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, replacement PC board assemblies for first generation McIntosh solid-state amps and custom designed amplifier/preamplifier modules. Contact: audio@northreadingeng.com

 

SERVICES
- Vintage Vacuum Tube restorations and repairs including power supply rebuilds, rechassis projects, sheet metal, machining and paint.
- Vintage Solid State Amplifier and Preamplifier restorations and repairs.
- Tube Amplifier design services including PC board, chassis CAD and fabrication of prototypes.

 

PRODUCTS

•  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.
  
    Note: For small added charge the amplifier can be delivered and setup at most customer locations in the New England region!

 Prices include (4) new JJ7591 power tubes (2 matched pairs) and (2) NOS 6GH8A triode-pentodes.

- Model 219A Amplifier with Hammond 1650PA Output Transformers: $2765
- Model 219B Amplifier with Hammond 1650PAP Output Transformers (shown above) : $3125
- Model 219C Amplifier with Lundahl LL1620PP Output Transformers with Lundahl Powder Coated Enclosures: $3300

 

• 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 AND PREAMPLIFIER 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 copy 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.)

 

• INTEGRATED AMPS MA230/MA5100/6100/6200 AND RECEIVERS MAC1700/1900
  Power supply sections restored, output sections repaired and restored, amp and preamp sections recapped, front panels re-lamped, switches repaired, glass faceplates repaired and replaced, blown semiconductor devices matched and replaced.

   

• AMPLIFIERS MC250/2505/2100/2105 REPAIR AND RESTORATION
  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.
See McIntosh vacuum tube restorations page!

 

AMPLIFIER TESTING AFTER SERVICING
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.

 

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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No part of the above may be copied and published, in part or in total, without permission.
Contact: audio@northreadingeng.com
Phone: (978).795.7172
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