re: Leslie Speed Change Noise

[random@well.sf.ca.us (Ben "Jacobs")]

Colin Spence:
>My Leslie 145 sometimes produces a "pop" or "snap" in the audio when changed
>to fast speed.  This is not someting that you would ever notice in a live
>mix, but I find it irritating at home.  The problem is variable and does not

Bradley Baker:
>I believe this may be characteristic of the unbalanced series of
>Leslies. The relay is switched with 115VAC. Depending on the line
>phase at the switching point a big transient can be coupled in to the
>unbalanced input signal. My 145 does it too. My 122-like model does
>not (non-stock switching). A couple of fixes come to mind, though i
>haven't settled on something i like yet. I want to fix this too but
>i'm not to anxious to hack up my stock 145 amplifier yet.

I experienced the same problem for awhile, on my 22H amp (in a 145/7
cabinet).  This is a balanced amp, I believe (six-pin connector).  My tech
was able to eliminate the problem by changing ONE capacitor.  Not too bad
of a hack (except to my wallet: $7 for the part, ouch).

Actually, the problem still does occur in some settings.  In particular,
speed changes on the Leslie often induce pops out of other amplifiers
placed nearby.  Physically separating the Leslie from the (over)sensitive
gear seems to help.

Anyhow, next time I have my tech looking at the amp, I'll try to find out
exactly what his trick is...  While not too serious in live rock
situations, this noise is indeed a BIG problem when recording... it can
really ruin that nice song ending...

- ben "jacobs" -- random@well.sf.ca.us
- (POB 2236, San Anselmo, CA 94979, USA)