they surprisingly answered the phone and were super helpful!

It turns out these amps were NEVER PRODUCED and they have no record of them existing. It's likely they were a prototype produced by Quicksilver but never released into the market.

So as far as we can tell from the experts themselves, these are one of a kind and are therfore priced accordingly. They are now part of our holy grail collection.

On top of that, after a lot of folks questioning if these were prototypes or not, another verified source contacted us: "I actually have a pair of those Quicksilver 300B push pull monoblocks. Quicksilver made a few of them as well as a few single ended 300B monoblocks but they never made it into the production line."

We tested them carefully and verified with the manufacture that they are configured in push-pull configuration, thus delivering close to 50W RMS into 8 ohms.

You see while the typical single ended configuration tends to deliver just a few watts per 301B, this method results in quite a bit more. Giving you many more options for speakers while still enjoying the amazing sound that this tube is capable of.

We used these rare beauties to power our newly acquired vintage Altec Lancing Magnificent speakers and received amazing results in clarity and authority.

The amps both look like new, with no scratches or pitting on their chassis or chrome.

We fitted both of these amps with brand new Sovtek NOS tubes, but if you want to take it to the next level you could match them up with one of our currently listed sets of NOS Western Electric tubes.

Click below to add our recommended matching cables from Kimber Kable, all brand new as SkyFi is an official Kimber dealer.

Kimber Kable - RCA Interconnects

Kimber Kable - Speaker Cables

Kimber Kable - Bi-Wire Speaker Cables

The SkyFi Testing Process for Tube Amplifiers:
We start with a visual inspection of all internal components to make sure there are no signs of stress or aging. Capacitors are checked for telltale sings of bulging or leaking, resistors are checked for signs of overheating or cracking, and tubes are inspected for signs of stress overheating or cracking.

We then power up the unit carefully and run a simple 1k sine wave while monitoring the output on an oscilloscope for signs of distortion or noise. Finally we run the amplifier to its full rated power into the appropriate resistive load provided by our Sencore amplifier tester. If there is an issue, it will usually be noticeable at this point. If it all looks clean we will often test for THD (Total Harmonic Distortion) measured by our Keithley distortion meter, and compare it against the original manufacturers specifications. The amplifier the remains powered on to "burn in" on our test bench for a few hours to make sure there are no heat related issues. If there are balanced inputs available they will also be tested.

We also test all tubes for output gain and leakage on our calibrated modern and professional tube tester against the original manufacturers specifications. If needed, the tubes will be replaced from our vast NOS (New Old Stock) vintage or modern inventory.



Original Box

YES Included!


Not Included


Not Applicable


Yes - Power Only

Physical Condition

8 / 10

Working Condition

10 / 10

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