transconductance power amplifier for current-drive loudspeaker?

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Building this one is high on my list but it is a complex one.

I have build an active 3-way speaker using 10W class A current drive amps (from Electronics World & Wireless World). Sounds good, but if it is better then normal voltage drive is another question. I looks as they are difficult to get stable. I had oscillations all over the place (60kHz up to 1.6MHz).

Problems are: you have to go active, you lose all damping of the woofer so you need active correction.

If you want to try, the EW&WW amp is much simpler (read: cheaper) and has some scope for experiments. Let me know if you are interested, I'll search the reference.
 
You may find the following articles of interest, unfortunatly they aren't available on-line:

DISTORTION REDUCTION IN MOVING-COIL LOUDSPEAKER SYSTEMS USING CURRENT-DRIVE TECHNOLOGY,
Mills, P.G.L., Hawksford, M.O.J.,
JAES, vol.37, no.3, pp.129-148, March 1989

TRANSCONDUCTANCE POWER AMPLIFIER SYSTEMS FOR CURRENT-DRIVEN LOUDSPEAKERS,
Mills, P.G.L., Hawksford, M.O.J.,
JAES, vol.37, no.10, pp.809- 822, October 1989


regards
James
 
reference

Havoc said:
Building this one is high on my list but it is a complex one.

I have build an active 3-way speaker using 10W class A current drive amps (from Electronics World & Wireless World). Sounds good, but if it is better then normal voltage drive is another question. I looks as they are difficult to get stable. I had oscillations all over the place (60kHz up to 1.6MHz).

Problems are: you have to go active, you lose all damping of the woofer so you need active correction.

If you want to try, the EW&WW amp is much simpler (read: cheaper) and has some scope for experiments. Let me know if you are interested, I'll search the reference.

Please,give the reference!
 
Sorry Alex, I found the article but there is no date on it. Most I can say of it is that is from before 1996 (then I made my pcb), is called "Transconductance amplifiers" by K. Lewis p580-582 in Electronics& Wireless World.

I'll try to mail you a scanned copy, as the file is to large for an attachement to this forum.
 
Well, the flat response is only a problem if go down in frequency. Because of the output impedance >10k there is no damping. For a good midrange or tweeter, this isn't a problem. And if you do some active correction, you can get a woofer also under control, but then the question is if it is still current driven.
 
tvi said:
You may find the following articles of interest, unfortunatly they aren't available on-line:

DISTORTION REDUCTION IN MOVING-COIL LOUDSPEAKER SYSTEMS USING CURRENT-DRIVE TECHNOLOGY,
Mills, P.G.L., Hawksford, M.O.J.,
JAES, vol.37, no.3, pp.129-148, March 1989

TRANSCONDUCTANCE POWER AMPLIFIER SYSTEMS FOR CURRENT-DRIVEN LOUDSPEAKERS,
Mills, P.G.L., Hawksford, M.O.J.,
JAES, vol.37, no.10, pp.809- 822, October 1989

regards
James

I'm sure I stumbled across Mr Hawksford's homepage at one point - on which there were links to all his published works on distortion reduction in .pdf format. Unfortunately I can't seem to find the link anywhere.
 
Havoc said:

If you want to try, the EW&WW amp is much simpler (read: cheaper) and has some scope for experiments. Let me know if you are interested, I'll search the reference.

I actually experimented some a couple of years ago, using the danish High Fidelity article as inspiration. It sounded really well. But for other reasons i never finished the project.

Anyway: I might be interested so Havoc - if you have a link to the EW&WW articel or a schematic I would very much like to see it.
 
I have got

Nelson Pass said:
Anybody got a current drive loudspeaker out there?

I am using the current drive system over 5 years.
 

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