PRODUCTS AND SERVICES
  - VINTAGE TUBE AMPLIFIER REPAIR AND RESTORATION:  MARANTZ, McINTOSH, SCOTT, FISHER, HARMAN-KARDON AND OTHERS
  - SOLID STATE AMPLIFIER REPAIR, RESTORATION AND MODIFICATION
  - POWER AMPLIFIER DESIGN AND PROTOTYPING
  - NOW OFFERING NEW MAKE TUBE AMPLIFIERS!

 

Contact North Reading Engineering at: audio@northreadingeng.com

WELCOME TO NORTH READING ENGINEERING
North Reading Engineering is all about audio amplifier engineering offering new make, USA manufactured tube amplifiers, restoration services for vintage tube classics and replacement PC board assemblies for first generation McIntosh solid-state amps. 

 

THE MODEL 219, 2-CHANNEL, PUSH-PULL AMPLIFIER
Super heavy duty chassis, extreme build quality, very low distortion, broad bandwidth and high reliability make the MODEL 219 a basic tube amplifier you must have!  Click on either photo below for additional information on this beautiful amplifier.

 

AMPLIFIER TESTING
All amplifiers serviced are tested extensively prior to release back to the customer.  Amplifier Bandwidth across multiple output power levels and %Total Harmonic Distortion (%THD) to full voltage output are characterized to demonstrate conformance to factory published specifications.  Hardware reliability and stability is bench assessed by swept sine testing at fixed percentages of the amplifier maximum RMS output voltage.  By putting "heat" into the hardware the testing helps to ensure it will perform as expected at the customer location.

 

SALLEN-KEY, 2-CHANNEL, BAND-PASS FILTER MODULE
For amplifier builders, the Sallen-Key module provides two, 4th order, band-pass small signals to amplifier inputs.  Designed to accept a wide range of capacitor values to implement band-pass filtering for woofer, midrange and tweeter applications.  On-board +/-15VDC regulated on-board supply, Sallen-Key filter topology USA made, through-hole PC boards with clear, bright silk screened component IDs are also available to allow amp builders to evaluate and modify the design to suit specific filter requirements.  For more information including performance data and ways to use this module is found HERE.

   

 

BALANCED 2-CHANNEL, BUFFER / 3-WAY ACTIVE SPLITTER FRONT END MODULE
EMI/RFI hardened amplifier front-end, XLR/TRS combination inputs, +/-15VDC regulated on-board supply, ultra-low distortion, super quiet buffer/splitter accepts inputs from any small signal source and splits them into three independent signals, each capable of driving an amplifier in a bi- or tri-amplified loudspeaker system.  Op-amp sockets enable users to evaluate different packages or replace a blown device.  High quality, USA made, through-hole PC boards with clear, bright silk screened component IDs are also available to allow amp builders to evaluate and modify the design to suit specific buffering requirements.  For more information including performance data and ways to use this module is found HERE (webpage) and HERE (video).

   

 

VINTAGE McINTOSH AMPLIFIER SERVICING
North Reading Engineering has the experience, tools and test instrumentation to properly assess the condition of your vintage tube or solid state amp or preamp and make it a whole lot better. More information on amp servicing can be found HERE.  A complete rework of an MC2100 amplifier is shown on the forum website HERE. 

PREAMP BOARD UPGRADE FOR MC2505, 250, 2105, 2100, 2300 AMPLIFIERS
First generation McIntosh solid state amps can be upgraded to make better sound.  This isn't a just a "clone" of the original design.  It's a re-engineered preamplifier section, designed as a direct swap for the 043-795 and 044-331 preamplifier boards (lower left).  The new preamplifier board (lower right) provides a significant, measureable performance upgrade to these vintage classics.  More information on the preamplifier section can be found HERE.  A beautifully done MC2105 customer install HERE.  (Note: Bare PC boards are no longer sold for customer assembly, only fully assembled and tested boards are available.)

POWER SUPPLY BOARD FOR MA6100 INTEGRATED AMPLIFIER
The North Reading Engineering MA6100 power supply board replaces the thermally distressed factory board (lower left) with a completely new, drop-in, PC board fabricated from a high current capacity, dual-trace, USA manufactured board.  The board and component selection have been engineered to manage the excessive heat generated by regular amplifier use.  The supply section has demonstrated superior heat management and excellent reliability.  The assembled and tested power supply board is also available for purchase for installation by the customer.  A high resolution image of the board top shown HERE and bottom HERE.  The development process of the power supply board showing the prototype R1.0 and final R1.1 version with installations shown HERE.  (Note: Bare PC boards are not sold for customer assembly, only fully assembled and tested boards are available.)

 

MA230/MA5100/6100, MAC1700/1900 RESTORATION AND REPAIR
Power supply sections restored, output sections repaired, preamplifier sections recapped, rocker switches repaired, glass faceplates replaced (based on availability), blown semiconductor devices replaced.

   

MC250/2505/2100/2105 REPAIR AND RESTORATION
Preamplifier, Power Supply and Output Stage Repair
Power supply and output power board capacitors replaced, output transistors replaced, potentiometers, RCA jacks, rockers switches replaced, chassis stainless steel cleaned, polished with new stainless steel chassis hardware.  Meter boards repaired, erratic meter behavior eliminated.  Chassis bottom, prepped and painted (lower right).   A reworked MC250 is shown HERE.

 

VINTAGE VACUUM TUBE AMPLIFIER RESTORATION
MARANTZ, McINTOSH, SCOTT, FISHER, HARMAN-KARDON AND OTHERS
Power supply rebuilds, power supply transformers replaced with new replacement units, power supply/bias supply recaps, board replacements, RCA jacks, barrier strips, potentiometers, meters replaced, chassis top sections replaced with new make reproductions (McIntosh), chassis bottom covers refinished.  Suppliers for powder coating, metal refinishing, sheet metal fabrication and CNC machining services available.  McIntosh vacuum tube restorations! 

 

NORTH READING ENGINEERING PAGES
MODELING THE KLIPSCHORN BASS HORN (Part I) - The Beranek Model, LTSPICE and a slew of measurements.
MODELING THE KLIPSCHORN BASS HORN (Part II) - Extending the model to simulate factory filter responses.
PHOTOGALLERY OF A KLIPSCHORN REPLICA BUILD - Building a Klipschorn is not for the faint of heart!
A KLIPSCHORN NETWORK FOR BUILDERS - A measured design you can build yourself.
UNDERSTANDING IMPEDANCE - Resistance, Reactance, Nyquist and Excel all in one place.

   
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Contact: audio@northreadingeng.com
Phone: (978).795.7172
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