EBS Fafner problems

Thexawakening · #1 09-04-2011, 11:13 PM

So here's the deal. I'm getting a kind of low frequency distortion from the preamp section, and yes it's beyond the shadow of a doubt that it's in the preamp. It happens no matter what, even with the gain turned down low way below clipping. It's like a kind of farting out sound in the low end only. Maybe I'm just picky. Any other fafner users experience this?

4-string · #2 09-05-2011, 04:46 AM

Have you checked the pre amp tube? That would be the obvious place to start. Easy to replace yourself, no biasing needed (self biasing).

Thexawakening · #3 09-07-2011, 01:57 PM

Yeah I've tried many tubes and it always does it, with the EQ flat, gain set to where I cant even get the clip LED to come on at all it'll kinda fart out but in a weird way, just the low frequencies do it. And no matter what setting the master is at. It does go away if I bypass the preamp though.

vedi · #4 09-07-2011, 02:23 PM

(disclaimer: my experience with HD350. not claiming everything applies to fafner)

hey,

I had a similar (possibly same?) problem with my ex, HD350... my electronically more educated friend called it "ground leakage". the thing is that every pot in the head is grounded by being screwed to the chasis, but any of those can oxidize and thus un-ground the pot, which will in return try (and succed) to send current the other way. so, I dissasembled the preamp PCB, and with very fine sanding paper did a few gentle swipes on the chasis and the pots where they touch. it solved the problem. I also experienced problems with send/return module: every jack is TRS and grounded, if there is no jack inside. as the venting fan is in nearby, it got a bit dusty, and as we know the dust isolates... you can imagine we checked EVERYTHING. until another guy, whose bass player owns a fafner, told us to just use a short cable to connect send into return... boy, did it work again.

probably not the case, but anyway: a couple of months after the warranty expired, I noticed a noticeable (sic!) drop in volume. it turned out that opamp at the input stage was at its last paces. the people at EBS were very prompt about solving the problem and mailed me the parts and schematics for free, so I could swap the opamp and solve the issue. also, my amp was of older revision, so they also included the parts to upgrade it and thus prevent the problem from reccuring. the new opamp turned out to be audio-grade, whereas the old one was just generic. (yes, I noticed the difference and asked the tech why is that.) how cool is that?

Thexawakening · #5 09-08-2011, 12:27 AM

Those are some great suggestions! I'm going to have to try doing that to the pots, it would make sense as this one is around 10 years old. I even replaced all of the bigger caps in the power supply, which actually gave the amp way more balls. I replaced the 4 main 10,000uf filter caps with 15,000uf caps, sounds better than ever. But I still get the flabby sounds when I play the low E, maybe I'm just picky, one thing too is the output from my bass is super hot, and bass heavy. I'm gonna dig into this thing more.

vedi · #6 09-08-2011, 03:35 AM

I would suggest that you first use multi-meter to check if everything is grounded as supposed... the guy that proposed the cable in send/return module had a few fafners on his repairing table, all with the same problem. but great amps, still wish I had HD350.