Navone NE-774V LOC test results

10/11/05

by Tom Morrow

The Navone NE-774V Line Output Converter is designed for connecting the speaker level outputs of factory head units to aftermarket audio processors and amps. I have been using it and am pleased that it doesn't seem to add any distortion. But it audibly rolls off the low frequencies, and I decided to see how much.

I tested by plugging the LOC into the speaker output of my home Harmon Kardon AVR80MkII receiver, while playing the 1/3 octave warble tones from Stereophile Test CD 2, and measuring the output voltage at the speaker terminals and at the RCA outs of the LOC in dbV with a Fluke 189 DMM.

As the chart above shows, it adds a bass peak of a few decibels at about 80Hz, and rolls off the frequencies below that at about 12 db/octave. I asked David Navone about this and he said I could get frequency response down another octave by buying and wiring in Jensen JT-11P-1 transformers to his LOC, replacing the transformers inside. Unfortunately those are expensive, at about $70 each, and one is needed for each channel.

The other thing I tested was the output level. The LOC marketing materials say it can put out a maximum of 9.5 Volts. How much would I get in actual practice? With my factory OEM amp (rated at 45 Watts per channel, driving a load of roughly 1.5 ohms) at max volume, playing track 99 from Autosound 101 CD (1kHz at 0 dbFS), I am seeing 8.22 Volts RMS on the input to the NE-774V, and 3.82V RMS on the output from the NE-774V, with the internal gain pot turned all the way up. This means that the LOC is putting out approximately half the voltage that comes in. David Navone confirmed that it has a 2:1 voltage divider, and that to get the max 9.5 volts output you would need about 20 Volts amplifier input, which is what a 50 watt into 8 ohm amplifier or a 100 watt into 4 ohm amplifier could provide.. If you are driving your LOC from an amplifier that provides lower power output, you should expect lower voltage outputs from the LOC. You can determine the theoretical output voltage of your head unit by plugging the watts and ohms into this converter. Then divide that number by two to get the expected LOC output voltage.

I would imagine the frequency response and output level issues described are not unique to this LOC, and that other passive LOCs might have similar issues to greater or lesser degrees.