4Volts pre out... where are they?

[Crazy 8s Drums]

23 minutes ago, movepage said:

Hi Crazy 8s Drum,

Thanks for the tip, will take me some time to do it, and I will rerout the RCA’s to the drive side and pass them below the drivers seat. However i don’t have much option when getting all the cables in the trunk.

Changing the rout of the cables, will reduce any unwanted noise, but still does not explain the big power drop I am getting - unless it s normal. I am getting more than 50% loss just on wire resistance.

On your system, at the point of connection to the amp, do you read 2Volts or less?

Thanks in advance

Movepage

 

I would leave your cables routed as they are for now.  The RF RCAs are shielded so it should be OK.  I wouldn't worry about the voltage drop you measured either.  The gains on the amplifier are there to compensate for voltage variances.  When you get everything playing, you can then fine tune everything and see if anything is lacking.  Being detail oriented is great, but don't overthink it! 

[Kyblack76]

Here's a thought. Use your dmm,  right at the HU,....rule put the rcas, or not. (Doubt that's your issue)

Then report back. 

[WalledSonic]

Voltage drop should be almost negligible, like a few thousandths of a volt at 5Vac. Something is wrong. Check resistance of each rca. Wiggle the wire when you do that to find if you have a break or something somewhere. Check your connections too. Its usually the simple stuff. 

[WalledSonic]

2 hours ago, Crazy 8s Drums said:

I would leave your cables routed as they are for now.  The RF RCAs are shielded so it should be OK.  I wouldn't worry about the voltage drop you measured either.  The gains on the amplifier are there to compensate for voltage variances.  When you get everything playing, you can then fine tune everything and see if anything is lacking.  Being detail oriented is great, but don't overthink it! 

50% voltage drop is unacceptable in any electric application.

That could be caused by a bad connection... that could end up spiking your amp, causing it to go into protect. This happened to me 6 wks ago. Thought i blew the amp. But was just a bad connection at the bass knob rca.

Or could be sign of a different problem that should be addressed. 

[Jessica]

5 minutes ago, WalledSonic said:

Voltage drop should be almost negligible, like a few thousandths of a volt at 5Vac. Something is wrong. Check resistance of each rca. Wiggle the wire when you do that to find if you have a break or something somewhere. Check your connections too. Its usually the simple stuff. 

first thought i had as well, AC voltage should have almost no noticeable drop over 20ft of wire unless there is something else wrong

[Crazy 8s Drums]

My suspicion was an incorrect measurement.

[AlpineNut]

6 hours ago, WalledSonic said:

Voltage drop should be almost negligible, like a few thousandths of a volt at 5Vac. Something is wrong. Check resistance of each rca. Wiggle the wire when you do that to find if you have a break or something somewhere. Check your connections too. Its usually the simple stuff. 

I was thinking the same thing, the RCA's seem to be off some place.

[movepage]

Hi,

Ok, got a possible explanaton for the difference in value, so my 5.2 Volts value where measured using a oscilloscope , and at this stage I am doing a peak measurement.

On the other hand the 2.5 measurement was done using a voltmeter which give you a average amplitude of the waveform over a wave cycle. For a wave like 40HZ or 1KHz the average value is approximately 0.637 of the peak value.

So, the formula should be something like:

(peak amplitude in volts) * 0.637 = multimeter reading (approximated value)

So the calculations are:

5,2Volts * 0.637 = 3.3124Volts ( multimeter value)

Currently my multimeter reading was 2.5V, that’s about 0,81 Volts down from avrage value. Although is still about 1Volt down, I guess at this stage I would need to take in to account that I will have a small cable loss on the RCAs , plus the quality of the measurments I took, to explain the 1Volt difference.

Hope this helps

Movepage

[WalledSonic]

Use the same tool to measure the voltage output from the head unit, then measure at teh end of the RCA.  

If you have a major difference still, measure the resistance in teh RCA alone.  

That *should* tell you everything you need to know.

[Kyblack76]

On 5/26/2018 at 10:18 AM, Kyblack76 said:

Here's a thought. Use your dmm,  right at the HU,....rule put the rcas, or not. (Doubt that's your issue)

Then report back.