Phono And Line Switch In Turntable

[marknewwood]

Hello guys, I am Mark.

I have recently entered the vinyl world and bought my first turntable - AT-LP120-USB. The setup is done by the technician from whom I bought this turntable and everything is working smoothly.

But, recently, I noticed a switch behind the body that says Phono and line. Currently, it is set to Phono.

I tried switching it to Line and my speakers started outputting a weird sound.

Can anyone please help me understand these?

[hFx]

As of old turntables outputs a quite weak signal and the amplifiers had a special phono input for turntables, with higher gain and some filtering (RIAA). As turntables went almost extinct those special inputs disappeared on some equipment, but line inputs that require higher inputs remained (from CD n cassette tapes).

Modern turntables often come with an internal amplifier to provide modern amplifiers with line level signals, so when you switch to "line" on your turntable, the signal is much stronger than your amplifier's phono input can handle, resulting in noise, hum and distortion.

[Rarebird]

More or less the problem I had when I got a new turntable. It was equiped with an internal amplifier, so I should connect it to a line-input, which was already in use for my instrument-mixer. So it had to be changed for another turntable, without build-in amplifier.

[alexclark4234]

Hi Mark,

The phono and line switch represent that your turntable has an in-built phono preamp. And, if it is switched to the "Phono" then it means you are either using an external phono preamp or you might be using phono input of stereo receiver or powered speakers.

Talking about the switch, the phono means that the turntable's in-built phono preamp is not engaged and the line means that the turntable's in-built phono preamp is engaged.

As you have explained switching it to Line causes speakers to output bad sound which means that when you switch it to Line, the turntable's in-built phono preamp is engaged, and as your setup already has a phono preamp included so this small tweak results in over-amplification of the phono signals which results in sound distortion.

The phono and line concept is a little confusing so I recommend you check out this article where this concept is explained in simple words: https://turntablewave.com/phono-vs-l...record-player/

I recommend you use the phono preamp only once in your setup. If you want to test things out then you can switch the PHONO/LINE switch to the line and transmit the turntable's output to line level input of the receiver or speakers, you will hear good quality sound from your speakers.

If you have any questions then you can always reply to this thread.

[3LockBox]

There are a couple of videos on YT suggesting the built-in preamp in some TTs are bare-minimum cheap and induce noise on the signal, even when you are bypassing the built-in preamp. Said videos also include a tutorial on how to electrically remove the preamp circuit to eliminate the problem.