Overview:

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The FRENZEL STP50/100 "Super Twin Plexi"  was designed as the ultimate amp for the serious player.  It  has a lot of soul that is generated by two separately voiced preamps each with its own separate Gain control, 3 band tone stack,  and Master level control. The CLEAN preamp is voiced like the classic Fender 5F8A Twin…the BOOST channel is voiced like the Marshall Super Lead Plexi. This amp is a unique one of a kind designed totally for the creative player in mind. It will give you just about any sound you ever dreamed of.  

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The heart of any amp is the preamp…it generates the signature tones. The preamp in this amp is a killer tone machine like none you have ever heard. It has High-Low separate input jacks for each channel. This allows you to match your pickup output impedance and to use an AB-Y switch select either channel or both to create your own unique tones! Each channel has separate F and M preamps each with its own Gain Control with a Bright pull switch or voice mode pull switch,  a 3 Band Tone Stack with a Deep pull switch on the Bass, and Master Level Control.   Both preamps share the same Presence control which is part of the output negative feedback circuitry. Also, we have put an Edge boost pull-switch on the Presence control that reduces the negative feedback level to produce a boost in volume and a soaring uncompressed sound for dynamic leads. The combination of all these options generates a wide ranges of tones from Clapton warm to Van Halen hot!  

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No matter how good any preamp is, it can always be fine tuned an Effects Loop to create your own unique tones with pedals.  The  Effects Loop uses a passive buffer amplifier to match low or high impedance pedals with the high impedance tube circuitry of the amp. This prevents tone suck and volume loss. 

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We left the output stage design of the amp pretty much undisturbed from the vintage design except  we replaced  the 5881’s  used in the Twin with the new higher plate voltage JJ 6L6GC'S to give more headroom and warmth, but we also added a bias switch to select EL34's for a more Marshall sound. For the output trannie we chose a vintage Marshall for the original classic vintage sound. This trannie provides you with extended low-end warmth and those  incredible enhanced Marshall overtones. All the while, maintaining a perfect balance between the highs, mids, and lows. The trannie  has  4, 8, and 16 ohm outputs.   A post output transformer Line Out with Line Out Level control is provided for recording or driving a power amp. The Line Out can be used without a speaker plugged in.  It has an auto switched internal load to simulate a speaker if a speaker is not plugged in. This allows you to produce true clean and overdrive distortion tones when recording without a speaker.

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For the power supply section we used an oversized custom power transformer which provides great voltage regulation so that you don’t sag too much when you get on it hard. The high-voltage is filtered for very low hum by an equally large choke and 8 filter capacitors.  We stayed with the Marshall choice of solid state rectifiers, but chose the newest type FRED ultra fast recovery rectifiers for tight dynamic bass response. 

The amp is built on a compact 17” x  10”  x 3” aluminum chassis and come with a retro steel mesh cage. All the parts in the amp are top-of-the line  including polypropylene coupling caps, precision mica tone stack caps, metal film resistors, Alpha pots, Neutrik jacks, high voltage sockets, etc…  This is a rock solid point-to-point hand wired amp….a real one of kind collectors item...designed to last for generations! 

 

Standard Features:

• Dual Channel - Each channel has High/Low input jacks, separate Gains, Tone Stacks & Masters.

• Channel 1  - Fender 5F8 Twin smooth  warm clean tones.  Channel 2 - Marshall Super Lead Plexi high-mid rock tones .  You can use an AB-Y switch to select or blend the channels to create your own distinct tones.

• Bright Pull Switch On F and M  channel Gain controls.

• Classic Bassman 5F6A style 3-BAND TONE STACK for extended flexibility in shaping your tone.

• Deep Pull Switch on Bass controls.

• Master level controls so you can crank the GAIN's up and overdrive the preamp without overdriving the output tubes.

• Presence control  - used to adjust the high-frequency response and damping factor of the power amp section.

• Boost - Unique NNFB "Edge" boost switch on the PRESENCE control that transforms the power amp section into a No-Negative-Feedback style amp for soaring dynamic leads. 

• Effects Loop - pure tube buffered serial effects loop designed to perfectly match the low impedance solid-state pedal levels with high impedance tube levels.

• Line Out - post output transformer LINE OUT with LINE OUT LEVEL control for recording or driving a power amp, Auto switched internal load to simulate speaker if speaker is  not plugged in. Inject great tone directly into the PA system with the Speaker Simulated Direct Interface.

• Custom heavy duty output transformer for extended low frequency performance with 4 - 8 - 16 ohm outputs.

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

• Solid-State FRED ultra fast recovery rectifiers for tight dynamic bass response.

• Standby Switch - Protects tubes from cathode stripping during warm-up

• Tube Complement: comes standard with 5 - 12AX7,  2 - 6L6, but you can substitute 12AT7's or 12AU7's in the preamp and driver for different tones and overdrive sounds. You can also substitute 5881's, KT66's or EL34's and KT77's when using the EL34/6L6 Bias Selector Switch  in the output stage for different sounds. 

 

Electrical Specifications: 

• Input Power  120 VAC 50-60Hz - 225 Watts Standard IEC plug-in three prong grounded power cord. (230 -240VAC available. See Upgrade Options) 

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

• Output Power - 50 watts RMS (100 Watt upgrade available)

• Speaker Output Impedance:  4-8-16 ohms.

• Line Out Impedance - 10K ohms

• Effects Loop Send Impedance - 10K ohms

• Effects Loop Return Impedance -  470K ohms

• Instrument Input Impedance - 1 Megohm

• DC on filaments to eliminate 60 hz hum.

• Star ground system to eliminate induced current chassis noise.

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 - Heavy gauge aluminum with welded corners.

• Weight -19 lbs. 

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

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

• 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:  F Input Jack, M Input Jack, F Gain with Bright Pull Switch, M Gain with Bright Pull Switch, Bass with Deep Pull Switch, Middle, Treble, Presence/Edge Boost Pull Switch, Standby Power Switch, Pilot Lamp, On/Off Power Switch

• Rear Panel:   Power Cord Connector, Fuse,  Effects Loop Return Jack, Effects Loop Send Jack,  Line Out Level, Line Out Jack, Speaker 4-8-16 Outputs.

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Upgrade Options: 

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