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Thread: M100 Amps thumping
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July 31, 2014, 10:57 PM #1
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M100 Amps thumping
I just bought what appear to be a nice pair of M100 mono block amps. I hooked them up, and they ran for about 20 minutes. At that time, one channel cut out most of the volume (the music degraded) and began a rhythmic three-beat thumping similar to a heartbeat. This sound persisted even after turning down the volume. No change on the preamp (conrad-johnson pv11) made any change to the noise. The music degradation bled over to the other channel, but once I pulled the speaker wires on the offending channel, the other channel returned to normal. I shut off the system, waited about half an hour, turned it all back on, re-biased the output tubes, and started listening again. It sounded great again, but, again, only lasted about 15 minutes, and then the same behavior occurred again.
Is this a simple issue of replacing output tubes? I have a stack of spare 6550s -- should I just replace all five and see if that fixes it? And if it does not, then what?
Thanks.
B.
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July 31, 2014, 11:20 PM #2
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Re: M100 Amps thumping
I would replace the output tubes one at a time with the same replacement tube and see if that is the problem. If not move to the driver tubes.
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August 1, 2014, 12:44 AM #3
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Re: M100 Amps thumping
Jack,
Thank you. Upon opening, I discovered 1 6550 and 4 KT88s. I replaced all 5 with 6550s, and I ran it for about an hour with no thumping. I will try again tomorrow for longer and see if it is cured.
B.
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August 1, 2014, 10:57 AM #4
Re: M100 Amps thumping
Sounds like nice amps but which brand are the M100's? I have Ray Lumley M100 tube monoblock amps that are also KT88 (currently using KT120's).
Main 2ch/HT:Acoustat 2+2,Axiom EP500,Ray Lumley M-100, Bedini BA-803,Threshold T3,JRDG Consumate Phono, Lenco L75, ZYX Universe cart,Oppo BDP 95(transport), Calyx Femto DAC,Bryston BDP-2,Pioneer F-91 tuner,Studer A807 r2r,Consonance d-Linear15 power filter, DVDO Matrix 4x4,Mitsubishi HC-5 projector, Audience Au24e and LectraLine Xe cables,Cullen Power Distribution Box with upgraded cable
Bedroom 2ch/HT:Tetra 406, Forte model2pre,Forte model3amp,TeacUD503,Faroudja DV1000,PioneerCLD-97 ld player,Thorens TD-146,PioneerTX-9800,Mitsubishi HC5 projector,Tetra Artet cables
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August 1, 2014, 12:05 PM #5
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Re: M100 Amps thumping
Well, I posted in the Audio Research Corporation forum . So, yes, they are ARC M100s.
This morning I went to test if the tube switch had worked, and it blew a fuse. I switched the fuse from the other amp, and the amp seemed fine. Not sure why it blew the fuse. Now I need to go buy more fuses.
Brian.
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August 1, 2014, 12:45 PM #6
Re: M100 Amps thumping
Oh, I missed that. ARC makes very nice gear. I have a PH3 phono amp that is very well made and works well.
My amp blew a fuse too when I first got them. After replacing I didn't blow another. Perhaps it was a faulty fuse?Main 2ch/HT:Acoustat 2+2,Axiom EP500,Ray Lumley M-100, Bedini BA-803,Threshold T3,JRDG Consumate Phono, Lenco L75, ZYX Universe cart,Oppo BDP 95(transport), Calyx Femto DAC,Bryston BDP-2,Pioneer F-91 tuner,Studer A807 r2r,Consonance d-Linear15 power filter, DVDO Matrix 4x4,Mitsubishi HC-5 projector, Audience Au24e and LectraLine Xe cables,Cullen Power Distribution Box with upgraded cable
Bedroom 2ch/HT:Tetra 406, Forte model2pre,Forte model3amp,TeacUD503,Faroudja DV1000,PioneerCLD-97 ld player,Thorens TD-146,PioneerTX-9800,Mitsubishi HC5 projector,Tetra Artet cables
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August 1, 2014, 12:51 PM #7
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Re: M100 Amps thumping
Yes, to some degree I wonder whether the tube issue and the fuse issue is not just related to rough handling by UPS. My last set of amps blew three tubes and two fuses before stabilizing and did not blow another for years.
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August 1, 2014, 07:44 PM #8
Re: M100 Amps thumping
The M100 amps are classics and still in demand and the price keeps going up. You may want to consider sending them back to ARC and having them recapped and given a general going through if you can afford it.
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May 1, 2016, 09:34 AM #9
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May 1, 2016, 09:54 AM #10
Re: M100 Amps thumping
You have two fuses on the back of the amp. One marked "mains" this should be 3A slo blow, the other is marked "HT" This is the 500ma.
Dan Santoni
Authorized service for (in no particular order) - Copland, Cary, Unison Research, Allnic, Modwright, Ayon, Hegel, Belles, Aesthetix, Coincident, Zesto and a whole bunch more
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www.dtsaudioelectronics.com
www.blackdoghifi.com
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May 1, 2016, 10:30 AM #11
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Re: M100 Amps thumping
I only recall seeing one, but I'll take a look later when I get home. I did end up replacing the 500 mg fuse with a fast low and everything seems to be working. I missed seeing the other fuse holder, but I'll look again
Sent from my iPhone using Tapatalk
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May 1, 2016, 01:28 PM #12
Re: M100 Amps thumping
It might be inside the amp.
Dan Santoni
Authorized service for (in no particular order) - Copland, Cary, Unison Research, Allnic, Modwright, Ayon, Hegel, Belles, Aesthetix, Coincident, Zesto and a whole bunch more
Custom Manufacturer of Blackdog HiFi.
www.dtsaudioelectronics.com
www.blackdoghifi.com
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AudioShark forum is a leading forum site for High End Audio Discussion, Stereo System Discussion, Home Theater System Discussion, Best Home Stereo System Discussion, Home Theater Installation Discussion etc.
The AudioShark forum was created for sharing the passion of high-end Audio. We have Audiophiles from all over the world participating and sharing their knowledge. From novice to experts, you will find a friendly environment for discussing about High End Audio, Stereo System, Home Theater System, Home Stereo System, Home Theater Installation, Amplifiers, Speakers, Subwoofers, Integrated System, Acoustic treatments & Digital Room Corrections and many more.
At AudioShark, we also have incorporated an exciting Marketplace where members can peruse terrific buys on used gear, as well as meet dealers and discuss the purchase of new gear.
We are as crazy about this hobby as you are! So come on in and join us! Audioshark.org the Friendliest Audio Forum!
Industry Participation Disclosure : The owner and administrator of Audioshark is the owner of Suncoast Audio LLC in Sarasota Florida. Suncoast Audio has a full brick and mortar presence in Sarasota with several great show rooms with many world class brands. More information can be found at http://www.suncoastaudio.com
Audioshark is a community of like minded individuals. Audioshark welcomes participation from all manufacturers and owners of all brands and products. It is our belief that online forums provide a community of like minded audiophiles and music lovers to encourage the growth of this wonderful hobby.
Sincerely,
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You should ask your dealer to bring the CH stuff he wants to sell you for home audition in your system. IMO there is no way to tell what will sound better in your system.
MSB Reference vs CH C1.2