Old amp meets new HU...

[pete0403]

Hello,

I've got an old JBL amp that accepts 4V Line Level inputs. If I buy a new HU with 6V Preouts and hook it into this amp, am I going to constantly be driving it into clipping? If so, are there decent line-level attenuators that I can use that won't introduce too much noise? Any ideas would be great. Thanks!!

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[themainjam 10+ year member]

there are line level "adjusters" i think squeak has the link.

but as long as you set your gain right usually you dont have a problem.....

 

[pete0403]

But would an amp that accepts 4V inputs not be fully driven by 4V at it's lowest gain setting? Then what about the 2V extra when the HU was driving the RCA's hard?

 

[themainjam 10+ year member]

But would an amp that accepts 4V inputs not be fully driven by 4V at it's lowest gain setting? Then what about the 2V extra when the HU was driving the RCA's hard?

whoa......

first off the RCAs dont care how many volts are goin through them....

Second the amp amplifies the signal from your HU if the HU send 6V the gain will just need to be set a little lower to get the maxc output form the amp....

gain is there because not all HU put out the same signal some do 2V some 8V the gain needs to be lower for 8V and higher for 2V to get the most from the amps...

 

[req 5,000+ posts]

whoa......
first off the RCAs dont care how many volts are goin through them....

Second the amp amplifies the signal from your HU if the HU send 6V the gain will just need to be set a little lower to get the maxc output form the amp....

gain is there because not all HU put out the same signal some do 2V some 8V the gain needs to be lower for 8V and higher for 2V to get the most from the amps...

good one.

so it will work. //content.invisioncic.com/y282845/emoticons/waycrazy.gif.f4a380c3f94043939fd369defd9e6be2.gif

 

[pete0403]

whoa......
first off the RCAs dont care how many volts are goin through them....

Second the amp amplifies the signal from your HU if the HU send 6V the gain will just need to be set a little lower to get the maxc output form the amp....

gain is there because not all HU put out the same signal some do 2V some 8V the gain needs to be lower for 8V and higher for 2V to get the most from the amps...

I understand all this stuff. That's simple.

So I guess my problem then is maybe I'm not fully understanding how gain settings work.

The specs on my amp say that "Linelevel input sensitivity" is 100mV - 4V

HU output is 6V max. At max, the HU is putting out TWO more volts than the max input specs of the amp. Understand my question?

So if I set the gain at it's lowest setting, I thought that since the input sensitivity of the amp was .1 - 4V, at it's lowest setting, the amp would be dirven to max by 4V. Am I wrong? If not, what happens when more voltage is put into the amp than it needs to drive it fully?

 

[squeak9798 5,000+ posts]

So I guess my problem then is maybe I'm not fully understanding how gain settings work.
The specs on my amp say that "Linelevel input sensitivity" is 100mV - 4V

HU output is 6V max. At max, the HU is putting out TWO more volts than the max input specs of the amp. Understand my question?

So if I set the gain at it's lowest setting, I thought that since the input sensitivity of the amp was .1 - 4V, at it's lowest setting, the amp would be dirven to max by 4V. Am I wrong? If not, what happens when more voltage is put into the amp than it needs to drive it fully?

First off, you need to understand that your headunit's preamp output's will not be putting out that 6V constantly. It is either a RMS figure or a Max figure (similar to an amps power ratings). As you turn up the volume the voltage output will increase, turn down the volume and the voltage output will decrease. Most headunits need to be at 75%-100% of their maximum volume to actually put out their rated voltage. During "normal" listening, you're probably getting less than 2-3V output from the preouts.

 

[themainjam 10+ year member]

correct me if i am wrong req

most amps can handle the extra 2V

as long as you set the gain so you get the correct output it shouldnt overload the amp.

 

[squeak9798 5,000+ posts]

Second the amp amplifies the signal from your HU if the HU send 6V the gain will just need to be set a little lower to get the max [unclipped] output form the amp....

You forgot a word //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[themainjam 10+ year member]

****it another F in english? man i quit school

 

[DBfan187 5,000+ posts]

you should go back

 

[pete0403]

Thanks for the answers guys...