Active speakers power supply question

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Autophase

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Joined
Oct 15, 2009
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478
Location
UK - Manchester
I have 2 Tannoy active monitors which had much studio use and I think need new drivers, they are just sat there now un used.
I was thinking I would quite like to remove amplifiers & power supplies and mount in a case as an amplifier. My question is:
Can I run both transformers off a single 240V connection safely, or will I need to replace them both with a single transformer.

Also, where would I insert a pot to to use as a volume/attenuator, being that the speakers dont currently have a volume control.

I know this may sound futile/pointless to some of the more experienced DIYers here, but it's just something I would quite like to do.
 
You would be able to wire them off of one 220v connection.  Think of it as a hardwired extension cord.
How did you control the speakers' volume before?  It would be easier to stick to that method.  Otherwise, I would guess that there is a buffer or unbalancer circuit immediately after the audio input connection.  A pot (something like this) between that and the next stage should do it.  A second buffer after the pot might be needed.  A FET buffer would be easy (mechanically and current-wise) to add.


*Fixed link
 
Autophase said:
I have 2 Tannoy active monitors which had much studio use and I think need new drivers, they are just sat there now un used.
I was thinking I would quite like to remove amplifiers & power supplies and mount in a case as an amplifier. My question is:
Can I run both transformers off a single 240V connection safely, or will I need to replace them both with a single transformer.

Also, where would I insert a pot to to use as a volume/attenuator, being that the speakers dont currently have a volume control.

I know this may sound futile/pointless to some of the more experienced DIYers here, but it's just something I would quite like to do.
You can certainly do that, however, the frequency response of the amplifier may be tailored for the speakers. You may have to override whatever EQ is built-in.
You may retain the two separate transformers.
 
lernith said:
You would be able to wire them off of one 220v connection.  Think of it as a hardwired extension cord.
How did you control the speakers' volume before?  It would be easier to stick to that method.  Otherwise, I would guess that there is a buffer or unbalancer circuit immediately after the audio input connection.  A pot (  http://sound.westhost.com/project01.htm  ) between that and the next stage should do it.  A second buffer after the pot might be needed.  A FET buffer would be easy (mechanically and current-wise) to add.

Thanks for both replies.
As with all answers... they raise more questions

So do i literally just wire both transformers to a single IEC socket?

In regards to the volume control, these particular monitors could only be controlled from the audio interface or mixing desk output, I think the assumption when they were being designed was they would always be used with some sort of desk. So I'll need to add a pot/attenuator at the input stage, that shouldn't be too difficult. I had a look for the schematic but to no avail. I'll just cross that bridge when I have them dismantled.

To the other poster regarding the taylored EQ, thanks for the heads up on that, I assume that will just be a series of resistors and caps on their own circuit? Its got me thinking about other possible mods, like having a bypass switch, or even go further and build a whole new EQ control.

Again, I realise this may seem futile to some, but I think I will enjoy it.


 
How are you monitoring?  Even if your monitors are connected directly to the soundcard of a computer you'd be able to control the volume from In the Box.  It wouldn't give you the satisfaction of a knob, of course.  I'm just stressing that it isn't necessary, might make an amplifier very unhappy, and take time away from other things....

I'm on an Elliot kick: http://sound.westhost.com/psu-wiring.htm
You want to disconnect the wires from the IEC socket lugs and transfer them to the identical lug on another IEC socket.  The wire that has the fuse in line will be the active line.  This needs to stay on the active lug (the IEC should be labeled).
 
lernith said:
How are you monitoring?  Even if your monitors are connected directly to the soundcard of a computer you'd be able to control the volume from In the Box.  It wouldn't give you the satisfaction of a knob, of course.  I'm just stressing that it isn't necessary, might make an amplifier very unhappy, and take time away from other things....

I'm on an Elliot kick: http://sound.westhost.com/psu-wiring.htm
You want to disconnect the wires from the IEC socket lugs and transfer them to the identical lug on another IEC socket.  The wire that has the fuse in line will be the active line.  This needs to stay on the active lug (the IEC should be labeled).

Yes, when I used to use these monitors in the studio I just controlled the volume from cubase. But this amp that I intend to make from the amps inside will probably not be used in my studio, hence the need for an independant volume knob.

Thanks for the advice RE the PSU, I'm probably going to do this over the festive period.
 
If you are putting both amps in a box, why not wire the chassis IEC out to two female IEC's?  When doing things like this I try to be as minimally invasive as possible.  For their big monitors, Genelec has the amps as rackmounted panels.  Use some nice 12 GA for the woofs and 16 for the tweeters.
And as for volume, you can "get away" with running them unbalanced through a dual gang log pot with a value 10K-100K.  Put the pot in a small box with "input" connectors and wire it as a fader.  Buy a few pots and find the best imaging as a 10% tolerance pot could track 20% differently L-R.

All that being said, I expect different response from them because you are removing weight from the cabinets.  Why bother?  You are making three boxes out of two.  It's not like the amps need more cooling or anything.
Mike
 
Thanks for the advice mate, all good stuff.
I dont necessarily intend to use those speakers with this new amp concotion, I want to make an amp I can use with other speakers.
Again, just for fun really.
 
Well, remember that it is amps, with a separate amp for tweeter and woofer, designed specifically to work with a unique cabinet and driver set.  Any other combo will yield a different frequency response.
Sell 'em and use the lucre and time to have fun building more recording chain equipment.
Mike
 

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