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General information

Tech Talk

Hard-to-find info, schematics


Was Sie selbst tun können (deutsch)


Was die Werkstatt für Sie tun kann (deutsch)

Hard-to-find information

AO-28 overall frequency response (Excel spreadsheet). Frequency generator attached with voltage divider 1kOhm/18 Ohm to drawbar 1' on pos. 8, others set to 0. See spreadsheet for details. This frequency response does not consider the manual tapering found on consoles (see below). Since signal is injected directly into the drawbars, it represents the organ amplifiers overall frequency response. Nice if you want to modify your spinet to a B3-like sound.


Manual tapering Scheme (PDF document) for console and spinett organs.Useful for tapering your spinett or replacing those resistor wires. Click picture to enlarge.

Old organ frequency response curve, made for Hammond technicians in the late 40ies.Click picture to enlarge.

Kon's TG calibration data, a valuable spreadsheet collection of new and old TG data, made by my friend Kon Zissis. For MS Excel. Here is a sample:


Check my schematics download section for circuit drawings. Captain Foldback's Hammond & Leslie Page also is a good source for Hammond/Leslie schematics and service manuals. Also try the HammondWiki.

If you understand german, read also here: Was Sie selbst tun können.