confused about balanced input amps

[husker77 10+ year member]

I was stating the configuration, not asking. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif. FYI

Heck I'm not even smart enough to know it wasn't a question.

The only advantage is high signal and low amp gain, to minimize noise.

Yep. One thing I should not have to worry about is noise. I think the stinger expert series rca cables are some of the best and then the 8v balanced outputs, I should be good on that end of things.

 

[maylar 10+ year member]

I have made my own balanced converters, using audio-grade op amps and 1% resistors, it's a pretty easy concept. At the transmitter/source the pin is as-is and the shield signal is inverted 180deg. Then the receiver inverts the shield signal, sums the two, and you get a 3dB signal gain. A second benefit is any noise common and in-phase on both wires, i.e. induced in the run, is cancelled. I was getting an 80dB noise reduction with my version. Balanced does nothing to reduce noise inherent in the source or amplifier.

So, you built a balanced line driver? One RCA in and two out? Cool. Got a schematic?

In summary, you can feed high-level inputs on some amps with you balanced outputs.

I thought about that too, but the 16V output in balanced mode is actually higher than a standard HU speaker output.

 

[keep_hope_alive Premium Member]

link to paper

https://skydrive.live.com/redir?resid=9BE5812AB35E1D9E!357

 

[keep_hope_alive Premium Member]

I thought about that too, but the 16V output in balanced mode is actually higher than a standard HU speaker output.

not really, the HU output is "balanced" and 16V peak-to-peak is achievable. Regardless, you'll only make that voltage out of the HU with test tones at full volume. Under normal conditions, using high level inputs would be fine. the kicker is what to do with the shields. i don't have a good answer for that, without accessing signal ground on the PCB directly.

 

[quackhead 10+ year member]

not really, the HU output is "balanced" and 16V peak-to-peak is achievable. Regardless, you'll only make that voltage out of the HU with test tones at full volume. Under normal conditions, using high level inputs would be fine. the kicker is what to do with the shields. i don't have a good answer for that, without accessing signal ground on the PCB directly.

say you put 16v to an amps' input section that adjusts down to 6v, will it hurt the amp? I always thought the excess was sort of "dissipated"..am I wrong?

 

[maylar 10+ year member]

not really, the HU output is "balanced" and 16V peak-to-peak is achievable. Regardless, you'll only make that voltage out of the HU with test tones at full volume. Under normal conditions, using high level inputs would be fine.

Specs on the OP's Eclipse say 8 VRMS per preout, 16V balanced. That's about 45V pk-pk

the kicker is what to do with the shields. i don't have a good answer for that, without accessing signal ground on the PCB directly.

Not sure what you mean.. in balanced mode you don't need them.

 

[maylar 10+ year member]

say you put 16v to an amps' input section that adjusts down to 6v, will it hurt the amp? I always thought the excess was sort of "dissipated"..am I wrong?

This is an extreme case.. the normal mode of operation would only be 8V. Having high input signal probably won't "hurt" anything, you'll just overdrive the amp and have no control of your output level.

 

[keep_hope_alive Premium Member]

Specs on the OP's Eclipse say 8 VRMS per preout, 16V balanced. That's about 45V pk-pk
Not sure what you mean.. in balanced mode you don't need them.

your math is off. Vp = Sqrt(2) * Vrms

16V rms is around 22V p-p

My xtant amps accept 18V rms inputs.

you want a signal ground to carry through whenever possible. XLR cables have 3 conductors for that reason. it really depends on the type of amplifier inputs.

 

[quackhead 10+ year member]

This is an extreme case.. the normal mode of operation would only be 8V. Having high input signal probably won't "hurt" anything, you'll just overdrive the amp and have no control of your output level.

IE; Clipping.

 

[maylar 10+ year member]

your math is off. Vp = Sqrt(2) * Vrms 16V rms is around 22V p-p

22.6V peak, 45V p-p. Picky, picky, I know... still above the typical 14V p-p HU speaker level.

you want a signal ground to carry through whenever possible. XLR cables have 3 conductors for that reason. it really depends on the type of amplifier inputs.

Assuming differential inputs, I would think the chassis ground at the preout RCA's connectors would suffice. Some pro audio gear has a switch to disconnect that ground, in the event of ground loop. I'd be inclined to tie the shield of a twisted shielded pair to chassis at the source end and leave the amp end disconnected.

 

[husker77 10+ year member]

Well if I wasn't confused enough before, I sure am now. //content.invisioncic.com/y282845/emoticons/wow.gif.23d729408e9177caa2a0ed6a2ba6588e.gif

 

[husker77 10+ year member]

link to paperhttps://skydrive.live.com/redir?resid=9BE5812AB35E1D9E!357

I've just skimmed it and I can already tell I am going to have to google half the words in the paper.

 

[quackhead 10+ year member]

22.6V peak, 45V p-p. Picky, picky, I know... still above the typical 14V p-p HU speaker level.


Assuming differential inputs, I would think the chassis ground at the preout RCA's connectors would suffice. Some pro audio gear has a switch to disconnect that ground, in the event of ground loop. I'd be inclined to tie the shield of a twisted shielded pair to chassis at the source end and leave the amp end disconnected.

My Pioneer Premier HU has a ground wire from the rca section that ties it's self back to the chassis and the tag states it is to ground the shield side of the rca outs to prevent ground loops. It is my understanding that differential inputs do the same thing inside the amplifier chassis in the input section....is this like what you describe?

 

[quackhead 10+ year member]

op' what speaker(s) do you plan to run 8kw through, anyways?

 

[keep_hope_alive Premium Member]

22.6V peak, 45V p-p. Picky, picky, I know... still above the typical 14V p-p HU speaker level.


Assuming differential inputs, I would think the chassis ground at the preout RCA's connectors would suffice. Some pro audio gear has a switch to disconnect that ground, in the event of ground loop. I'd be inclined to tie the shield of a twisted shielded pair to chassis at the source end and leave the amp end disconnected.

You are correct.

I agree. I think it will be a case-by-case basis. Amps can have different input section topology and handle noise differently.