After experiencing a thermal shutdown of both of my MC501 amplifiers a few days ago, as discussed in the thread MC501 Thermal Shutdown, I decided to follow Serge's advice to pull the amplifiers out of the Salamander rack, and try to repeat the thermal shutdown with the amplifiers in unrestricted air space.

I pulled both MC501 amps out of the rack, but left them connected as they were in the rack, that is C1000P to MEN220 to MC501 amps. I played the same Charles Earland CD, and let the amps play for 30 minutes at 32 volume setting on the preamplifier (0.5 watts peaks). Using my Fluke 65 Digital Infrared Thermometer I measure the temperature of the heat sinks at 96.8° on the left channel amp,and 97.7° on the right channel amp. Raising the volume to 44 on the preamp (25 watt peaks), waiting 15 minutes, the temperatures were 112.6° on the left channel amp, and 114.5° on the right channel amp. Raising the volume to 55 on the preamp (200 watt peaks), waiting 10 minutes, the temperature was 141.6° on the right channel, and 141.8° on the left channel amp. Within 20 seconds or so the right channel amp went into thermal protection, and the heat sink measured 146.8°. The left channel amp remained operating, and measured 142°.

The MC501 amplifiers have two heat sinks each. Immediately after the thermal shutdown of the right channel amplifier I measure both sides of the heat sinks. The heat sink on the right side of the amp was 146.8°, yet the heat sink on the left side of the amplifier was 119°. I found this peculiar, so I measured the temperatures of the heat sinks on the left channel amplifier, which had yet to go into thermal shutdown. The right side heat sink measured 141.3°, and the left side heat sink measured 112.0°. This is very unusual.

After shutting the system down, and giving the amplifiers 30 minutes to cool down, I removed the MEN220 from the signal path, wiring the interconnects directly from the C1000P to the MC501 amps. I energized the system, and began again. This time I immediately raise the volume to 68 on the preamp (500+ watts peaks) and let the amps play, waiting to see if they would go into thermal shutdown. After 30 minutes, with both amplifiers peaking 500+ watts and no thermal shutdown, I measure the heat sink temperatures. The left channel amp measured 120.7° on the right heat sink, and 118.9° on the left heat sink. The right channel amplifier measured 121.2° on the right heat sink, and 118.8° on the left heat sink. I let the amplifiers continue to plat at 500 watt peaks for another 15 minutes, remeasured the temperatures, and found them to be +/- 1° for the previous readings. Both amps were operating properly without any signs of heat related issues.

Without the MEN220 in the signal path, running the amps for 45 straight minutes at 500 watt peaks, the maximum temperature of the heat sinks was 121.2°, with less than 3° difference between the left and right heat sinks on each amplifier. With the MEN220 in the signal path, running the amps at 200 watt peaks, the right channel amplifier maximum temperature reached 146.8° on amplifier's right side heat sink, and 119° on the left side heat sink.

Whatever is taking place in the signal path between the C1000P and the MC501 amplifiers with the MEN220 in the signal path, the MC501 amplifiers are responding in a peculiar manner, and causing the transistors attached to the right heat sinks to run considerably hotter than the transistors attached to the left heat sinks on each amp, and causing thermal shut down from over heating. This is disturbing, and is certainly cause for concern, and will require some investigation to determine the cause.

I have the MEN220 back in the signal path for now, and will keep my volume level below 50 watt peaks. Even at this level, the amplifiers are running hotter with the MEN220 in the signal path than without, but are operating within safe temperature levels. The mismatched temperatures between the left and right heat sinks are still there, just not as dramatic at the lower volume levels. My next step is yet to be determined.



MC501's with MEN220 in signal path.




MC501's without MEN220 in signal path

__________________
Dan


Living Room System: McIntosh C2300, MC601 (2), MCD1100, MS750, MR85, Sony DAT 60ES, Nakamichi BX-300, Micro Seiki DD-40, Ortofon 2M Black, Sonos ZP90, Oppo BDP-83SE Blu-ray, PMC EB1i, Fathom f113 w/ Sound Anchor stand, Power Plant Premier (2), PS Audio Soloist Premier SE (3), Rollerblock Jr.'s, Wireworld Silver Eclipse IC's & PC's, Kimber 8TC with WBT Solid Silver Angled Locking Banana Connectors.
Studio System: McIntosh C1000C/P, MC2301 (2), MCD1100, MR88, Michell Gyro SE w/SME 309/Ortofon Cadenza Black, Sonos ZP90, PS Audio Power Plant Premier, PS Audio Soloist Premier SE, Sonus Faber Amati Anniversario, Rollerblock Jr.'s, Wireword Silver Eclipse IC's & PC's, Wireworld Silver Eclipse speaker cable.
Studio Home Theater System: McIntosh MX120, MC452, Oppo BDP-95 Blu-ray, PS Audio Soloist Premier SE, JBL LSR-6332 (2), JBL LSR-6328P (3), McIntosh XLS112 (2), Sony 52XBR9, Tributaries Silver IC's, Wireworld PC's.
Vintage: McIntosh MA5100, MR74 tuner, JVC XL-Z1050 K2 CD player, Wyred 4 Sound DAC2, Tandberg 3008A and 3026A, JBL4312A , McIntosh 4300V for deck speakers.

This certainly puts a new wrinkle in the MEN 220 situation.

__________________
2-Channel McIntosh C45, McIntosh MCD 500, McIntosh MC 501 x 2, Clearaudio Emotion, B&W 803D, JL Audio F-113 Oppo BDP-95, Richard Gray, Kimber Kables
Theater - McIntosh 205, B&W 804s, 805s, HTM3S,JL f113 subwoofer, Oppo BDP-83SE, Onkyo Preamp, Panasonic AE4000 projector, Richard Gray

Dan, I suspected as much.

I am waiting for Ron-C to explain the cause as he said the MEN220 will actually make the amps run cooler and more efficient...

My own gut feeling Dan would be that with your speakers placed close to the walls, you are experiencing peaks and dips/bass suck out. Now, there is only one thing that would make an amp run hotter, more juice into a speaker into an impedance swing of the speaker at certain frequency ranges... The men220 compensates, the 501s get hotter.... I am trying to figure it out, will get back to you on this one....

Dan,
Without owning a MEN220 or being able to see/read the manual this suggestion might be moot. What outputs are you using? Low or High? I noticed this from the literature:

MAXIMUM VOLTAGE
OUTPUT
4.5V Unbalanced and Balanced
(Low Sensitivity)
2.25V Unbalanced and Balanced
(High Sensitivity)

If you're using the Low try switching to the High maybe????

__________________
MBL 4006, MF A5cr, Wadia 170i, Verity Audio Rienzi, WireWorld Cables

Hi
It must be something else, I don't think it has to do with MEN220 adjusting the freq response and causes the amp to run hotter.
Thanks

Hi
Or, check the unbalance and balance feature.

I find this surprising, and peculiar as to why one side of the heat sinks would run hotter than the other.

What Serge is saying does seem to make lots of sense. It does also, as thughes commented, put a new wrinkle in the MEN220 situation....I wouldn't want to live with that. I'll follow with interest to see how you get this worked out Dan...


Pete

__________________
Main System: Harmon Kardon T60 TT/Ortofon MC10, McIntosh: MR80, MCD7009 (as transport), MVP841, C40, MC501's (3), Soundcraftsmen: RP2215-R Eq/AS1000 Real time analyzer, DBX 3BX II, Carver C9, SAE 5000, Nakamichi Dragon, Crown SX724, JVC HM-DH40000U, Toshiba SD-394 Combo Player, Sony Bravia KDL-55EX720 3D LED TV, JBL L220A's, JBL B460/BX63A, AudioQuest Diamondback IC's, Terk AF-1 Powered Antenna, Panamax M5100-EX Line conditioner, Integra DBS-30.1 Blu-Ray Player, Wyred for Sound DAC-2 Digital to Analog converter

Florida Room/Studio System: Pioneer PL-L1000 TT/Audio Technica ATS52W2, McIntosh: MR77, C32, MC2205; Hafler DH-500A, Soundcraftsmen RP2215-R Eq, JBL 4313B's, JBL 2241-based Sub, JBL BX63, Cheapie Panasonic DVD/VCR Combo, Sony KV-27FS100 TV, Terk AF-1 Powered Antenna

Master Bedroom System: McIntosh: MX117, MC2125; Soundcraftsmen RP2212 Eq, Pioneer Elite DV-09, Phase Technology PC80 Towers, Hitachi 31CX4B TV, Terk AM-FM Pi Powered Antenna, Panamax 1000

Office System: McIntosh MR78, Crown IC150A, Crown DC300, Carver SD/A-490t, Soundcraftsmen RP2212 Eq, Toshiba SD-394 Combo player, JBL 4401's, JBL PB10 Sub, Sony KV-27FS100 TV, Terk AF-1 Powered Antenna

Serge.......One of the other things I noticed was that without the MEN220 in the signal path I had a higher preamp volume number for a given output power. With the MEN220 in the signal path, not only was I getting more amplifier output at lower preamp volume settings, but I also noticed that the right channel was about 2 dB higher than the left channel. I assume this is due to the way the MEN220 is compensating for the speaker placements.

What really puzzles me is the 25° temperature difference between the right heat sink and the left heat sink on the same amplifier.

__________________
Dan


Living Room System: McIntosh C2300, MC601 (2), MCD1100, MS750, MR85, Sony DAT 60ES, Nakamichi BX-300, Micro Seiki DD-40, Ortofon 2M Black, Sonos ZP90, Oppo BDP-83SE Blu-ray, PMC EB1i, Fathom f113 w/ Sound Anchor stand, Power Plant Premier (2), PS Audio Soloist Premier SE (3), Rollerblock Jr.'s, Wireworld Silver Eclipse IC's & PC's, Kimber 8TC with WBT Solid Silver Angled Locking Banana Connectors.
Studio System: McIntosh C1000C/P, MC2301 (2), MCD1100, MR88, Michell Gyro SE w/SME 309/Ortofon Cadenza Black, Sonos ZP90, PS Audio Power Plant Premier, PS Audio Soloist Premier SE, Sonus Faber Amati Anniversario, Rollerblock Jr.'s, Wireword Silver Eclipse IC's & PC's, Wireworld Silver Eclipse speaker cable.
Studio Home Theater System: McIntosh MX120, MC452, Oppo BDP-95 Blu-ray, PS Audio Soloist Premier SE, JBL LSR-6332 (2), JBL LSR-6328P (3), McIntosh XLS112 (2), Sony 52XBR9, Tributaries Silver IC's, Wireworld PC's.
Vintage: McIntosh MA5100, MR74 tuner, JVC XL-Z1050 K2 CD player, Wyred 4 Sound DAC2, Tandberg 3008A and 3026A, JBL4312A , McIntosh 4300V for deck speakers.

Yes, me too.

Pete

__________________
Main System: Harmon Kardon T60 TT/Ortofon MC10, McIntosh: MR80, MCD7009 (as transport), MVP841, C40, MC501's (3), Soundcraftsmen: RP2215-R Eq/AS1000 Real time analyzer, DBX 3BX II, Carver C9, SAE 5000, Nakamichi Dragon, Crown SX724, JVC HM-DH40000U, Toshiba SD-394 Combo Player, Sony Bravia KDL-55EX720 3D LED TV, JBL L220A's, JBL B460/BX63A, AudioQuest Diamondback IC's, Terk AF-1 Powered Antenna, Panamax M5100-EX Line conditioner, Integra DBS-30.1 Blu-Ray Player, Wyred for Sound DAC-2 Digital to Analog converter

Florida Room/Studio System: Pioneer PL-L1000 TT/Audio Technica ATS52W2, McIntosh: MR77, C32, MC2205; Hafler DH-500A, Soundcraftsmen RP2215-R Eq, JBL 4313B's, JBL 2241-based Sub, JBL BX63, Cheapie Panasonic DVD/VCR Combo, Sony KV-27FS100 TV, Terk AF-1 Powered Antenna

Master Bedroom System: McIntosh: MX117, MC2125; Soundcraftsmen RP2212 Eq, Pioneer Elite DV-09, Phase Technology PC80 Towers, Hitachi 31CX4B TV, Terk AM-FM Pi Powered Antenna, Panamax 1000

Office System: McIntosh MR78, Crown IC150A, Crown DC300, Carver SD/A-490t, Soundcraftsmen RP2212 Eq, Toshiba SD-394 Combo player, JBL 4401's, JBL PB10 Sub, Sony KV-27FS100 TV, Terk AF-1 Powered Antenna

Hi
Dan.... Have you been running the amps that high before?