Peave VB-2 noise (hiss)

walknbluez · #1 03-23-2012, 02:21 AM

My Peavey VB-2 has suddenly developed some noise. Sort of a constant hissing. It varies when I turn the EQ knobs. Is this a tube problem? There is no difference with the bass plugged in or not plugged in. Here is what the noise sounds like (recorded with my phone). amp noise 3.wav - File Shared from Box - Free Online File Storage

It's probably not as loud as it sounds there when I'm in rehearsal space, but it is noticeable. What could this be?

BbbyBld · #2 03-23-2012, 07:12 AM

If that's with the gain cranked wide open, then it's normal. If not, then one of your 12AX7s is noisy, most likely the first. You can try swapping positions if the noise bothers you. It's helpful to wear rubber gloves to pull the tubes.

walknbluez · #3 03-23-2012, 09:31 AM

The clean gain is on 6. The variation I noise occurs when turning the EQ knobs. What does swapping positions mean, taking the first one out and putting the second one in it's place, then putting the first one where the second one was? When you say first position, is that the one on the far left looking toward the back of the amp?

Tractorr · #4 03-23-2012, 09:35 AM

BbbyBld,

Not to hijack the thread but this is related to the preamp tubes. Is one tube for the clean and one tube for the drive channel? Or is the drive channel the tubes cascading one into the other?

walknbluez · #5 03-27-2012, 12:33 PM

Can anyone clarify what Bobby meant by swapping tubes?

jastacey · #6 03-27-2012, 01:26 PM

The First position is the far left when viewed from the front and yes your description of swapping the tubes is correct

walknbluez · #7 03-27-2012, 01:29 PM

Thanks jastacey. Just out of curiosity, why would this solve the problem?

jastacey · #8 03-27-2012, 02:23 PM

It could be a noisy tube, just swap it out if it fixes the problem ....

walknbluez · #9 03-27-2012, 03:01 PM

Well what I meant is how does just swapping positions as Bobby described, without putting in a new tube, solve the problem?

jastacey · #10 03-27-2012, 03:15 PM

If the noise follows the tube you swapped out then you know that it's the tube .... example: if the hiss moves to channel two, then you know it's the tube ....you replace the tube with a known good tube ... also if you move a tube from another section of the amp ( providing it's the same type of tube ( 12AX7 ) with the one from channel one and the hiss goes away, then you know the tube is the issue ... my question is ....what is/was the MAIN volume set at when you did the recording ... if you set the channel one at 6 and had the MAIN wide open that could be what some folks consider normal floor noise also what kind of cabinet are you using does it have a tweeter? and is the tweeter turned all the way up .... inexpensive tweeters will give an exaggerated/harsh hiss level

walknbluez · #11 03-27-2012, 03:35 PM

Quote:

Originally Posted by jastacey

If the noise follows the tube you swapped out then you know that it's the tube .... example: if the hiss moves to channel two, then you know it's the tube ....you replace the tube with a known good tube ... also if you move a tube from another section of the amp ( providing it's the same type of tube ( 12AX7 ) with the one from channel one and the hiss goes away, then you know the tube is the issue ... my question is ....what is/was the MAIN volume set at when you did the recording ... if you set the channel one at 6 and had the MAIN wide open that could be what some folks consider normal floor noise also what kind of cabinet are you using does it have a tweeter? and is the tweeter turned all the way up .... inexpensive tweeters will give an exaggerated/harsh hiss level

Yes, that is about right. Main is wide open, and channel is on 6. But the noise is louder than I ever remember it being when I've had it at this same setting. It was always pretty quiet and this does seem odd. I always make sure to turn the tweeter off but I'll double check.

jastacey · #12 03-27-2012, 04:25 PM

Keep in mind the new tubes that are available today, are not like the ones that were made 25/30 years ago ....you have to go through 2-5 tubes before you find a tube with a low hiss floor .... a suggestion .... in V1 use a NOS Phillips JAN 5751 ...when I had a VB-2 that's what I used and it had a very low hiss factor

BbbyBld · #13 03-28-2012, 09:49 AM

There is not a separate tube for each channel. The crunch channel kicks in an extra tube stage for more gain. There is guide in the manual that lists what the tubes do and where they are located on the chassis.

If you have a noisy tube at the beginning of the preamp signal chain, sometimes you can move it to a spot later in the signal chain and the noise won't be as much of an issue. If you have a noisy tube up front, the noise gets amplified all the way through the preamp. It's something to try before spending money.

walknbluez · #14 01-25-2013, 01:23 AM

I've been living with the hiss since I started this thread. It's like white noise when the master is on 10. Today I put two new 12AX7 preamp tubes to replace the ones that were in there. Same issue. But this is with the master on 10 and the gain at about 6. When I reduce the master to 7 it turns into more of a low hum. Could it possibly be the one 12AT7 tube?