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MC352 Inverted or Non-Inverted??

briandrex

briandrex

Active Member
I'm trying to drive the bass towers of Infinity RS1B speakers with an MC352 amplifer. On the back of the SERVO there is a switch for non-inverted and inverted. The ADCOM GFA-355 I was using was fine on non-inverting, when I hook the MC352 up with pre-amp (C2300) volume on zero it just makes a clicking sound about every three seconds, not a thump or anything bad just a click like a relay switch going on and off.

I hooked the ADCOM back up and everything works fine so I'm positive it's not a bad connection. I don't want to change it to inverted as I know if this is set wrong I could damage the speakers or the amplifier. I've searched the internet and can't find an answer for this. I did read somewhere where McIntosh said most of there amplifiers especially all the newer ones are non-inverting. It this is indeed the case does anyone have a reason why this is happening with the MC352. The amplifier works fine in a traditional setup with other speakers. I double checked to make sure it wasn't something wrong with the amp.
 
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I think your speakers servo feedback section is reacting with the amp as if it was bridged.
 
c_dk said:
I think your speakers servo feedback section is reacting with the amp as if it was bridged.
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Is there a way around this? I know on the back of the ADCOM GFA 355 that I was using initially it has a stereo or bridged switch. The only switch on the MC352 is stereo or mono. I'd really like to use the MC352 if possible. I'm currently using an MC452 on the EMIMs and EMITs tower with no issue. Could I possibly use the MC452 on the woofers and MC352 on EMIMs and EMITs?
 
Do you have a schematic for the servo input for the Infinity?

If the input is bonded to the ground of the house and the output of the amps aren't, you have a major issue as 1/2 the output is shorted to ground.
 
c_dk said:
Do you have a schematic for the servo input for the Infinity?

If the input is bonded to the ground of the house and the output of the amps aren't, you have a major issue as 1/2 the output is shorted to ground.[/Q
damacman said:
The MC352 is not a common ground output design - rather, it's fully balanced so the negatives are not common to ground. Is a common ground amplifier a requirement of the speakers?
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The only thing the manual for the speakers talks about is being in absolute phase. Basically they say if your amp is inverting then the outputs of the amp are in phase with the inputs. When running through the servo on the bass towers this means switch is set to non-inverting and if the outputs of the amp are not in phase with the inputs then you switch to inverting. For the EMIMs and EMITs towers there is no switch so non inverting is + to + and - to - if the amp is inverting then you would hook + to - and - to + when connecting. I have an MC452 and I used it as I normally would on the mids and highs with no problem so I assume the MC452 is non inverting.

Just cant seem to understand what's going on with the MC352, I assume it would be similar to the MC452.
Click to expand...
 
c_dk said:
Do you have a schematic for the servo input for the Infinity?

If the input is bonded to the ground of the house and the output of the amps aren't, you have a major issue as 1/2 the output is shorted to ground.
Click to expand...
I do not have a schematic with the owners manual but I'm sure I can find one online. Thank you for this information, makes sense. Now to find a schematic and see what is going on.
 
There's a different scenario going on here, the MC352 is quad balanced and therefore the negative speaker terminal is not common to ground, its floating.
 
kevzep said:
There's a different scenario going on here, the MC352 is quad balanced and therefore the negative speaker terminal is not common to ground, its floating.
Click to expand...
So is there a solution to how I can hook this up or is this just not the right amplifier to use with these speakers?
 
Well, none of us here know squat diddly about the speakers you're using. So, the first thing to determine would be if the servo input requires the use of an amplifier whose speaker negative terminals are common to ground. If that is the case, then the MC352 (or MC452) cannot be used with this portion of the speakers as neither has the speaker negatives common to ground.
 
damacman said:
Well, none of us here know squat diddly about the speakers you're using. So, the first thing to determine would be if the servo input requires the use of an amplifier whose speaker negative terminals are common to ground. If that is the case, then the MC352 (or MC452) cannot be used with this portion of the speakers as neither has the speaker negatives common to ground.
Click to expand...
Thank you for this information. This will now give me a good starting point.
 
Early today I found online a owners manual for the speakers.

I think it specifically said no bridged amps.

While the Mc352 is not bridged in the traditional sense of a non output transformered bridged amp it still is a bridged like design.
 
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c_dk said:
Early today I found online a owners manual for the speakers.

I think it specifically said no bridged amps.

While the Mc352 is not bridged in the traditional sense of a non output transformered bridged amp it till is a bridged like design.
Click to expand...
Thank you for this information. I do know that from the manual as well but didn't know that the MC352 would be considered bridged. Does the MC452 fall into the same category at the 352 or it different?
 
briandrex said:
Thank you for this information. I do know that from the manual as well but didn't know that the MC352 would be considered bridged. Does the MC452 fall into the same category at the 352 or it different?
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452 is the same. All quad balanced amps are this way.

Would need a schematic to see what the story is.
 
kevzep said:
452 is the same. All quad balanced amps are this way.

Would need a schematic to see what the story is.
Click to expand...
I'm going to try and track down a schematic. I also need to find the person that posted they use an MC452 on the bass towers and MC275 on the EMIMs and EMITs on this forum. Maybe they have a better understanding of how this servo circuitry works.
 
briandrex said:
I'm trying to drive the bass towers of Infinity RS1B speakers with an MC352 amplifer. On the back of the SERVO there is a switch for non-inverted and inverted. The ADCOM GFA-355 I was using was fine on non-inverting, when I hook the MC352 up with pre-amp (C2300) volume on zero it just makes a clicking sound about every three seconds, not a thump or anything bad just a click like a relay switch going on and off.

I hooked the ADCOM back up and everything works fine so I'm positive it's not a bad connection. I don't want to change it to inverted as I know if this is set wrong I could damage the speakers or the amplifier. I've searched the internet and can't find an answer for this. I did read somewhere where McIntosh said most of there amplifiers especially all the newer ones are non-inverting. It this is indeed the case does anyone have a reason why this is happening with the MC352. The amplifier works fine in a traditional setup with other speakers. I double checked to make sure it wasn't something wrong with the amp.
Click to expand...

Oh, what's an Adcom GFA-355? I've never heard of that one...? :idea:
 
I can't see why you can't drive the unbalanced inputs of the MC352 or any other Quad balanced amp with that Low pass output.

Are you going into the Balanced inputs on the 352?
 
Hmmm . . . where does this doo-dad you have go in the signal path? Is it a passive device that goes between the preamp and the power amps?

Educate us about the general layout and connectivity of the components that make up these speakers.
 
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