electron's
 
 

HIGH POWER AUDIO AMPLIFIER
and
MODULATOR CIRCUITS









 

This page is dedicated to the memory of all those valiant people who have given a lifetime of commitment to the pursuit of high fidelity and design excellence in high power audio sound reproduction.

It seeks to recognise their contribution by recalling the great advances made by builders of commercial amplifiers and sound reproduction equipment.

This page presents, for your information and interest, a selection of high power audio amplifier and broadcast modulator amplifier circuits having a power output of 15W rms to 3,000W rms.

If you are aware of any other circuits that contribute to the application or understanding of thermionic tube theory in high power audio amplifier or modulator design or use, email me details and I will include them in this page if suitable.

Please read the important notices below.
 
 

AMPLIFIER CIRCUITS:

15W to 75W RMS - WILLIAMSON AMPLIFIERS

45W RMS LIPMAN - 7 tube Transformer Drive

45W RMS LIPMAN - 6 tube Transformer Coupled

50W rms BERESKIN

60W RMS - ACROSOUND

70W RMS - AWA MODEL G56827

75W RMS TRIAD HF40 - 6146 tubes

75W RMS - NTS MODEL AM1080

100W RMS - ACROSOUND TO350 - 6146 tubes

100W RMS - ACROSOUND - 4 x KT66 tubes

100W RMS - BOGEN MO100A

100W RMS - GEC

100W RMS - RTVH     (caution - note wrong polarity of bias supply filter caps)

100W RMS - McGOHAN MODEL M1001

100W RMS - McGOHAN MODEL M1003

100W RMS - STC

100W RMS CHICAGO-OLSEN

120W RMS -DYNACO MK VI

120W DYNACO

150W RMS - GOTHAM MODEL PFB-150WA

150W RMS - STROMBERG-CARLSON MODEL AP80

150W RMS -STROMBERG CARLSON MODEL AP80 - OFFICIAL WEBSITE

GOTHAM POWER SUPPLY

150w (200W) RMS - McGOHAN MODEL M1501

200W RMS - ALTEC MODEL 1570B

250W RMS - STC

STC 250W Parts List

STC POWER SUPPLY

STC PS Parts List

250W RMS - ALTEC MODEL 260a

350W RMS - AMPEG SVT V9
Note: 6550 Plate Supply B+ 695v, Screen Grids 350V, Bias -47v.
This amplifier was also produced with 6146B/8298A Tubes, Plate Supply B+ 660v, Screen Grids 220v, Bias -47v
Both designs use the same output transformer.

350W RMS - McIntosh MC3500

400W RMS - GEC

700W RMS - CARVER SILVER 7A

1000W RMS - MULLARD

1000W RMS - WOLFF INSANITY BROWNOUT 1000

100W to 1000W - Great set of Chinese high quality industrial grade amp designs - well worth a look (these are really special and incorporate design features I have not previously seen from anyone)

3000W RMS - Bereskin
 
 


The mighty McIntosh MC3500, or its industrial version the McIntosh MI-350, designed by Mile Nestorovic in about 1968, is unsurpassable - in my humble opinion, the greatest commercial tube audio amp ever made.

This amp is derived from the 1949 original McIntosh unity coupled design and was produced by McIntosh between 1968 and 1971.

This is it!! (Click to see details)

IF YOU CANNOT GET HOLD OF A TUBED McINTOSH  - ANY ONE - THEN GRAB A DYNACO.

IF NEITHER OF THESE OPTIONS ATTRACTS YOU THEN EXPLORE THE LINKS LISTED ABOVE AND BELOW, FOR YOUR AUDIOPHILIC PLEASURE!!

Of course there are many other fine amplifiers available and my enthusiasm for McIntosh is not intended to denigrate those with other ideas and approaches to the challenges of reliably reproducing high-fidelity sound.

A currently available high-quality Australian designed and manufactured heavy-duty commercial high-fidelity 60 W RMS Rack Mounted Studio-Monitor Tube Amplifier is the ELAN AUDIO - Type CMA-01 "Enigma". This amplifier incorporates innovative features to the driver stages and custom designed extra high-quality output transformers. Comprehensive design and performance specifications are available from the Elan Audio website.
 

Here is an opportunity to look and learn from some of the true GURUS of audio, who have left us a priceless legacy of audio wisdom!!

Roger Russell's McIntosh History Page

Dave O'Brien's McIntosh Amplifier Clinic Page

Bruce De Palma

Circuit Diagrams - Triode Electronics

MC240 (2 x 40W RMS per channel)

MC275 (2 x 75W RMS per channel)

MC3500 (350W RMS Mono)

AmpsLAB Schematic Library
 

SAFETY WARNING:

VACUUM TUBES AND CIRCUIT COMPONENTS OPERATE AT HIGH VOLTAGES OF BOTH ALTERNATING CURRENT AND DIRECT CURRENT THAT CAN BE FATAL.

VACUUM TUBES OPERATE AT HIGH VOLTAGES AND TEMPERATURES THAT CAN CAUSE PERMANENT  INJURY, DISFUNCTION OR DISABILITY - TO YOU OR SOMEONE ELSE.

DO NOT ATTEMPT TO CONSTRUCT, TEST, WORK ON, OR COME INTO PHYSICAL CONTACT WITH, LIVE ELECTRONIC EQUIPMENT UNLESS YOU ARE TRAINED OR OTHERWISE QUALIFIED TO DO SO.

NEVER REMOVE A PROTECTIVE COVER FROM ELECTRONIC EQUIPMENT UNLESS YOU ARE TRAINED OR OTHERWISE QUALIFIED TO DO SO, BECAUSE LETHAL MAINS AND HIGHER VOLTAGES ARE PRESENT INSIDE.

Extra care should be taken with circuit designs using the B+ voltages listed in this guide.

Safety is of extreme importance and live wiring should be fully insulated to prevent electrocution of yourself and/or users.

Tubes for use at B+ voltages over 450v DC require sockets made from materials that can withstand high voltages. Inferior materials may cause flashover or arcing, leading to burning, short-circuits and/or tube damage. The use of octal sockets is not recommended for B+ voltages exceeding 600VDC, because the spacing between adjacent pins is not adequate to ensure reliable insulation or dielectric strength.

Many tube types listed require a top cap plate connection and such tubes must be carefully mounted to minimise wire length, proximity to other components and risk of accidental contact. Insulated caps are recommended.

Most vacuum tubes are glass encased devices that  have been evacuated of air - ie they contain a vacuum atmosphere. If dropped or impacted they are likely to implode, shattering glass in any direction. Handle with care and respect. Do not drop or impact. Always pack and store in padded wrapping or the manufacturer's carton.

When inserting into a tube into its socket always take care to align all the tube pins correctly with the matching socket. Incorrectly aligned tubes may result in high voltages being applied to low voltage circuit compomnents or systems, and may result in short-circuit fault currents being applied with resultant expensive damage to tubes and equipment.

To avoid serious and permanent tube damage when constructing an amplifier, always ensure the grid bias voltage is present at grids 1, 2 and 3 before applying B+ high voltages to the circuit. In this regard, cathode bias and back bias configurations are safer, more reliable, and offer less risk than designs using fixed bias.

Always ensure large HV electrolytic capacitors are fitted with suitable bleeder resistors to automatically discharge them after the amplifier is switched off - otherwise you may expose yourself to lethal current if you accidentally touch a live conductor.

Never short-circuit or open circuit an amplifier when energised.

Large amplifiers should be protected by separate magnetic circuit breakers (preferably of the core-balanced earth leakage type) in the mains and filament/heater supply circuits to minimise damage in the event of tube or component failure.

Always use surge-supressor devices in the mains supply to protect the equipment from mains over-voltages.
 
 
 

IMPORTANT COPYRIGHT NOTICE:

Copyright and intellectual property in these audio amplifier designs and circuits remains with their original owner.

Their inclusion in this page as reference materiel is not a license to reproduce or use them for any purpose contrary to the terms of any original copyright notice or license.

These circuits are presented for historical information and education purposes only and are not intended for construction.

No warranty is given of any kind as to fitness for purpose or performance or rating.

Their source is not acknowledged here because I am unable to determine their origin.
 
 

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This page was last modified 05 December 2015

This page is located at http://www.oestex.com/tubes/amps.htm