Fosi V3 Mono Balanced output / Not recommmend for High Line Subwoofer connections?

[Eron]

Hello everyone..

So the kickstarter for the Fosi V3 mono is over.. There's been talk over there in the comments over some subwoofers having a common ground for the high line inputs. Fosi says this is therefore not recommended for connecting to a subwoofer.

To me, this would make them useless..

Any thoughts or insight on this here?

 

[Joachim Herbert]

So you got one of these some?

Just a thought.

 

[antcollinet]

Hello everyone..

So the kickstarter for the Fosi V3 mono is over.. There's been talk over there in the comments over some subwoofers having a common ground for the high line inputs. Fosi says this is therefore not recommended for connecting to a subwoofer.

To me, this would make them useless..

Any thoughts or insight on this here?

This applies to any amp with BTL (bridge tied load) outputs. Pretty much all the chip based class D amplifiers.

With most subs, you should be able to use just one of the speaker outputs to go to the red input of the sub, then connect the black input back to a ground point on the amp. Probably worth checking with your particular sub manufacturer though.

As an alternative you could put the sub connection through an isolation transformer.

 

[Eron]

This applies to any amp with BTL (bridge tied load) outputs. Pretty much all the chip based class D amplifiers.

With most subs, you should be able to use just one of the speaker outputs to go to the red input of the sub, then connect the black input back to a ground point on the amp. Probably worth checking with your particular sub manufacturer though.

As an alternative you could put the sub connection through an isolation transformer.

I'm currently using 2x A07 Max's with the High line of the right Amp going to a RSL 12s on my right, and the High line of the left going to a 12s on my right. It works. Am I at risk of an explosion? ;p

Thanks for the replies!

 

[antcollinet]

If it was going to explode I'd have expected it to be instant, so you should be alright. I'd still check with the manufacturer though.

 

[Joachim Herbert]

This is probably a dumb question, but why not the other way around: source > sub > power amp.

This is why they included all this:

• Low Pass Crossover Frequency: 30-250 Hz variable (with integrated bypass switch)
• Low Pass Crossover Slope: 24 db/oct.
• High Pass RCA Output Crossover Frequency: 30-250 Hz variable (with integrated bypass switch)
• High Pass RCA Output Crossover Slope: 24 db/oct.

 

[gwing]

This is probably a dumb question, but why not the other way around: source > sub > power amp.

This is why they included all this:

• Low Pass Crossover Frequency: 30-250 Hz variable (with integrated bypass switch)
• Low Pass Crossover Slope: 24 db/oct.
• High Pass RCA Output Crossover Frequency: 30-250 Hz variable (with integrated bypass switch)
• High Pass RCA Output Crossover Slope: 24 db/oct.

Not a dumb question at all. That is a good way of doing things.

 

[Eron]

This is probably a dumb question, but why not the other way around: source > sub > power amp.

This is why they included all this:

• Low Pass Crossover Frequency: 30-250 Hz variable (with integrated bypass switch)
• Low Pass Crossover Slope: 24 db/oct.
• High Pass RCA Output Crossover Frequency: 30-250 Hz variable (with integrated bypass switch)
• High Pass RCA Output Crossover Slope: 24 db/oct.

You are asking me why I am not going from my source, to the sub first and then out to my pre-amp/power amp? Thought about it. Not sure I'd make use of any high pass filters with my Lintons, they do a fine job with the full range. Also, supposedly subs are better with high line.. But, you never know I may play.

 

[Joachim Herbert]

Also, supposedly subs are better with high line.

What lead you to believe this? Those inputs are a last resort for those who cannot go the other way.

 

[Eron]

What lead you to believe this? Those inputs are a last resort for those who cannot go the other way.

Paul Mcgowan at PSAudio recommends it.

 

[Joachim Herbert]

Paul Mcgowan at PSAudio recommends it.

View attachment 372602

Now if Paul said so...

 

[antcollinet]

Paul Mcgowan at PSAudio recommends it.

View attachment 372602

You're gonna find PMG's opinion doesn't carry much weight around here.

 

[Joachim Herbert]

And that is for a reason, I might add.

 

[antcollinet]

Paul Mcgowan at PSAudio recommends it.

Just to explain why he is wrong.

1 - High level input:
The signal at line level is amplified by your amp, and output on your speaker terminals. This will include all the distortion and noise introduced by power amplification. This is sent both to your speakers and sub. It will be subject to FR issues caused by the output impedance of your amp, interacting with the speaker impedance characteristic.

Then once at your sub, it has to be converted back to low level (line level) signals to go into the Subs built in amplifier.


2 - Low level input.
The line level signal is simply sent directly to the input of the sub amplifier


1 is never going to be higher fidelity than 2.

 

[motorstereo]

You're gonna find PMG's opinion doesn't carry much weight around here.

Exactly; in my case he lost all credibility with his video claiming his noise harvestors turn electrical noise into light. My emi meter shows they do nothing other than put hole in one's wallet and a light show at $75 each and several are needed.

 

[Eron]

Just to explain why he is wrong.

1 - High level input:
The signal at line level is amplified by your amp, and output on your speaker terminals. This will include all the distortion and noise introduced by power amplification. This is sent both to your speakers and sub. It will be subject to FR issues caused by the output impedance of your amp, interacting with the speaker impedance characteristic.

Then once at your sub, it has to be converted back to low level (line level) signals to go into the Subs built in amplifier.


2 - Low level input.
The line level signal is simply sent directly to the input of the sub amplifier


1 is never going to be higher fidelity than 2.

Very interesting, and thanks for bringing me up to date around here. ;p

The problem for me to use RCA's to my subs are logistical more than anything. I'd have to come out of my DAC, into one sub, then go all the way around a huge area to the other sub (over 50ft RCA) and then back to my preamp/amp. Where as using high level I can just go direct from each L/R amp to each sub with a 12G wire.

So, I guess it is what it is. It works and sounds fantastic with my A07 Max's, and I guess if those work the v3 Mono's should work. The real question here is, why am I even bothering going from the A07's to the V3 Monos...

Likely 0 difference if anything good at all.. The PFFB likely won't make a lick of difference in my listening.

Ah the joys.

 

[Joachim Herbert]

Always good to know the use case. Still have a hard time to understand.

You might run line level from DAC or preamp (cinch) to the left (right) sub and to the left (right) monoblock from there.

Not sure what the amp is good for.

On a sidenote you might buy a second A-07 to go dual mono in that case.

 

[antcollinet]

So, I guess it is what it is. It works and sounds fantastic with my A07 Max's

In spite of my comments above, I am not surprised. The disadvantages I described of high level connection are going to be small to inaudible in most cases. It was just a description of why it is not optimised for maximum sound quality, and why it is objectively wrong to describe high level connections as 'the best way"

And I perfectly understand your logistical issues.

 

[Eron]

I am running 2x A07's already.

Anyone here think I should even bother with the v3 monos?

 

[antcollinet]

I am running 2x A07's already.

Anyone here think I should even bother with the v3 monos?

Not if you don't need the added power.