SVT CL has 4 and 2 ohm settings. oK at 8 ohms?

[bhoff5150]

i've always heard that tube amps don't care about the ohm load. My SVT Classic has settings for 4 ohm and 2 Ohm. Is it OK to run this amp with an 8ohm cabinet?

I have new power tubes on order and don't want to destroy them.

Thanks in advance to anyone who can help me out.

 

[gelinas666]

Hi. I've been using All Tube Bass heads for years and was told in all tube amps ,from my Amp Techs and other respected players, too high a load impedance (or a disconnected load) can result in damage to the output tubes or output transformer.. So try and stick in the 4ohm to 2ohm area for the SVT CL..

 

[sharkbait130]

There are some folks in here (TB) that have run a Classic at 8 ohms. While it won't result in catastrophic failure , it is hard on the tubes and NEVER turn on an SVT Classic without the speakers being hooked up first. A blown output transformer is usually the result. So , yeah , stick with the recommended loads for this amp.

 

[Jim C]

Agree with the above.
I've done it for a few minutes at low volume but would not go farther than that.

 

[RoadRanger]

i've always heard that tube amps don't care about the ohm load.

What maroon told you that?

 

[BogeyBass]

Not really a bad statement. Many classic amps can handle huge mismatched impedances.

8ohm speaker on 4 ohm load usually be fine for most part. With tradeoff on how it effects the output load line. Typical you see higher voltages with a higher impedance

And usually see dramatic increase in screen voltages

So on lower powered tube pairs or quads not being pushed to maximum limit. Impedance mismatch not to big deal. Less currennt load on plates and higher voltages..

But SVT is going max plate .max screen already. So changing load line probably not good idea specially at high power or clipping.

Low volume real quick ok ish
High volume at practice or show.
Depending on how tough the tubes are and what year svt. Id expect the screen resistors or actual tubes to go....pop

No load on transformer means super high voltages on the transformer and possibly burn through in wire insulation.

Svt had protection diodes across the transformer for slight overvolt protection. Likewise newer svts use low value screen resisistors to actually burn up and open. This of course destroys the tube with it. But saves the transfomer somewhat from possible arc over

 

[bhoff5150]

Thanks for the replies everyone.

The amp is a 2006 (at least that's what the seller told me). It is a St. Louis USA made SVT.

I have 2 Mesa 4x10s (each 8 ohm) that I'll pair together to run it at 4 ohms.

 

[anderbass]

I have 2 Mesa 4x10s (each 8 ohm) that I'll pair together to run it at 4 ohms.

You could wire in a series/parallel switch in one of your cabs if each of the speakers are 8-ohm. That way you could simply flip the switch to become a 2-ohm cab for use all on its own, then you could flip the switch back to the 8-ohm positing for using that cab along with your other. Although you'd probably need to bypass the horn circuitry to preform this mod: