USNRET Posted March 4, 2017 Share Posted March 4, 2017 So I connected the Mc 275 in to the system tonight BLAHHHHH! On the first song the wife started yelling to turn that off. Same proofed Oppo BDP-105, C2500 pre, cables and KHorns At very low levels it is ok, any higher and it is a shrill blur I have heard all components except the amp together (using an Adcom, and 2 different Emotivas) and it was good. This is a one year old amp / tubes from that Audio Klassics place. Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted March 4, 2017 Share Posted March 4, 2017 Ground loop problem or its the HOUSE again? Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted March 4, 2017 Share Posted March 4, 2017 oh dear.. Quote Link to comment Share on other sites More sharing options...
USNRET Posted March 4, 2017 Author Share Posted March 4, 2017 4 minutes ago, JL Sargent said: Ground loop problem or its the HOUSE again? No hum, zero ground floor noise. It has bass, centered vocals and all sound good until I get it above about 60-65 dB and then all of the mids/highs turn to crap. What's the term? Sibilance? For instance I tried Adele and her voice was ringing on and on. Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted March 4, 2017 Share Posted March 4, 2017 Both channels? Quote Link to comment Share on other sites More sharing options...
USNRET Posted March 4, 2017 Author Share Posted March 4, 2017 Just now, JL Sargent said: Both channels? Yep, a cohesive smear Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted March 4, 2017 Share Posted March 4, 2017 using the correct taps? (assuming it has both 4ohm and 8ohm) Quote Link to comment Share on other sites More sharing options...
USNRET Posted March 4, 2017 Author Share Posted March 4, 2017 Using 8, I just shut down to cool off and try something? It has 4/8/16 ohm. Pizzed and not excited to investigate but between rums I will do something. The amp is under warranty but I hope it's not back to the drawing board on what to pick. Quote Link to comment Share on other sites More sharing options...
Thaddeus Smith Posted March 4, 2017 Share Posted March 4, 2017 Just to confirm, you have heard the Khorns sound like one would expect them to sound. Correct? Quote Link to comment Share on other sites More sharing options...
jimjimbo Posted March 4, 2017 Share Posted March 4, 2017 I really hate to state the obvious, but sometimes that what is what is needed. Do you have the amp on an isolation platform where it is not being vibrated in anyway? Have you checked all of your connectors? Have you checked the settings on the Oppo? I am really sorry for your troubles.Do you have a spare set of tubes you could substitute in? Quote Link to comment Share on other sites More sharing options...
russ69 Posted March 4, 2017 Share Posted March 4, 2017 Wasn't the MC275 around when PWK said the world needed a really good 5 watt amp? Sometimes even the best of the best just doesn't work out. You may have a combo that just doesn't do it for you? Quote Link to comment Share on other sites More sharing options...
USNRET Posted March 4, 2017 Author Share Posted March 4, 2017 33 minutes ago, Thaddeus Smith said: Just to confirm, you have heard the Khorns sound like one would expect them to sound. Correct? Yes Quote Link to comment Share on other sites More sharing options...
USNRET Posted March 4, 2017 Author Share Posted March 4, 2017 Doing a couple of cable swaps but so far nothing works. I will try unbalanced next. In answer to Jim's isolation question, here is the setup. I am not using the APC UPS pictured. The pre and amp are on one outlet, the Oppo on another of the same circuit. None of the other components are interconnected or plugged in (UPS is live but no outlets are connected). All preamp trims are zeroed; trimming treble makes it worse. No Jim, I have no tubes left here. Quote Link to comment Share on other sites More sharing options...
richieb Posted March 4, 2017 Share Posted March 4, 2017 Some Mc power amps have their own gain controls. If by chance yours does can you remove the preamp and run the OPPO or any other source direct to the 275? We have been concentrating downstream of the KHorns, have you checked for proper connections within the crossovers themselves? And that all drivers are connected and in phase? I feel your pain --- Best Quote Link to comment Share on other sites More sharing options...
USNRET Posted March 4, 2017 Author Share Posted March 4, 2017 5 minutes ago, richieb said: Some Mc power amps have their own gain controls. If by chance yours does can you remove the preamp and run the OPPO or any other source direct to the 275? We have been concentrating downstream of the KHorns, have you checked for proper connections within the crossovers themselves? And that all drivers are connected and in phase? I feel your pain --- Best No gain controls on this amp. Speakers sounded fine with all previous amps connected. Unbalanced sounds crappy as well. Just for grins I swapped +/- on one speaker lead at amp; once a cool down and a smoke (mine) occurs, I will try again. Quote Link to comment Share on other sites More sharing options...
jwc Posted March 4, 2017 Share Posted March 4, 2017 2 hours ago, USNRET said: At very low levels it is ok, any higher and it is a shrill blur uh, you mean 80Hz " shrill blur" then 100Hz a problem? What nets? Quote Link to comment Share on other sites More sharing options...
USNRET Posted March 4, 2017 Author Share Posted March 4, 2017 Lower volume levels (very low) everything sounds good, the higher the volume the worse the "mids and highs" sound. Stock networks AK5 (I haven't seen them) but the speakers sounded great on other amps at all volume. Quote Link to comment Share on other sites More sharing options...
richieb Posted March 4, 2017 Share Posted March 4, 2017 A pain I know but try another amp again just to see if something went astray in the amp change. Or try another source other than the OPPO. I've been here and this does suck --- Quote Link to comment Share on other sites More sharing options...
Schu Posted March 4, 2017 Share Posted March 4, 2017 Is there an impedance mismatch? I dont see the specifications on the 275. I'd like to know what tubes are being used... Quote Link to comment Share on other sites More sharing options...
USNRET Posted March 4, 2017 Author Share Posted March 4, 2017 OK, right speaker connection at amp was swapped +/-. I have been using the same wires thru out and polarity has been verified several times thru out the reconfiguration. With the polarity swapped the harsh upper is gone sounds good BUT I have lost center image. Playing with toe (KHorns are enclosed as I have no corners) I still cannot get the center. Wide stage and full range without the crappiness but it is left and right wide, very little center stage. I will swap back to the original polarity just to confirm. Quote Link to comment Share on other sites More sharing options...
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