From the forever wonderful Kitrae Big Muff Site:

Circa 1977-1978 (Pots typically date as early as 1976 and as late as 1979)

Model Number: EH3003

Circuit Designer: Bob Myer with Mike Matthews

Circuit Variants: Approximately 10

Edition Versions: 3 - First edition with no AC marked on front, and second edition with AC adaptor jack added, 3rd edition with TONE BYPASS added. Some first editions have no AC power jack.

True Bypass: No

Power: Current draw approximately 3 mA. 9V battery or AC power adaptor jack. Jack is 1/8" (3.5mm) plug tip positive. See POWER section below for important adaptor and daisy chaining power requirements.

Around 1977 the graphics changed to the now iconic, bold red and black design that the Big Muff is most associated with. This version 3 of the Big Muff also gained an AC power adaptor jack, a first for the Big Muff. There was a third edition of the V3 with a tone bypass switch added that was made simulaneously with the V4 and V5 op-amp Big Muffs. Externally it looked idetical to the version 6, but internally it had the same circuit board as the V3, and the same offset pots, making the knobs all have different zero points. Though the new V3 graphics were first advertised in late 1976, I do not believe these were available until 1977. True V3 Big Muffs are somewhat rare. Note that the early V9 Big Muff is often confused with the V3 due to the fact that they have the same graphics and knobs, but the V3 never had an LED or battery door on the bottom. The list price was around $49.95, but these could be found for $32 or less.

GRAPHICS - The graphics on the front of the box changed radically to a red and black design with huge red Big Muff letters in a blocky font (ITC Pioneer). This graphic was so popular that it remained on all subsequent USA made Big Muffs, including the Big Muffs reissued in 2000, and others that followed. Red and black colors just seem to go together well, especially in simple but dominant designs. Throughout history these colors have made lasting symbols, from the flags and emblems of Third Reich in World War II to the iconic Coca-Cola logo, and now the Big Muff Pi. Most of the Version 3 Muffs have the letters "AC" printed on the front face, above the new power jack, but the very early production V3 Muffs did not have the AC or power jack. Third edition V3's replaced the ON/OFF graphics with the words TONE BYPASS. There was a rare color variant, likely a mistake when making the silk screens, where the lines above and below the Big Muff logo, normally red, were printed in black.

CONTROLS / KNOBS - The on/off switch from previous versions continued to be on the back of the V3. The foot switch is a Carling SPDT. Pots had plastic D shafts, as on previous Muffs. Almost all V3 Muffs used the same black plastic Daka-Ware style knobs that were introduced on the V2 Big Muff. Some V3 third (tone bypass switch) editions were made with the new black plastic "hockey puck" shaped knobs. After years of using knobs from other suppliers, E-H decided to invest tooling money to make these puck knobs, injection molded in Taiwan. Similar knobs are still used on the V9 NYC reissue versions being produced since 2001, and many other E-H pedals. Some examples may be seen with different or after market replacement knobs. As on all previous Muffs, none of the three control knobs start at zero in the same place. On the TONE knob, treble was to the right and bass to the left. This is due to the potentiometers (pots) being mounted to the circuit board with the leads wrapping over the edges of the board - one over the left side, one over the top, and one over the right side. A third edition of the V3 was produced around 1978-79 with the on/off switch changed to a Tone Bypass switch. This appears to have been in production at the same time the tone bypass V5 op-amp Big Muff was, and prior to the V6 tone bypass transistor Big Muffs. Switching the bypass on disabled the tone circuit. The tone knob had no effect when in bypass mode.

CIRCUIT - All V3 circuit boards were marked with the number 3003 and a stylized “EH” symbol, with an identical circuit trace pattern to the V2. The component values, while much more consistent than V1 and V2 Big Muffs, varied slightly from unit to unit, with at least six variants being identified.

Some of the very first V3 Big Muffs made have exactly the same circuit as the last V2 Big Muffs, with no power jack or power filtering components, typically useed PNP BC239C (TO92 package) transistors, white box caps, and mostly large carbon comp reisistors. Those first edition V3 Muffs can be identified because they lack the letters "AC" on the front face, and are essentially Ram's Head production Big Muffs with different graphics.

V3 Big Muffs were also made with NPN (negative ground) 2N5088 half cylinder shaped (TO92 package) transistors and PNP (positive ground) 2N5087, NPN MPSA18, and possibly others. Around 1978 a Tone Bypass was added in place of the power switch. Most of those have MPSA18 transistors.

There is an additional resistor and a large capacitor added for the AC power section, not found on the V2.

Some V3 circuits are seen with ceramic or polymer caps, but most are box shaped polyester film and barrel shaped electrolytic type caps. A few V3 Muffs have been seen with 'tropical fish' tone caps. The rectangular shaped caps are easily identified by their multi colored bands.

Resistors were large carbon composition type mixed with smaller carbon film type in early V3s, but eventually all caps changed to the smal carbon film type.

Diodes are silicon, with blue or red cases.

Circuit board colors varied through the production, roughly in this order: brown, yellow, orange, white, light green, tan.

BC239 Transistors, new screws

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