GK Amp Humming

BassSlug123 · #1 08-12-2011, 11:31 AM

Hey everyone!

I play a 700RB2 head through a 410 RBH and 410 RBX cab. I love the tone and warm sound that this GK rig offers. I have run into a slight problem though. There is some humming coming from the rig that gets louder as the volume is turned up. Any suggestions on troubleshooting this issue?

I do have another concern. Originally, I only played through the 410 RBX cab, but I ran into a sweet deal that I couldn't pass up for the 410 RBH. It sounded great, and when I run the head through both cabs, it increases it's power output to 480W plus 50W to the horn. Each cab is rated to be able to support 800W. The concern I have is whether or not I am underpowering the head and possibly damaging it by pushing it too hard.

Thanks!

WingKL · #2 08-12-2011, 12:44 PM

Welcome to TB. Underpowering is a myth. Look up the FAQ about it. Advice on troubleshooting? Are you getting a hum only if your bass is connected to the amp? If so it's the bass, probably single coils and not shielded or the cable. If you get the hum with nothing connected to the amp, bring it to the tech. It should be a simple fix for them. If you want to do it yourself, use the divide and conquer method. Look at your rail voltages to see how much it's rippling. Check the preamp out to see if you can see the hum. If you dont, the hum is coming from the power amp section. Continue tracing the signal to see which point the hum is coming from. You do have an oscilloscope and a schematic to the 700RB right?

RickenBoogie · #3 08-12-2011, 12:54 PM

+1 to above. Take it in for a check up.

georgestrings · #4 08-12-2011, 03:40 PM

Are both cabs 8 ohm?? If not, you'll be letting out the magic smoke on that amp soon, and that might be why it's humming - too low of a speaker load...

- georgestrings

RickenBoogie · #5 08-12-2011, 03:50 PM

Good point^

BassSlug123 · #6 08-14-2011, 12:37 PM

Quote:

Originally Posted by georgestrings

Are both cabs 8 ohm??
- georgestrings

Yep, both are 8 ohms

BassSlug123 · #7 08-14-2011, 12:43 PM

Quote:

Originally Posted by WingKL

Welcome to TB. Underpowering is a myth. Look up the FAQ about it. Advice on troubleshooting? Are you getting a hum only if your bass is connected to the amp? If so it's the bass, probably single coils and not shielded or the cable. If you get the hum with nothing connected to the amp, bring it to the tech. It should be a simple fix for them. If you want to do it yourself, use the divide and conquer method. Look at your rail voltages to see how much it's rippling. Check the preamp out to see if you can see the hum. If you dont, the hum is coming from the power amp section. Continue tracing the signal to see which point the hum is coming from. You do have an oscilloscope and a schematic to the 700RB right?

Thanks a ton! Apologies for being ignorant, but what exactly is an oscilloscope and a schematic? I do have the manual and made sure that everything was connected properly. I am playing with a heavy duty monster cable and a brand new post 2009 warwick rockbass with passive single coil pickups (will they cause humming?), but I don't think that either of those should be the problem. I did make sure I had a direct connection to an outlet instead of using a surge protector as someone at a local music shop advised me to do to make sure I had enough power supply (which did help, but there is still some humming). They also advised that I should get a "power conditioner" for the head. You seem very knowledgeable, so what's your take on that? Also, the hum is comming from both cabs (I ran each cab on its own).

Thanks!

RickenBoogie · #8 08-14-2011, 01:29 PM

No on the power conditioner- big waste. It's just a glorified, overpriced power strip. And yes, single coil pups can cause hum, that's why god created "humbucking" pups. But, that's beside the point, single coils are still a good choice for bass, (Jazz bass, Rickenbacker, etc). You know, electric instruments make noise sometimes, and we just learn to live with it. If it's covered up when playing with the band, it's not an issue. If however, it's noticeable all the time, maybe you should take it in to an amp tech for a check up- since your posts lead me to believe you yourself are not qualified to go into the amp and work on it.

BassSlug123 · #9 08-14-2011, 01:42 PM

Quote:

Originally Posted by RickenBoogie

maybe you should take it in to an amp tech for a check up- since your posts lead me to believe you yourself are not qualified to go into the amp and work on it.

I may end up taking it in some time, but I do play with a group, so it's not a huge problem, just a bit annoying seeing as how I invested in such an awesome rig. But I definitely do not have to expertise to actually go in and take the thing apart. Either way it is a great setup, it's just disappointing to hear it hum when I practice by myself, but oh well.

Thanks!

**B-string** · #10 08-14-2011, 01:45 PM

Try a new power cord first. You can "borrow" one from a computer, I have seen power cords with bad grounds before.

Slowgypsy · #11 08-14-2011, 01:49 PM

With single coil pups... trying running both equally. By that I mean if you have a blend control turn it dead center. If you have 2 separate volume controls turn both full on. Does that setting help minimize the noise?

Also, is there a noise level difference if you have your hands on the strings versus no hands on strings?

BassSlug123 · #12 08-14-2011, 03:43 PM

Quote:

Originally Posted by Slowgypsy

With single coil pups... trying running both equally. By that I mean if you have a blend control turn it dead center. If you have 2 separate volume controls turn both full on. Does that setting help minimize the noise?

Also, is there a noise level difference if you have your hands on the strings versus no hands on strings?

Either way it hums. I made sure to see if it was feedback, but that doesn't seem to be the case either. And yes, I have tweeked with the balance as well as the eq's on the bass itself. Volume on the bass is always at max. And I am probably going to try another power cord. From what I here, I can exchange my monster cable for a new one if it's not working properly.

Thanks!

Slowgypsy · #13 08-14-2011, 04:48 PM

Just turn on the amp with no cord plugged in. Does it hum?, play with the volume (master & woofer knobs) to see if it hums.

What are your settings on the RB 700-II?

WingKL · #14 08-14-2011, 10:40 PM

That heavy duty Monster cable you're using to connect your bass to the amp, does it say speaker cable or instrument cable on it?

BassSlug123 · #15 08-15-2011, 11:37 AM

The cable says instrument cable and was what seemed to be a solid investment after talking to some people. The settings on my head are all flat at 12:00 except for the contour which is at about 9:00 to ensure that most of the sound is coming from the bass. But I will definitely see if it hums without anything plugged in.

Thanks!

BassmanPaul · #16 08-15-2011, 01:42 PM

Quote:

Originally Posted by BassSlug123

The cable says instrument cable and was what seemed to be a solid investment after talking to some people.

Just because it's expensive doesn't mean that it's good. I think you talked to the wrong people!.

**B-string** · #17 08-15-2011, 06:43 PM

Quote:

Originally Posted by BassmanPaul

Just because it's expensive doesn't mean that it's good. I think you talked to the wrong people!.

+ 10 trillion