On the Bench: Restored Webcor All-Tube Amp

NOS Output Transformers, replaced Certain Capacitors, and NOS Tubes. (cheapo tester speakers in pic).

Webcor was known for their fairly complicated Tube amps with interesting topologies. This is a stereo version of the Webcor 4905.

This is a Stereo Push-Pull Amp. It uses a 5Y4 rectifier tube, 12AU7/12AX7/noval signal splitters, and 2x 12AB5 per channel that do the Push/Pull. The total output is about 8.2W/Channel. Remember that these are “old watts” so it really performs like amps with 3-4x’s the rated RMS wattage. It was full of nice Allen Bradly resistors that haven’t drifted almost 45 years later!

I have already started the modifications after getting it back in working order. There is a headphone output, potentiometer, and better power cable being added as we speak. From there, I have some really nice capacitors that will be put in the 4 spots in the signal path to each of the 12AB5’s and hidden Nippon Chemicon Negative Black caps for the power section to replace the old electrolytic 3-in-one.

Here is some info on the 12AB5 courtesy of Pete Millett’s website: http://www.pmillett.com/tubebooks/tubedata/hb-3/receiving_tubes_part_2/12AB5.PDF

Let me know if you would like to see anything else done to it (other than a re-case – which will happen!).