This is a super rare 1930s era K300 amp from Sound Projects of Chicago, (later known as LectroLab).  Rescued from eBay and restored to its vintage glory

The amp is very warm and round sounding, great for Jazz or Blues, and puts out around 10-11Watts through vintage big bottle 6L6Gs (NOT modern 6L6GCs!)

I spent weeks researching this amp circuit and then reverse engineering the schematic based on similar models from the era.  This is the ONLY example of the K300 that I could find, but I am 99% sure that the circuit design is correct.

Here are the circuit details:

Pre-amp and phase inverter: 2 - 6C8B (1 Ken-Rad, 1 GE)

Power Tubes: 6L6Gs - (1 Ken-Rad, 1 Sylvania)

Rectifier Tube: 5Z3 (Sylvania)

It features a vintage 10" AlNiCo 8ohm speaker, 3 inputs (1 low and 2 high), a power/volume knob and vintage tone for days.

I am including the "before" pictures so you can see where this started and here is the list of the work done on the amp:

  • Convert to 3-prong power cord
  • Added 1.5Amp fuse (inside the chassis so that I didn't drill an extra hole)
  • Tested and replace all capaciters (not a single one was close to the original specs - Replaced with F&T and Orange Drop)
  • Tested all resisters and replaced as needed.
  • Cleaned potentiometer.
  • Stripped, repaired and recovered Cabinet.
  • Replace damaged grill cloth.
  • Replaced broken handle.
  • Replaced broken feet.
  • Replaced 1 power tube with NOS Ken-Rad.

I did NOT alter the circuit in any way beyond the fuse and power cable, so this still looks, feels and SOUNDS as vintage as you will find and I would stack it up against pre-war Gibson amps for tone and feel.

As with all amps of this age and design, there is some  noise when you crank the volume all the way up, but it sounds fantastic with both humbuckers (my 1962 ES-335) and single coils (G&L ASAT [tele] with Charlie Christian bridge.)

I will include an extra pre-amp tube and the schematic that I created for the amp.

Happy to answer any questions I can.

This item is sold As-Described

This item is sold As-Described and cannot be returned unless it arrives in a condition different from how it was described or photographed. Items must be returned in original, as-shipped condition with all original packaging.Learn More.

Listed3 months ago
ConditionExcellent (Used)
Excellent items are almost entirely free from blemishes and other visual defects and have been played or used with the utmost care.learn more
  • Sound Project / Lectrolab
  • K300
  • Brown Leatherette
  • 1930's
Made In
  • United States

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Henry Custom

Reseda, CA, United States
Joined Reverb:2020

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