Untitled - Tdl-tech.com

MODEL 408A – OPERATION
The model 408A is designed for moving magnet (MM) cartridges only.
To operate the preamp connect your turntable output cables to the RCA input connectors on the
preamp’s rear panel. Connect the preamp’s output RCA connectors or the stereo phone jack to your
amplifier, recorder or sound card line-input. (Red connectors are the “right” channel and black or
white connectors are the “left” channel.) Plug the 24 VDC wall power supply into an outlet on the
same circuit and as physically close as possible to the outlet supplying power to your turntable
because this will (probably) help minimize hum pickup. The power-on LED on the 408A will light.
To make the preamp as quiet (low output noise) as possible there is no on-off switch because
operation from a switched power strip is assumed.
There is a blue 5-way binding post near the input connectors that connects to only the cast aluminum
enclosure. You may get a lower amount of hum at the preamp’s output if the binding post is
connected to the turntable’s frame with a separate wire. Also, the turntable’s power plug polarity
can make a difference in hum pickup so try reversing the plug in the outlet and keep the position
with the lower hum. It is helpful to look at the preamp’s output with a computer sound card (use the
line-input) and a spectrum analyzer program.* This lets you see and minimize the output hum and
noise. Don’t forget to turn on the turntable motor before making you hum measurements.
Adjust the Volume control (gain) as needed. The maximum gain is 52, 56 or 60 dB as set by four
easy-to-change jumpers on the preamp’s circuit board. There is a diagram showing how to set the
jumpers on the under-side of the top cover plate and also in this User Guide. Don’t set the max gain
higher than necessary because this can cause output signal distortion. 52 dB (the factory setting)
should be sufficient for a pickup cartridge with a 5 mV output (see your cartridge spec sheet). Use
a higher max gain if your cartridge has a lower output or if your sound card’s line-input has a low
sensitivity.
Turn on the 20 Hz Rumble Filter by flipping its toggle switch up. The filter is bypassed when the
switch position is down.
The original model 408 was designed at the time when CD’s were the main restoration media so
lowpass filters were included in a preamp’s output to limit the frequency response to 22 kHz. This
corresponds to the Red Book CD standard which uses a 44.1 kHz sampling rate. The 408A filters
can be bypassed with the front-panel toggle switch for wider-range listening and recording higher
resolution digital files. The filters are bypassed when the switch is in the down position.
* A good choice is TrueRTA (TM), Real Time Audio Spectrum Analyzer. It can be downloaded
from www.trueaudio.com.

MODEL 408A – OPERATION
The model 408A is designed for moving magnet (MM) cartridges only.
To operate the preamp connect your turntable output cables to the RCA input connectors on the
preamp’s rear panel. Connect the preamp’s output RCA connectors or the stereo phone jack to your
amplifier, recorder or sound card line-input. (Red connectors are the “right” channel and black or
white connectors are the “left” channel.) Plug the 24 VDC wall power supply into an outlet on the
same circuit and as physically close as possible to the outlet supplying power to your turntable
because this will (probably) help minimize hum pickup. The power-on LED on the 408A will light.
To make the preamp as quiet (low output noise) as possible there is no on-off switch because
operation from a switched power strip is assumed.
There is a blue 5-way binding post near the input connectors that connects to only the cast aluminum
enclosure. You may get a lower amount of hum at the preamp’s output if the binding post is
connected to the turntable’s frame with a separate wire. Also, the turntable’s power plug polarity
can make a difference in hum pickup so try reversing the plug in the outlet and keep the position
with the lower hum. It is helpful to look at the preamp’s output with a computer sound card (use the
line-input) and a spectrum analyzer program.* This lets you see and minimize the output hum and
noise. Don’t forget to turn on the turntable motor before making you hum measurements.
Adjust the Volume control (gain) as needed. The maximum gain is 52, 56 or 60 dB as set by four
easy-to-change jumpers on the preamp’s circuit board. There is a diagram showing how to set the
jumpers on the under-side of the top cover plate and also in this User Guide. Don’t set the max gain
higher than necessary because this can cause output signal distortion. 52 dB (the factory setting)
should be sufficient for a pickup cartridge with a 5 mV output (see your cartridge spec sheet). Use
a higher max gain if your cartridge has a lower output or if your sound card’s line-input has a low
sensitivity.
Turn on the 20 Hz Rumble Filter by flipping its toggle switch up. The filter is bypassed when the
switch position is down.
The original model 408 was designed at the time when CD’s were the main restoration media so
lowpass filters were included in a preamp’s output to limit the frequency response to 22 kHz. This
corresponds to the Red Book CD standard which uses a 44.1 kHz sampling rate. The 408A filters
can be bypassed with the front-panel toggle switch for wider-range listening and recording higher
resolution digital files. The filters are bypassed when the switch is in the down position.
* A good choice is TrueRTA (TM), Real Time Audio Spectrum Analyzer. It can be downloaded
from www.trueaudio.com.

Frequently Asked Questions – Model 408 (and 408A)
The 408 arrived Monday, and I've had some time to play with it. It sounds great - nice and quiet. I
have two quick questions:
1) Is it normal to perceive a large drop in output/volume when going from a flat turnover to the
standard RIAA 500Hz setting? I was listening to a few acoustic 78rpm's (flat) and then put on some
newer vinyl (500Hz) and had to really increase the gain to come close to the same levels as before
(The sound was fine - just checking if it was normal to lose so much output).
(Answer)
Yes, this is normal.
Unlike other processors such as the Owl One and the Re-equalizer, the 408 (and 408A) use fixedgain
turnover and rolloff amplifiers in order to minimize phase and frequency distortions. This does
result in a volume drop at mid and high frequencies when switching from a FLAT to RIAA response
as shown in the graph on the following page. All other turnover and rolloff settings will produce
response curves lower than FLAT. The 408 (and 408A) use the same turnover and rolloff circuits
as the model 4010 so for some additional response curves please see the FAQ section in the 4010
User Guide.
Comparisons to the Owl One and Re-equalizer show identical response curves at various
turnover/rolloff settings. The 408 (and 408A) like the 4010 provides accurate playback response.
The 408 (and 408A) RIAA curve differs by less and 0.5 dB from the “ideal” RIAA curve.
The Re-equalizer is available from Esoteric Sound, www.esotericsound.com
The Owl One is not in production but may be available as “pre-owned equipment.”
March 2011

MODEL 408A – HOW DOES IT WORK?
In Figure 1, the dual, low-noise opamps (U1 and U2) provide all the preamp gain and frequency
response shaping with the RC networks. Because of the circuit design, the gain and frequency
response of each stage (U1 and U2) are independent. The value of R3, R10, R15 and R22 can be
changed by moving jumpers on jumper-blocks (JB1 through JB4) to set the maximum gain to 52,
56 or 60 dB. All jumpers should be set to the same gain or the frequency response will not be
correct.
To eliminate ground loops (for lower output noise), the circuit board common (ground) is connected
to the aluminum enclosure at only one point: at the left input connector.
Response shaping is done by the RC networks with rotary switch S1 controlling the Turnover
frequency and S2 controlling the Rolloff gain at 10 kHz. Many texts detail calculating the
component values for these networks so we wrote a couple of computer programs to make the
calculations easier (they are freely available on our website under Downloads).
U3 with its associated components are the Rumble filters with corner frequencies of 20 Hz. They
may be switched in or out (bypass) with toggle switch S3. U5 buffers the output of the dual Volume
control and provides the stereo signal to the output connectors when the output lowpass filters are
bypassed. The filter is switched IN or to bypass with toggle switch S4. Figure 3 shows the output
lowpass filters that are used only when they are switched IN by S4.
The 24 VDC from the wall power supply is very noisy so it enters the preamp into a separate
shielded enclosure that contains noise filters and voltage regulators (Figure 4). The 24 volts is “split”
into positive and negative levels of about ±12 volts. These voltages are then regulated to ±6 volts
with U6 and U7.

PHONOGRAPH EQUALIZATION SETTINGS
The following TABLE provides suggested starting values for playback equalization of mono
recordings. Don’t be afraid to experiment as even this extensive table may be incorrect.
This information was taken from several sources: The Operating Manual for the Rek-O-Kut Re-
Equalizer, the Dial Your Discs chart which appeared in High Fidelity magazine in the early 1950s,
the chart provided by OWL Electronics, the chart compiled by James R. Powell, Jr. and published
in the ARSC Journal, and the jackets of early LPs. In addition, equalization data was found on the
web sites listed in the NOTES section.
When a recording is mastered (recorded) the amplitudes of the bass frequencies are reduced for
primarily mechanical reasons. When the recording is played, these low frequencies amplitudes must
be increased. The TURNOVER is the frequency below which the amplitude must be increased
during playback.
ROLLOFF is the amount of treble (high frequency) attenuation (cut) at 10 kHz required during
playback to compensate for the treble boost used during mastering. Some charts list Rolloff as a
frequency instead of an attenuation so a correspondence list is included at the end of this Table.
MATRIX is a “number” (may be a combination of numbers and letters) molded into the record just
outside the center label. This number is the “matrix” or mold identifier used to press the record. It
can be used to determine, at lease approximately, when the record was manufactured. In some cases,
the two sides of a record can have very different matrix numbers which means the two side may
need different equalization settings.
Remember, there was no equalization standard before 1955 so this table is a list of suggestions!
Increase the Turnover if the bass sounds too thin. Increase the Rolloff if the treble sounds too strong.
Manufacturer Speed Turnover Rolloff
Acoustic Records ALL 300 FLAT
Acoustic Records – alternate 78 FLAT FLAT
AFRS Transcriptions 33 RIAA FLAT
1944 some or if NAB specified RIAA -16
12 inch transcriptions 629 FLAT
Allegro 33 LP -16
Allied 33 RIAA -16
American Recording Society 33 RIAA -12
Angel 33 RIAA FLAT
Angel – alternate 33 RIAA -12

Arizona (until 1955) 33 400 -12
Artist 78 RIAA -16
Atlantic 33 RIAA -16
Audiophile 33 RIAA -12
78 400 FLAT
Autograph (Marsh Electrical) 78 1000 FLAT
Audio Fidelity (901 - 903) 33 RIAA -16
Bach Guild (501 - 529) 33 LP -16
Bach Guild – alternate 33 RIAA -16
Balkan 78 RIAA -5
Banner (up to 10002) 33 LP -16
Bartok 33 LP -16
(301 - 307, 309, 906 - 920) 33 629 -16
Berliner 71.29 300 FLAT
BBC Transcriptions (1930 - 1949) (70000) ALL 300 -9
(“P” matrix) (1954 - 1956) 33 400 -10
(“R” matrix) (

(1001 - 1022) 33 629 -16
Canyon (up to C6160) 33 400 -12
Capitol (4095 / E2KP > 9607) 33 RIAA RIAA
Contemporary 33 400 -12
(3501, 2501/2/5/7, 2001/2) 33 400 -12
(2504) 33 RIAA -16
(after AP121) 33 RIAA RIAA
Cook 33 RIAA -12
(binaural - inside band) 33 RIAA FLAT
Coral (1946 - 1954) 78 629 -12
(Up to MG4400) (with raised matrix) 33 800 -8

Cylinder records ALL FLAT FLAT
Decca (US) (pre 1946) 78 300 FLAT
(1946 - 1954) 78 629 -12
(Up to MG4400) (with raised matrix) 33 800 -8
Decca – alternate 33 400 -12
(1951) 33 300 -14
(1953) 33 LP -11
(Until Nov 1955) 33 RIAA -16
Decca (1934) – alternate 78 400 -12
(1949) 78 250 -5
Decca (English) 78 300 FLAT
FFRR (1944) (ARL1186 - 1B) 33 RIAA -10
(>ARL2530 - 2A) 33 RIAA RIAA
DGG (Deutsche Grammophone) 33 LP -10
78 300 -5
Dial 33 LP -16
45/78 LP -16
Ducretet-Thomson 33 LP -11
Edison 80 FLAT FLAT
Early 78s (Mid 1930s) 78 RIAA FLAT
Electra (2 - 15, 18 - 20, 24 - 26) 33 629 -16
(17, 22) 33 400 -12
(16, 21, 23, 24) 33 RIAA RIAA
Electrical 78's (1925 - 1938) 78 300 FLAT
(1932 - 1938) 78 300/RIAA FLAT
(1938 - 1946) 78 300/RIAA FLAT, -5
(1947 - 1954) 78 300/RIAA -16
Electrola 78 800 -10
EMI (1931 - 1953) 78 300 FLAT
(1949-53) (2XEA213-392/XAX561-817)(1N,2N) 33/45 RIAA FLAT
(July 17, 1953) 33/78 RIAA FLAT
EMS 33 400 -12

Epic 33 LP -16
Epic – alternate (Until 1954) 33 RIAA -16
Esoteric (ES500, 517, EST5, 6) 33 400 -12
(E2KP to 9607) RIAA -12
European 78s (General) 78 300 -5
Festival 33 LP -16
Folkways 33 LP -16
Fraternity Records (Up to F-1013) 33 RIAA FLAT
Good Time Jazz (3, 9 - 19) 33 400 -12
(1, 5 - 8) 33 RIAA -16
Gramophone Company 78 300 FLAT
Handel Society 33 LP -16
Haydn Society (

London (Pre 1944) 78 300 FLAT
FFRR (1944) (ARL1186-1B) 33 RIAA -10
(>ARL2530-2A) 33 RIAA RIAA
London (Up to LL-846) – alternate 33 450 -11
London International 33 450 -11
Lyricord (Before 1953) (E0 - E3 matrix) 33 400 -12
(XTV matrix) 33 LP -16
(If “629" listed on jacket) 33 629 -16
Majestic 78 RIAA -16
Marsh Laboratories (Electrical) 78 1000 FLAT
Mercury (MG10000 series, approximate fit) 33 RIAA -10
(Through Oct 1954,

Overtone – alternate 33 RIAA -16
Oxford 33 LP -16
Pacific Jazz (1 - 13) 33 400 -12
Parlophone
1925 - 1953 78 300 FLAT
1949 - 1953 33 RIAA FLAT
Parlophone – alternate 78 RIAA FLAT
Period (Up to 576) 33 RIAA -16
Philharmonia 33 400 -12
Polydor 33/78 300 -10
Polymusic 33 RIAA -16
Binaural – inside band 33 RIAA FLAT
Rachmaninoff Society 33 LP -16
RCA-Victor
Early Acoustics 71.29 300 FLAT
Later Acoustics 76.59-78 300 FLAT
1925 78 300 FLAT
1931 (Program transcriptions) 33 800 FLAT
1935 78 300/RIAA -5
1938 - 1954 78 RIAA -8
1954 (New Ortho only) 78 RIAA RIAA
1930 - 1950 (European) 78 300 FLAT
1949 (D9 to E0LRC3980) 33/45 800 -8
1950 - 8/1952 (>E0LRC3981) 33/45 RIAA -12
8/1952 (New Orthophonic) (>E2RP4094) 33/45/78 RIAA RIAA
Remington (Up to 199-135) 33 RIAA -16
Riverside 33 400 -12
Renaissance 33 LP -12
Stradivari 33 LP -16
Supraphone 78 400 FLAT
Technicord 78 800 -12

Telefunken 78 400 -5
Tempo 33 RIAA -16
Transcriptions (Many pre-WWII) 33/78 RIAA FLAT
(Old vertical-cut) 33 300 -5
(NAB vertical-cut) 33 400 -16
Transradio 33 LP -16
Ultraphone 33/78 400 FLAT
Urania (Old - up to XTV20383) 33 RIAA -16
Later (E2KP9607) 33 RIAA RIAA
Urania – alternate 33 400 -12
Vangard (411 - 422, 6000 - 6018, 7001 - 7011,
8000 - 8004, up to XTV20383) 33 LP -16
Vangard (411 - 422, 6000 - 6018) – alternate 33 RIAA -16
Vox (Up to XTV20386, PL8400) 33 RIAA -16
War Department - Special Services 12 inch 33 800 -5
Westminster (E0 matrix) 33 800 -8
(Up to E2PK9607) 33 RIAA -12
(Up to XTV20383) 33 LP -16
Westminster (Before 1956) – alternate 33 400 -12
Westrex (English Western Electric) 78 200 FLAT
Victor ALL See RCA-Victor
Vitaphone (motion picture) 33 300 FLAT
Vocalion (Electrical) 78 300 FLAT
Western Electric (Early transcription) 33 300 FLAT
Zonophone 78 300 FLAT
(Early) 71.29 300 FLAT

A TABLE OF CORRESPONDENCES
TURNOVER
FLAT
150 Hz
200 Hz
250 Hz = FFRR (1949)
300 Hz = FFRR (1951)
400 Hz = AES
450 Hz = LP = FFRR (1953)
500 Hz = RIAA = NAB
629 Hz = “629"
800 Hz
1000 Hz
ROLLOFF
FLAT 0 dB
6500 Hz -5 dB = FFRR (1949)
5500 Hz -6 dB
4800 Hz -7 dB
4300 Hz -8 dB
3800 Hz -9 dB
3300 Hz -10 dB
3000 Hz -11 dB = FFRR (1953)
2500 Hz -12 dB = AES
2122 Hz -13.8 dB = RIAA = FFRR (1951)
1600 Hz -16 dB = NAB
NOTES:
For a very comprehensive list (104 pages) of 78 RPM EQ settings see: “Playback
Equalizer Settings for 78 RPM Recordings” by James R. Powell, Jr. and Randall G.
Stehle. This book is available from http://www.78rpm.com and perhaps from other
sources.
These web sites deal primarily with 78 RPM information and equalization:
http://www.sound.westhost.com/project91.htm
http://www.shellac.org/slumber/equal.html
http://www.rfwilmut.clara.net/repro78/repro.html

J1
J3
J2
LEFT
INPUT
P1 and H1
RIGHT
INPUT
R2 10K
R1
47K
JB1
R3
6490
5
6
+
-
R4
200K
+6V
8
4
-6V
+
7
C1
470uF
C2
100nF
R5 10K
S1A
R36
1
S1-1 f = flat response
S1-2 f = 250 Hz, R6 & R18 = 2490, C3 & C14 = 255nF
S1-3 f = 300 Hz, R7 & R19 = 2000, C4 & C15 = 265nF
S1-4 f = 400 Hz, R8 & R20 = 1430, C5 & C16 = 279nF
S1-5 f = 500 Hz, R9 & R21 = 1100, C6 & C17 = 286nF
S1-6 f = 750 Hz, R34 & R35 = 715, C29 & C30 = 297nF
H2 and P2
2 3 4 5
6
5
6
+
-
R10
6490
R11
200K
+6V
8
4
7
C7
100nF
C8
100nF
R12 1000
S2-1 FLAT RESPONSE
S2-2 -5 dB, C9 & C18 = 25 nF
S2-3 -8 dB, C10 & C19 = 37 nF
S2-4 -12 dB, C11 & C20 = 64 nF
S2-5 RIAA, C12 & C21 = 78 nF
S2-6 -16 dB, C13 & C22 = 100 nF
S2A
C31
100 nF
1
H4 and P4
2 3 4 5 6
C9 C13
CASE
R14 10K
R13
47K
JB2
R15
6490
A B
60 dB 52 dB
56 dB
3
2
+
-
R16
200K
R3A 1800
R3B 4020
1
U1 OPA2227 dual opamp
R17 10K
S1B
R37
R6
C3
H3 and P3
R9
C6
R34
C29
JB3
A B
60 dB 52 dB
56 dB
3
2
+
-
R22
6490
-6V
R10A 1800
R10B 4020
U2 OPA2227 dual opamp
R23
200K
1
R24 1000
S2B
H5 and P5
C18 C22
A B
60 dB 52 dB
56 dB
R15A 1800
R15B 4020
R18 R21
C14 C17
R35
C30
JB4
A B
60 dB 52 dB
56 dB
R22A 1800
R22B 4020
Fig. 1 -- Model 408A input amplifiers with Turnover and Rolloff networks.
C23
1 uF
C24
1 uF
TO LEFT
RUMBLE
FILTER
TO RIGHT
RUMBLE
FILTER

FROM
FIG, 1
FROM
FIG. 1
R25
120K
+6V
C25 C26
100nF 100nF
R26
160K
5
6
+
-
7
R29
5000
P7 H7
RUMBLE FILTER
H2 P2
OUT IN
2-POLE BESSEL
S3
P8 H8
C27
100nF
R27
120K
C28
100nF
R28
160K
3
2
U3 OPA2227
+
-
4
1
R29
5000
-6V
Fig. 2 -- Rumble filters, gain control and output selector switch
Revised circuit board: MAIN408A
TO FIG 3 "A"
R30 1740
5
6
U5 OPA2227
TO FIG 3 "B"
R31 1740
3
2
+
-
+
-
+6V
8
4
-6V
7
1
H12 P12
1
2
FROM FIG 3 "C"
H9 - 2
S4
H9 - 7
FROM FIG 3 "D"
R32 49R9
R33 49R9
H9 P9
1
3 - 4
6 - 5
8
CASE
J3
J4
J5
LEFT OUT
RIGHT OUT

FROM FIG 2 "A"
C32
2200pF
R38 15.4K
5
+
C33
680 pF
6
-
FROM FIG 2 "B"
C36
2200pF
R41 15.4K
C37
680 pF
10
9
+
-
Fig. 3 -- Output lowpass filters, revised circuit board: MAIN408A
7
8
+6V
C34
3300pF
R39 2870 R40 19.6K
C35
220 pF
3
1
2
+
-
U4 OPA4227 Quad opamp
Dual 4-pole Butterworth lowpass, fc = 25 kHz
C38
3300pF
R42 2870 R43 19.6K
C39
220 pF
12
13
+
-
-6V
4
14
11
C40
100 nF
C41
100 nF
C44
100 nF
TO FIG 2 "C"
TO FIG 2 "D"
C42
470uF
+
C43
100 nF

+24 VDC
IN
J7
CAST
ALUMINUM
SHIELD
HAMMOND
TYPE 1590A
+
C50
2200uF
78L06
TOP
IN
COM
OUT
R52 1240
U6
R50
604
+
C51
1000uF
C52
100nF
78L06
+
C53
1000uF
C54
100nF
R51
604
+
C55
1000uF
C56
100nF
U7
79L06
+
C57
1000uF
C58
100nF
COM
IN
OUT
79L06
TOP
Fig. 4 -- Model 408A phono preamplifier power supply
P10
H10 H11 P11
TO LED
+6VDC
COMMON
-6VDC
D1

Parts List
Model 408A Stereo Phono Preamplifier
QUANTITY REFERENCE VALUE DESCRIPTION MANUFACTURER
MAIN408A.PCB
2 R1, R13 47K 1%, 1/4 w, metal film
4 R2, R5, R14, R17 10K 1%, 1/4 w, metal film
4 R3, R10, R15, R22 6490 1%, 1/4 w, metal film
4 R3A, R10A, R15A,
R22A 1800 1%, 1/4 w, metal film
4 R3B, R10B, R15B,
R22B 4020 1%, 1/4 w, metal film
4 R4, R11, R16, R23 200K 1%, 1/4 w, metal film
2 R6, R18 2490 1%, 1/4 w, metal film
2 R7, R19 2000 1%, 1/4 w, metal film
2 R8, R20 1430 1%, 1/4 w, metal film
2 R9, R21 1100 1%, 1/4 w, metal film
2 R12, R24 1000 1%, 1/4 w, metal film
2 R25, R27 120K 1%, 1/4 w, metal film
2 R26, R28 160K 1%, 1/4 w, metal film
2 R30, R31 1740 1%, 1/4 w, metal film
2 R32, R33 49R9 1%, 1/4 w, metal film
2 R34, R35 715 1%, 1/4 w, metal film
2 R36, R37 4990 1%, 1/4 w, metal film
2 R38, R41 15K4 1%, 1/4 w, metal film
2 R39, R42 2870 1%, 1/4 w, metal film
2 R40, R43 19K6 1%, 1/4 w, metal film
2 C1, C42 470 uF 16 V, radial electrolytic
12 C2, C7, C8, C25,
C26, C27, C28,
C31, C40, C41,
C43, C44 100 nF 5%, 50 V, polyester film
2 C3, C14 255 nF 5%, 50 V, polyester film
2 C4, C15 265 nF 5%, 50 V, polyester film
2 C5, C16 279 nF 5%, 50 V, polyester film
2 C6, C17 286 nF 5%, 50 V, polyester film
2 C9, C18 25 nF 5%, 50 V, polyester film
2 C10, C19 37 nF 5%, 50 V, polyester film
2 C11, C20 64 nF 5%, 50 V, polyester film
2 C12, C21 78 nF 5%, 50 V, polyester film
2 C13, C22 100 nF 5%, 50 V, polyester film
2 C23, C24 1 uF 5%, 50 V, polyester film
2 C29, C30 297 nF 5%, 50 V, polyester film
2 C32, C36 2200 pF 5%, 50 V, polyester film
2 C33, C37 680 pF 5%, 50 V, polyester film
2 C34, C38 3300 pF 5%, 50 V, polyester film
2 C35, C39 220 pF 5%, 50 V, COG (NPO) ceramic

4 U1, U2, U3, U5 OPA2227PA Dual opamp, 8-pin DIP
1 U4 OPA4227PA Quad opamp, 14-pin DIP
2 H1, H8 3-pin male header Molex 22-03-2031
4 H2, H3, H4, H5 7-pin male header Molex 22-03-2071
1 H6 5-pin male header Molex 22-03-2051
3 H7, H11, H12 2-pin male header Molex 22-03-2021
1 H9 8-pin male header Molex 22-03-2081
1 H10 4-pin male header Molex 22-03-2041
2 P1, P8 3-pin shell Molex 22-01-2037
4 P2, P3, P4, P5 7-pin shell Molex 22-01-2077
1 P6 5-pin shell Molex 22-01-2057
3 P7, P11, P12 2-pin shell Molex 22-01-2027
1 P9 8-pin shell Molex 22-01-2087
1 P10 4-pin shell Molex 22-01-2047
57 Terminal pins for Molex shells Molex 08-50-0114
4 JB1 - JB4 3-position jumper block with jumper
PWR432.PCB
2 R50, R51 604 1%, ½ w, metal film
1 R52 1240 1%, ½ w, metal film
1 C50 2200 uF 35 V, radial electrolytic
4 C51, C53, C55, C57 1000 uF 16 V, radial electrolytic
4 C52, C54, C56, C58 100 nF 5%, 50 V, polyester film
1 U6 78L06 +6 volt regulator
1 U7 79L06 -6 volt regulator
ENCLOSURE MOUNTED PARTS
1 D1 Red LED Power-on indicator Lumax SSI-LXR1612ID
(DigiKey 67-1147)
2 J1, J3 RCA, panel mount RCA connector, black Mouser 161-1052
2 J2, J4 RCA, panel mount RCA connector, red Mouser 161-1053
1 J5 Stereo phone jack, 1/4 inch
1 J6 5-way binding post, blue
1 J7 2.5 mm male, insulated, panel mount,
power input connector
Mouser 163-4303-EX
1 R29 5000 Dual audio taper Volume Control Mouser 313-2420F-5K
2 S1, S2 Rotary switch, 2-pole, 6-positions Mouser
105-SR2511F-26S
2 S3, S4 DPDT miniature toggle switch
1 Cast aluminum enclosure MPJA type 16292-BX

1 Cast aluminum enclosure Hammond type 1590A
4 Stick-on rubber bumpers DigiKey SJ5523-0
2 Knob for S1, S2
Misc hardware, wire and shrink tubing
1 Wall DC power supply,
24 VDC at 100 mA or higher Various manufacturers