Manley 440 monos to drive low impedance ribbons?

Jstones, I just don't think that 1/2 ohm impedances and tubes go together in the same sentence.You are going to need a SS amp, or maybe you could use one of those autoformers from Zeroimpedance to help, but I don't know how good those things work. The output impedance of all the tube amps I know of is too high for a 1/2 ohm impedance load. They are all going to go unstable at that kind of load. I would highly recommend researching this before you go blowing up some very expensive amps.

I see. That's of course were I started from, too.
Then, Mr. Henry Wolcott, kindly enough to address
the problem, assured me that:
he thinks that his 220M's (2x175W) are able to properly drive the Scintillas, because, at 0.5 Ohms, his tubes amps will still deliever 70watts to the speakers. Also, reminded me, that "tube watts", count as 3 to 4 times more that "transistor watts" as a given and scientificaly proven fact.
As I didn't have the chance to get a second hand Wolcott,
I assumed that a 2x275W / 2x540W Manley, won't prove less.
Here I might of course be wrong, that's why I was looking
for any possible confirmed opinion. BTW, Ms. Manley thinks
that it's gonna work. What a great lady, she is!
Do you have any hard facts, or (just like me) assumptions?
Thanks,

John

A couple of things...

First of all I think that using tubes on such a low load is an incredibly bad idea. You will be wearing down the tubes and transformers and really overworking the amplifier, and that is assuming that you can get the amp to perform in a stable manner given the impedance of your speakers.

Second, even if it does work and you are able to play anywhere near the listening levels you'll want to attain, it'll sound like garbabe. Tubes don't sound good when they are overworked in terms of the load presented. You will suffer poor bass control, shrill highs, poor tonal balance, mediocre imaging... shall I continue? Even out of two ohm taps (which some amps offer or can be modified to provide) you are talking about a far too challenging load.

Third - I don't care who says what about power output. That is completely irrelevant. We can argue about this until the sun sets. Mathematically you may have plenty of power but remember at the end of the day, watts RMS is a pretty misleading spec all thing considered.

Fourth - why are you trying to do this? Just use solid state. It's going to sound infinitely better in this case, it'll be far more reliable, and you'll be able to play much louder. You will also save yourself a lot of time and energy. Do you realize how much it's going to cost to retube your monoblocks? And you will have to do this quite frequently if you run the amps into half an ohm.

I understand that a lot of people want to run tubes instead of solid state. I am fully aware of the appeal of tubes - I run them myself at home in my own system and many of my customers are tube gurus. However, using tubes purely for the sake of using tubes makes no sense IF they are not going to perform as well as solid state for a given application. When customers come to me I decide what amp will work best for them based on a variety of variables (room size, listening volume, and most importantly speaker impedance) If the customer is open minded and has speakers which will present a realistic load to an amp, I often recommend tubes. But in your case I think it's an incredibly bad idea.

Bear in mind that you really must pick a solid state amp carefully too - a lot of solid state amps will either limit current output or shut down all together into that impedance. Make sure you go with a solid state amp that will run all the way down.

It's your money. But if you want hard facts, then ask them what the damping factor will be with a 1/2 ohm load. Ask them how they will handle 90 degree phase shifts at that kind of load. Ask them if the amp will tend to be "brittle" sounding at that load. And as Hackmaster above states, ask them how hard the amp will be working, and how that will affect tube life? Just the ability to deliver power at that load is impressive, but power delivery is not any assurance of sound quality. I am a tube guy, and own all tube equipment. I love tubes. But, I believe that this is a SS application, if I've ever seen one. And just as Hackmaster says, choose even the SS amps very carefully, since that speaker will shut down most of the SS amps out there. If the amp won't drive a direct short circuit without shutting down, it won't handle your speaker. It will have to be a feedback design that swings the output impedance into negative territory to provide damping factor. I believe that when you press these manufacturers into answering these questions, they will back off their positions. A good way to do it, would be to ask them if they will repair the amp for free, if it ever blows up or chews up tubes, from this low load. And that still doesn't guarantee you good sound. Even the best amp in the world will not sound too great when it is stressed to the limit, in terms of load. And when you are using all the current it can deliver, just to drive a simple load, what will happen when dynamics occur?

This is sort of like buying a 500 hp engine, so you can drive at highway speeds in 1st gear. What do you think will happen to the engine when you run it at redline continuously? How much accelleration will you have, when you are already at redline? I think that this is a bad idea.

Thank you guys. Looks that you saved me out
of lot of potential loss and trouble.
As they say, I was only following my heart, but...
glad that I asked. Cheers!

John