The Hammond H has a built-in connector for an external speaker and includes controls for main/echo/main+echo on the front panel. In Hammond/Leslie lingo these terms are defined as follows:
Main: activates the built-in speakers (this is the default when no external speaker is attached). There is a little switch next to the connector at the back that enables/disables the external connector feature all together…
Echo: activates the external speaker and disables the internal ones
Main+Echo: Well you’ve guest it… It activates both internal and external speakers
As I’ve written about before, my Hammond’s main/echo switches behavior has been hacked. On my Hammond the switches controls the reverb. I’ll eventually look it to that and rewire the switches to the stock behavior. I do not know if this was common or a factory mod at the time. If you do have a H Hammond and could confirm this, let me know.
The picture above shows the connector (7 pin – well 5 if you don’t count the 2 guides) and the switch that activates the connector and front panel switches.
Below are the schematics for the related circuit (click on the images to make them clearer). In the first schematic you will see the connector P304… which is our external speaker connector.
Hammond connector pins detail
|1||Channel A output|
|7||Channel B output|
Before you go further you will need to define the type of Leslie you have. Careful if you don’t use the right wiring you will blow things up.
By default, the H series Hammond is meant to be used with a special Leslie that has 2 channels + bass… model 205 or610. If that is what you have you will have to use a 008030A kit. You can find the documentation for the kit on the internet. Just install the kit between the Leslie (9pin) and the Hammond connector at the back of the organ, flip the black switch on the back and the main/echo tabs on the front of the organ. Enjoy. I’ve never tried a 610, so I have no idea how it sound, but given that it is stereo and has a bass speaker and uses 8 X 7189 tubes… It’s probably very loud.
(note: you should look for the excellent Leslie Speaker Description Chart, compiled by Harvey Olsen for details on the various Leslie models)
If you have a 122/142 Leslie (type 6H), which means the Leslie uses a balanced input, you will need to use a 008216 or 008240A or 024216 kit (they seem to be equivalent), you can find one on eBay or on the web. This sums both channels (from stereo to mono) and has a volume and tone control. I have not used this kit (I just used the metal box and plugs from the one I ordered) so I do not know how it sounds. I’ve read on the web that the vibrato/chorus circuit does not sound good when summed to mono.
In my case, I have a 225 Leslie which is in the 125/147/145 family (type 6W), this type of Leslie has an unbalanced output. So I just routed the wires as needed, using the diagram below. I only wired channel A instead of summing both channels, as I read that the vib/chorus sounds better this way.
Leslie 6W pins detail
|2||Fast/Slow Switch – Pin1|
|3||AC + Fast/slow Switch – Pin2|
|6||Signal – Chan A or Chan B|