Hi level inputs

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mikeeastman

Hi level inputs
« on: 1 Apr 2018, 06:01 pm »
I presently feed my sub amps for my Super 7s off my pre but I going to try a digital vol and was thing of using the hi level inputs to feed my sub amp. Will I lose any SQ using the hi level? Can I still use the low level output from the Super7 amps  sub amp to feed my sub amp?

HAL

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Re: Hi level inputs
« Reply #1 on: 1 Apr 2018, 06:39 pm »
The line level inputs on the A370 from the preamp and then HPF line level output to the subs should be fine.  If it is stereo subs, just use one channel from each A370 to feed one sub amp.  That is if the subs do not go above the 80Hz filter on the line level output of the A370.  May not be a problem for the subs.

poseidonsvoice

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Re: Hi level inputs
« Reply #2 on: 1 Apr 2018, 06:47 pm »
Mike,

If you are using the 1200AS as your 2ch main amplifier and you are going to connect a speaker cable from 1200AS to the Rythmik plate amps at speaker level then you cannot.

The reason is because the 1200AS output stage is a bridged tied load configuration (BTL) design. In other words the negative speaker binding post on your 1200AS is not tied to ground. It presents output voltages on both the positive and negative speaker outputs and the voltages are quite high. 

Doing so may damage the 1200AS, Rythmik plate amp or both. It would also put you at an electrical risk. The 1200AS does have a protection feature for this but why risk it?:

From the 1200AS datasheet-> “Due to the balanced operation, it is not possible to connect one of the outputs to ground. The module is protected against such an event.”

Stick with your line level configuration and enjoy the music  :wink:  :thumb:

If I misunderstood, my apologies but I don’t want you to endanger yourself.

Best,
Anand.

mikeeastman

Re: Hi level inputs
« Reply #3 on: 1 Apr 2018, 07:20 pm »
Anand,

You understood perfectly , thanks for the info. I'll have to find a different way to try it out.

debjit.g

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Re: Hi level inputs
« Reply #4 on: 1 Apr 2018, 07:28 pm »
This was bought up in the 1200AS thread in context to REL subs which also needs ground for the high level input. I think there are some who is using the -ive speaker terminal for the ground to the RELs and was reported to be working fine without issues.

bavmike

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Re: Hi level inputs
« Reply #5 on: 1 Apr 2018, 08:42 pm »
This method can always be used:

https://youtu.be/3F5WTOu60hE

Even though OHenry is running his subs from the speaker outputs on the 1200AS to the high level inputs on his sub. With his measurements he was unable to measure any DC from the - leg. I haven't tried myself.

rythmik

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Re: Hi level inputs
« Reply #6 on: 1 Apr 2018, 10:09 pm »

It is not DC issue. When there is no signal, all legs are at perfect 0 DC. It is when the signals begin to swing, one lead of the amp output will swing up and another will swing down, referenced to ground.  To demonstrate how hazardous anyone try to connect BTL to plate amp via high level inputs, I have a customer did just that and the entire preamp board is fried. This is because the negative leads from BTL amps output are not at the same voltage level (unless your left channel is exactly same as the right channel).  Now if one says but I have two subs, one for each channel, would that work?  The fact that the negative lead is connected to the speaker level input black terminal, meaning ideally, as soon as you start playing, the same disaster should have happened. However, some have reported successfully working this way ONLY BECAUSE the amp does not have power ground pin (ie it uses 2 prong power cable). If this gent accidentally touch the subwoofer amplifier chassis when it is playing, he can get electrical shock because negative speaker level input is essentially tied to chassis ground. REL speaker level inputs are like XLR inputs. In that case it needs 3 wires. No two-wire system can work without creating some sort of hazard. 

Think of it this way, in any signal transmission, at least one wire needs to be ground. Without that power ground takes over signal ground. When there is neither signal ground nor power ground connection, the chassis becomes floating.





 

poseidonsvoice

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Re: Hi level inputs
« Reply #7 on: 1 Apr 2018, 11:20 pm »
It is not DC issue. When there is no signal, all legs are at perfect 0 DC. It is when the signals begin to swing, one lead of the amp output will swing up and another will swing down, referenced to ground.  To demonstrate how hazardous anyone try to connect BTL to plate amp via high level inputs, I have a customer did just that and the entire preamp board is fried. This is because the negative leads from BTL amps output are not at the same voltage level (unless your left channel is exactly same as the right channel).  Now if one says but I have two subs, one for each channel, would that work?  The fact that the negative lead is connected to the speaker level input black terminal, meaning ideally, as soon as you start playing, the same disaster should have happened. However, some have reported successfully working this way ONLY BECAUSE the amp does not have power ground pin (ie it uses 2 prong power cable). If this gent accidentally touch the subwoofer amplifier chassis when it is playing, he can get electrical shock because negative speaker level input is essentially tied to chassis ground. REL speaker level inputs are like XLR inputs. In that case it needs 3 wires. No two-wire system can work without creating some sort of hazard. 

Think of it this way, in any signal transmission, at least one wire needs to be ground. Without that power ground takes over signal ground. When there is neither signal ground nor power ground connection, the chassis becomes floating.

Thanks for the perfectly understandable clarification Brian. It is vitally important to understand this especially from a safety standpoint and your engineering prowess is respected.

Best,
Anand.

Captainhemo

Re: Hi level inputs
« Reply #8 on: 2 Apr 2018, 05:07 am »
Thanks  Brian and  Anand for  the clarification, good info

jay