I have just bought a Pro-Ject Debut Carbon DC with an Ortofon 2M Red cartridge. I plan to buy a new amp and speakers later. Up until now, I've run my previous turntable through the auxiliary input on my receiver (Grundig R 120 from sometime in the nineties), and it's worked well enough, though with some limitations sound-wise.

In the manual for my new turntable, it says if not using a preamp, I should only connect it to a receiver with a phono input, which

offers correct matching and amplification for the used cartridge. Line inputs (such as CD, Tuner, Tape or Video) are not suitable.

What are the consequences of connecting the turntable to Aux, and is there any risk of damaging any part of the equipment (receiver, speakers or turntable)?

As a note, here are the relevant (to the best of my little knowledge) technical specifications for the cartridge:

Channel separation: 22 dB / 1 kHz
Output voltage: 5.5 mV
Recommended load impetance: 47 kΩ / amplifier connection – MM-input

Technical specifications for the receiver:

Load impedance: 47 kΩ
Music output: 4Ω, 2 x 45 W
Speaker impedance 4–16Ω
Input sensitivity/impedance: 180 mV / 47 kΩ
The receiver appears to have ground on an input labeled AM/loop

Also, I don't know what half of this means.

  • I think the problem would be the opposite. As turntable delivers the lowest signal, a phono input includes a pre-ampli to have a correct level. If you connect to line, line doesn't have the same level of pre-ampli so the signal will be too low. – Bebs Feb 24 '17 at 21:57
  • That is what I'm suspecting, but I know too little about these things, and need to know for sure whether it could actually damage any of the equipment (in any way, big or little). What actually happens when I make such a connection? – Canned Man Feb 25 '17 at 8:15
  • On my experience, the level will be very low, so will hear almost nothing. The opposite could be more problematic : pluggin a line signal into phono input. Check this. – Bebs Feb 25 '17 at 8:24
  • Also, you could try electronics SE or sound SE. – Bebs Feb 25 '17 at 8:24
  • 1
    Post clear pictures of the receiver, front & back - I can't find any reference to an R 120 receiver on Grundig's site or online manual sites. – Tetsujin Feb 25 '17 at 11:30
up vote 1 down vote accepted

I think the main issue won't be that it's too quiet [which it will be] but that it will sound like complete c**p without an RIAA pre-amp.

A phono pre-amp has a very specific EQ [treble & bass] curve applied, which is the opposite of that applied in the record manufacturing process. Without one, your records will sound horribly thin & tinny; to a greater degree than it would be possible to correct with the regular bass & treble controls.

Additionally, a dedicated phono pre-amp will have a switch to match to the two different types of pickup - Magnetic Cartridge - that are manufactured. These are MM (Moving Magnet) found in lower-end decks & MC (Moving Coil) in more expensive systems.

The advantage to you is that even the cheapest pre-amp will be MM-compatible, even if it isn't MC-compatible.

A separate pre-amp will then have outputs that will correctly match the inputs on your receiver.

A quick Google found pre-amps for less than 15 bucks/pounds/euros

btw, AM/loop is for an arial/antenna. Don't connect it to ground/earth.

  • So I take it from your answer that there is no risk of harm, just of really shitty sound, and that one really should buy a preamp if there is no phono input on the amp. If so, could you include that in your answer? – Canned Man Feb 25 '17 at 18:43

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