The road to nirvana

My journey into Photography, Horology, and Audiophilia

Softone Model8-300B

October 14, 2023

The road back to single-ended triodes

I have an itch to scratch, and that is reconnecting with the single-ended triode sound. Decades ago, I had a dual tube setup using Anthem Amp1 and Pre1-L combo, and my DIY 2A3. I still lack the motivation to rekindle the DIY romance I had in the past and the fact that I can't find my remaining Tubelab SE parts doesn't help in my single-ended triode DIY comeback.

So, the grand plan was to buy a commercial SET power amplifier that will be fed from the balanced output converted-to-unbalanced from the Burson Audio Soloist 3X Professional. Having watched many, if not all available videos of Cube Audio, choosing a Tektron SET amplifier is a no brainer and my sights were set on the Tektron TK ONE 300B-PS.

I always do extensive due diligence on the products I'm interested in, but this time I'm having a woeful time with Tektron due to lack of information from their website.

The segue

While watching many videos that influenced my build of the Mark Audio Pluvia7 PHD cabinet from (@spcjpnorg channel on YouTube) I realized that many of their [Air-Recording] videos use the Softone Model8-300B as the amplifier.

I started looking into the product and most of the information I need is available from their website Model8 Stereo Power Amplifier with  Technical Description aptly covered. Here are the key points I extracted from those web pages that align with my own prejudice:

  • fixed bias operation, automatic plate current operation
  • three-stage, direct-coupled (12AU7>2SJ181(S)>300B
  • low-noise DC/DC filament voltage supply
  • low-noise HT power supply using MOSFET
  • soft-start operation (about one minute delay)

Shoichi Yoshimoto

He's the main man at Softone. As I have an upcoming trip to Osaka, I inquired if it's possible to ship the Model8-300B to my hotel, to which he replied positively to my delight. The process from here on was straightforward, from the issuance of the PayPal invoice to the actual delivery.

Before my arrival at Osaka on August 17, I was informed by Mr. Yoshimoto that bad weather may cause delays in the delivery. I replied back saying that as long as it arrives before I leave, it's all good.

Lo and behold, after I returned from touring parts of Osaka after my check-in, I received an email notification from Yamato Transport that the Softone Model8-300B has been delivered!

I am now free to enjoy Summer Sonic 2023 and the rest of Osaka without worry!

Initial impressions

The amplifier is a little bit over 8kg and feels solid. The build quality is good and the silver front plate is a nice contrast to the all black chassis. The tubes are unbranded, a pair of 300B and one 12AU7.

The rear input and output have labels (unlike Burson, cough) and appropriate warnings near the IEC inlet are clearly printed. Supplied items include a power cord and the manual.

Initially, I tested it with my desktop speakers and I verified it is properly working. Ultimately, it goes to my main system where both the Cube Audio F8 Magus and the Mark Audio Pluvia7 PHD are.


Matching woes

The purpose of the SET amplifier is to take advantage of the single-driver Cube Audio F8 Magus drivers. At 94dB sensitivity, the 300B is a good candidate and this is the role the Model8-300B is supposed to fill.

But I'm not convinced...

Honestly, I am nearly disappointed with the matching of the Softone and the Cube Audio. I was trying to convince myself, but I just can't. I then hooked up the Mark Audio Pluvia7 and I was surprised with what I heard, it can actually rock!

It remained a mystery to me as to why the Softone cannot maximize the potential of the Cube Audio in terms of sonics, and why the Mark Audio sounds superb.


Thanks to the builti-in volume control, which by the way is a stepped version of an ALPS potentiometer, I decided to take the Burson Audio Soloist 3X Professional out of the signal path. I connected the unbalanced output from the AQUA La Voce DAC into the Model8-300B and I was stunned how the sonic quality changed for the better. Now *this* is what a SET amplifier sounds like!

Obviously, the Soloist 3X Professional has influenced the sound of the Softone to the point of "polluting" the signal causing the questionable sonic performance with the Cube Audio drivers.

Why the Softone sounds good with the Mark Audio drivers is something I'm not going to investigate anymore, as the primary problem has been demystified.


How that the Soloist 3X Professional cannot perform its duties as a pre-amplifier, and having three different sources to deal with, the simplest solution is to use the Audio Hungrary Qualiton X200 as an active switcher as it has a pair of fixed level output

Coming together 

The Softone Model8-300B sounds superb with the Cube Audio F8 Magus via Nordost Blue Heaven speaker cable, and the input via the old and trusted Sonic Art silver interconnect cables from the Qualiton X200 fixed level output. The power cord has been upgraded to a thicker version and draws voltage from the Oyaide R1 AC inlet.


I got a working configuration but I can't sacrifice tubes burning and power (about 500 watts in idle) unnecessarily consumed as the Qualiton X200 acts as the switcher. I am now deliberating with myself should I go the passive or active route for the input switcher duties.