2. vintage
  3. 190761-168476

Intermittent Left Channel Outage-- Older McIntosh System--Love my system appreciate Help!

I would greatly appreciate any suggestions from any of the bright people out there regarding a sporadic, but consistent, left channel cut out on my older (1978/79) McIntosh system.

[The system consists of a Mc 2125 Amp, a C28 pre amp, a MQ 101 Environmental Equalizer (used by McIntosh in conjunction with Mac XR5 speakers), and McIntosh Speaker control relay box.  The order of things is: streamer to preamp, preamp to both speaker control relay box and MQ101--  MQ 101 to Amp and then amp wired to speaker control relay box, which is then wired to separate main (Mac XR5) and remote (Definitive BP20) speakers.  Also in the system, but not affecting the cut out issue are a Bluesound NodeX streamer, a REL S510 subwoofer, and McIntosh XR5 loudspeakers.  BTW-- I know the speakers are not the issue since I run a second set of remote speakers (the Definitives) which cut out as well.]

The issue, which follows a consistent pattern is everything works well when first turned on.  After about 10-15 minutes of listening (streaming Tidal from the NodeX) the left channel cuts out.  However, if I quickly push in either the main or remote speaker switch on the preamp, I hear a static "pop," and the left channel comes on again.  After another 5-10 minutes the same thing happens (left speaker cuts out) and another static pop from pushing the main or remote speaker switch restores the left channel.  However, after another 5 minutes the left channel goes out and the static pops do not restore it.  However, if I leave the system on for a couple of hours and come back and create another static pop by pushing the main or remote speaker switch the left channel returns and then will run flawlessly as long as I choose to listen.   I do not think the issue is the preamp, since I run a line out from the preamp to a Soundcast (outdoor speaker) wireless network box, hence bypassing the amplifier, and the left channel works perfectly.  I've taken the system to a McIntosh repair center and they couldn't duplicate the issue.  On my last call they thought the issue was the pre amp, which I highly doubt since I can send a signal wirelessly from the pre amp to my soundcast outdoor speaker and the left channel does not cut out.

Sorry to be so wordy.  Not sure how to communicate this without stating all the "facts."  BYW-- after 45 years the system is finally in the right acoustical setting  and creates for me a better than you are there listening experience.  So don't want to ever give it up.  But that's another post!  Thank you in advance

robertc_f
boxcarman
422 posts
 

If it is 45 years old, you're gonna need to get it serviced if you haven't already.  Control knobs cleaned, maybe new caps, etc.

robertc_f OP
12 posts
 

Thank you.  Great suggestions.  Regarding the speaker control relay and connecting the speaker wires directly to the amp--- should I unplug the speaker control relay connection cable from the pre amp at the same time, when I directly connect the speakers to the amp?  Perhaps that is an improvement anyway, being a more direct connection.  The only downside would be not being able to use the second set of speakers, which I don't use anyway, as the XR5's and REL S510 sound much better.  If this works the S510 subwoofer could then be connected also directly to the amp through its high level connection cable.  The Mac dealer did check out the rest of the equipment and said it didn't need service.  Thank you again for the suggestions.

gs5556
1,235 posts
 

Once you disconnect the speaker cables from the amplifier input of the relay then the relay has nothing to switch. It won't make a difference, but the point here is not to troubleshoot just the relay  but also the control circuit from the preamp to the relay. Disconnect the relay in it's entirety (including power cables if you're using the relay as a power strip for the amp or other sources) in addition to the control cable.

If you took everything to the service center where they couldn't duplicate the problem, I'll bet you didn't bring the relay with you.

Ag insider logo xs@2x
bernardwilliams
23 posts
 

I think the problem is your mac speaker control relay box. Try your system with out it with just two speakers.

robertc_f OP
12 posts
 

Thank you all again-- hoping to test the system by bypassing the speaker control relay early next week.  I will post the results.  One thing to add is that when the left channel goes out, the left channel blue/green meter on the amp shows no signal.  If the issue is the speaker control relay which I believe receives information from the pre amp (via its connection cable--  i.e. preamp to speaker control relay), and power from the amp via left/right channel wires), wouldn't the amp's power meter show activity??  In my simplistic way, I envision if the speaker control relay is the issue, the breakdown in the signal would come after the amplifier--- and hence the amp would show activity in its left power meter.  Am I confused here?

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