Here you'll find a modest collection of some interesting audio tube amplifier schematics.
- Audio Innovations
- Audio Note
- Audio Research
- Beard Audio
- Conrad Johnson
- Copland
- Dynaco
- Grant Amplifiers
- JoLida
- Harman Kardon
- Heath Kit
- Magnatone
- Marantz
- McIntosh
- QUAD
- Radford
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Audio Innovations was (probably) founded in 1984 by Erik Andersson. In 1986 David Chessel joined Audio Innovations as technical director. David Chessel conceived Audion in 1987.
L2 Preamp.
The Audio Innovations L2 line stage preamp was introduced in 1992. It uses two ECC82's, a 5687 and two 0A2's.
L2 Main PCB Preamp schematic, 1 of 2 (Audio Innovations, 1992)
L2 Main PCB PSU schematic, 2 of 2 (Audio Innovations, 1992)
L2 Switch and Pot circuit, (Audio Innovations, 1992)
L2 Parts List S/N 220448, (thanks to Thor-Inge Nęsset)
See the Audio Note's A modified Audio Innovations L2 preamp article by Peter van Willenswaard. Recommended reading!
300 2x 10W Integrated Amplifier.
The Audio Innovations 300 integrated amplifier was introduced in 1986. The 300Mk2 was introduced 5 years later in 1991. It is a 2x 10W Push-Pull amp using two ECL86's per channel in the power amp. It features 5 line inputs (4 for the Mk2) and a phono input.
300 Mk2 Schematic of the power amp, (Dr.Tube)
300 Mk2 Schematic of the phono pre amp, (Audio Innovations)
500 2x 25W Integrated Amplifier.
The Audio Innovations 500 integrated amplifier was designed by Erik Andersson and was introduced in 1987. It is a 2x 25W class A Push-Pull Ultra-Linear amp using two EL34's per channel in the power amp. It features 5 line inputs and a phono input.
The output transformers have a primary impedance of 5k6 ohm with the usual 43% UL taps.
500 Phono input schematic, 1 of 4 (Audio Innovations, 1989)
500 Input switching, 2 of 4 (Audio Innovations, 1989)
500 Power amp schematic, 3 of 4 (Audio Innovations, 1989)
500 PSU schematic, 4 of 4 (Audio Innovations, 1989)
500 Phono input schematic, (Dr. Tube)
500 Power amp schematic, (Dr. Tube)
700 2x 25W Integrated Amplifier.
The Audio Innovations 700 integrated amplifier was introduced in 1993. It is a 2x 25W class A Push-Pull Ultra-Linear amp using two EL34's per channel in the power amp. It features 4 line inputs and no phono input. The power amp section of the 700 is based upon the 800Mk3 power amp.
700 Input schematic, Z711/06/01, 1 of 3 (Audio Components, 1993)
700 Power amp schematic, Z711/07/01, 2 of 3 (Audio Components, 1993)
700 Power supply schematic, Z711/08/01, 3 of 3 (Audio Components, 1993)
700 Voltage measurements, Z711/09/01 (Audio Components, 1993)
700 Bill of materials.
Hi-Fi Choice review (March 1993).
800 2x 25W Power Amplifier.
The Audio Innovations 800 amplifier was introduced in 1986. The 800Mk2 followed in 1989, to be changed again that year. The 800Mk3 was introduced in 1993. The 800 amplifier is a 2x 25W class A Push-Pull Ultra-Linear amp using two EL34's per channel in the power amp.
800 Mk1 Schematic
800 Mk3 Schematic, (Dr. Tube)
1000 1x 50W Power Amplifier.
The Audio Innovations 1000 amplifier was introduced in 1987. The 1000 Mk2 followed in 1989. The Mk3 followed in 1991. It is a 50W mono class A Push-Pull Ultra-Linear amp using four EL34's and four ECC88's. The 1000 Mk3 was fitted with two ECC82's and two ECC83's instead of four ECC88's.
1000 Mk3 introduction (1992)
1000 Mk3 valve layout (1991)
1000 Mk3 amp circuit (1991)
1000 Mk3 PSU (1991)
1000 Mk3 component list of K4025 PCB (1991)
1000 brochure (1992)
What Hi-Fi review (October 1992)
Classic 25 2x 25W Integrated Amplifier DIY Kit.
The Audio Innovations Classic 25 integrated amplifier was a DIY Kit version of the 700 integrated amplifier. It is a 2x 25W class A Push-Pull Ultra-Linear amp using two EL34's per channel in the power amp. It features 4 line inputs and no phono input.
Classic 25 Schematic, (Dr. Tube)
Classic 25 Photograph
See the Audio Note's Articles Tweaks Section for tweaks on the AI P2 and L2 pre amps by Peter van Willenswaard.
Do also check out Stefan Pickl's Audio Innovations Page.
If you want to know what Audio Innovations is up to today (it isn't anything tube related) go see their homepage.
Check out Marc Heijligers Audio Innovations Classic 25 Page. It has a detailed circuit description and some mods for the Classic 25. Interesting reading!
M7 Pre amplifier
Schematic, (Audio Note Japan, 1991)
M10 Pre amplifier
Schematic, (Audio Note Japan, 1996)
Kit 1 Amplifier
Amp schematic
PSU schematic
Ankoru Amplifier
Schematic, Issue 11 (Audio Note UK, 1992)
Ankoru review, Sound Practices 12, by Andy Grove
P3 Amplifier
Schematic, Issue 3 (Audio Note UK, 1995)
P4 Amplifier
Schematic, Issue 3 (Audio Note UK, 1995)
Conquest Amplifier
Schematic, Issue V10 (Audio Note UK, 1996)
Quest Amplifier
Schematic, Issue V10 (Audio Note UK, 1996)
Ongaku Amplifier
Schematic, (Audio Note Japan, 1994)
If you want to know what Audio Note (UK) is up to today go see their homepage.
Check out Stefan Pickl's Audio Note Page.
D40 Power amplifier
Schematic with 1x ECC81, 1x ECC83, 1x 6FQ7 & 2x 6L6GC (Audio Research)
VT100 Stereo Power amplifier
Schematic (of one channel) with 4x 6922 & 4x 6550C (Audio Research)
See this page for a detailed description of how to bias a VT100.
See the Audio Research Database for lots of information of almost all AR products.
Bill Beard founded Beard Audio in the mid 1970's. He retired in 2002.
P35 2x 35W Power Amplifier
The Beard P35 amplifier uses 2x ECC81 and 12x EL84 tubes.
P100 2x 100W Power Amplifier
The Beard P100 amplifier was originally fitted with 4x either Gold Lion KT88's or GE 6550A's. It also uses an ECC81, an ECC82 and an ECC83 tube.
Check out the Beard Audio site for some more information and support for Beard Audio products.
PV2 Pre amplifier
Schematic, (Conrad Johnson)
PV3 Pre amplifier
Schematic, (Conrad Johnson)
Line stage schematic, (Courtesy of Tom Howe, slightly redrawn by Dr.Tube)
PV5 Pre amplifier
Schematic, (Conrad Johnson)
Parts list, (Conrad Johnson)
PV6 Pre amplifier
Schematic, (Conrad Johnson, 1983)
Parts list, (Conrad Johnson)
PV10 Pre amplifier
Schematic, Revision A (Conrad Johnson, 1998)
Parts list, (Conrad Johnson)
PV12 Pre amplifier
Schematic, (Conrad Johnson, 1993)
MV75 Power amplifier
Schematic, (Conrad Johnson)
CTA401 Integrated amplifier
Schematic, (Copland, 1992)
SCA35 Pre amplifier
Schematic (bad scan), (Dynaco)
ST70 Power amplifier
Schematic, (Dynaco)
Check out Bob Latino's Dynaco Manuals Page for lots of free Dynaco manuals.
See Gary Kaufman's Dynaco Page for many Dynaco schematics and lots of other Dynaco info. If you're into Dynaco stuff this Dynaco Page is a must see.
Or check out Greg's Unofficial Dynaco Page for lots of Dynaco info and links.
See Curcio's Audio Engineering Dynaco Doctor Page for Dynaco spare parts and replacement boards.
G60AMS Mono power amplifier
Schematic, (Dr. Tube)
G60S Stereo integrated amplifier
This is a stereo version of the G60AMS amp, with a phono input and a line stage.
Picture, (Dr. Tube)
GL100AM Power amplifier
Schematic
SJ-302A / SJ-502A amplifier
Schematic, (JoLida)
Harman Kardon
A250
Schematic
Citation 1
Schematic
Citation 2
Schematic
See Jim McShane's Citation Page for a lot more HK Citation information.
W5M
Schematic
See the Heathkit Virtual Museum for more Heathkit information.
Not much info here yet. See the Vibro World Unofficial Maganatone Amp Site for more Magnatone information and schematics.
Model 2 Power amplifier
Schematic, (Marantz)
Model 5 Power amplifier
Schematic, (Marantz)
See HiFiLit's Marantz Page for scans of brochures of the old Marantz amps.
MC40 Mono power amplifier
Schematic
MC60 Mono power amplifier
Schematic
Voltage chart
MC240 Stereo power amplifier
Schematic
MC275 Stereo power amplifier
Schematic
See Roger Russell's McIntosh History Page for more information and history of McIntosh.
See Berner's McIntosh Page for more schematics and pictures of McIntosh amps.
The Acoustical Manufacturing Company was founded by Peter Walker in London in 1936. In 1941 the factory was moved to Huntingdon after the London factory was bombed.
Initially the Acoustical Manufacturing Company produced PA amps, but soon the move to the production of domestic hifi equipment was made. This led to the acronym Quality Unit Amplified Domestic. Many fine and revolutionary amps and radios were produced. Some schematics of the tubed equipment can be found below.
Peter Walker passed away december 10th 2003 at the age of 87.
QUAD AM2 AM Radio
Schematic
QUAD FM16 FM Radio
Schematic
QUAD II Power amplifier
Schematic
QUAD 22 Pre amplifier
Schematic
If you want to know what QUAD is up to today have a look at the QUAD UK site.
Do also check out Stefan Pickl's QUAD Page.
Radford Audio Ltd. was founded by Arthur Radford in the 1960's. In 1989 Arthur retired and Radford Audio was no more. Many fine amplifiers were designed and produced by Radford Audio. You'll find a couple of schematics below.
STA-15 Stereo Power Amplifier
Schematic
STA-25 Stereo Power Amplifier
Schematic
STA-25 Renaissance Stereo Power Amplifier
Schematic
STA-100 Stereo Power Amplifier
Schematic, (Radford, 1967)
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