Can I connect 1/8" modules to 1/4"
modules
and can I connect them both to banana plug modules?
YES!
Background:
In this article three terms will be used interchangeably in this
article.
'Ground' = '0Volts' = 'Shield'.
For the purposes of this topic it is safe to assume that all three
terms are synonymous.
 1/8" (3.55mm) and 1/4" connectors are
2-CONDUCTOR types.
The center conductor (tip) carries the SIGNAL
The other conductor (sleeve) carries GROUND
The Ground conductor does two jobs:
-it connects the ground from the power supply of the device at one end
of the cable to the ground of the power supply at the other end of the
cable.
-it SHIELDS the signal from interference that may be in the environment
around the cable. At the level of signal on most analog synths, this
shielding function is rarely necessary because the signal is many
hundreds of times stronger than any airwave interference
If the cable is connecting two jacks that SHARE a power supply (ie 2
jacks on the same device) then the ground connection serves no
transmission purpose whatsoever other than it's rather superfluous
shielding function.
(The ONLY difference between a 1/8" and 1/4" connector is physical
size. You can chop a 1/8" end off one side of a cable and solder-on a
1/4" and it will work perfectly)
Enter the BANANA plug!
Banana cables are ONE conductor, SIGNAL only cables. They dispense with
the Ground/Shield conductor andconnect only the SIGNAL conductor. Per
the above, AS LONG AS YOU ARE CONNECTING JACKS THAT SHARE A POWER
SUPPLY. This signal-only scheme works exactly the same as the shielded
(1/8-1/4)scheme, because only the connection of the signal conductor is
actively doing anything.
The only problem arises when you connect a signal-only cable between
jacks that are on two different devices that have ELECTRICALLY SEPARATE
power supplies.
So, what are we losing when we lose the
Ground?
A signal is a RELATIONSHIP. It can only do it's job if it knows where
it's 'Ground' is.
Ground is a REFERENCE.
1 Volt is only 1 Volt if the machine knows where 0 Volts is.
9 Volts is only 9 Volts if the machine can tell that it's 9 times
higher than 1 Volt was from that previously mentioned 0 Volts.
With a two-conductor (1/8,1/4) cable, the cable carries it's own 0-volt
reference to each end. When you connect (ie) a 1/8" cable from a Blact
VCO to an Arp 2600 you are , in addition to connecting the signals,
connecting the 0-Volt Ground of the Blacet power supply to the 0-volt
Ground of the Arp power supply. As soon as that jack is plugged-in, the
two power supplies instantly 'Agree' on where 0-Volts is.
Now here's where it gets subtle...
If you plug another 1/8" cable in between the Blacet and the Arp, you
import another signal but you also REPEAT the Ground/0-Volt connection
of the power supplies. This is VERY redundant and inefficient from a
pure engineering standpoint.
Only ONE conductor need connect the Ground/0V of one power supply to
another. Once that connection is made, both power supplies are using
the same reference and then you only need ONE conductor to carry
signals back and forth.
So...
if you connect ONE wire among the Ground connections of ALL the power
supplies in your rig (and thus, ALL of your power supplies agree on
where 0 Volts is) then you can use a cable with (ie) an 1/8"
two-conductor plug on one end and a single-conductor banana on the
other. You can just leave the shield Unconnected (and insulated) on the
banana end. This hybrid connection can be accomplished with special
patch bays and mults too. But such simple (mostly empty) passive
devices are not NECESSARY for the translation.
There is no reason why 1/4, 1/8 and banana systems can't be
interconnected easily and with no issues whatsoever.
The secret is to connect the grounds of
ALL your power supplies together.
written at Mabuse Manor in 2008 by doc
drmabuce
at
yahoo.com
An illustration of some common analog
synthesizer DC power distribution systems and the location of Ground
plus common symbols for Ground if you are comfortable reading schematics
PS:
Did you find the mistakes in this
article?
Good for you!
Here's a parable:
I have read many times in a well known Electronic Music Magazine that
one should NEVER disconnect the ground (third) pin from an AC power
cord even if it does break a ground loop and stop an audible AC hum in
a critical audio path. The magazine is exactly correct in taking this
position. Breaking the earth-ground path creates a serious potential
safety hazard. This is good and responsible advice.
I once attended a roadshow that was sponsored by this magazine. There
was to be a jam at this event. The band consisted of then-current
members of the magazine's editorial staff. I was connected with the
venue in which the show took place. A portable stage had been set up in
the middle of a large exhibition hall and the power to the stage was
directed through a 75-foot industrial extension cord. During soundcheck
the house signal was beset by a nasty line hum and all attempts to stop
it by the professional soundtechs on the crew failed. A half hour
before the show I was talking to one of the band-member/editors about
the line hum. It bears mentioning that this particular editor was one
of the authors whom I know had stressed the proscription against
'lifting' the ground on AC power in several of his articles. He grabbed
his setup toolbox followed the AC extension cord to its wall plug and,
without warning his colleagues that he was cutting stage power, he
pulled the plug, put a 3-to-2 pin adapter on it and plugged it back in.
Of course the line hum dropped to nearly inaudible, the soundcrew
experienced a few seconds of panic at the unexplained 'power outage'
but everybody seemed relieved that the mysterious event had killed the
hum.
The moral of this story is that there is no such thing as uncompromised
quality. The universe (and yes this DOES include the laws of physics,
Scotty!) has a thousand tricks up its sleeve and it changes the rules a
little bit every nanosecond. A quiet channel today can be noisy one
tomorrow even when YOU didn't change anything and real-deal audio
engineers are all world-class at ADAPTING.
Specifically...
It is true that there are differences in quality between shielded and
unshielded signals and it is also true that the audibility of these
difference can be significant under some conditions, in some
environments.
No scheme is perfectly quiet .... and ....while it may be absolutely
indisputably true that it is NOT raining between the drops. Somehow we
all get wet in the rain.
The principles here are practical not pedantic.
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