Bassamp power issues.

[sl2lover]

I just got an Ampeg svt 4 pro of the bay, and it seems that its not putting out the power it should! I'm running a 1/4 cable into a 4x10 and it should be rumbling! So then I talked to Ampeg and they told me I could plug my (800watt/8 ohm) cab mono-bridged at (1200watts @ 8ohms). Which doesn't sounds like it would blow my cab!! Could it be a bad tube? Should I plug it mono-bridged with all the volume/gain down? Any suggestions?
Thanks!

[horns666]

Not famliar with THAT Ampeg. I've owned both classic SVTs and the SVT II. Bad advice from ampeg..IMO. 1200 (?) watts into a cab that can handle 800 watts (?) rms @ 8 ohms...hmmm that's sounds like CERTAIN distaster at band levels to me. Especially when dealing with 10" speakers. It'll blow...I know this!! Besides, I never heard of a Ampeg 4 X 10 cab that can handle 800 watts..maybe 400 watts. Both my Ampeg 8 X 10 cabs were rated at 800 watts..that's 100 watts per speaker. Unless they changed things since I've switched to Carvin.

To be honest I've always used biamped sytems w/ 4 X 10 cab for the highs and a 1 X 18 cabs for the "rumble". The only time I've used mono system was with the Ampeg 8 X 10 cab which is rated at 800 watts with a vintage SVT putting out 400 watts.

If your amp had a sudden loss of power its most likely a tube and correvting that would be the only remedy. I'd strongly advise to get yourself another Ampeg 15" or 18" cab to handle the low freqs. Those freqs are way too much burden on 10's..no matter what power rating.

With your 800 watt @ 8 ohm bridged..you could safely split the difference with TWO cabs set @ 16ohms for each cab. OR set the amp @ 4 ohms and run both cabs @ 8 ohms.

But the prob doesn't sound like a biamped/bridged/speaker/ohm prob..it sounds like a bad tube that shoud be fixed.

[toejam]

a 1/4 cable into

Speaker cable or regular instrument cable? Only use a speaker cable going from the head to cab. Don't use instrument cables for anything except for effects or guitar/bass to amp input. Not sure if that's your problem, but just in case.

[horns666]

Speaker cable or regular instrument cable? Only use a speaker cable going from the head to cab. Don't use instrument cables for anything except for effects or guitar/bass to amp input. Not sure if that's your problem, but just in case.

Jesus Christ no..listen to Joe!!

[shadowcat]

Not sure if it's related but just in case:

I had volume issues on my ENGL Fireball last month (didn't go much above speaking volume), changing power tubes made no difference, so I brought it to an amp tech.
Turned out to be the phase inverter tube going bad... amp tech changed the tube, Fireball rumbling again.

[sl2lover]

Its a Markbass 4x10 (800watt)that i got underneath it. I think the problem is, that the svt 4 has to built in amps, Amp A/Amp B. And if you run a 8ohm cab, you'l be at 2x350 watts to that cab. If I read/understood the manual correctly... So in essence if I had a 4 ohm cab I could (and again according to the manual if I read it right) I would get 2x625watts each. So i guess I shoulda bought a 4 ohm cab for this particular amp, to be running at 625 watts per cab, instead of an 8 ohm at 350 watts per cab. My next stupid question is can I change the resistance(ohm) of my cab?

And ya im running a speaker cable.

Thanks guys!!!!

[markD]

if you change the speakers. sometimes it can be done through different wiring, series vs. parallel or something - i THINK....i am not 100% sure though.

[Dreamland_Rebel]

if you only have one cab i would run it bridged mono and get the most watts out of the head.

remember that your cabs impedance = the amount of power drawn from the head.
the lower the impedance the higher the wattage.

[sl2lover]

if you only have one cab i would run it bridged mono and get the most watts out of the head.

remember that your cabs impedance = the amount of power drawn from the head.
the lower the impedance the higher the wattage.

Well see thats 1200 watts! And my cab is rated at 800, so that wouldn't work. I am planning on adding another cab but it would be running off of the other built in amp.

[Dreamland_Rebel]

from the website
RMS Power Output: 300-Watts x 2/900 (mono-bridged @ 8 Ohms)
RMS Power Output: 490-Watts x 2/1200 (mono-bridged @ 4 Ohms)
RMS Power Output (2 Ohms): 600-Watts x 2

so you'll only be 100w over @ 8 ohms bridged. i don't think you'll be turning up to full volume so i wouldn't worry about it. you'll be just fine.

[sl2lover]

from the website
RMS Power Output: 300-Watts x 2/900 (mono-bridged @ 8 Ohms)
RMS Power Output: 490-Watts x 2/1200 (mono-bridged @ 4 Ohms)
RMS Power Output (2 Ohms): 600-Watts x 2

so you'll only be 100w over @ 8 ohms bridged. i don't think you'll be turning up to full volume so i wouldn't worry about it. you'll be just fine.

Ya thats what the Tekkie at Ampeg said, if my cab can handle 800watts@8ohms
RMS, 900watts@8ohms should be fine as long as I don't crank it etc...

My other dilema was that i was stuck using each individual amp for each 8ohm cab at only 300 watts each! Which sucks for a 1200 watt amp! But now I learned I can daisy chain both cabs and run it mono-bridged at 1200 watts(4 ohms).

Tricky fucking AMP!!

Thanks guys!

[OnlineStageGear]

300 watts is what the Classic is rated at. My bass player has one and he can't get it above 2 1/2 without drowning us all out so your amp if working correctly should be plenty loud reguardless of your Ohms. If your 4x10 cab is 8 ohms mono, then odds are they are all 8 ohm speakers which means you "could" change the ohms of your cab by rewiring it, but you on have 3 options: Wiring all the speakers in series which will give you 32 ohms, series/parallel which will give you 8 ohms, or all parallel which will give you 2 ohms.

Matt