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AUDIO PREAMPLIFIER entries in Index to How To Do It Information
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Detailed entries for one subject from the INDEX TO HOW TO DO IT INFORMATION.
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To obtain a copy of any magazine article contact your local public library or the publisher.

AUDIO PREAMPLIFIER
sa   AUDIO PREAMPLIFIER POWER SUPPLY
sa   MICROPHONE PREAMPLIFIER
sa   PHONOGRAPH PREAMPLIFIER
x   PREAMPLIFIER (AUDIO)
xx   AUDIO AMPLIFIER
xx   AUDIO EQUIPMENT

Improve your Dynaco PAT-4 stereo preamplifier. (1) Replace the tone controls (2) Increase the bass response in the phono equalization. (3) Change resistors. (4) Shield the power switch pilot light. (Other ideas provided by some of the following ADDED INFO references).
AUDIO AMATEUR 1/1970 [Winter 1970] (v.1#1) pg. 14
Added Info AUDIO AMATEUR 2/1970 [Spring 1970] (v.1#2) pg. 22
Added Info AUDIO AMATEUR 3/1970 [Summer 1970] (v.1#3) pg. 20
Added Info AUDIO AMATEUR 2/1971 [Nov 1971] (v.2#2) pg. 18
Added Info AUDIO AMATEUR 3/1971 [Apr 1972] (v.2#3) pg. 18
Added Info AUDIO AMATEUR 2/1972 [Jan 1973] (v.3#2) pg. 20, 30
Correction AUDIO AMATEUR 3/1972 [Mar 1973] (v.3#3) pg. 32
Added Info AUDIO AMATEUR 1/1973 [Dec 1973] (v.4#1) pg. 16
Correction AUDIO AMATEUR 1/1973 [Dec 1973] (v.4#1) pg. 28
Added Info AUDIO AMATEUR 4/1973 [Aug 1974] (v.4#4) pg. 18
Added Info AUDIO AMATEUR 3/1974 [Feb 1975] (v.5#3) pg. 18, 36
Added Info AUDIO AMATEUR 4/1974 [Apr 1975] (v.5#4) pg. 43
Added Info AUDIO AMATEUR 2/1975 [Nov 1975] (v.6#2) pg. 38, 40
Added Info AUDIO AMATEUR 4/1976 [Dec 1976] (v.7#4) pg. 52
Added Info AUDIO AMATEUR 1/1977 [Feb 1977] (v.8#1) pg. 39
Added Info AUDIO AMATEUR 2/1977 [May 1977] (v.8#2) pg. 69

A low noise tape playback preamplifier. Circuitry on a plug-in board is adaptable to both a high-quality tape copier and a four channel player.
AUDIO AMATEUR 3/1970 [Summer 1970] (v.1#3) pg. 5
Correction AUDIO AMATEUR 4/1970 [Fall 1970] (v.1#4) pg. 18
Correction AUDIO AMATEUR 2/1972 [Jan 1973] (v.3#2) pg. 21

The 20/20 Mark II preamp.
AUDIO AMATEUR 2/1971 [Nov 1971] (v.2#2) pg. 11
Correction AUDIO AMATEUR 4/1971 [Jul 1972] (v.2#4) pg. 13
Added Info AUDIO AMATEUR 3/1972 [Mar 1973] (v.3#3) pg. 22
Added Info AUDIO AMATEUR 1/1977 [Feb 1977] (v.8#1) pg. 36
Added Info AUDIO AMATEUR 2/1977 [May 1977] (v.8#2) pg. 46

A super op amp audio frequency preamplifier circuit produces midband gain in the order of 30 to 40 dB.
AUDIO AMATEUR 1/1972 [Oct 1972] (v.3#1) pg. 16
Correction AUDIO AMATEUR 2/1972 [Jan 1973] (v.3#2) pg. 21
Added Info AUDIO AMATEUR 2/1972 [Jan 1973] (v.3#2) pg. 30
Added Info AUDIO AMATEUR 3/1972 [Mar 1973] (v.3#3) pg. 32
Added Info AUDIO AMATEUR 4/1975 [Mar 1976] (v.6#4) pg. 40
Added Info AUDIO AMATEUR 2/1976 [Jul 1976] (v.7#2) pg. 40

Loudness control circuit for a 30 watt amplifier (60 watts stereo) was developed in a Dynaco PAT-4 pre-amp and control component, but can be adapted to other pre-amps.
AUDIO AMATEUR 3/1972 [Mar 1973] (v.3#3) pg. 26

Tip on shielding a Southwest Technical model 198/A stereo preamplifier using aluminum shields and grounding.
AUDIO AMATEUR 3/1973 [Jul 1974] (v.4#3) pg. 22

Tip on improving the Dynaco PAS-2 preamplifier by replacing the carbon composition resistors.
AUDIO AMATEUR 4/1973 [Aug 1974] (v.4#4) pg. 29

A perfectionist's PAS preamp. Modification of the tube-type Dynaco PAS to have a flat response, low noise and virtually immeasurable distortion.
AUDIO AMATEUR 1/1974 [Oct 1974] (v.5#1) pg. 4
Correction AUDIO AMATEUR 2/1974 [Dec 1974] (v.5#2) pg. 27, 28

An IC preamp/console. Part 1. How an audio console functions as the collector, processor and distributor of all sound sources within your system (phonos, tapes, tuners, oscillators, synthesizers, etc.).
AUDIO AMATEUR 2/1974 [Dec 1974] (v.5#2) pg. 4

An IC preamp/console. Part 2. Planning your own console. Circuits for the various subsystems (mixer, cue, monitor, preamps, etc.).
AUDIO AMATEUR 3/1974 [Feb 1975] (v.5#3) pg. 9
Added Info AUDIO AMATEUR 3/1977 [Aug 1977] (v.8#3) pg. 52

An IC preamp/console. Part 3. Operation manual
AUDIO AMATEUR 4/1974 [Apr 1975] (v.5#4) pg. 22

Classic circuitry. Schematic and parts list for the Marantz 7C stereo preamplifier.
AUDIO AMATEUR 4/1974 [Apr 1975] (v.5#4) pg. 36

Classic circuitry. Schematic and parts list for Audio Research Corporation's SP-3A-1 preamplifier (circa 1974).
AUDIO AMATEUR 1/1975 [Jun 1975] (v.6#1) pg. 38
Added Info AUDIO AMATEUR 2/1975 [Nov 1975] (v.6#2) pg. 41
Added Info AUDIO AMATEUR 2/1976 [Jul 1976] (v.7#2) pg. 40
Added Info AUDIO AMATEUR 3/1976 [Oct 1976] (v.7#3) pg. 40
Correction AUDIO AMATEUR 3/1976 [Oct 1976] (v.7#3) pg. 42
Added Info AUDIO AMATEUR 3/1977 [Aug 1977] (v.8#3) pg. 52
Added Info AUDIO AMATEUR 4/1978 [Nov 1978] (v.9#4) pg. 45
Added Info AUDIO AMATEUR 2/1979 [Apr 1979] (v.10#2) pg. 30

Report on assembling the Basic Stereo Preamp kit from Ace Audio Company.
AUDIO AMATEUR 1/1976 [May 1976] (v.7#1) pg. 26

Remodify the Dynaco PAS preamplifier. Improvements to the phono stage, high-level stage, power supply, etc.
AUDIO AMATEUR 2/1976 [Jul 1976] (v.7#2) pg. 21
Correction AUDIO AMATEUR 4/1976 [Dec 1976] (v.7#4) pg. 50
Added Info AUDIO AMATEUR 1/1977 [Feb 1977] (v.8#1) pg. 49, 50
Added Info AUDIO AMATEUR 3/1977 [Aug 1977] (v.8#3) pg. 40, 54
Added Info AUDIO AMATEUR 1/1978 [Mar 1978] (v.9#1) pg. 69, 70
Added Info AUDIO AMATEUR 1/1979 [Feb 1979] (v.10#1) pg. 36
Added Info AUDIO AMATEUR 1/1980 [Jan 1980] (v.11#1) pg. 58

Tips on modifying a Dynaco SCA-80 using some of the modifications for the PAT-4 stereo preamplifier.
AUDIO AMATEUR 1/1977 [Feb 1977] (v.8#1) pg. 52
Added Info AUDIO AMATEUR 4/1977 [Dec 1977] (v.8#4) pg. 56

A PAT-5 modification. Turn the Dynaco PAT-5 into a refined audiophile's preamp with significant improvements in audible performance.
AUDIO AMATEUR 1/1978 [Mar 1978] (v.9#1) pg. 7
Correction AUDIO AMATEUR 2/1978 [Jun 1978] (v.9#2) pg. 49
Added Info AUDIO AMATEUR 2/1978 [Jun 1978] (v.9#2) pg. 49
Added Info AUDIO AMATEUR 3/1978 [Sep 1978] (v.9#3) pg. 48
Correction AUDIO AMATEUR 3/1978 [Sep 1978] (v.9#3) pg. 53
Added Info AUDIO AMATEUR 4/1978 [Nov 1978] (v.9#4) pg. 55
Added Info AUDIO AMATEUR 1/1979 [Feb 1979] (v.10#1) pg. 49, 51, 53
Added Info AUDIO AMATEUR 2/1979 [Apr 1979] (v.10#2) pg. 49, 52
Added Info AUDIO AMATEUR 3/1979 [Jul 1979] (v.10#3) pg. 5, 61
Correction AUDIO AMATEUR 3/1979 [Jul 1979] (v.10#3) pg. 57
Added Info AUDIO AMATEUR 4/1979 [Oct 1979] (v.10#4) pg. 56, 59
Added Info AUDIO AMATEUR 1/1980 [Jan 1980] (v.11#1) pg. 59, 62
Added Info AUDIO AMATEUR 1/1981 [Feb 1981] (v.12#1) pg. 48
Added Info AUDIO AMATEUR 3/1981 [Jun 1981] (v.12#3) pg. 50

Simple way to reduce crosstalk and help prevent clipping on transients in a normal stereo amplifier or preamp.
AUDIO AMATEUR 2/1978 [Jun 1978] (v.9#2) pg. 42

Classic circuitry. Ulric J. Childs' control-preamplifier model 1045A (circa 1950).
AUDIO AMATEUR 2/1978 [Jun 1978] (v.9#2) pg. 44
Correction AUDIO AMATEUR 4/1978 [Nov 1978] (v.9#4) pg. 47

Report on assembling and testing the DH-101 solid-state preamplifier kit from the David Hafler Co.
AUDIO AMATEUR 3/1978 [Sep 1978] (v.9#3) pg. 33
Added Info AUDIO AMATEUR 3/1980 [Jun 1980] (v.11#3) pg. 50
Added Info AUDIO AMATEUR 4/1980 [Nov 1980] (v.11#4) pg. 63

LZ-1. A low distortion IC preamplifier/control unit. Two circuit boards (phono preamp and high-level buffer/tone control) provide volume, bass, treble and balance control.
AUDIO AMATEUR 1/1979 [Feb 1979] (v.10#1) pg. 5
Added Info AUDIO AMATEUR 3/1979 [Jul 1979] (v.10#3) pg. 57, 62
Added Info AUDIO AMATEUR 4/1979 [Oct 1979] (v.10#4) pg. 61
Added Info AUDIO AMATEUR 3/1982 [Aug 1982] (v.13#3) pg. 52
Added Info AUDIO AMATEUR 2/1984 [May 1984] (v.15#2) pg. 56

A comparison of preamplifier construction projects. (1) Williamson 20/20 preamp semi-kit. (2) Southwest Technical Products' (Meyer) Super Op Amp. (3) Compact phono preamp based on the National Semiconductor LM381A IC. (4) Leach preamp featured in Audio magazine.
AUDIO AMATEUR 2/1979 [Apr 1979] (v.10#2) pg. 11

Tips on the Hafler 101 preamp. (1) Curing 120 Hz buzz. (2) Zeroing the tone control. (3) Pilot light fix.
AUDIO AMATEUR 2/1979 [Apr 1979] (v.10#2) pg. 39

The PAT-5/WJ-1A (a PAT-5/WJ-1 update). A look at specific areas which could yield audible improvements within the general PAT-5 chassis framework. Includes detailed modifications for the power supply, interconnecting wiring and high level card, and the phono circuit. [NOTE: related article in issue 1/1978 p7].
AUDIO AMATEUR 3/1979 [Jul 1979] (v.10#3) pg. 24
Added Info AUDIO AMATEUR 4/1979 [Oct 1979] (v.10#4) pg. 48, 57, 58, 60
Added Info AUDIO AMATEUR 1/1980 [Jan 1980] (v.11#1) pg. 42, 56
Added Info AUDIO AMATEUR 2/1980 [Mar 1980] (v.11#2) pg. 50, 51, 53, 54
Correction AUDIO AMATEUR 3/1980 [Jun 1980] (v.11#3) pg. 50
Added Info AUDIO AMATEUR 3/1980 [Jun 1980] (v.11#3) pg. 55, 56, 57
Added Info AUDIO AMATEUR 4/1980 [Nov 1980] (v.11#4) pg. 61, 63
Added Info AUDIO AMATEUR 2/1981 [Apr 1981] (v.12#2) pg. 58, 59
Added Info AUDIO AMATEUR 3/1981 [Jun 1981] (v.12#3) pg. 54
Added Info AUDIO AMATEUR 2/1988 [May 1988] (v.19#2) pg. 44

Eliminate 60Hz/120Hz hum problems in a SWTP 198A preamp with this modification. Est. cost: $10.
AUDIO AMATEUR 3/1979 [Jul 1979] (v.10#3) pg. 41

Classic circuitry. Schematic of a Dynaco PAS-2/PAS-3X preamp.
AUDIO AMATEUR 3/1979 [Jul 1979] (v.10#3) pg. 56

Classic circuitry. Schematic for Audio Research Corp. SP-6/SP-6A preamplifier (circa 1978).
AUDIO AMATEUR 4/1979 [Oct 1979] (v.10#4) pg. 54
Added Info AUDIO AMATEUR 2/1980 [Mar 1980] (v.11#2) pg. 46, 48

Classic circuitry. Schematic for the McIntosh C-22 preamplifier (circa 1963).
AUDIO AMATEUR 1/1980 [Jan 1980] (v.11#1) pg. 54

Simple modification for the Hafler DH-101 preamp leaves it continually powered, but still switches appropriate outlets in the back panel. This eliminates turn-on thumps and prolongs capacitor life.
AUDIO AMATEUR 2/1980 [Mar 1980] (v.11#2) pg. 56

Modifying the Hafler DH-101 preamplifier. (1) Circuitry. (2) Parts placement.
AUDIO AMATEUR 4/1980 [Nov 1980] (v.11#4) pg. 7, 9
Correction AUDIO AMATEUR 2/1981 [Apr 1981] (v.12#2) pg. 57
Added Info AUDIO AMATEUR 2/1981 [Apr 1981] (v.12#2) pg. 60, 62
Added Info AUDIO AMATEUR 3/1981 [Jun 1981] (v.12#3) pg. 49, 52
Added Info AUDIO AMATEUR 4/1981 [Sep 1981] (v.12#4) pg. 57
Added Info AUDIO AMATEUR 2/1982 [May 1982] (v.13#2) pg. 54

Designing active RIAA equalization networks for vacuum tube preamplifiers.
AUDIO AMATEUR 4/1980 [Nov 1980] (v.11#4) pg. 42
Correction AUDIO AMATEUR 1/1981 [Feb 1981] (v.12#1) pg. 45

Classic circuitry. Schematic of the McIntosh C8 monophonic tube type preamplifier with an outboard D-8A power supply (circa 1956).
AUDIO AMATEUR 4/1980 [Nov 1980] (v.11#4) pg. 49

Modifying the Audio Research SP-6, SP-6A and SP-6B preamplifiers. Improve the power supply and RIAA equalization. A change in biasing for improved large signal linearity is also suggested.
AUDIO AMATEUR 1/1981 [Feb 1981] (v.12#1) pg. 7
Added Info AUDIO AMATEUR 2/1981 [Apr 1981] (v.12#2) pg. 63
Added Info AUDIO AMATEUR 2/1983 [Jun 1983] (v.14#2) pg. 62
Added Info AUDIO AMATEUR 5/1983 [Jan 1984] (v.14#5) pg. 55

Modifying the Marantz 7C preamplifier.
AUDIO AMATEUR 1/1981 [Feb 1981] (v.12#1) pg. 20
Correction AUDIO AMATEUR 2/1981 [Apr 1981] (v.12#2) pg. 57
Added Info AUDIO AMATEUR 2/1981 [Apr 1981] (v.12#2) pg. 58
Added Info AUDIO AMATEUR 4/1981 [Sep 1981] (v.12#4) pg. 63
Added Info AUDIO AMATEUR 1/1982 [Jan 1982] (v.13#1) pg. 52
Added Info GLASS AUDIO 3/1997 (v.9#3) pg. 57

Tip on rewiring a preamp's switching facilities to reduce the number of switch contacts in the signal path.
AUDIO AMATEUR 4/1981 [Sep 1981] (v.12#4) pg. 38

A short, programmable calculator program (HP-41C or HP-25) for checking the RIAA accuracy of your preamp.
AUDIO AMATEUR 1/1982 [Jan 1982] (v.13#1) pg. 30

Passive RIAA networks for vacuum tube preamplifiers.
AUDIO AMATEUR 1/1982 [Jan 1982] (v.13#1) pg. 30

A new test for preamps and amplifiers is proposed. Involves using white noise coupled with a very narrow and deep tunable notch filter.
AUDIO AMATEUR 1/1982 [Jan 1982] (v.13#1) pg. 58

Preamp switching and control circuitry has a minimum number of contacts in the signal path but still allows for a low-cut filter and extensive tape switching.
AUDIO AMATEUR 2/1982 [May 1982] (v.13#2) pg. 20
Correction AUDIO AMATEUR 5/1982 [Jan 1983] (v.13#5) pg. 53

Modifications for Southwest Technical's 198A Preamp, 207 Power Amp, and 210 Power Amp are suggested.
AUDIO AMATEUR 2/1982 [May 1982] (v.13#2) pg. 50
Added Info AUDIO AMATEUR 3/1982 [Aug 1982] (v.13#3) pg. 50
Correction AUDIO AMATEUR 4/1982 [Oct 1982] (v.13#4) pg. 54

Rephasing tricks for preamps to better distribute the heavy bass loads.
AUDIO AMATEUR 2/1982 [May 1982] (v.13#2) pg. 53

Improvements for Hafler's DH-101 preamplifier and two power amplifiers (DH-200 and DH-500).
AUDIO AMATEUR 3/1982 [Aug 1982] (v.13#3) pg. 32
Added Info AUDIO AMATEUR 2/1984 [May 1984] (v.15#2) pg. 56

The last PAS. Modifications applicable to all of the Dynaco PAS model tube phono preamplifiers. Includes a new front panel, phono stage, high level board, B+ supply, tube heater, controls, connectors and wiring. Part 1. General concepts of the changes to modify the Dynaco preamp into the PAS MOD Mk. III.
AUDIO AMATEUR 4/1982 [Oct 1982] (v.13#4) pg. 24
Correction AUDIO AMATEUR 5/1982 [Jan 1983] (v.13#5) pg. 53
Added Info AUDIO AMATEUR 2/1983 [Jun 1983] (v.14#2) pg. 56, 62

Classic circuitry. Schematics for the Dynaco PAM-1 preamplifier and the Dynaco PAS-3X preamplifier.
AUDIO AMATEUR 4/1982 [Oct 1982] (v.13#4) pg. 42

The last PAS. Part 2. Step-by-step procedures for transforming the Dynaco preamp into the PAS MOD Mk. III.
AUDIO AMATEUR 5/1982 [Jan 1983] (v.13#5) pg. 28
Correction AUDIO AMATEUR 1/1983 [Apr 1983] (v.14#1) pg. 54
Added Info AUDIO AMATEUR 1/1983 [Apr 1983] (v.14#1) pg. 56
Added Info AUDIO AMATEUR 2/1983 [Jun 1983] (v.14#2) pg. 54
Correction AUDIO AMATEUR 2/1983 [Jun 1983] (v.14#2) pg. 58
Added Info AUDIO AMATEUR 5/1983 [Jan 1984] (v.14#5) pg. 51
Added Info AUDIO AMATEUR 2/1984 [May 1984] (v.15#2) pg. 50
Added Info AUDIO AMATEUR 4/1984 [Sep 1984] (v.15#4) pg. 58
Added Info AUDIO AMATEUR 5/1984 [Oct 1984] (v.15#5) pg. 52
Added Info AUDIO AMATEUR 4/1987 [Nov 1987] (v.18#4) pg. 58

Modifications for the Integral Systems model 10 preamplifier to improve its performance dramatically.
AUDIO AMATEUR 1/1983 [Apr 1983] (v.14#1) pg. 34
Correction AUDIO AMATEUR 3/1983 [Sep 1983] (v.14#3) pg. 56

Equipment review of the Hafler DH-110 preamp.
AUDIO AMATEUR 1/1983 [Apr 1983] (v.14#1) pg. 51
Added Info AUDIO AMATEUR 3/1983 [Sep 1983] (v.14#3) pg. 48
Added Info AUDIO AMATEUR 4/1986 [Oct 1986] (v.17#4) pg. 55

Classic circuitry. Schematic for the Pedersen Electronics model PRT-1 series B preamp.
AUDIO AMATEUR 2/1983 [Jun 1983] (v.14#2) pg. 44

Review of the Fujitech A-502 stereo preamp kit.
AUDIO AMATEUR 4/1983 [Nov 1983] (v.14#4) pg. 36
Correction AUDIO AMATEUR 1/1984 [Mar 1984] (v.15#1) pg. 52

New devices for audio from National Semiconductor. Circuits included for a differential amplifier, operational amplifier, phono preamp, line level amp, etc.
AUDIO AMATEUR 5/1983 [Jan 1984] (v.14#5) pg. 7
Added Info AUDIO AMATEUR 1/1985 [Jan 1985] (v.16#1) pg. 55

Classic circuitry. Schematic for Grommes Hi-Fidelity Model 208 preamp (circa 1958) from Precision Electronics Inc. (Franklin, IL).
AUDIO AMATEUR 3/1984 [Jul 1984] (v.15#3) pg. 46

Report on the PV-3 tube preamplifier kit from Conrad-Johnson Design.
AUDIO AMATEUR 5/1984 [Oct 1984] (v.15#5) pg. 44
Added Info AUDIO AMATEUR 1/1987 [Jan 1987] (v.18#1) pg. 44

Classic circuitry. Schematic for the Leak preamplifier and power amplifier (circa 1952).
AUDIO AMATEUR 5/1984 [Oct 1984] (v.15#5) pg. 48

Classic circuitry. Schematic of Grommes Hi-Fidelity model 212 preamp (circa 1957).
AUDIO AMATEUR 1/1985 [Jan 1985] (v.16#1) pg. 24

Daniel. A vacuum tube preamp designed to (1) minimize the amplification stages, (2) use sonically premium components, and (3) use regulated power supplies. Est. cost: $320.
AUDIO AMATEUR 2/1985 [Mar 1985] (v.16#2) pg. 7
Correction AUDIO AMATEUR 3/1985 [Jul 1985] (v.16#3) pg. 51
Correction AUDIO AMATEUR 4/1985 [Oct 1985] (v.16#4) pg. 54
Added Info AUDIO AMATEUR 4/1985 [Oct 1985] (v.16#4) pg. 54, 55
Added Info AUDIO AMATEUR 1/1986 [Feb 1986] (v.17#1) pg. 36
Added Info AUDIO AMATEUR 2/1986 [May 1986] (v.17#2) pg. 50, 53
Added Info AUDIO AMATEUR 4/1986 [Oct 1986] (v.17#4) pg. 52, 56
Added Info AUDIO AMATEUR 3/1989 [Aug 1989] (v.20#3) pg. 62

The great preamp shootout. A listening test of ten (10) preamps which have been featured in previous issues of The Audio Amateur. May help in determining which preamp to build, buy, and/or modify.
AUDIO AMATEUR 2/1985 [Mar 1985] (v.16#2) pg. 19
Added Info AUDIO AMATEUR 3/1985 [Jul 1985] (v.16#3) pg. 51
Added Info AUDIO AMATEUR 2/1986 [May 1986] (v.17#2) pg. 47

Borbely preamp. A top-quality preamp project features discrete circuitry (instead of IC op amps). Est. cost: $480. Part 1. The RIAA-1 and RIAA-2 sections.
AUDIO AMATEUR 4/1985 [Oct 1985] (v.16#4) pg. 7
Added Info AUDIO AMATEUR 3/1986 [Aug 1986] (v.17#3) pg. 56
Added Info AUDIO AMATEUR 1/1987 [Jan 1987] (v.18#1) pg. 54, 55

Classic circuitry. Schematic of the Grommes Hi-Fidelity Model 207A preamp (circa 1957).
AUDIO AMATEUR 4/1985 [Oct 1985] (v.16#4) pg. 45

Borbely preamp. Part 2. Line amp, tape buffer and power supplies.
AUDIO AMATEUR 1/1986 [Feb 1986] (v.17#1) pg. 18
Added Info AUDIO AMATEUR 3/1988 [Aug 1988] (v.19#3) pg. 51
Added Info AUDIO AMATEUR 4/1989 [Oct 1989] (v.20#4) pg. 55, 60
Added Info AUDIO AMATEUR 1/1990 [Feb 1990] (v.21#1) pg. 57
Added Info AUDIO AMATEUR 3/1993 [Sep 1993] (v.24#3) pg. 38
Added Info AUDIO AMATEUR 3/1996 [Sep 1996] (v.27#3) pg. 40

Classic circuitry. Schematic of the Grommes Hi-Fidelity Model 260A preamp from Precision Electronics (circa 1958).
AUDIO AMATEUR 1/1986 [Feb 1986] (v.17#1) pg. 47

Tips on upgrading the Hafler DH-200 preamp using Musical Concepts' M-200 and M-200DX modifications.
AUDIO AMATEUR 2/1986 [May 1986] (v.17#2) pg. 50

Modifying the Hafler DH-100 preamplifier. Changes include faster ICs, removing inter-stage coupling caps, tone control bypass, infrasonic filter, etc.
AUDIO AMATEUR 3/1986 [Aug 1986] (v.17#3) pg. 26
Added Info AUDIO AMATEUR 4/1986 [Oct 1986] (v.17#4) pg. 58
Added Info AUDIO AMATEUR 2/1987 [Mar 1987] (v.18#2) pg. 50

Borbely preamp. Part 3. Setup procedure.
AUDIO AMATEUR 4/1986 [Oct 1986] (v.17#4) pg. 14
Added Info AUDIO AMATEUR 2/1988 [May 1988] (v.19#2) pg. 53

The grid isolation resistor. Improve the sound of tube-type preamplifiers by interposing resistors between tube preamplifier grids and the rest of the circuitry.
AUDIO AMATEUR 4/1986 [Oct 1986] (v.17#4) pg. 38

Classic circuitry. Schematic of the RCA SV-1 preamp (circa 1950).
AUDIO AMATEUR 2/1987 [Mar 1987] (v.18#2) pg. 46
Added Info AUDIO AMATEUR 4/1987 [Nov 1987] (v.18#4) pg. 54

The Aurora. A state-of-the-art preamplifier built around a Dynaco PAS tube preamp.
AUDIO AMATEUR 3/1987 [Jul 1987] (v.18#3) pg. 13
Correction AUDIO AMATEUR 4/1987 [Nov 1987] (v.18#4) pg. 50
Added Info AUDIO AMATEUR 1/1988 [Feb 1988] (v.19#1) pg. 48
Added Info AUDIO AMATEUR 4/1988 [Oct 1988] (v.19#4) pg. 52
Added Info AUDIO AMATEUR 1/1989 [Feb 1989] (v.20#1) pg. 48, 56
Added Info AUDIO AMATEUR 3/1989 [Aug 1989] (v.20#3) pg. 56
Added Info AUDIO AMATEUR 4/1989 [Oct 1989] (v.20#4) pg. 60

Audio components design. A systems approach. Looks at the traditional audio chain, the crossover, the preamp, and the crossover filter.
AUDIO AMATEUR 2/1988 [May 1988] (v.19#2) pg. 27
Added Info AUDIO AMATEUR 3/1989 [Aug 1989] (v.20#3) pg. 58
Added Info AUDIO AMATEUR 3/1994 [Sep 1994] (v.25#3) pg. 48

Tips on updating the Dynaco PAT-4 preamp.
AUDIO AMATEUR 2/1988 [May 1988] (v.19#2) pg. 42

Test report on the ADCOM GTP-400 FM tuner/preamp.
AUDIO AMATEUR 2/1989 [Apr 1989] (v.20#2) pg. 42

The PAT-4 preamp reborn. Upgrading Dynaco's PAT-4 preamplifier.
AUDIO AMATEUR 4/1989 [Oct 1989] (v.20#4) pg. 22

A mostly MOS preamp. Part 1. Passive RIAA network design, amplifier device properties, line driver, tape driver, etc.
AUDIO AMATEUR 1/1990 [Feb 1990] (v.21#1) pg. 8
Correction AUDIO AMATEUR 2/1990 [Apr 1990] (v.21#2) pg. 5
Added Info AUDIO ELECTRONICS 2/2000 [Mar 2000] (v.31#2) pg. 51

A mostly MOS preamp. Part 2.
AUDIO AMATEUR 2/1990 [Apr 1990] (v.21#2) pg. 26
Added Info AUDIO AMATEUR 4/1990 [Oct 1990] (v.21#4) pg. 55
Correction AUDIO AMATEUR 1/1991 [Feb 1991] (v.22#1) pg. 62
Added Info AUDIO AMATEUR 1/1992 [Mar 1992] (v.23#1) pg. 58

Modifying the Crown IC-150 preamplifier as an alternative to buying an Adcom or other good quality, modern preamp. Est. cost: $50-$200.
AUDIO AMATEUR 3/1990 [Aug 1990] (v.21#3) pg. 28

The new Borbely preamplifier (EB-1190/202). Layouts and parts lists for the modules (RIAAs and Class A line amplifiers).
AUDIO AMATEUR 2/1991 [Apr 1991] (v.22#2) pg. 32

SRPP (shunt regulated push-pull) tube preamplifier.
AUDIO AMATEUR 2/1991 [Apr 1991] (v.22#2) pg. 62
Added Info AUDIO AMATEUR 3/1991 [Aug 1991] (v.22#3) pg. 43
Added Info GLASS AUDIO 2/1991 (v.3#2) pg. 61, 65
Added Info GLASS AUDIO 3/1992 (v.4#3) pg. 47
Added Info GLASS AUDIO 4/1992 (v.4#4) pg. 40
Added Info GLASS AUDIO 1/1993 (v.5#1) pg. 40
Correction AUDIO AMATEUR 1/1996 [Mar 1996] (v.27#1) pg. 50

Linear Technology preamp modifications and corrections.
AUDIO AMATEUR 3/1991 [Aug 1991] (v.22#3) pg. 43

Curcio Daniel preamp troubleshooting and suggested circuit changes.
AUDIO AMATEUR 3/1991 [Aug 1991] (v.22#3) pg. 46
Added Info AUDIO AMATEUR 1/1992 [Mar 1992] (v.23#1) pg. 54

A new control preamplifier. Back to the future? A look at various types of tone controls and their role in preamps and equalizers. Part 1. The preamp and how it works.
AUDIO AMATEUR 4/1991 [Oct 1991] (v.22#4) pg. 10

A new control preamplifier. Back to the future? A look at various types of tone controls and their role in preamps and equalizers. Part 2. Circuit card layouts, parts lists and assembly instructions for the "Preamp 90" prototype.
AUDIO AMATEUR 1/1992 [Mar 1992] (v.23#1) pg. 12
Correction AUDIO AMATEUR 2/1992 [Jun 1992] (v.23#2) pg. 52
Correction AUDIO AMATEUR 4/1992 [Dec 1992] (v.23#4) pg. 39

Encapsulated modules. Potted amplifier modules in epoxy-filled cases are plugged into the main circuit board to form a preamplifier. Encapsulating offers simplicity, great strength, compact size, modular design, and isothermal benefits.
AUDIO AMATEUR 3/1992 [Sep 1992] (v.23#3) pg. 24

The Gaertner-Borbely line-level preamp. A high-level-only preamp which includes buffered inputs, a 24-stepped attenuator volume control, no balance control, generous input and function switching capabilities, and high-quality relays with multilayer contacts for all audio switching. Part 1.
AUDIO AMATEUR 1/1993 [Mar 1993] (v.24#1) pg. 8

The Gaertner-Borbely line-level preamp. Part 2.
AUDIO AMATEUR 2/1993 [Jun 1993] (v.24#2) pg. 19

RIAA network limitations. Understanding one more principle for successful preamplifier design.
AUDIO AMATEUR 3/1993 [Sep 1993] (v.24#3) pg. 30
Added Info AUDIO AMATEUR 2/1994 [Jun 1994] (v.25#2) pg. 41

Avoiding amp clipping. How to use a test CD to adjust your separate audio preamp and amplifier to avoid clipping.
AUDIO AMATEUR 4/1993 [Dec 1993] (v.24#4) pg. 35
Added Info AUDIO AMATEUR 3/1994 [Sep 1994] (v.25#3) pg. 50

Valkyrie. A line-stage preamplifier. Utilizes high-performance op amps in the signal path. Provides a modest voltage gain of about 5 (14dB), but can be increased.
AUDIO AMATEUR 1/1994 [Mar 1994] (v.25#1) pg. 10
Correction AUDIO AMATEUR 3/1994 [Sep 1994] (v.25#3) pg. 42
Added Info AUDIO AMATEUR 3/1994 [Sep 1994] (v.25#3) pg. 45
Correction AUDIO AMATEUR 2/1995 [Jun 1995] (v.26#2) pg. 45
Added Info AUDIO ELECTRONICS 3/1999 [Jun 1999] (v.30#3) pg. 39

The Bride of Zen preamplifier. A single gain stage MOSFET circuit to accompany the Pass Zen 10W single-ended Class A power amplifier.
AUDIO AMATEUR 4/1994 [Dec 1994] (v.25#4) pg. 22
Added Info AUDIO AMATEUR 1/1995 [Jan 1995] (v.26#1) pg. 47
Added Info AUDIO AMATEUR 4/1995 [Nov 1995] (v.26#4) pg. 52
Added Info AUDIO ELECTRONICS 2/1997 [Apr 1997] (v.28#2) pg. 33
Added Info AUDIO ELECTRONICS 6/1998 [Dec 1998] (v.29#6) pg. 42

An instrumentation preamp. A generic, reusable preamp enclosure lets you easily change the audio circuit board while keeping the same line amplifier, power supply, front panel, I/O ports, etc. Ideal for testing various audio circuits.
AUDIO AMATEUR 2/1995 [Jun 1995] (v.26#2) pg. 8
Added Info AUDIO AMATEUR 3/1995 [Aug 1995] (v.26#3) pg. 50

Feedforward error cancellation. Part 3. Topology of a feedforward preamplifier, analysis of the noise in a preamplifier-cartridge system, selecting passive and active components, and constructing and tuning the preamplifier.
AUDIO AMATEUR 2/1996 [May 1996] (v.27#2) pg. 10
Added Info AUDIO ELECTRONICS 2/1997 [Apr 1997] (v.28#2) pg. 34

Simple mods for the Audio Alchemy VITB active and passive RIAA.
AUDIO ELECTRONICS 3/1997 [Jun 1997] (v.28#3) pg. 45

Bride of Son of Zen. The next generation. A preamplifier circuit which performs linear amplification without negative feedback. It has an identical topology and is perfectly suited for driving the Son of Zen amplifier.
AUDIO ELECTRONICS 5/1997 [Oct 1997] (v.28#5) pg. 6
Correction AUDIO ELECTRONICS 2/1999 [Mar 1999] (v.30#2) pg. 46

A trial-balloon passive control. Construction of a simple passive preamplifier (audio switch) which eliminates the power-line noise found in an active preamplifier.
AUDIO ELECTRONICS 2/1998 [Apr 1998] (v.29#2) pg. 12

Passive preamp project. Features include six inputs (including phono and video sound pass-through), a buffered source selector for tape or a second room, 24-position 50k ladder attenuators, separate power supply, etc.
AUDIO ELECTRONICS 4/1998 [Aug 1998] (v.29#4) pg. 26

A simple line-stage low-pass circuit. A simple circuit modification that you can easily and inexpensively insert into any preamp configuration, thus enhancing the signal through the system.
AUDIO ELECTRONICS 1/1999 [Jan 1999] (v.30#1) pg. 32
Correction AUDIO ELECTRONICS 3/1999 [Jun 1999] (v.30#3) pg. 39

Review of the Velleman K4100 digital controlled preamplifier kit includes construction and modification tips.
AUDIO ELECTRONICS 3/1999 [Jun 1999] (v.30#3) pg. 44

Review of the Marchand Electronics PR41 Passive Preamplifier kit.
AUDIO ELECTRONICS 2/2000 [Mar 2000] (v.31#2) pg. 45

Williamson-style preamp phase-splitter circuit utilizes a twin triode.
AUDIOXPRESS Mar 2001 (v.32#3) pg. 88

Review of the Mapletree Octal 6 Duplex Stereo Preamplifier available in kit form.
AUDIOXPRESS Apr 2001 (v.32#4) pg. 54

Another subminiature preamp. Circuit for a differential input/constant-current source and cathode-follower output line-stage preamplifier.
AUDIOXPRESS May 2001 (v.32#5) pg. 90
Correction AUDIOXPRESS Jan 2002 (v.33#1) pg. 72

Schematic diagram of a vintage Marantz Audio Consolette control preamplifier-equalizer.
AUDIOXPRESS May 2001 (v.32#5) pg. 96

A valve preamplifier. Design is based on the ECL86 triode-pentode combination. Part 1.
AUDIOXPRESS Jun 2002 (v.33#6) pg. 8

A valve preamplifier. Part 2. Choosing components, assembly and wiring.
AUDIOXPRESS Jul 2002 (v.33#7) pg. 44

Updating Borbely's line amp (preamplifier).
AUDIOXPRESS Oct 2002 (v.33#10) pg. 32

Odyssey of a line stage. Taking a simple transformer-output line stage through many experiments and choices which result in a state-of-the-art parafeed design. Part 1.
AUDIOXPRESS Feb 2003 (v.34#2) pg. 20

Odyssey of a line stage. Part 2.
AUDIOXPRESS Mar 2003 (v.34#3) pg. 22

A tube preamp for 24-bit computer-based soundcards like those found in digital audio editing and multitrack equipment.
AUDIOXPRESS Jun 2003 (v.34#6) pg. 36

Plug-in preamplifier for cheap tape recorders. Est. cost: $6.
ELECTRONICS ILLUSTRATED Sep 1965 (v.8#5) pg. 41

Build the "Tubehead" preamp to mellow the harsh sound of compact discs. A hybrid circuit that combines both low-noise solid-state op-amps and vacuum tubes. Est. cost: $79.
ELECTRONICS NOW Jun 1994 (v.65#6) pg. 33
Added Info ELECTRONICS NOW Dec 1994 (v.65#12) pg. 10

Real McTube. Construct a vacuum-tube based preamplifier and distortion unit. Use it with a solid-state audio amplifier to simulate the "vintage sound" and "warm-tube distortion" of a vacuum tube amplifier. Est. cost: $50.
ELECTRONICS NOW Feb 1999 (v.70#2) pg. 31
Added Info ELECTRONICS NOW Apr 1999 (v.70#4) pg. 7
Correction ELECTRONICS NOW May 1999 (v.70#5) pg. 25

Low-distortion hi-fi volume expander uses an FET circuit to provide up to 30 db expansion of the dynamic range or broadcast music. Est. cost: $30.
ELECTRONICS WORLD Jun 1971 (v.85#6) pg. 54

Circuit for an equalized tape head preamplifier uses the type 741 opamp. Bargain priced tape decks can be made operational with these electronics.
ELEMENTARY ELECTRONICS May-Jun 1975 (v.15#3) pg. 84

Superbass amplifier is used between a guitar, organ, or other electronic musical instrument, and the amplifier. It strips the highs from the instrument's output and amplifies the low frequencies. Powered by a 9-volt battery.
ELEMENTARY ELECTRONICS Mar-Apr 1980 (v.20#2) pg. 76

A line level preamp. Designed to drive a transformerless power amp (featured in 2/1990 issue).
GLASS AUDIO 2/1991 (v.3#2) pg. 1
Added Info GLASS AUDIO 4/1993 (v.5#4) pg. 37
Added Info GLASS AUDIO 6/1995 (v.7#6) pg. 66
Added Info GLASS AUDIO 5/1996 (v.8#5) pg. 59
Correction GLASS AUDIO 6/1996 (v.8#6) pg. 62, 64

Improving the classic tube preamp. An improved circuit replaces the traditional cathode followers.
GLASS AUDIO 2/1991 (v.3#2) pg. 12

Upgrade tips for the Dynaco PAS-3 or PAS-2 to eliminate a major hissing problem.
GLASS AUDIO 1/1992 (v.4#1) pg. 45

An octal tube preamplifier. A companion to the 35W power amp featured in Audio Amateur (1/92).
GLASS AUDIO 3/1992 (v.4#3) pg. 1
Added Info GLASS AUDIO 2/1993 (v.5#2) pg. 38
Added Info GLASS AUDIO 3/1993 (v.5#3) pg. 38

Asymmetrical mu-follower preamp circuit gives the same performance with two vacuum tubes that most circuits only deliver with three.
GLASS AUDIO 1/1993 (v.5#1) pg. 35
Added Info GLASS AUDIO 3/1993 (v.5#3) pg. 40

Resurrection for Lazarus. Modifying the Lazarus Cascade Basic preamp with a four-tube design and separate power supply.
GLASS AUDIO 3/1993 (v.5#3) pg. 6
Correction GLASS AUDIO 4/1993 (v.5#4) pg. 39

Tip on adding a low-impedance cathode follower to a Dyna PAS-2 preamp.
GLASS AUDIO 4/1993 (v.5#4) pg. 41
Added Info GLASS AUDIO 2/1994 (v.6#2) pg. 47

A new upgrade for the Dynaco PAS-3 and 3X preamplifier.
GLASS AUDIO 2/1994 (v.6#2) pg. 10
Added Info GLASS AUDIO 3/1994 (v.6#3) pg. 43
Added Info GLASS AUDIO 4/1994 (v.6#4) pg. 49
Added Info GLASS AUDIO 5/1996 (v.8#5) pg. 65
Added Info GLASS AUDIO 3/1998 (v.10#3) pg. 58

Schematic for the Heathkit Mono vacuum tube Preamplifier WA-P2.
GLASS AUDIO 4/1994 (v.6#4) pg. 44

Experimenting with pentodes as voltage amplifiers in audio preamplifiers. Schematics for single-ended stage, series feedback pair, and mu stage are included.
GLASS AUDIO 2/1995 (v.7#2) pg. 49

Circuit for an asymmetrical mu follower. Use it as a buffer stage in a CD player, or to convert a transistor preamplifier into a tube preamplifier.
GLASS AUDIO 4/1995 (v.7#4) pg. 57

The greening of the cascade feedback pair (CFP). A simple circuit solution to the inherent problems of the two-tube preamp line stage as found in the Dynaco PAS series of preamps.
GLASS AUDIO 5/1995 (v.7#5) pg. 20
Added Info GLASS AUDIO 6/1996 (v.8#6) pg. 57
Correction GLASS AUDIO 1/1997 (v.9#1) pg. 48
Added Info GLASS AUDIO 2/1998 (v.10#2) pg. 53

A grounded grid line stage. A preamp circuit that includes the little-used grounded-grid connection to hook up a triode.
GLASS AUDIO 5/1995 (v.7#5) pg. 40
Added Info AUDIOXPRESS Oct 2002 (v.33#10) pg. 58 (Improved version)

Build a triode-pentode local feedback control. How to adapt triode-pentode tubes (normally used for television) for use in an audio preamplifier.
GLASS AUDIO 6/1995 (v.7#6) pg. 42
Added Info GLASS AUDIO 3/1996 (v.8#3) pg. 73

Product review of the McIntosh C-22 Commemorative Edition stereo preamplifier. Includes ideas for upgrading.
GLASS AUDIO 6/1995 (v.7#6) pg. 48

Audio preamp tubes. A survey of vacuum tubes for audio use looks at which triodes are best to use.
GLASS AUDIO 6/1997 (v.9#6) pg. 1
Added Info GLASS AUDIO 2/1998 (v.10#2) pg. 48, 49

The search for linearity (the perfect linear system) examines active load triodes. Part 3. Preamp and power amp circuits.
GLASS AUDIO 6/1997 (v.9#6) pg. 42
Correction GLASS AUDIO 2/1998 (v.10#2) pg. 44
Added Info GLASS AUDIO 4/1998 (v.10#4) pg. 56
Added Info GLASS AUDIO 2/1999 (v.11#2) pg. 60

Adding a remote-control to the mute switch found on an Audio Research SP-8 preamplifier.
GLASS AUDIO 2/1998 (v.10#2) pg. 59

The beta-follower amplifier. How to transform a transistorized Marantz model 3300 preamplifier into a vacuum tube unit that incorporates a phono amplifier, a passive RIAA correction, a linear amplifier with a low-pass filter, and a third amplifier with switching capability for tone control.
GLASS AUDIO 4/1998 (v.10#4) pg. 1
Correction GLASS AUDIO 6/1998 (v.10#6) pg. 70
Added Info GLASS AUDIO 2/1999 (v.11#2) pg. 58

Build the FAB 50 line stage. A vacuum tube version of the Nelson Pass "Bride of Zen" solid-state line stage incorporates the 50C5 beam power tube.
GLASS AUDIO 4/1998 (v.10#4) pg. 46
Correction GLASS AUDIO 4/2000 (v.12#4) pg. 59

Shunt-regulated push-pull (SRPP) control preamplifier project features tone controls.
GLASS AUDIO 1/1999 (v.11#1) pg. 1
Correction GLASS AUDIO 3/1999 (v.11#3) pg. 58

A pocket preamp. This line stage demonstrates what you can do with vacuum tube technology in a very small space. The ideas can be applied to other tube projects.
GLASS AUDIO 4/1999 (v.11#4) pg. 26
Added Info GLASS AUDIO 1/2000 (v.12#1) pg. 63
Added Info AUDIOXPRESS Oct 2002 (v.33#10) pg. 62

Basic 50W stereo system. Part 2. The preamplifier. Design and construction of a two-channel tube preamp.
GLASS AUDIO 3/2000 (v.12#3) pg. 26

Review of the AE-3 Class-A triode preamplifier from Audio Electronics Supply. Also available in kit form. Est. cost: $400.
GLASS AUDIO 4/2000 (v.12#4) pg. 33

Simple circuit for a stereo preamp uses two 741 op-amps plus a few resistors and capacitors. Provides over 20-dB gain in each channel.
HANDS-ON ELECTRONICS Jul-Aug 1986 (v.3#4) pg. 16
Added Info HANDS-ON ELECTRONICS Nov 1986 (v.3#6) pg. 17

Solid-state audio circuits. Part 2. Analysis of audio preamplifiers and tone-control circuits.
MODERN ELECTRONICS [2] Oct 1986 (v.3#10) pg. 56

Experimenting with audio circuits. Using op-amps to build a variety of professional audio circuits to suit different requirements.
MODERN ELECTRONICS [2] Mar 1988 (v.5#3) pg. 34

Two-by-two stereo preamplifier. Solid-state unit uses printed circuit boards. Has input control switch, bass, treble, and volume controls.
POPULAR ELECTRONICS [1] Mar 1967 (v.26#3) pg. 69

Build a distortionless preamplifier providing 23- to 60-dB of gain with an output level of 12 volts rms. Est. cost: $40.
POPULAR ELECTRONICS [1] Jun 1972 (v.1#6) pg. 58

Circuit for a preamp uses an op amp IC.
POPULAR ELECTRONICS [1] Dec 1974 (v.6#6) pg. 90

Guide to "home brew" preamp design. Why RIAA signal processing is used, and how it affects preamp design. Typical preamp circuits using ICs are shown.
POPULAR ELECTRONICS [1] Sep 1976 (v.10#3) pg. 60

A look at some rare semiconductor devices. The constant-current diode, the photo-Darlington, and the LM387 preamplifier.
POPULAR ELECTRONICS [1] Nov 1976 (v.10#5) pg. 89

Build a disco preamp/mixer. Provides multi-source inputs and mixing/fading. Est. cost: $70 for preamp only; $110 for preamp/mixer.
POPULAR ELECTRONICS [1] Sep 1978 (v.14#3) pg. 61
Correction POPULAR ELECTRONICS [1] Mar 1979 (v.15#3) pg. 6

Circuit can turn a moderately amplified audio signal (such as 30 volt AC stereo-headphone output) into a line-level equivalent (under 8 volts) for recording or amplification by a different amplifier.
POPULAR ELECTRONICS [2] Apr 1993 (v.10#4) pg. 74

An in-depth look at National Semiconductor's LM38X series of audio linear preamp IC's.
RADIO-ELECTRONICS Feb 1990 (v.61#2) pg. 54

Ultra-low-noise balanced preamp circuit that uses the Linear Technology LT1115 audio op amp.
RADIO-ELECTRONICS May 1990 (v.61#5) pg. 70

Build an integrated circuit preamplifier. Est. cost: $8.
RADIO-TV EXPERIMENTER #780 Apr-May 1966 (v.20#2) pg. 56