SVT 4 Pro...volume surges??

A Simple Plan · #1 07-04-2011, 10:31 PM

Hello...I purchased a SVT 4 Pro back in Feb of 2011. I am getting volume surges while playing. Has anyone experienced this before and what could be causing it? I am playing into 2 SVT 410HLF cabs...sometimes in only 1 cab...the problem is happening in both...stereo and bridged.

Thanks for any help!

Jerrold Tiers · #2 07-05-2011, 06:59 AM

What do you call a "surge"?

Slow or fast?

Is volume normal and then jumps really loud? or low and then gets to normal?

Have you cleaned all the jacks, especially loops and pre-out power amp in?

A Simple Plan · #3 07-05-2011, 09:59 PM

It just goes from normal volume up quite a bit...so much that I have to dial it down on my bass and then it goes back to normal and I have to turn up on the bass. The timing is intermitant of when it happens.

I have not tried cleaning the jacks...I will definitely do that.

Is this something you have heard about before with this amp?

A Simple Plan · #4 07-05-2011, 09:59 PM

fast surge

**B-string** · #5 07-05-2011, 10:11 PM

Read Jerrolds Sig!

A Simple Plan · #6 07-06-2011, 04:04 PM

Sorry...Newbie here...what is a "Sig" and how do I get to it??

coreyfyfe · #7 07-06-2011, 05:51 PM

Signature, they appear at the bottom of all of your posts. He was referencing the fact that Jerrold used to be an engineer at ampeg and would definitely be a good resource to help diagnose your issue.

A Simple Plan · #8 07-07-2011, 06:45 AM

Thanks...I'll send him a message

boisebassco · #9 07-13-2011, 01:33 AM

I just got a USA SVT 4 Pro in a partial trade deal. I must admit... I have never owned an Ampeg head in my life.. and even after finding the manual online tonight... I'm confused. It has 2 "Stereo" speaker outs... and one "Bridged" mono speaker out. My question is.... What if you just wanted to use one 8 ohm 4x10 cabinet.. rated at only 600 watts? The manual never explains what would happen if you plugged the single cab into say the left speaker out.... I presume that would be around 400 watts at 8 ohms... no problem for the cab. I would have no use for 1200 or 1600 or whatever watts this thing has in bridged mode... and I didn't get the magic bridge cable that is required anyway. So... does the amp catch on fire and kill everyone in the neighborhood if I only use one of the "Stereo" speaker jacks for one 8 ohm cab? Or am I forced to run a second cab on the other side in true "Stereo". Too complicated for me... and too heavy. I think it needs to go, but I'd like the answer to this before I decide. Any help?????

boisebassco · #10 07-13-2011, 02:36 AM

Quote:

Originally Posted by caaraa

Is this something you have heard about before with this amp?

Hello, if you were referring to my question... I have no experience with these amps... but all the info I can find shows two setups. 1 bridged mono speaker cable, (Center), going to a 4 ohm minimum load... and having some crazy amount of power far beyond what my little 4x10 would want.... and 2 speaker cables going to a stereo setup, one on each side, (Left and right). No one seems to use one single 8 ohm cab, or any other single cab only using one of the L/R outputs. Just curious if it is safe to do so... or what?

kawika5150 · #11 07-13-2011, 02:48 AM

Quote:

Originally Posted by boisebassco

Hello, if you were referring to my question... I have no experience with these amps... but all the info I can find shows two setups. 1 bridged mono speaker cable, (Center), going to a 4 ohm minimum load... and having some crazy amount of power far beyond what my little 4x10 would want.... and 2 speaker cables going to a stereo setup, one on each side, (Left and right). No one seems to use one single 8 ohm cab, or any other single cab only using one of the L/R outputs. Just curious if it is safe to do so... or what?

I use one single 8 ohm Orange SP410 off of one output and it pounds! I believe the cab only gets 300w or so, but it works just fine. I have not had a need to use the bridged mode. I have a second SP410 if I need it, and would just run it off the other output. I havent needed to do so....yet.

boisebassco · #12 07-13-2011, 02:04 PM

Quote:

Originally Posted by kawika5150

I use one single 8 ohm Orange SP410 off of one output and it pounds! I believe the cab only gets 300w or so, but it works just fine. I have not had a need to use the bridged mode. I have a second SP410 if I need it, and would just run it off the other output. I havent needed to do so....yet.

That's exactly what I wanted to know.. thanks! I too have Orange cabs... But wanted to know if it was possible to just run one side of this head without causing an issue.... The manual never addresses it. It just talks about bridged mono or stereo use... no mono off one side only. Thanks, and as a former 808 resident.. Aloha!

mastervolume · #13 07-17-2011, 07:00 PM

The last pro 4 I owned lasted many years until it recently started having the output volume jump up and down randomly. It finally stopped working on one channel. I think it may have a bad solder joint that let go. You should have it checked before it ruins some other parts of the amp.

chaosMK · #14 07-17-2011, 09:08 PM

Back in the day (about 10 years ago) I had to use Mono Bridge with a Speakon to run a single cab. I guess they've upgraded them. An issue I always found with that head was- unless you dial in a strong midrange orientation, you can get a weak high range (say, 12th fret position on A/D/G) relative to nice sounding low B/E tones.

Jerrold Tiers · #15 07-17-2011, 10:11 PM

haven't seen this thread for a while.....

OK, could easily be a bad solder joint... something in the preamp, quite possibly, there are lots of "loading" resistors arrranged such that if they came loose, the volume could go up some amount, varying on which it is.

if you found that some control changed function, or stopped having the right range, etc, that would narrow it down. No guarantee that the loose part, if there is one, will change the function of a control, though.

kawika5150 · #16 07-18-2011, 02:39 PM

Quote:

Originally Posted by boisebassco

That's exactly what I wanted to know.. thanks! I too have Orange cabs... But wanted to know if it was possible to just run one side of this head without causing an issue.... The manual never addresses it. It just talks about bridged mono or stereo use... no mono off one side only. Thanks, and as a former 808 resident.. Aloha!

Thanks brah, same to you. We plan on playing in pretty decent sized venue soon. If I don't have FOH support (which I've heard they have), then I'd have to use two of the cabs each off of their own outputs.

OTOH, I'm awaiting the arrival of a GBE1200. I can't to hear how this thing sounds from Orange cabs.