Sound City Schematics

Please note that some of the following schematics are PDF files and others are JPEG files. Print quality might be affected accordingly. Also, some links are external, so if anything is broken, please let me know.

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Model "One Hundred" (Lead 105; Mark 1) Schematics

• Lead 105 Preamp (courtesy of Chris M. and Mark H.)

L/B100 (Mark 3) Schematics

• L/B100 (Mark 3) (not so clean)
• L/B100 (Mark 3) (very clean)

L/B200 (Mark 3) Schematics

• L/B 200 (large schematic, left side)
• L/B 200 (large schematic, right side)

50 Plus (Mark 4) Schematics

• L/B50 Plus (Dallas Arbiter)
• L/B50 Plus (Dallas Arbiter)
• L/B50 Plus (DMI) (huge schematic, left side)
• L/B50 Plus (DMI) (huge schematic, right side)
• L/B50 Plus Tube Layout Diagram 1
• L/B50 Plus Tube Layout Diagram 2 (w/ the ECC81 between the EL34s)

L/B120 (Mark 4) Schematics

• L/B120
• L/B120 (huge schematic)
• L/B120 (w/Mods) (copyright, Satamax, et al.)
• L/B120 Tube Layout Diagram

Please Note: In the following two transformer wiring diagrams, orange wires are indicated. According to some users, however, these wires might be a sort of tan or light brown; therefore, please use caution and apply common sense when referring to the following two transformer wiring diagrams.

• L/B 120 Partridge Output Transformer Wiring Diagram
  This wiring diagram was courtesy of Doug Stalters of Vintone Circuits.
• L/B 120 Partridge Power (Mains) Transformer Wiring Diagram
  This wiring diagram was also courtesy of Doug Stalters.
• L/B 120 Noise Reduction Mod
  Caution: The preceding mod was performed on my SC 120 and SC 200 Plus, and it works well, but I want to stress that you should use caution working on your amp. Here is what the tech who performed this mod had to say about it...

"Rest assured that the circuit [shown in the preceding schematic] is correctly installed. The center tap has been disconnected. That's what the schematic shows, and this was done instead of connecting the two 100-Ohm resistors to ground, as is done in numerous designs. The center tap is connected to a DC voltage. (See the 50V designation?) This effectively raises the AC heater supply above the noise floor (0 volts). Simple, effective and cheap. I use this on all my amps."

L/B200 Plus (Mark 4) Schematics

• L/B 200 Plus (Mark 4)
• L/B 200 Plus (Mark 4) Tube Layout Diagram

SMF Tour Series (DMI) Schematics

• SMF Tour Series 1
• SMF Tour Series 2
• SMF Tour Series 3

Bass 150 (DMI) Schematics

• Bass 150 (DMI)
• Bass 150 (DMI)
• Bass 150 (DMI) (large schematic, left side)
• Bass 150 (DMI) (large schematic, right side)
• Bass 150 (DMI) Tube Layout Diagram

Miscellaneous Schematics

• Reverb Circuit, All Models (large schematic)
• Reverb Interface Circuit (allows the use of an Accutronics reverb tank: overlay it on the schematic above)
• Concord Combo ("Lead" model)
• Concord Combo Tube Layout Diagram ("Lead" model)
• PA 200 R (DMI)
  Here's a real odd one for you... four KT88s and a solid-state preamp!
• Miscellaneous SC Schematics for Sale (external link that has no affiliation with the SC site; $$$)

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