Tx 102 transformer attenuator for Vandersteen SW volume control...works !

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  • Consulting Structural Engineer
I had been having trouble getting the proper sw output -volume- from my Vandersteen 2w sw in conjunction with my Reference 3a deCapo's. The sw output was not sufficient and I gather for these reasons: 1 The 2w is old from circa 1992 although it sems to work well, and 2, the efficiency of the deCapo's is 92 db, almost the limit of the sw attenuation -which is 94db- dial so there is not much volume control leeway.

The 2w xover is a line level passive 6db per octave for high pass at 80 hz in the preamp and the sw is connected to the power amp outputs and then the sw amp xover equalizes the low frequency respose from there. So how could I increase the sw output? In came the Tx 102 volume control with the 6db gain set in. Voila! It did it. I connected the amp outputs to the tx inputs and from there on to the sw. Instant audditional sw output! I can dial any output i want. But the curious thing is the the output is increased by dialing the voume dial counterclock wise, so I gather that it has to do with the impedance the amplifier output is increasing as one dials the control counterclockwise. If Mr. Chapman could comment on this I would appreciate it. Thanks. MV

John Chapman

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I need to stop by the forum  a lot more often! Sorry for this late reply....

I am glad that it did the trick. The TX102's were a bit of overkill size wise - which is likely why it worked out for you. Usually putting a line level device like that on the output of an amp would overload the device.  I still have to wonder if it might be pushing it too hard - distortion would increase on the feed to the 2W but the mail speakers would not 'see' this'. I would not have expected the counterclockwise turn to increase volume either - That would be what I expect if we fed the TX102 with a silly high output the amp output impedance  but the amp output impedance will be extraordinarily low in comparison...

If I can help along the way please let me know and sorry again for the long delay replying...