What can make a preamp blow the amp's fuse???

Ricardo

I need some help from the experts...

Here's the story; yesterday I got a used AES AE3 DJH (long name) preamp and hooked it up with the JBL Urei amp; I noticed that when I switched the amp on, there was a new "thump" on the speakers, sometimes relatively loud; never had that with my Dared preamp. Anyway, I didn't give it much importance because after the thump things quieted down, no hums or anything.

Today I received the Belles from George D., hooked it up and when I turned it on, the Belles' fuse was gone. Long story short and after two additional burnt fuses (had to drive all the way up to PArts Express in Dayton to get them....no one carries them around here), I put back the Dared in the system and everything is working fine; no thump, hum, nothing.

So, what could be the cause of the thump with the JBL and the fuse burning in the Belles? I tried two sets of different tubes in the AES, with the same result.

I am going to call AES on Monday, but anyone here has any idea of what should I look for?

Thanks.

Ricardo.

RuSsMaN

Caps in the AES charging.

How long after you turned it on, did you power up everything else? More than a couple minutes?

Ricardo

couple of minutes? no....I have an Adcom ACE-515 line conditioner that provides a sequencial power on, I think the amp goes on 10 seconds later.

So, do you see this as a normal thing that can be avoided by waiting those couple of minutes?

Thanks!!

RuSsMaN

I'd try it, I'm not familiar with that design, but it's worth at least giving time for the voltage on the tube plates to stabalize, along with any power supply caps.

Turn it on, wait 5, power up the amp, report back.

Ricardo

Ok; unhooked the Dared; had to stop to go get my son from a party; came back, hooked the AES and turned it on; grabbed a couple slices of pizza, ate the pizza, had a beer and turned on de CD player; went out for a smoke (yes I started smoking again ), came back in, turned the amp on....and IT WORKED!!!

Russ, you are a genius. I need to remember this now...or maybe leave the pre on all the time; the Adcom has an unswitched plug that's always hot for this pupose.

THANKS!!!

RuSsMaN

Your 10 second auto delay just isnt enough. It may need only 30 seconds or so, but it obviously needs more time than it was getting. No genius here, I've just been down that same fuse blowing road before.

Rock on.

univera

Great thread. This is what makes this a great forum. May not need this info now, but great info to tuck in the back of the brain for future reference.