Glow Master Series GM-70 Pure Class-A Monoblock Single Ended Parallel Power Amplifier
Hi-End audio is complex, the solution is simple.

The new GlowMaster GM-70 is a large format monophonic power amplifier employing parallel vacuum tubes on its output stage running in pure Class-A to deliver the best quality of 70 watt/RMS of pure Directly Heated Triode characteristic power.

The output section: Each monoblock is equipped with two Russian NOS GM-70 vacuum tubes working in parallel SE Class-A. This vacuum tube is originally designed to be used in military environment thus having extremely linear and durability characteristics when used in audio amplifier. Its massive anode structure with heavy glass envolop reduce unwanted vibration or microphonic usually associated with other type of vacuum tube. By successfully buidling several custom made GM-70 SE amplifiers with one tube, we decided to reach further and higher for the completion and the perfection in the design of cost no object apparatus to withstand the test of any other challengers. The parallel configuration of GM-70 tubes appeared to be the best answer and to outperform one tube, works need to be done from all aspects of the design and implementation. Starting from newly development of SILK Super Output Transformer (SILK model S-3000GM70) to allow the two tubes configuration to work in ideal condition without degradation in harmonic or frequency characteristic over smaller output transformer. This task require the unique winding technique and winding arrangement evolve from several trial and error in the developing process. Although the transformer must withstand the voltage swing close to thousand volts and heavy current generated by two tubes, the outcome is amazing giant output transformer with 1,000watt power reserve that have bandwidth close to 80KHz with very low distortion and constant impedance throughout its working range allowing two tubes configuration to work successfully.

The power supply section: By having the solution with the best output transformer, next development is to design and build the best power supply section to feed both power hungry tubes with lowest impedance. Eight 1.5KVA Super Diodes work together with massive 1.3KVA handwound power transformer with special electro-magnetic shield to help ensure sufficient current supply when the load is at its most severe. The supply filter section comprises of audio grade large type filter capacitors and DC choke filter that block all noises from the rectifiers to get into main audio circuit. Additional low voltage separate power supply section is built around a naturally soft start vacuum tube rectifier (5Y3) with classic Capacitor-Choke-Capacitor configuration. This power supply section feeds the input and driving circuit directly thus completely eliminate any power drop off during maximum peak current drawing from the output tubes. These two power supply sections improve the sounding performance of the amplifier to the next level.

The input and driving section: Only the best vacuum tube and circuit are selected to work in this section as it is one of the most critical element to determine the sound of the amplifier. GlowMaster GM-70 has special NOS 6N1P dual triode vacuum tube to work as input tube generating precise and natural sonic signature with unparalleled clarity and dynamic range extending beyond ordinary tube amplifier. The driving section forms a solid backbone of the amplifier since it needs not only to supply pure signal, but also very high driving force to meet GM-70 extreme requirement. Only NOS 6BL7 large size medium mu twin triode in special anode choke loaded circuit can meet such demand of GM-70 to produce the extraordinary sounding amplifier.

  Special features: Making good power amplifier is not easy, maintaining one to perform at its best throughout its service life is even harder task. GlowMaster GM-70 has simpler solution with its real time current indicator on the front LCD display to observe the bias status of the output tubes assuring perfect working condition. Also located at both sides of the chassis near GM-70 tube are the bias adjustment pots which enable user to response to any deviation in bias without having to flip the heavy amp over to make such bias adjustment inside the chassis.

Inside each monoblock you'll only find the art of know-how in selecting parts to compliment each other developing great natural sound and the master craftmenship of point to point hard wiring, layout in very elegant and simple appearance yet provide simple maintainance and minimize sonic degradation.

Tube cover cage can be easily removed
to clearly display the magnificent lighting of the GM-70 tubes.

  Not only our GlowMaster GM-70 sounds very good, but it has good characteristics and measurable evident to prove. Not just numbers on charts. Here is a result of our extensive research and non-stop development to build the better sounding machine. Our true dedication and determination are reflected in each of our products.  

Click for enlarge image

Test Report
Real total harmonic characteristic measured at 1 watt (the most important watt, many people believe) As can be seen here, only second harmonic dominate the spectrum and its level is very low (-62dB or THD of 0.079%). This is much lower than any other single ended amplifier.
This picture depics frequency characteristic measured at 1 watt RMS. Top curve is phase angle which have smooth transition from 20hz to 20KHz. The lower curve is frequency response and it is almost flat from 10Hz to 30KHz while having small dip at around 40KHz, the total bandwidth is still reach further to +70KHz. It is evident that this SE amplifier outperforms many push-pull amplifier or even solid state in bass frequency response.
At 10 watt RMS, the total harmonic distortion is still very low at only -51dB (0.28%) Second harmonic is still dominate the spectrum with accomodation of small third harmonic and forth harmonic.
At almost highest power output of 60 watt RMS, the harmonic distortion is still lower than most other single ended amplifier. At -36dB (1.58%) with majority of harmonic spread out in second, third, forth and fifth in decade, it is still very difficult for even well trained listener to detect such distortion since it will still appear to be more pleasing. Also it is unusual for most listener in any circumstance to encounter such a high sound pressure level
At 60 watt RMS, the frequency response is still flat from 20Hz to 30,000Hz.
Product Type:
Monophonic Vacuum Tube Power Amplifier
Input Tube:
Driver Tube:
Output Tubes:
Ulynov GM-70 x 2
Output Power:
70 watts/CH pure class A, 100 watts peak power
Frequency Response:
5-70,000Hz (-3dB) at 1 watt
20-30,000Hz at -3dB at full power
Input Sensitivity:
0.96V for full power output
Overall Gain:
Negative Feedback:
Moderate 6dB (can be special ordered with zero feedback)
THD + noise:
Less than 0.08% at 1 watt RMS, Less than 5% at rated power
S/N ratio:
below 88dB
(W) 35 x (D) 56 x (H) 28 cm.
Approx 35 kg.
Direct From Factory Price :
Please Contact.