• Check out the Annual AK Secret Santa exchange Program, signup before November 23rd in the AK Charities & Christmas forum!

Hafler 9270 hum

C

ccrnnr9

Member
I purchased a Hafler 9270 yesterday with original box. The seller purchased it at a flea and did a quick demo and all seemed well - exceptionally clean. Got it home, powered up unconnected, and let it warm up for about 30min. Tested DC offset and am getting 25mV right and 14mV left. Connected my NAD 1300 and ADS 730 and was greeted with a very heavy hum coming out of both speakers. I powered off and tried the following:

1. Disconnected all inputs and repowered on - hum still loud and present at both speakers.
2. No change in hum when adjusting gain on either channel.
3. Tried two different power cords (one that came with unit & one that is about a month old and is exact specs listed in Hafler manual)
4. Tried 2 different outlets (one same outlet as all other components and one separate - both cases plugged tried plugged into power strip and directly into wall)

None of them above changed the noise in any way. Just to be sure I tried 3 other amps in its place with all other equipment the same (Yamaha MX-630, Hafler DH-200, 3e Audio A7) and all three are dead silent and work as usual.

Any thoughts on issue? I’ve exhausted my knowledge. Not a whole lot of info on the 9270. Bummer I was really excited to hear how this compared to the DH-200 with Fantasia upgrade circuit!

N
 
Last edited:
Register to hide this ad
I haven’t tried that and in my mind it would kind of make sense given the Hafler manual mentioning it be necessary that only one ground loop be present. I’ll pick one up today and give that a shot. I hope it works as I was eager to see how this compares to the Fantasia modded DH-200 (which does not have this issue in the identical system).
 
I'd had a hum from my Hafler non commercial DH220 amp that had started after about 40 years from when I'd soldered it from a kit. I replaced the filter capacitors and the rectifier with good results. Not sure your situations the same though.
 
You must log in or register to reply here.
Back
Top Bottom