Yamaha MX1 Power Amp- common ground

Hi,
I have a MX1 Yamaha power amp and I'd to use it with a vintage pair of Polk SDA-SRS 2.3 speakers. Polk states you need to use a common ground power amp with these speakers because of the interconnecting cable.
Does anyone know if the MX1 is considered a common ground amp?
Thanks

NHBEM said:

Hi,
I have a MX1 Yamaha power amp and I'd to use it with a vintage pair of Polk SDA-SRS 2.3 speakers. Polk states you need to use a common ground power amp with these speakers because of the interconnecting cable.
Does anyone know if the MX1 is considered a common ground amp?
Thanks

Click to expand...

I know nothing about polks, post a pic of the connectors on the speaker and label plus the speaker cables, are they special???

Bubo
Here's a link to the manual for the Polk SDA SRS 2.3 speaker manual.
The reference to a common ground amp is on page 4,section 3.
http://www.polksda.com/pdfs/SDASRS1-2.pdf

Thanks for reviewing my post. Many people on Polk forums are stating that you need to use a Volt Ohm Meter to check whether there's continuity between the negative posts of the power amp. Since I didn't have a VOM I could not confirm whether the MX1 was a common ground amp and was hoping that someone on the forum had done this already.

forum.polkaudio.com › Special Interests › Vintage Speakers
Sep 24, 2013 - 28 posts - ‎11 authors
How can I tell if the amp I'm using is a "common ground" type. ... Another piggy- back in case this info is of use to anyone else: I recently bought ...

At this point I've decided to E Mail Yamaha support and ask them.

You can check for continuity between the (-) connections with your Ohmmeter.


I took a look a the PDF service manual and from the schematic it appears not to have common (-) connections between the left and right channels and the A and B speaker connections.

See the first picture below, it would appear that the (-) connections are not common, note the separate wires connected to each (-) connection for the right and left channel.


But in following those wires (I believe I did it correctly) on the schematic it appears that they end at the same common ground. They are the connections labeled E

See the second picture.

Thanks for checking the schematics for me. I'll probably try to get an ohmmeter from where I work and check the continuity. It's probably the only way that I'm going to get an answer to my question.
Can you supply me some details on how to do this since I have no experience using an ohmmeter?
I appreciate the input.

JBL GUY said:

You can check for continuity between the (-) connections with your Ohmmeter.


I took a look a the PDF service manual and from the schematic it appears not to have common (-) connections between the left and right channels and the A and B speaker connections.

See the first picture below, it would appear that the (-) connections are not common, note the separate wires connected to each (-) connection for the right and left channel.


But in following those wires (I believe I did it correctly) on the schematic it appears that they end at the same common ground. They are the connections labeled E

See the second picture.

Click to expand...

Dumb question

Almost all of the gear that I have ever seen, the board is tied to the chassis, I assume at one point to prevent loops on the board.

If he just hooks up the speakers and there is no hum, is it mission accomplished??

Maybe someone from your work can show you how.

Here is a short video. The exact setting of the DMM will depend on what you have.

It the DMM is auto ranging, just set it for the resistance function or if it has manual range selection, choose the lowest resistance (Ohms) range and just for a test, touch the two probes together as shown in the video and note the indication.

Then with the speakers not connected to the MX1, touch the probes, one each, to the (-) connections of the left and right channels for speaker A. If there is a common ground, the indication on your meter should be very close to what was indicated when you touched the two probe to each other.

You may do the same thing for speaker B, the from looking at the schematic, it appears to be the same as speaker A.

This should be done with the power MX1's power turned off, in fact everything connected to it should be turned off just to be on the safe side.

Bubo said:

Dumb question

Almost all of the gear that I have ever seen, the board is tied to the chassis, I assume at one point to prevent loops on the board.

If he just hooks up the speakers and there is no hum, is it mission accomplished??

Click to expand...

The short answer is no.

Some audio amplifiers have all of the speaker output terminals balanced with respect to ground.

If any speaker terminal is connected to ground or if any two of the speaker terminals, either (+) or (-) of the respective left or right channels are connected together, there may be damage to the amplifier.

That is (+) and (+) connected together or (-) and (-) connected together or either connected to ground.





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Thanks JBL Guy.
You gave me exactly the info I need.
I'll be checking out the grounding with a meter that I borrow from work next week. Hopefully it will be a common ground setup.

Good luck with your project.

The MX-1 is confirmed common ground. Hifienge has the service manual with schematic.

Thanks, that is what the pictures of the schematic that I poste shows.

But with my medications, sometimes it is difficult for me to follow the lines.

I was going to post a link to the schematic, but I forgot.

Avionic
That's great news!
I'll probably go through the exercise anyway. Also I have a second amp which is a Luxman M4000 which I'd like to check out also.
Thanks for helping out.