MPX-50 Mono Power Amp


  • Ultra Linear Mono Power Tube Amp

  • 50 Watts Output 6L6 or EL34

  • 100 Watt Upgrade Available

  • 4-8-16 Speaker Impedance

  • Volume Level Control

  • Presence Control With Edge Boost

  • Line Out Record Level Control

  • 6L6 - EL34 Bias Switch

  • Dual Rectifier 5AR4 & Solid State

  • Tubes: 2-12AX7, 2-6L6, 5AR4

  • Custom Upgrade Options

  • MSRP: $995.00

  • Sale Price:  $693.75



The  FRENZEL MPX-50 Mono Power Amp  was designed for the tube purist to be used as a musical instrument power amp or as a home stereo power amp.  It uses an all tube circuitry in the amplifier section for those vintage warm tube tones with a choice of tube or solid-state rectifier in the power supply for smooth warm jazz or tight dynamic bass response. Two 12AX7/ECC83 tubes are used as  preamp buffer drivers. The output uses a Class AB Ultra-Linear Push-Pull design with fixed bias for each channel.  The amp comes standard with 6L6's.  A 6L6/EL34 bias switch allows the use of EL34's with no bias adjustment. This design allows the use of many of the octal base output tubes including the 6V6, 6L6, 5881, 6550, KT66,KT77 & KT88.   Ultra-Linear transformers are used to give crystal clear tones. This amp will faithfully reproduce what you put into it. Classic open chassis design with oak side panels. 

Standard Features:

  • Input Jacks isolated from chassis for low noise, eddy currents, and hum. 

  • Classic  Knobs, Toggle Switches and Jewel Pilot Light 

  • DC on filaments for low 60 hz hum.  

  • Star ground system to reduce induced current chassis noise. 

  • Input Level Controls  for each channel

  • Classic Type 5F6A Style Presence control.  

  • Unique NNFB "Edge" switch on the PRESENCE control that transforms the power amp section into a No-Negative-Feedback style amp for more open, less compressed tones. 

  • Ultra Linear High Performance Output transformers

  • EL34/6L6 Bias Selector Switch - Allows you to use either 6L6 or EL34 type power output tubes.

  • Post output transformer LINE OUT with LINE OUT LEVEL control for driving a another power amp, PA system or recording,  Auto switching internal load if speaker is not connected to protect amplifiers and to give you true loaded simulated speaker  output.

  • IEC detachable plug-in three prong grounded power cord. 

  • STANDBY switch to turn off the plate voltage during warm-up.   

  • Rock solid point-to-point hand wiring using only the best of parts...low noise tubular polypropylenes caps, metal film resistors, Micalex long-life sockets, premium Neutrik jacks...etc. 

  • Tube compliment:  2 - 12AX7,  2 – 6L6GC, 1 - 5AR4​

Electrical Specifications: 

  • Input Power  - USA Model: 120VAC, 300VA, Export Model: 230VAC, 300VA. Standard IEC plug-in three prong grounded power cord. (100VAC & 240VAC export upgrade available. See Upgrade Options) 

  • Output Tubes - Class AB Push-Pull 6L6's - Fixed Bias

  • Output Power - 50 watts RMS

  • Speaker Output Impedance - selectable by switch 4-8-16 ohms.

  • Line Out Impedance - 10K ohms

  • Input Impedance - 1 Megohm

  • Frequency Response: 20 to 20,000 hz

  • Harmonic Distortion: Less than 1%

  • Preamp Tubes: 2– 12AX7 (input driver/buffer)

  • Power Amp Tubes: 2 – 6L6 (2 per channel)

Physical Data: 

  • Retro Vintage Cage Head - heavy duty lightweight steel mesh cage provides protection and excellent ventilation for tubes. Comes with easy carry Fender style strap handle. Overall  Dimensions - 17" Wide x 12" Deep x 10" High (Includes feet, handle and knobs)

  • Chassis Dimensions: 19"Wide x 10"Deep x 12"High

  • Weight -  18lbs. 

  • Chassis Material - Heavy gauge aluminum with welded corners. Oak side panels.

  • Rock solid point-to-point hand wiring with military style tie-wrapped wiring harnesses for long life and reliability.

  • DC on filaments to eliminate 60 hz hum.

  • Star ground system to eliminate induced current chassis noise.

  • Input and Output Jacks isolated from chassis for low noise, eddy currents, and hum.

  • Classic Pointer Control Knobs

  • Heavy Duty Toggle Switches

  • Vintage Glass Jewel Pilot Light

  • Components:  Only the highest quality parts are used including heavy duty transformers, low noise tubular polypropylenes capacitors, metal film resistors, Micalex sockets, Neutrik jacks. All parts are rated for commercial high use conditions. Wherever possible we use parts made in the USA.

  • Front Panel:  Volume Level Control,  Presence/Edge Boost Switch, Standby Power Switch, Pilot Lamp, On/Off Power Switch

  • Rear Panel:   Power Cord Connector, Fuse,   Line Out Level, Line Out Jack, Speaker Output Jack, Speaker 4-8-16 Impedance Selector Switch.

Upgrade Options:

These options allow you to  customize your amp to meet your special individual requirements.

240 VOLT POWER TRANSFORMER - for operation outside the USA  where 240VAC line voltage is used. Add $55.00

100 VOLT POWER TRANSFORMER - for operation outside the USA  where 100VAC line voltage is used. Add $55.00

100 WATT QUAD 6L6'S -   Increases power output to 100 watts.   Add $200.00. 

RACKMOUNT CHASSIS MODEL  - Replace retro cage cover with rack mount chassis. Includes 2U control pane and 2U vent panel. Add $225.00 - Sale Price $150.00  



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