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Discussion Starter · #1 · (Edited)
Hi guys. I'm editing this in hopes of being more clear with my question. Which is...
If you have a source that outputs a higher voltage on its RCA's that the equipment that it is feeding accepts, what damage could potentially occur.
What solutions are there available for it?
Every article or thread I read deals with the subject of gain matching a head unit to an amplifier as if they always mate well with each other or if the pre-outs are not of a high enough voltage to drive the amp properly.
I can not find an answer, or a suitable answer, anywhere to the question of what to do if You have too much voltage.
Which in my case at least it really isn't a huge issue. I can simply limit the Head Units max volume level. But I'd like to at least know what I am doing to my equipment and SQ here, and I don't. What are the potential options to deal with this?

I have a Pioneer DEH-80PRS head unit that pre-outs a solid, very clean 5 Volts by anyones standards. I have (2) old Rockford Fosgate amps, a 60x2 and a 200x2 Trans_Ana amplifiers. (These are almost exactly like RF's DSM series of amplifiers if those are more familiar to you.) The amps "accept between150mv and 3V" according to the manuals. . This is what I am setting when I adjust my "gain level" and is the lower and upper range limit for signal input voltage if I understand correctly.

This is where I get lost a bit...
This deck has been on both of these amps before.. spoiler alert, it works. But I did have to limit the volume level to keep some type of noise out. I didn't think that it sounded like cipping per-se, as it sounded a bit different to me than clipping does. Is it over modulation perhaps?
Anyway, I can work within the constraints by limiting my maximum volume level. At least if its me on the controls.
But it ain't always me.
Is there any remedy for this?
Basically guys and gals, that's what I know.
I would just like to better understand what all is at play here. And how could I handle it better if that is even possible?
I know enough to know that it's possible. But not enough to know by what route.

Anyone feeling kind enough to clue me in?
And my apologies for the length. I have tried to describe this in a way that others could use later if any information is consolidated here that people think could be helpful.
And my apologies if this post is confusing. I've edited it some to clean it up a bit.

Many thanks to all that have chimed in so far.
Mods please feel free to scold and mod at will.
 

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Sounds like a non-issue to me. If it works there's no problem in this situation.

If it's bothering you I think the only solution is get another amp that doesn't make noise when the HU is turned up. The input section on the amp might benefit from a cleaning. I believe that if noise introduced from that small voltage compatibility difference that the amp isn't operating 100% correctly.

The HU output voltage isn't usually maxed unless the volume knob is maxed. Then there's the voltage drop from traveling down the RCA's. So yeah I doubt the HU ever of it something the amp couldn't handle in tip top shape.
 
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Sorry, missed that bit. Embarrassed to admit I'm not savvy with the features of the holy grail of pioneers, but having a few pioneers in the past, there should be source level adjustment. If so, dial those down a few clicks to get closer to 3v output.
 

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It was difficult to get the point out of your long winded question, but if I'm understanding correctly you just want to know if the 5 volt output of your head unit is going to be a problem for the 3 volt input of your amps, even if somebody else decides to take control of the volume knob. Is that it?

The 80PRS will only put out 5 volts at max volume, with test tones. Just a few notches below max volume it will be putting out much less than 5 volts because the relationship between power and SPL scales logarithmically. In addition to that, music is not a test tone, and will have much less energy than a sine wave.

If I understand your question correctly, you don't have anything to worry about. You will almost certainly never send more than 3 volts to the amp, unless the head unit is within a handful of clicks from max. The music will be uncomfortably loud at this point, and still likely well under 3 volts.

The only way someone would send more than 3 volts to the amp is if they are being very intentional about maxing out the head unit's volume.
 

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Discussion Starter · #7 ·
There is indeed a source level adjustment! That is definitely one way that I could deal with the situation. The first time I had this set-up installed I addressed it by limiting the volume level on the HU, and that does work. I am really more interested in learning just what all is at play here as anything else. I am aware of all the potential benefits of a higher source voltage such as lowering the noise floor etc. But try as I might, I just can't seem to find where anyone has ever addressed what occurs when that voltage becomes too high for an amplifiers input. Or at least not in a way that my feeble little mind can wrap around.
Thank You guys for taking the time to answer my question. I really do appreciate it!
 

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Discussion Starter · #8 ·
gijoe YES! I guess you were posting that as I was typing my last comment. Thank You very much, your answer is headed towards what I am trying to learn here.
It does answer the question as to my specific case.
But could you elaborate further on what to do in a similar situation if the two peices of gear were not as closely (un)matched as mine are for me please?
Say my head unit put out 10v and my amp only accepted 2v.
Is there a way to deal with that that I have managed to miss in my years of tinkering with car audio?
I'm not trying to be difficult, I've just never ran into this before so I'm trying to understand any potential pitfalls of this and the possible solutions for it.
 

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Discussion Starter · #9 ·
This is an article about gain overlap, which is what I've got going on. It's as good an explanation as I have ever heard and it is well worded to be easily understood. Or I think so anyway.

 

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Hook up an o-scope and see what voltage you're actually seeing at the end of your RCAs.

Make sample test tones at 0db, -3db, -10db and do some testing. Listening to music you are likely not seeing the 5v like has already been said, but it would be nice to know what voltage you are seeing at various levels.
 

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Discussion Starter · #11 ·
Hook up an o-scope and see what voltage you're actually seeing at the end of your RCAs.

Make sample test tones at 0db, -3db, -10db and do some testing. Listening to music you are likely not seeing the 5v like has already been said, but it would be nice to know what voltage you are seeing at various levels.
I agree, it would be nice to know. And that is all I am trying to accomplish here really. Just trying to learn more about the hobby. Which in turn, will allow me to learn more about some other hobbies that I have.
What I believe that I should probably learn more about first is this whole decibel thing.
There is more to those two little letters than might first be apparent I tell ya!
Like the fact that it isn't just a measurment of sound.
But I digress...
IDK, really I was just curious as to what people usually did about what is likely viewed by many to be a complete incompatibility between two pieces of equipment.
OH! and as an aside... I was looking at an owners manual for a slightly earlier Rockford amp that is rated the same 150mv to 3v only on that ones spec sheet it says that input's of up to 17v can be used... And I've yet to understand completely why it is then that they list these amplifiers max as being 3v when apparently 17 will do as well, but I'm getting there.
Thank you for your input. I believe that I will do exactly as you've suggested. Once I've done that I will report back.
 

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Discussion Starter · #12 ·
The power supply on my O-scope has **** the bed so it may be a while. I'm looking into handhelds thinking that I'll just replace it rather than try to fix it for now. But it's a heathkit that my dad built. So it'll get fixed eventually as I become more knowledgeable.
 

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He stated that he can't keep it at a specific volume because others touch it.
I have been running old rockford's with the 80prs. Simple solution is only to allow people that you know won't abuse you car-fi to drive your car.
You could also place a label that says: Max stereo volume 35.
I think the 80prs has source dependent volume right? So maybe you could limit max volume by adjusting the volume down for all your sources...?
Adjusting the eq to cut all frequencies should also limit the output voltage.
If that doesn't work maybe you could use a power resistor on the lineout??
 

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I have been running old rockford's with the 80prs. Simple solution is only to allow people that you know won't abuse you car-fi to drive your car.
You could also place a label that says: Max stereo volume 35.
I think the 80prs has source dependent volume right? So maybe you could limit max volume by adjusting the volume down for all your sources...?
Adjusting the eq to cut all frequencies should also limit the output voltage.
If that doesn't work maybe you could use a power resistor on the lineout??
You would need two resistors to make a voltage divider, an no power resistor... assuming the "lineout" is an RCA??
 

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Discussion Starter · #15 ·
I have been running old rockford's with the 80prs. Simple solution is only to allow people that you know won't abuse you car-fi to drive your car.
You could also place a label that says: Max stereo volume 35.
I think the 80prs has source dependent volume right? So maybe you could limit max volume by adjusting the volume down for all your sources...?
If that doesn't work maybe you could use a power resistor on the lineout??
Hey WinWiz thanks for your input. I too am curious about limiting it with a resister. Although my hunch is that it wouldn't be a very beneficial thing to do for the over-all sound quality? But you're right on the 80PRS beiing able to adjust source levels and that is very likely the thing to do as far as limiting the likelihood of someone else getting in and damaging something by cranking it up. I'm mostly curious as to what damage could possibly occur by NOT limiting it. Is it going to cause the same potential damages as clipping? IS it clipping? All I can relate it to in my mind is over attenuating a microphone, at least I feel like that is what's happening more or less anyway. I'm still trying to wrap my mind around what exactly is at play there..
 

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Discussion Starter · #16 ·
Yo HOLMZ! Care to elaborate on that any? It is indeed RCA connections that I am working with. What could be done using resistors and what would be the negatives of doing it?
 

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Yo HOLMZ! Care to elaborate on that any? It is indeed RCA connections that I am working with. What could be done using resistors and what would be the negatives of doing it?
  • The output impedence of most HUs, preamps, etc is 600 ohms, but could be up to 1-2k ohms.
  • The input impedence of most amps is 50k-100k ohms.

So there is no significant current flowing. Hence you would need a voltage divider to lower the RCSs voltage.

It sound more acheiable to just turn off the amp's gain pots down a touch, or have a DSP with a separate tune which has a lower output gain for all the channels.

Z1 and Z2 should probably be 2.5k to 25k... I would start with 10k for each to halve output.
 

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You could introduce a Kicker Keyloc into the chain. It has the ability to not only flatten the signal but attenuate it too. Check it out online and read the owners manual and watch a couple videos. I'm sure you could adjust it dow the output signal from the keyloc would be less than 3v's.
 

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Just use the source level adjustment. Again, you wouldn’t need to lower it by much in order to keep the output voltage low enough. You’re still worrying about a 1 in a million situation where someone is in your car and literally maxes out the head unit volume, but lowering the source level will take care of the issue.
 
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