Muso terminology query

[N Cook]

Just replaced , with metal bushed one, the broken original plastic 1/4 inch
domestic amp headphone socket used on guitar input, of a made year 2003
,Fender Bass combo.
Could someone tell me what the 2 terms
Mid Scoop and Ground Lift mean , both switchable functions from the front
panel.

 

[mwpmorris]

Mid scoop is an EQ function - "to scoop out" a load of the mid-range
frequencies. Ground lift is something to do with isolating the earth of
the device from the electrical supply earth - I think it's acheived
with a transformer. Ground lift is commonly seen on DI (Direct
Injection) boxes to eliminate mains hum.

 

[niftydog]

Could someone tell me what the 2 terms

Mid Scoop and Ground Lift mean , both switchable functions from the front
panel.

Mid scoop = smiley face eq curve. Basically, attenuating a big chunk of
midrange.

Ground lift is to do with the DI output which is often used to connect
amps to mixing desks. The earth lift disconnects the XLRs ground pin
(pin 1) so that the amps signal ground is not directly connected to the
mixing desks signal ground - this can help eliminate ground loops (which
can cause audible hum.)

It does not compromise the "safety" ground (or mains earth) and the amp
remains referenced to ground at all times.

Transformers are not used in this context, but the balanced signal
present at a DI output can be created by using a "balancing transformer."

nifty

 

[N Cook]

Mid scoop = smiley face eq curve. Basically, attenuating a big chunk of
midrange.

Ground lift is to do with the DI output which is often used to connect
amps to mixing desks. The earth lift disconnects the XLRs ground pin
(pin 1) so that the amps signal ground is not directly connected to the
mixing desks signal ground - this can help eliminate ground loops (which
can cause audible hum.)

It does not compromise the "safety" ground (or mains earth) and the amp
remains referenced to ground at all times.

Transformers are not used in this context, but the balanced signal
present at a DI output can be created by using a "balancing transformer."

nifty

It would seem a style of playing by some bass guitarists benefits by cutting
out some of the mid-range frequencies.
I've come across hum loops of course but am not familiar with the tems used
in relation to DI boxes.

 

[niftydog]

I've come across hum loops of course but am not familiar with the tems used
in relation to DI boxes.

It's just the same as any other ground loop situation. Two devices that
share a common mains earth as well as having their signal grounds
connected in some way can form a ground loop. So, the ground lift
removes the signal ground connection. Worth mentioning that by doing
this it also disables phantom power to the DI - which is not needed for
DI outputs built into amplifiers any way.

nifty

 

[N Cook]

It's just the same as any other ground loop situation. Two devices that
share a common mains earth as well as having their signal grounds
connected in some way can form a ground loop. So, the ground lift
removes the signal ground connection. Worth mentioning that by doing
this it also disables phantom power to the DI - which is not needed for
DI outputs built into amplifiers any way.

nifty

I will add to my abbreviations etc file , this weekend
http://www.divdev.fsnet.co.uk/abbrev.htm

 

[Dave Plowman (News)]

Just replaced , with metal bushed one, the broken original plastic 1/4
inch domestic amp headphone socket used on guitar input, of a made year
2003 ,Fender Bass combo. Could someone tell me what the 2 terms Mid
Scoop and Ground Lift mean , both switchable functions from the front
panel.

Ground lift removes an earth connection somewhere. If it's a passive
pickup with an unbalanced output it would also remove the signal. ;-) It's
of use where there are two earth paths causing a hum loop.

Mid scoop will alter the frequency response around the 'presence'
frequencies - ie about 3-5 kHz, approx.