2 bass heads with one cab?

[JeremyJJackson]

Hello everyone Im new to the forum and i just had a question, What would the point in using 2 bass heads and on cab be? ive seen this in a couple bands and when the cab is on its side it looks awesome. Is it used for tone switching?

 

[slyjoe]

You shouldn't use two amps into a single cab. Sure way to destroy amps.

Maybe what you saw was someone using a preamp of one amp feeding the other amp.

 

[JeremyJJackson]

Ah i suppose that is possible. Never thought of that. Thanks.

 

[slyjoe]

No problem - and welcome to the forum.

Just watch out for the classifieds - you can go broke in there.

 

[JeremyJJackson]

Ill keep that in mind lol but i am looking for some new stuff though.

 

[SpamBot]

It's fine if you have a stereo cab. I know Marshall guitar cabs have this, and I'm sure there are bass cabs like this out there. Basically, it's a cab that can work as two. Instead of all 4 or 2 speakers working from one source, half of them work on one, and half one the other. This can be used both for tone switching and tone blending. For example, if you want a sound that combines distortion and clean, you use one amp for each (Possibly a tube guitar amp for the distortion) and run them into the stereo inputs of the cab.

 

[JeremyJJackson]

Thats probably what they were doing then because they were using a ampeg classic 8x10 wich is stereo. Both heads were the same though so im supposing it was for blending

 

[GearHeadBassMan]

Ill keep that in mind lol but i am looking for some new stuff though.

Looking at your gear, it looks like you shouldn't be looking hahah.

and how bad is this for your amps? my guitarist runs an orange tiny terror and a jcm 800 2204 into the same cab, and runs them off an a/b/ab switch. should i tell him to stop before he ruins the tubey goodness? (it sounds incredible)

 

[JeremyJJackson]

Ya im never satisfied lol. I actually need a good rack tuner if any one knows of one. And Spambot how would i run that blending setup your talking about using 2 ampeg SVT classics and 8x10 ampeg classic cab? ie guitar to head, head to? and so on. Would i need any other equiptment?

 

[GearHeadBassMan]

a splitter would work between two amps, at least, both amps will make sound.

 

[JeremyJJackson]

thats what i was thinking.ill try that i think i have a splitter sitting around somewhere and if i dont ill get one from my guitar friend.

 

[SwamiRob]

I've seen some people with 2 or more amps in their rack setup running only 1 cab in quite a few places and always wanted to know this, I always kinda assumed that they were just for backup in case one of them blew.

 

[GC4]

I dont think you can use two svts into one Ampeg 810, or at least its not advisable. Wouldn't using the stereo mode on the 810 reduce it to 8 ohms which is higher than the recommended 2 or 4 ohms setting?

 

[JeremyJJackson]

well the ampeg 8x10 classic is rated for 4 ohms mono and 2x8ohms stereo so no it would not be that bad. running a 4 ohm amp into a 8 ohm cab doesnt really hurt the cab to my knowledge it just wont give you all the power you need. if you were running 4 ohms into a 2 ohm cab however that is not advisable.

 

[anderbass]

You could split your basses signal into 2 amps, each connected to your stereo cab.

As far as safely running tube powered SVT's into 8 ohm cab loads: Theres no danger to the cab, its the amp. To explain why I've posted a couple quotes from Jerrold Tiers. (Ampeg factory design engineer)

People run SVTs at 8 ohms. Many have no problems, apparently, but I don't recommend it.

Lots of amps are NOT pushing the power and voltage ratings of the tubes. The SVT is. The power supply is about 660V, meaning the tubes get 1320V peak to start with. Then there are transients.

"Spike " voltages are higher at 8 than at 4, when the amp is clipped, which is going to happen more at 175 or so watts than at 300. It happens plenty at 300W.

Particularly with modern tubes that are often not made as carefully as, and may not have the same QC as the old tubes, "pushing" matters is not as safe. And, some tubes these days are even "counterfeit", rejects re-labeled, etc. The old US manufacturer tube manual voltage ratings may not be reliable when applied to Russian and Chinese copies of the tubes.......

Failed tubes can cause more damage. I've seen it happen, mostly when pushing the amp fairly hard (not in an SVT). Fountains of "white fire" in the tube, bad noises, and "eventually" the fuse opens......

If you DO use it at 8 ohms, I suggest laying off and not clipping hard. You need to realize that you are using the amp in a way not intended by the designers, and so YOU are taking responsibility for it working OK.

BTW, it isn't going to be much lower volume, audibly, at 8 vs 4. So if that was the goal, it does little good.

________________________

The SVT is designed for a 2 or 4 ohm load, connected to the appropriate tap. That certainly is "optimum".

It was not designed to run at 8. Running at 8 would have needed another tap, and that tap, for various reasons, was not included. Therefore, 8 ohms is NOT an intended load....... But 2 and 4 ohms are both intended loads.

Putting an 8 ohm load on the 4 ohm tap is similar to putting a 4 ohm load on the 2 ohm tap, and that isn't recommended either.

You may get away with it fine. And after you change tubes, you may not..... or after a while you may not.......

Is it going to kill your amp right now? 'Probably' not.

But it does operate the unit outside of the intended application. That does pose certain technical problems/issues as mentioned several times in past threads as well as this one. If you do it, don't be surprised by problems __________________
Yes I USED TO work for Ampeg...but I haven't forgotten everything.

 

[coreyfyfe]

well the ampeg 8x10 classic is rated for 4 ohms mono and 2x8ohms stereo so no it would not be that bad. running a 4 ohm amp into a 8 ohm cab doesnt really hurt the cab to my knowledge it just wont give you all the power you need. if you were running 4 ohms into a 2 ohm cab however that is not advisable.

In the case of a splitable cab, such as the ampeg 8x10 you would have two 8 ohm 4x10s, and it is not advisable to run them with an 8 ohm load as they are designed to run either 2 or 4 ohms. Search for "impedance matching" (or mismatching) in relation to tube amps and you'll find some good info, especially by PsychoBassGuy or JerroldTiers.

You can connect two heads to one cab if you're using something between the heads and cabs (like an A/B switch) that will ensure you are not connecting the two power sections together but you shouldn't do this with a tube head. Essentially what you are doing with the A/B switch is removing the load from one head to run the other. While you can do this with a solid state amp because they are designed to withstand infinite impedance situations, you cannot do this to any amp with an Output Transformer like your SVT-CL has.

 

[JeremyJJackson]

Ah thanks for correcting me. thats good to know. Im just asking because ive seen this done with 2 ampeg SVT VR's and a classic 8x10 and it sounded amazing because of the blend im supposing. If your not pushing your head ie not cranking it to the roof, would it work without hurting your amp. Im supposing that since ampeg rates their cabs at 8ohms stereo it would not hurt the cab.

And if it will hurt my head then i guess i will just have to use either 2 4ohm 4x10s or go overkill and use 2 8x10s