Plate amp input question...

Jack Gilvey · 02-02-2004, 09:15 PM

What would be the best way to feed a third high-(speaker-) level channel to a plate amp equipped with the standard L/R high-level inputs? Possible?

GrahamT · 02-02-2004, 09:48 PM

I could be wrong here but maybe you could just connect two channels to one set of the input terminals. The signals are all combined anyways and it wont hurt anything to try. I dont see why this wouldn't work unless someone else has another suggestion.

Brian Bunge · 02-02-2004, 11:27 PM

Jack,

I can't answer your question, but would like to ask one of my own. What are you trying to accomplish?

Aaron Gilbert · 02-03-2004, 02:43 AM

Quote:

I could be wrong here but maybe you could just connect two channels to one set of the input terminals. The signals are all combined anyways and it wont hurt anything to try. I dont see why this wouldn't work unless someone else has another suggestion.

This is a bad idea, as you would be connecting the receiver's/amplifier's left and right outputs to each other. While it may not hurt anything, as most solid state devices have protection circuitry built-in to prevent damage from this, I wouldn't take the chance.

Unfortunately, I do not have another suggestion, so I am with Brian and am curious what you are trying to accomplish, Jack?

Aaron Gilbert

Jack Gilvey · 02-03-2004, 07:46 AM

Hi all,
What I'd like to do is have a multichannel music system for SACD/DVD-A that uses no bass-management at all. I'd like to run the all speakers as "Large" and just bring in a dipole sub underneath. This would be output from a receiver, so I won't use something like an ICBM for a line-level crossover. The surrounds would be a separate issue.

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ThomasW · 02-03-2004, 11:04 AM

Jack,

Quote:

What I'd like to do is have a multichannel music system for SACD/DVD-A that uses no bass-management at all

Sort of difficult, if what you're talking about is summing the bass from all 3 L>C>R speakers.

Marchand and Paradigm X-30's will sum the bass from the L&R channels. That's what I do in my HT since I don't like the sub out from the pre/pro. This leaves the center to run fullrange. Not a loss of much bass since it's primarily a dialog channel anyway.

For a 4 channel surround the only way to do this and not have the sound quality suffer big time, is to use 2 active XO's that sum the L&R LFE signal. In theory you could run the summed LFE out from the front XO to one VC (or driver), and the summed LFE out from the rear/surround XO to a different VC (or driver).

Seth_L · 02-03-2004, 03:44 PM

Does your reciever have pre-outs for the front 3 channels Jack? If so you need a Behringer ULTRADRIVE PRO DCX2496 http://www.behringer.com/02_products...TOKEN=74394370

That will take care of your problems.

Ryan Schnacke · 02-03-2004, 09:51 PM

I think the schematic for this amp (or one very similar to it) is still available on the apexjr site. Looking at the input stage you'll notice that the only difference between the high-level input path and the low-level input path is that the high-level has a different voltage divider.

But it sure seems like with the addition of a couple of resistors you could make a low-level input look just like the high-level inputs. The resistors could be mounted externally and the signals would be summed through the first op-amp. This way you could feed up to 4 high-level signals into the amp.

The usual disclaimers apply - I offer no warranty with my crazy ideas.

Jack Gilvey · 02-04-2004, 08:29 AM

Quote:

Sort of difficult, if what you're talking about is summing the bass from all 3 L>C>R speakers.

Yeah, that's the idea. I don't want to use the bass-management as currently implemented in SACD/DVD-A players and don't want to use an outboard crossover...or any crossover. I'd like to set the player to send the "multichannel-direct" signal to all speakers and just run parallel speaker cables to the sub amp, rolling in the sub using the amp's own LP crossover.

Quote:

This leaves the center to run fullrange. Not a loss of much bass since it's primarily a dialog channel anyway.

Do you think this would apply to the hi-rez music formats also?

Fwiw, I'm thinking of using these new Magnepans with my dipole sub(s). Looks like a sweet deal, and their crossoverless/"Full-range" nature intrigues me.

Seth, I'm sticking with the high-level inputs.

Quote:

But it sure seems like with the addition of a couple of resistors you could make a low-level input look just like the high-level inputs. The resistors could be mounted externally and the signals would be summed through the first op-amp. This way you could feed up to 4 high-level signals into the amp.

Hmm...have to look into that.

ThomasW · 02-04-2004, 12:49 PM

Quote:

Fwiw, I'm thinking of using these new Magnepans with my dipole sub(s). Looks like a sweet deal, and their crossoverless/"Full-range" nature intrigues me

Those do look great, I'm tempted to use some as surrounds in the family room.
Don't be fooled though, I'm pretty sure Magnepan is expecting the drivers to be used with the appropriate output setting from a pre/pro.
My MMG's (used as surrounds in the HT) roll-off quickly below ~50Hz. They are the most happy when set to "small" at the pre/pro.
Since the 'new' Maggies are even smaller than MMG's; I see no way around using some form of active/passive XO, or similar device to separate the frequencies