Re: 147 hum, XB-2 1147 pre-amp.

[Ted Thompson <tthompsn@mail.bcpl.lib.md.us>]

Ian Jackson wrote:
> 
> I connect my XB-2 to a Leslie 147 via a line-out to a Leslie connector box
> (one 5pin, one 6pin socket, side-by side, + sockets for Leslie chorale/trem
> switch and reverb channel). I don't use a pre-amp.
> 
> With the 147 impedence selector switch in the 'open' or '16ohm' position, I
> get loud hum from the Leslie that can only be cured by lifting the ground
> on the XB-2 (the 147 is already ungrounded...).
> 
> With the impedence switch in the central '8ohm' position, there is no hum,
> but then the Leslie volume is really low.
> 
> The obvious answer is probably to get a pre-amp, but:
> 
> Is the 1147 pre-amp kit available in a UK configuration (i.e. 240V mains
> supply), or can the 110V version be adapted?
> 
> Why does the 16ohm or 'open' setting on the 147 amp give loud hum? There is
> obviously a grounding problem, but why should this occur with the switch
> set to '16ohms' or 'open', and NOT when set to '8ohms'?
> 
> Is there a workaround, to give the high Leslie output level of 16ohm or
> open setting, but with no hum?
> 
> Any other suggestions for 240V-compatible pre-amps/configurations?
> 
> Thanks in advance
> 
> Ian Jackson

Hi ya.... I am a Hammond/Leslie Tech in Maryland, USA.   Just send me the 
amp......  =-)  Just kidding.  It sound to me like you should check that 
tap switch.  Most likely the open and 16 ohm positions aren't making.  
Try grounding the ground pin, currently connected to the switch (Either 1 
or 6 I can't ever remember with out the amp in front of me.)   Just 
temporaraly take the switch out of the circuit.  And you may need a cable 
(Leslie cable that is) that has a shielded conductor for the audioline.  
Lemme know if this works or if not what happens when you try it, and I'll 
try and help more if needed.

Good luck,
Ted Thompson
Maryland Organ Service