direct drive ribbon amp

[hancock]

Anybody here know if a follower circuit could be practically built that could drive a ribbon directly (ie without a step-down transformer)?

[Joules]

Or mutible ribbons in series, as in a line array, to make driving them easer?

[karellen]

It depends on the ribbons... how many Ohms ( or fraction of ohms ) ar we talking about?

BTW apart from the "la folia proyect" , do you know about a suitable DIY ribbon plans (Not a kit, please)? nowadays this kind of loudspeaker seem to have vanished on the air...

thanks in advance for the info

[hancock]

I haven't done the math to figure out the exact impedance. Just ballparking it, the impedance would be between one and two orders of magnitude lower than a typical driver, ie. 0.6 to 0.06 ohms, with most of that impedance coming from the air load (the good news is I'll be horn loading, which raises the impedance of the air load). I wouldn't need much power, but I simply don't know if there are any suitable transisters that could provide the required current and achieve a low-enough output impedance. I'm used to building amps with tubes and I know for sure there aren't any suitable tubes for this purpose.

John

[Joules]

Since a large percentage of the cost of a ribbon is the transformer, How many transformerless ribbons would it take to create a driveable impedence for a line array tweeter and would it be of reasonable cost.
At .6 ohm each it would take 6-7 ribbons to equal 4 ohms.
Hmmmm (just fantasy)

[hancock]

Originally posted by Joules
Since a large percentage of the cost of a ribbon is the transformer, How many transformerless ribbons would it take to create a driveable impedence for a line array tweeter and would it be of reasonable cost.
At .6 ohm each it would take 6-7 ribbons to equal 4 ohms.
Hmmmm (just fantasy)

Hi Joules,

The 0.6-0.06 ohm estimate is already for a 6ft ribbon, so unfortunately, no it won't work. Thanks for the idea, though.

John

[hancock]

Originally posted by karellen
It depends on the ribbons... how many Ohms ( or fraction of ohms ) ar we talking about?

BTW apart from the "la folia proyect" , do you know about a suitable DIY ribbon plans (Not a kit, please)? nowadays this kind of loudspeaker seem to have vanished on the air...

thanks in advance for the info

Sorry, I don't know of any plans. I did come across a web site once where some guys (in Sweden, I think) were looking to do a group purchase of some neo magnets from China to do a project. I'll see if I can find that again,

John

[Variac]

So far about all these points have been discussed here:

DIY'ing ribbon drivers?

[akb1212]

For this you should consider current amplifiers. Pass is actually fiddling with that kind of amplifiers. And he has written articles about it. You can find it on the first-watt site.

Driving ribbons must be one of this kind of amps favorite. This because it is almost a pure resistance. And you would be able to skip the transformer.

The problem is to find schematics of such amps...... Dear mister Pass, or anyone else with deep knowledge of the inner workings of a power amp: How would we have to modify lets say the Aleph-X or even more normal amps to achieve this.
I know setting a series resistance is one way, but to set an 8 ohm series resistance with a driver with 0.1 ohm seems like wasting a little too much energy for my taste.

A fairly low powered amp for driving ribbon tweeters or a small compression driver or something as an active source is really appealing to me. And the Aleph-X seems to me to be a perfect candidate for this. The problem is the implementation of currend feedback.

Your idea may be to use it as full range too, but then you need WAY much more power, I know! I have a playing La Folia set that I built 14 years ago! And a 500W beefed up bridged A-40 amp seems to not be enough….. A X-1000 modified for current feedback seems like the thing for that kind of speakers…..

[akb1212]

After finding a link to the First-Watt F1 ( http://www.firstwatt.com/products.htm ) it occured to me that this is what we need.....
Only we have to change the working point to optimize it for the working range (the F1 is obviously made for 8 ohm drivers) of the ribbons (in the 0.8 ohm and below range).

So all we have to do now is to wait for this to be released for DIY

But I would love to rebuild the Aleph-X too...... I'm sure they arn't that diffrent from each other.