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I am happy to share details and insight into vintage amplifier restoration. My present focus is documenting amplifiers of Australian origin and sympathetically restoring them - often as a guitar and/or bass amplifier, but sometimes as original. Inherent safety and circuit protection are typically improved or added, and performance is improved where appropriate. This website has sections on amplifier restorations (including additional material on Williamson amps and Selmer organ), supporting sound and test equipment, self-split push-pull including Parry Cathamplifier, valve reliability, some other valve related goodies, and some articles I've put together. Linked files sometimes get updated, so please refresh your cache (F5) if you want the latest file version.
Information on self-split push-pull circuits, valve reliability articles, other valve related goodies, and articles I've put together.

I have amplifier restoration details on the following:

Australian 15W amplifier circa 1952. Unknown manufacturer - probably from Melbourne. Microphone and Pickup inputs via separate front panel 2501 microphone sockets. Switched microphone to 6J5. Summed MIC and PU to 6AU6. 6J7 split-load/concertina PI. 6L6G PP 15W. Ferguson OP58 10k OT. Trimax TP1895 PT with 5V4G rectifier.

Australian 6GW8 amplifier circa late 1960's. Unknown manufacturer - probably a kit of parts. Two 2-pin input sockets. Two 4-pin speaker sockets. Zephyr Mic step-up transformer. EF86 gain stage. 6GW8 triode gain stage and cathodyne PI. 6GW8 pentode, cathode bias PP output stage. Ferguson PF170 PT, and A&R OT2632 OT.

7W Stereo Amplifier circa 1959-1960 - Made by Australian Sound & T.V. for Royal Melbourne Technical College. 6BM8 PP UL 9k output stage; cathodyne PI with direct coupled triode preamp; 12A?7 input preamp with baxandal bass/treble tone controls and volume and balance controls; 12A?7 gain recovery.

Victorian school PA System circa mid 1960's - Made by Australian Sound & T.V.. Combination radio, record-player, microphone input, monitor speaker, PA amplifier in free-standing steel cabinet. Features high quality construction, Woden MT101 mic transformer and 12AX7 preamp, EF86-12AU7-quad 6CA7 PP amplifier with A&E 2096 PT, and 2596 OT, and 6AL3 plate-ground catch diodes for PP stage. Essential school additions include a Bell pot and EF86 relaxation oscillator bell generator module with rate and decay pots, plus Garrard TA MkII for playing the national anthem.

Australian Sound Systems A13 amplifier circa 1946-7. Australian Sound Systems from Melbourne closed in 1947. Three input (MIC, PU, Radio) channel PA amplifier. 6J7 anode load RC tone. Voltage divider PI common cathode biased 6SN7. 6V6G cathode biased PP.

AWA PA774. MIC input 12AX7 triode stage, with PU mixer 12AX7 triode stage, 2x 6BM8 cathode biased PP with floating paraphase PI, 8W. Circa mid 1960's. Details on restoration of 2nd amp.

AWA PA806. MIC input 12AV6 triode stage, with PU mixer 12AX7 triode stage, 12AX7 stage with output winding feedback, 6V6GT cathode biased SE, 5W. Circa late 1950's.

AWA PA827 70W Amplifier. 6AU6 mic preamp. 6AV6 Phono-Radio preamp. 6AU6 mixer. 12AU7 self-balancing, floating paraphase PI with unbypassed cathode biases. Quad KT66 cathode biased PP; separate feedback winding to PI stage cathode. 5R4GY rectifier; 6AQ5 regulated screen voltage. Separate filament transformer; elevated dc voltage heater humdinger pot. Circa mid 1950's.

AWA PA829 AC/DC 20W Amplifier. 3x 6AU6 or EF86 mic inputs, 6AU6 mixer, 12AX7 self-balancing floating paraphase PI with unbypassed cathode biasing, 2x KT66 cathode biased PP. V5123 vibrator for 12VDC. 2x 6X4 rectifier. Circa late 1950's.

AWA PA872 20W Amplifier. 12AX7 mic input, 12AX7 mixer, 12AX7 self-balancing floating paraphase PI with unbypassed cathode biasing, 2x KT66 cathode biased PP. 5V4G rectifier. Circa 1964.

AWA PA1001BY. Multi-input channel 100W PA amplifier with tuning unit. EF86 mic preamp. 12AX7 preamp and mixer. 12AX7 PI. 12AU7 bootstrapped driver. McIntosh unity-coupled PP output stage with screen-to-cathode capacitors for each of the quad 6L6GC. Circa early 1970's.

AWA PA1002BY. Three input channel 50W PA amplifier. McIntosh unity-coupled PP output stage with screen-to-cathode capacitors, and bootstrapped drivers. Circa early 1960's.

AWA PA1003. 2x 12AX7, floating paraphase PI, cathode biased 7027A PP, 25W, using 12AX7 heaters for cathode bias. SS diode doubler power supply.

AWA PA1005. 2x 12AX7, floating paraphase PI, cathode biased quad 6AQ5 PP, 12.5W. A little Green Terror !

The Parry 'Cathamplifier'. Details about this brief flowering of aussie ingenuity.

Eminar 200W PA. 4x 12AX7, 6x 6CA7 fixed bias PP.

FI-SONIC 30WGR. 30W guitar head circa 1966-7. 4x 12AX7, 6AV6, 6BM8, 2x 6L6GC, 6V4. 2 normal and 2 brilliant inputs. Bass/treble fender style tone stack. Neon/LDR tremolo. Reverb for 300 ohm input pan. LTP PI with output feedback to cathode tap. Cathode biased and bypassed PP. A&R 5547 PT and 2783 OT.

McPherson Twin-Channel 60W Instrument Amplifier - 12AX7, 6AN8, 2x KT88, 5AS4 - 1964.
McPherson Mk IV 55W guitar amplifier - 3x 12AX7 cathodyne PI, 2x 6CA7 fixed bias PP - 1965.


Philips 952. Three input (2x MIC, 1x PU) channel PA amplifier. 807 PP, grounded cathode, grid driver Tx. Circa early 1950's.

Philips 961. 2x 6AD8, 6N8, 6SN7 cathodyne PI, 2x 6CA7 fixed bias PP, 100W. Circa late 1950's. Modified: 12AX7 replacing 6AD8s, 6N8 - WIP.

Philips 979. Five input (4x MIC, 1x PU) channel PA amplifier. 2 MIC inputs to 2x EF86. 2 MIC inputs to 12AX7. 6N8 mixer. Half 12AX7 tone make-up, with feedback to part-cathode. Half 12AX7 cathodyne PI. 6CA7 fixed bias PP, with spark-gap protection. 2x 5U4G Doubler HT. 6V4 for negative bias supply. Circa 1955-6.

Philips 1137. 6N8, 12AU7 cathodyne PI, 2x 6M5 cathode biased PP, 8W.
Circa early 1960's.

Philips EV4437A. 2x 12AX7, concertina PI, sextet 6CM5 fixed bias PP, 100-120W, with neon and incandescent driven LDR limiter. Circa 1969.

Philips LBH1015. 2x 12AX7 concertina PI, quad 6CM5 fixed bias PP, 60-80W.
Details at Mat Janssen's website http://members.chello.nl/m.janssen36/Amplifiers-with-valves.htm. Circa late 1960's.
Information notes.

Playmaster No.11 Amplifier. EF86, 12AX7, 2x 6BQ5 cathode biased PP, 16W. Circa mid-late 1950's.
Modified to original Vox AC-15 with 2007 Heritage additions and Vintage 30.

Playmaster Control Unit No.6 Preamplifier. 2x EF86. Circa mid-late 1950's.

Radiogram stereo power amp - 6DX8 push-pull, with triode preamp and triode split-load PI. Circa 1969.

Radio Television & Hobbies July 1960, 100W Public Address Amplifier. Professional kit. EF86, 2x 6CG7, 2x KT88. Ferguson PF1546 PT. Being restored to use 12AU7.

STC 28-SU-204 35W valve amplifier. CL5244-2 step-up mic transformer in to EF86. 7027A PP. 3-valve radio. Ferguson PF172 PT and OP383 OT. Circa 1961.

Steane's Sound Systems M265. 2x 6C6, 6SN7 paraphase PI, 2x 6V6 cathode biased PP, 10W - circa 1950.

Steane's Sound Systems S304. Two input (MIC, PU) channel PA amplifier. 2x 6N8 MIC amps, 6SN7 mixer. 6V6 PP cathode biased. 5V4G rectifier. circa 1952.

Steane's Sound Systems combo PA amp and speakers. Two input (MIC, PU) channel PA amplifier. 2x 12AX7 for MIC gain, mixer, tone and PI stages; 6M5 PP cathode biased; 6V4 rectifier; rebadged Philips 976B amplifier with twin open-backed Rola 8M speaker boxes acting as a carrying case. circa 1958.

VASE PA100. 12AX7 PI, 2x KT88 fixed-bias PP, 100W. Circa 1966.
Modified: added 12AX7.

Williamson Amplifier (1949 'new' version) & Control Unit Preamplifier - Australian make circa early 1950's. A UK Miller Organs 'new' version Williamson amplifier for Mark IV organ. Also a compendium of articles and references to the Williamson amplifier.


I have details on the following equipment:

Morley Rotating Sound Expression (RSE) Pedal. An early oilcan in pedal format.
Morley Vol and Wah/ Vol variants.
MXR Flanger (1978 Grey box).
Locobox Spaceship FL-01.
General Radio 783A Audio Power Load and meter - including manual.
AWA Valve RC Oscillator Type 3A57150 - need manual.
HP 3325A synthesiser/function generator - including manual.
AWA audio oscillator G231 - including manual.
TMC Low distortion oscillator. Typ 0.06% distortion level - need manual.
Wavetek Model 111 Oscillator - including manual.
AWA F240 Distortion Meter - including manual.
HP 54201A Digitizing Oscilloscope - including manual.
USB soundcard modifications for PC oscilloscope.
EA construction project Aug 1998: Front-end for PC soundcard. Plus notes.
Systron Donner Model 7004 digital multimeter - including manual.
Systron Donner Model 7205 digital multimeter - including manual.
Keithley 197 autoranging microvolt digital multimeter - including manual.
Car cigarette lighter socket voltmeter.
B&K Random Noise Voltmeter Type 2417 - need manual.
Systron-Donner 6250A Frequency Counter - need manual.
Hickok 1890M In-circuit transistor tester (large file!) - including manual.
Paton Electrical VCT-2 Valve Tester. Includes restoration notes, operating manual and schematics.
BPL Megohmmeter RM 175-LZ MK II - need manual.
BPL A.C./D.C. Breakdown & Insulation Tester RM215-L - need manual
12VDC car converter for mains VAC 5W.
12VDC car converter for 220VAC 75W.
Alesis 1622 mixer.
Guarda KM1200S operating manual.
Behringer Eurorack UB2442FX Pro - power supply schematic (the bit that fails).
SoundTech A600 Operation and Service Manual and schematics.
SEAS D014 passive crossover network 3-way 600Hz 3kHz 8 ohm circa 1974
For 2x 25-TV-EW, 15/11-TV-2XM, H87, H8014. Used by Interdyn in SEAS 60.
SEAS D036 passive crossover network 3-way 800Hz 4kHz 8 ohm circa 1974
For 25F-EWX, 10FM, H-086. Used by Interdyn in P33 or S33 but with own Interdyn crossover.
TOCORD Brochure for SHF SP speaker cable.

Partridge PA Manual from circa 1938.
Partridge Amplifier Circuits from circa 1938.
Partridge Transformer Price List from circa 1938.
The Partridge Manual from Oct. 1947. An updated replacement to the two earlier manuals.
Partridge Transformer Price List from Jan 1948, Appendix 1 to The Patridge Manual.

Selmer Concert Organ Information

Information on self-split push-pull circuits, valve reliability articles, and other valve related goodies.

Updated: 16 Sept 2016. Email tim for comments/details.

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