From bjlove15@yahoo.com Wed Aug 16 10:34:05 2006
Subject:Re: Roland VR-760 outputs/schematic

UPDATE

tonysounds, John C & jake

Thanks a lot for your replies. I do have the manual but was looking to
reconcile what is printed with what my fingers felt and ears heard
when plugging into the 1/4" outputs. I did some experimenting this
morning that answered my questions. In short, the good news is the
L/MONO 1/4" output is summed mono, the bad news is the 1/4" outputs
are not balanced.

My curiosity was piqued by a recent change in my set up. I've been
playing thru a pair of first generation JBL EON 15s connected to the
VR-760 with balanced XLR cables. When feeding the FOH system (always
mono in our case) I sent a balanced feed from the loop in one of the
EONs. My monitor sound was great onstage but I was always nervous that
FOH was only getting "half the sound" - particularly on piano patches
with a fairly wide stereo spread (bass-left, treble-right). And the
pair of EONs, whether on stands, milk crates, or in their angled
position on the floor, commanded an awful lot of real estate on the
small stages our band plays on most of the time. I tried one of the
little Groove Tubes amps about a month ago - loved the sound (and the
portability!) but it just wasn't loud enough even with a small
sub-woofer. Then last week I acquired a Fender SFX 200 - same stereo
technology as the Groove Tubes amp, just bigger, uglier, heavier, but
LOUDER. Much LOUDER. The amp sounds great too. No horn "honkiness" on
the piano patches, terrific stereo imaging - particularly the Roland's
Leslie sim.

The Fender's connections are all balanced TRS. When I connected the
VR-760 with 1/4" TS cables, predictably I got a ground loop buzz.
Naturally, it disappeared if I lifted the ground off the amp or
keyboard, but I hate doing that so I connected the two with some
XLR-TRS adapters. Now I had to work out how to feed the FOH system.
The Fender has Left and Right balanced TRS line outs, but I didn't
want to take a feed from just one side since there is some special
stereo enhancement processing going on in the amp. I was set up fairly
close to the FOH board on our last gig, so I gave the sound guy an
unbalanced 1/4" TS feed from the L/MONO output of the Roland. He
seemed happy with it but I was still hinky about giving him half the
sound. So.......

This morning I performed the following experiments:

BALANCED OR UNBALANCED?
I connected the Roland & Fender together with 1/4" TRS cables. The
ground loop came back. Unbalanced. No doubt.

SUMMED MONO OR HALF-STEREO?
I ran the 1/4" outputs into a Mackie 1202 connected to my studio
monitors, called up a Rhodes patch and set the stereo ping-pong
tremolo to maximum depth, minimum rate so the sound slowly panned
fully from side to side. Next I unplugged the cable from the Right
output of the Roland. Ah-ha! No tremolo. Just an annoying little
hiccup as the effect reached the end of each cycle. Summed Mono. No doubt.

While I had everything in front of me I performed two more Mono/Stereo
experiments and learned that the balanced XLR outputs are always
stereo. Connect only the left XLR and you get full Left-only tremolo;
connect both XLRs and only the L/MONO 1/4" and you get full stereo
tremolo at the XLR destination and summed mono hiccup at the 1/4"
destination.

In conclusion, (Finally, eh? Sorry to be so long-winded, but I thought
this was information others might be able to use.)I have been giving
FOH half the sound. There are 2 ways to get a mono signal to FOH -
give them feeds from both the XLRs and center pan them at the board or
give them the 1/4" unbalanced L/MONO signal through a direct box. On
the VR-760, the balanced outs noticeably hotter than the 1/4". The
manual doesn't give the spec, but I'd be surprised if it was as much
as +4/-10. Doesn't seem like that big a difference - should easily be
able to make up the difference in the gain by turning up the volume
on the instrument or turning up the input trim at the main board. It's
really up to the sound guy; if he's going to run mono he can get a
nice clean hot signal that takes up two cable runs and two inputs on
the board or get one mono signal from a DI.

And lastly, never use stereo tremolo with a summed mono system!

bj