Feedback, Mercedes and Boogie for Beginners

[pycraft@elec.gla.ac.uk (Dr M. P. Hughes)]

There was a recent debate in which the Obie and JamBod were referred to as
a Merc. and VW bug respectively, probably by owners (/designers) of the
former ;)  Lest we forget, in the history of looping people have used EH
16sec delays, DOD pds series, a tape recorder with the tape wound around
distant chairs...!
Let's be fair; the JM is pretty solid peice of work.  If we're going for
car analogies, then the Obie is probably a Merc (E or S series) - high
prestige, and filled with gadgets that the owners insist they could never
live without - air cond, power steering.  The Lex is an Audi, BMW 3-series
or Volvo - a quality, refined dirving experience which will get you from A
to B in style, if not necessarily pampered.  Finally, the boomerang is an
off-roader - fun to drive, not necessarily the smoothest ride, but with a
growing cult status.  Even if it can't do the things the others can, there
are places it can go that leave the others behind.  After that, leave Zoom,
Dod etc to fight it out for Ford.. :)

John Ott described his setup::
>Yep,  Digitech RP-6 (cabinette simulator) -> Mackie (with JamMan in
>effect loop)  -> main PA or recording.
>The draw back with this setup is generating feedback, so I send a aux
>out to a fender amp for use as a monitor and to generate and control 
>feedback.
> 

Now, this is something which concerns me greatly - what governs feedback? 
I had a Lab Series L9 until recently which, despite pushing 120 watts into
a 15" speaker, was nigh on impossble to feed back.  However, the Boogie
Subway Blues will do it with the volume on 5, with reverb and mid all the
way up (my fave tone). 

I love getting feedback on low-gain, big-reverb sounds (too much Peter
Green in my youth) - the kind where you can play softly and not distort, or
dig in and leave the note going forever.  I've been looking at the Trace
Elliot 3-channel hybrid preamp recently, but in the shop I couldn't get
feedback using the (onboard) digital rvb.  Is the feedback occuring due
mechanical vibration feeding back at the (spring) reverb in the Boogie?  If
so, would connecting a rackmount spring reverb in the FX loop of the Trace
give me the potential for low-volume, low-gain feedback once more?  And is
it preferable to run that through a guitar amp rather than a PA?

Finally, Kim Corbet wrote:
>>I just started learning guitar.  

And then wrote
>>...can they really achieve the variety I'm used to with a mesa boogie???

You're just starting... and you have a Boogie.  Way to go!  You've learnt
the important bit already - buy The best kit!  I take it you loop using a
JamMan..?

Michael

Dr Michael Pycraft Hughes      Bioelectronic Research Centre, Rankine Bldg,
Tel: (+44) 141 330 5979        University of Glasgow, Glasgow G12 8QQ, U.K.
    "Wha's like us?  Damn few, and they're a' deid!" - Scottish proverb