GK 800RB users.. help please

gustobassman · #1 05-18-2011, 10:32 PM

Any ideas.. please read..

First off, i run an american standard jazz v through a Sansamp Bass Driver with all the 800RB eq flat - i run the Sansamp with a little bass boost, a minor treble cut and the drive almost off. I switched the inst. output to line because there wasn't enough volume for the gig i was playing.. i forgot to adjust my input volume on the 800RB. I've owned the 800RB for about 10 years, my workhorse, it has it's share of 50,000 note checkups, so....

The amp shut down at the very end of a 50 min set.... no go.. I waited 3 days, turned it back on and got sound! but then i realized no matter what cables, cabs, or bass i use i am getting a very audible hiss, kinda like a real loud fan. The fuse is fine, i'm a real dumba$$ for not adjusting the input volume on the 800RB, but obviously something is wrong...

so.. 800RB owners... does this fix sound expensive?? just asking, i may have to look into other options..

gustobassman · #2 05-18-2011, 10:36 PM

before you ask, yes, i have taken everything possible out of the signal chain, just bass, cable, head and cab. no matter what combinations i run i am still getting the hiss... thanks...

G

lbwdog · #3 05-19-2011, 12:20 AM

My '87 800RB has always had a little hiss, as some other G-Ks I've played, but it's never been a problem live or in studio.

I suspect that your's may be the same, but the hiss has been masked or EQd out by using the Sansamp, and now your ears are focused on it..........just a thought.

Standalone · #4 05-19-2011, 09:59 AM

My 800RB has that slight hiss, too. I imagine that you pushed something too hard and put one of the old transistors or capacitors out of tolerance.

You might want to take it in for a thorough going-over by a tech to see if s/he can find what's going on.

From what I've gathered, the 800RB is a very straightforward amp to work on and fix.

You might also want to try the old cleaning the send/return jacks thing.

When I need more volume for a gig, I cut the low bass-- a sacrifice to increase the headroom of the amp and still be heard. I think groove is about time, not so much the deep deep stuff. I leave that to the DJ's...

TripleDouble · #5 05-19-2011, 10:09 AM

800RBs are easy to work on, and every tech in the world worth his/her solder has experience with them. I'm not going to speculate what yours is doing, but as mine got older the caps dried out and the hiss of the amp increased and i noticed a bit of an output drop, so I took it to be serviced. It was an affordable fix, I think ~$100, and now that amp roars on...

Kael · #6 05-19-2011, 10:10 AM

I'd check other 800's in local store to see if they also hiss if that's an option. Seeing as how you've used this head for 10 years, I am assuming that you are familiar enough with it that you are aware of the previous level of hissiness. Take it in to a tech and have him go over it. Seems to me that you probably drove the input a little harder than it likes. Not sure how the boost function works on that head. A hotter input might just have pushed it into clipping like turning up the boost knob would. My gut tells me that while a tube amp might work that way, the 800 does not work that way though.

sidenote: I use a SABDDI quite a bit. Actually I recently got a paradriver and have been giving that a shot for the past month. The juryis still out on which one I prefer. I lightly boosted bass for a couple years on my SABDDIl before finding that cutting the treble to 11 o'clock and leaving bass flat accomplishes the same thing and leaves the tone thicker up the neck. Boosting bass sounded great lower, but leaves the bass sounding thin in the upper registers. If you find a loss of clarity fromcutting the treble, roll the presence up a tad. 9 o'clock is usually plenty for me.

gustobassman · #7 05-19-2011, 12:08 PM

thanks guys.. i've had it worked on a few times.. it has always been a relatively easy fix (blown power switch, blown transistors etc.. ), this was just a new sound i haven't heard. I have always noticed the slight hiss, but this sounds more like a big fan...

Just to be sure i tried it with a couple more cable-power outlet-cab combinations and i found the most disturbing noise yet. The head was turned off and i plugged in a speaker cabinet to the head and heard a loud pop through my cab. the thing was off for crying out loud.. crapola

oh well... repair shop here i come!!!

Standalone · #8 05-19-2011, 12:28 PM

I do know that the 800RB lacks a circuit that prevents the power-on speaker pop. It's pretty worrisome that it's popping w/o poer on! See yor tech.

**BLDavis** · #9 05-19-2011, 12:44 PM

Seek professional help before anymore damage is done.
Contact Brian at GK.

gustobassman · #10 05-19-2011, 02:08 PM

all good.. I took it to Top Gear here in SD.. Tim has been the only one that has worked on this amp in the past.. i trust him.. thanks for all the info guys. Only problem with them being probably the best amp repair shop in town is... the wait... oh well. Should be 2-3 weeks but i'm supposed to do some fixes from my last recording session next week. anybody got a power amp i can borrow?

hahaha

cchorney · #11 05-19-2011, 02:38 PM

Check your "boost" volume. On my 800RB that thing is super noisy, and the reset may have activated it if you don't have a footswitch attached. Could be that easy of a fix.

...but that pop while turned off thing should still be looked at!

gustobassman · #12 05-19-2011, 04:33 PM

Quote:

Originally Posted by cchorney

...but that pop while turned off thing should still be looked at!

absolutely!! Tim told me the speaker jacks could still have a tiny bit of an electrical charge even when turned off. especially since i had it on for about 20 minutes before i shut it off and then the pop happened. He also said since there was sound coming out, it shouldn't too bad.. Kind of like an old VW, if it's turnin' over you can probably fix it.

lbwdog · #13 05-19-2011, 05:52 PM

Quote:

Originally Posted by PetePuma

Once our Band's singer plugged our sound system's power amp into my Sunn Concert Head (I don't know what the heck he was thinking). It fried it. The guitarist tried to soldier some new capacitors and transistors and totally ruined it beyond repair (cost effectiveness that is). I replaced it a GK400RB but the 15" Altec's didn't sound nearly as good. Moral, if you leave it in a studio take the fuse out and take the chord with you when you leave.

Young musicians can do some dumbass shl+, can't they?
BTW, I'm including myself there, even though it's been a while since I was a "young musician"!

Come to think of it, old musicians can do some stupid shl+ too!!