Speaker load question

[Robert]

My Avatar cab 2x12 makes my Vox AD50VT sound so much better. However, will I fry my Vox if I keep doing this, since the Vox is designed for an 8 ohm speaker load and my Avatar cab is 16 ohm? I understand it is a really bad idea to run a 4 ohm cab with it, since it would make the load too much for the amp, but going the opposite way and make the load lighter I'm not really sure about.

I am thinking about selling the AD50VT and get a 60 or 120 Vox AD head instead. Or a Vox AC30 CC head. Or a Germino. Or a Valve JR. Or a Bandmaster. Or a Maz Jr. Or a [insert favorite GAS amp head here...]!

 

[TS808]

My Avatar cab 2x12 makes my Vox AD50VT sound so much better. However, will I fry my Vox if I keep doing this, since the Vox is designed for an 8 ohm speaker load and my Avatar cab is 16 ohm? I understand it is a really bad idea to run a 4 ohm cab with it, since it would make the load too much for the amp, but going the opposite way and make the load lighter I'm not really sure about.

I am thinking about selling the AD50VT and get a 60 or 120 Vox AD head instead. Or a Vox AC30 CC head. Or a Germino. Or a Valve JR. Or a Bandmaster. Or a Maz Jr. Or a [insert favorite GAS amp head here...]!

I'm not positive, but I remember having a Fender solid-state amp that was wired for 8 ohms, and a qualified amp tech explained to me a way to wire the speakers to 16 ohms, to increase the load and drop the wattage. If I remember correctly, with a solid-state, you can do this, but don't quote me on that. It's been a while. I know there are a few websites that explain this.
If anything, increasing to a 16ohm load will decrease the power somewhat.

If you like the avatar cab, I would agree with you and purchase a head to go with it. Lugging around a head and cab is a bit easier than carrying a combo and a cab. I'm really digging the Vox AD60VTH...the tone is incredible, and with the VC-12 floorboard, it gives you a ton of options. If you can find a NOS AD60VTH, the prices are pretty good right now. The 60 is plenty of power.

 

[Robert]

Yeah, the AD 60VTH seems terrific. I'm looking on eBay to see what they go for. I am thinking about going that route. I am just a bit worried about the reliability issues and buying used.

 

[TS808]

Yeah, the AD 60VTH seems terrific. I'm looking on eBay to see what they go for. I am thinking about going that route. I am just a bit worried about the reliability issues and buying used.

I haven't had my AD60VTH too long, so the jury is still out on the reliability factor. Hopefully it will hold up. The reviews on Harmony Central are favorable though.

The tones from the AD60VTH and the AD100VT are like night and day though.
The AD60VTH sounds much better and there are more options with the foot controller. If you can find one at a good price that is in good shape, it will probably be worth it.

 

[duhvoodooman]

Interesting reading on the subject in THIS old newsgroup posting. But I'm still not sure of the answer after reading it, due to the mixed tube/SS nature of the Valvetronix amps....

 

[Plank_Spanker]

I've been involved in more than a few rather spirited debates on speaker loads and amps.......

Here's my take on the issue:

There are two different schools of thought based on tubes, or SS. With a SS amp, you can safely go above the nominal rated impedance. Going below the rated minimum impedance is bad juju for the final amps.

The argument heats up with tubes. I talked to Greg Germino about this and he said that an impedance mismatch of plus or minus 50 percent is usually safe with a tube amp.

Using a cab rated at double the amp's rated impedance is dancing with the devil and risking flyback. The output transformer won't like it one bit. Going lower with the cab's impedance is usually safe with a tube amp, but I wouldn't want to start dancing around the 2 ohm mark.

Of course, it's always best to take the easy way and just match the impedance.

 

[tot_Ou_tard]

Robert,

If it does turn out to be a problem (or even if it doesn't) you might want to check out
Speaker Mate from Sherlock Audio in Canada.

http://www.sherlockaudio.ca/

I haven't read any reviews, but it is supposed to do the impedence matching for you as well as allow you to connect up 4, 6, or 8 (depending on which model you get) seperate cabs each with different impendence requirements. These are all under US $100.

The site even claims that you can use this with a combo even if it doesn't have external speaker outs (I don't understand) and choose whether you want the combos speakers engaged or disengaged as you run external cabs.

 

[Robert]

Thanks for the help everyone, it sounds like most of you think I should be okay with the 16 ohm cab hooked up to my 8 ohm speaker out on the Vox. Am I right?

That sherlockaudio site has some interesting products. I will keep that in mind. Thanks.

 

[Plank_Spanker]

Thanks for the help everyone, it sounds like most of you think I should be okay with the 16 ohm cab hooked up to my 8 ohm speaker out on the Vox. Am I right?

You shouldn't have any problems.