How to measure pre-out voltage?

[scoob8000 10+ year member]

Just what the title says.

When you see a HU with 5 volt preouts, how is that measured?

I just bench tested two old headunits, and regardless of what frequency tone I play I don't get anything even close to what they are rated at.

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[jco1385 5,000+ posts]

AC volts. inner pin is +

IIRC

 

[skmfkr 5,000+ posts]

and then outer ring is neg, you will need to play like a 50hz tone and the volume at max

 

[TurdFergueson2 5,000+ posts]

Just what the title says.
When you see a HU with 5 volt preouts, how is that measured?

I just bench tested two old headunits, and regardless of what frequency tone I play I don't get anything even close to what they are rated at.

Be interested in knowing which 2 HUs

 

[skmfkr 5,000+ posts]

i know the panasonic decks ive tested were rated at 5v but only did 4v

 

[scoob8000 10+ year member]

Okay, well that's what I did. I get a bit more with a 1khz tone, but the best I've seen is about half a volt with a 60hz tone, volume up about 85% of the way.

Both are older decks (sony and pioneer). I need to go check the one in the truck.. (yes this is related to my alpine amp thread in this section)..

 

[thch 10+ year member]

keep in mind the volume scale is based on a percentage increase per tap, so "85%" might be more like 25%.

eg, if you have 50 taps, and each tap changes by 1db (12.2%), then a setting of 40/50 (80%) gives a signal of -10dB, or 31.6%. for a 5V pre-out this would be 1.56V vs the 4V expected.

while this may annoy you because you are attempting to make measurements, it does end up giving each tap a more consistent increase in volume.

other settings may also decrease the measurement, balance, fade, crossovers, pre-out level, EQ's and any other processing.

 

[scoob8000 10+ year member]

keep in mind the volume scale is based on a percentage increase per tap, so "85%" might be more like 25%.
eg, if you have 50 taps, and each tap changes by 1db (12.2%), then a setting of 40/50 (80%) gives a signal of -10dB, or 31.6%. for a 5V pre-out this would be 1.56V vs the 4V expected.

while this may annoy you because you are attempting to make measurements, it does end up giving each tap a more consistent increase in volume.

That makes sense I guess. I guess it's pretty normal then, by the time you venture into the area of distortion on the deck your finally getting near the rated RCA voltage..