300B Push-Pull Fully Balanced Amplifier

This project was initiated by a gentle man who charllenged us to propose "one of a kind solution" amplifier which could merit his uncompromise demands:
1) Pure class A power amplifier that can deliver full drive force to any ineffcient loudspeaker
2) Fully Balanced circuitry from input to out (but must be able to play RCA with no loss of performance)
3) Very wide bandwidth, 100KHz is the minimum acceptable power bandwidth (-3.0dB)
4) Lowest harmonic and intermodulation distortion, since he owns very critical ears especially at high tone.
5) Must implement "Simple" approach as much as possible.

300B tubes are among the best direct heated triode that we select. We know that when employ in push-pull Class A, 300Bs blend sweet refine sensation, triode sound with precision in bass control, impace and full body sound. (whereas when employ in most SE class-A, 300B can easily have bass boom since THD at low frequency is very high) We developed fully balance input circuit, driving circuit, and output circuit to meet the customer's request; however, we also experienced that the whole combination would generate just a little bit more extending in details, pace, and soundstage of conventional push-pull class-A circuit (with ordinary RCA input) if the new fully balanced output transformers were not created.

As of many prototypes we were finally address the major issue of unbalance leakage inductance and parasitic capacitance of conventional output transformer that caused performance bottleneck in the full balance topology circuit. To solve this issue, we have created new SILK balanced winding technique that allow all new SILK balanced output transformers to fully realize the benefit of balanced circuit topology. This new balance output transformer is so good that allow us to minimise the use of negative feedback while maintain the frequecy response beyond 100KHz at -3dB full power.

With many new techniques to combine into one amplifier project, we're not only meet but also exceed customer and ourself expectation.
The sound characteristic of this combination is very accurate and powerful while capture all details with great refinement.
Therefore, these new techniques of fully balanced circuitry & new SILK balanced output transformer will be incorporated into our upcoming SILK amplifier products in near future.

Product Type:
Mono Block Vacuum Tube Power Amplifier with RCA and XLR Input
Pre-Amp/Input Tubes:
6N1P x1
Driver Tubes:
6N1P x 2
Output Tubes:
300B TJ Full Music. x 4
Rectifier :
Super Diode TD-15
Filter Capacitor:
1,000uF x 4 Nichicon Audiophile Grade
Filter Choke:
Low Loss 3H/400mA
Coupling Capacitors:
Hovland Musicap
Signal Resistors:
Kiwame Carbon Film type
Interstage Transformer
Output Transformer:
SILK P-5500(Fully Balance) Output Transformer
Output Power:
25 watts/CH class A1 design
Frequency Response:
1Hz-100,000Hz (-3dB) at full power
Input Sensitivity:
1.5V (RCA), 2V (XLR) for full power output (at maximum volume gain)
Overall Gain:
THD + noise:
Less than 1.5% at rated power, Less than 0.1% at 1 watt
Signal /Noise+THD ratio:
below 90dB
(W) 43 x (D) 37 x (H) 20 cm.
Approx 25kg. x2
Direct From Factory Price :
Please Contact.