Crown CTs Fan Mod

[johanwholst]

Dear Rob!

Thanks for the hint connecting two 12V in series.

I did it today, and it is more silent than silent. I used ULN NFA8. Not much airflow (35m3/h) compared to the papst, but hopefully more than enough for a living room system seldom playing over 80dB.

Johan

[Jonas_h]

Johan, sent you a PM but might as well ask here as others could use the info.

Sounds really nice with the Noctua solution! So let me know if I understand you correctly:
- Unplug stock fans from "Output 1" and "Output 2"
- Connect two 12v fans in series to "Output 1" leaving "Output 2" empty.

Have you had any issues with the Noctua ULN and overheating? They move way less air than the stock.

[Jonas_h]

I just setup my system with the fan modded Crown CTs2000 driving a subwoofer... I only played low level, but after 5 minutes, the "Thermal" lamps lighted up, and the amp went into fault-mode. I have them placed in a rack.

I replaced the Noctua with the stock amps again, and the amp did not go into thermal mode anymore. But after one hours of low level listening again, it made a huge "bang" and went all read. THe smell of burned metal was noticable instantly. Goodbye amp

So I would NOT advice anyone to do a fan mod on the Crown Class-I amps if they want to keep their amps Maybe it would work if they are free-standing in a ventilated room, but in a rack, it's no-go.

[sebackman]

I am really sorry to hear that!

I do not have a CTS2000 or CTS3000 but I do run my CTS1200 pretty (4x 2226) hard and have not had any problem. I use MC2 amps for more power and there I use Papst fans as per above. No problem with them either. A T2000 drives my two sealed SUB1500 and has been for years.

Did you use any Noctua resistors or just the two 12V fans in series? No problem with connectors? Was the rack open in the back? Clean air flow in? Open the lid to see if it is clean inside or full of dust. I had a CTS1200 that came out of a fixed installation and it went into protect with original fans and when opened it was completely filled with dust so there was virtually no air flow. Please see pictures.



It sounds like the I-class amps may be different when it comes to protection. I have had CTS600, 1200, 4200 and 8200 go into protection mode from all sorts of stupid things I have done, like shortening outputs, have too many speakers in parallel and not opening the rear of the case for exhaust air). But no one has died on me so far.

Worth noting is that you used the ULN (Ultra Low Noise) version with only 35m3/h and I have used, as per post above, the 1800rpm and 2200rpm versions that flows 53m3/h but more important creates a much higher static pressure to draw air through the chassis.
http://noctua.at/en/products/fan

It may or may not have helped you and it is sad what happened nevertheless.

Anyway, I concur with the issuing a warning here.

DO NOT CHANGE TO LOW REV FANS ON CTS2000 or CTS3000, UNLESS YOU REALLY KNOW WHAT YOU ARE DOING.


IF YOU DO, PLEASE PROCEED AT YOU OWN RISK.

DO NOT USE NOCTUA ULN (Ultra Low Noise) VERSIONS AS THEY PROVIDE TO LOW FLOW AND TOO LITTLE STATIC PREASSURE.

CONSIDER USING PABST FANS WITH HIGHER AIR FLOW AND LOW NOISE.

THE ONLY NOCTUA VERSIONS THAT SHOULD BE CONSIDERED IS THE 1800 OR 2200 RPM VERSIONS WITH HIGHER AIR FLOW AND HIGHER STATIC PREASSURE. CHECK TEMPERATURE AT FULL POWER BEFORE INSTALLING.

NOTE THAT THIS SWAP HAS BEEN DONE ON CTS600, 1200, 4200 WITHOUT PROBLEMS BUT THAT DOES NOT MEAN THAT IT WILL WORK ON CTS2000 AND 3000

TOROUGH CLEANOUT IS MANDATORY ON THESE AMPS IF THERE ARE FROM AN EARLIER INSTALLATION AS THEY CAN FILL UP WITH DUST THAT WILL RESTRICT OR EVEN STOP THE AIRFLOW.

Best regards
//RoB

[Jonas_h]

I have three CTS1200 For my LCR and they run Noctua as well with no issues. Have done this several years. The class I is a different beast regarding heat

[gferrell]

I put thermal switches in mine on the heat sinks. The fan comes on at 120 degrees and go off at 90 degrees so it will cycle on and off unless playing really loud. So the fan does not come on until the amp hits 120 degrees. By then the music drowns out the fan. Really budget friendly.

[baldrick]

This could also very well happen without fan mod so it's not at all certain that the fan mod is the cause. I had i.e. a CTS3000 With bad soldering that caused similar problems.