What is ‘LINE UNBAL’ on front of my Amplifier

Aubrey_Thicket

Hi all

I have picked up a cheap amplifier to go with a pair of speakers I had in the loft. This Amp is a a pulse audio PMH200. I want to play music from my laptop into this amplifier and into the speakers. However I am not sure how best to do it. On the back of the amplifier there are two phono sockets that are labelled CD/TAPE IN. Therefore I went out and bought myself a cable that has Jack on one end (that I can plug into my laptop speaker socket) and at the other end it has two red and white phono plugs. So, now I am 99% sure that this is how I should feed the laptop music into the amp. However, I would like to know what the large jack socket (LINE UNBAL) on the front is for.

Thanks all.

EssexExile

Unbalanced usually means coax instead of a twisted pair. The signal is on one wire & the other is earth rather than the signal on both wires.

googler

Your PMH200 is a Public Address System, designed for use by bands or the like, not primarily for home use.

https://www.inta-audio.com/background-music-systems-c475/active-pa-systems-c594/pulse-pmh200-kit-pa-system-pa-head-and-speakers-p6342

Each channel on the front has a balanced Mic (Microphone) input, and a matching unbalanced mono 1/4" jack input, for keyboards, possibly guitars, and other sources. It's designed to mix a number of different music sources into a pleasing whole, not primarily for playback of one source.

Definitely use the Tape in on the back of the amp, but use the Line Out or Headphone output from the laptop, not a Speaker output.

Heedtheadvice

Googler has a good bit of info there for you...........
.....but

Unbalanced usually means coax instead of a twisted pair.

posted by the Exile.........err, not quite! but very close. So worth a bit more explanation....

Balanced circuits have two signal wires that have equal impedance (in very simplistic terms 'resistance') between each signal wire and the system ground. When the two wires are run close together then any outside interference is induced about equally onto both signals and the input at the amplifier then amplifies the difference between the signals that effectively cancels out the commonly induced interference (that is on both signal wires).
It thus gives a higher quality signal rejecting interference. That is particularly of value where the signals are low level, cables are long or an environment where there is lots of interfefence around such as is often experienced with microphones. Signal levels can be microvolts to millivolts (sometimes higher still with very loud sounds).

Unbalanced signals do not have equal 'resistance' to ground. One signal wire often is ground. Interference is not induced equally and therefore is not cancelled out by the amp. Interference rejection relies just on the screening affect of screened wires. It thus gives poorer rejection of interference. That is fine where the signal level is significantly higher than any induced noise, cable runs are short or the environment is benign. Often this is for signals from guitars, other electronic musical instruments, pc outputs, tape/cd, radios etc -generally in a domestic environment or bands and cheap PA quipment. Sometimes also for microphones in non critical situations. Signal levels are in the region of hundreds of millivolts to a few volts in some circumstances which is how low millivolt or less interference can be tolerated better.

Your amp has inputs for both balanced (jack sockets or phono sockets) at that higher line level and balanced inputs (the three pin xlr sockets) that will accept microphone outputs and other lower level signals. The cd/tape inputs and outputs are also unbalanced line level.

The higher level signals are often referred to as line level. There are several standards for that level but all in the region of 300mV for consumer goods. If you want to learn more an american site (oooooh!) has quite a good explanation of things audio https://geoffthegreygeek.com/

So you have a mono amp (not stereo) that will feed two speakers, mic inputs on xlr sockets, line level signals on jacks. Your pc probably has mic and line level inputs (unbalanced) and line level (again unbalanced) output for powered pc speakers? Use the line level output to the line level inputs - mono to front panel jacks but, as you have done stereo to the cd/tape inputs (though they will be amplified as a mono signal!).

Oh and to conclude referring back to Essex's brief outline:
unbalanced (especially in consumer equipment interconnections) is often a single screened wire......but not necessarily so.
Balanced interconnects are nearly always two wires (a twisted pair) and are also screened so with those three conductors they are terminated in three pin xlr connections.