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RE: older Sound Labs

Posted by Simon Templar (A) on June 8, 2021 at 01:04:05

In Reply to: RE: older Sound Labs posted by Ralph on May 6, 2021 at 11:49:47:

>>>>>>>>The toroid version which replaced the first one can be driven by MA-1s after a simple mod. The problem is that the impedance of the Sound Lab is a moving target with frequency so a resistor is used to help set the crossover point. Modelling was used to design the crossover and it was off by a country mile.

But it turns out that if you just remove that resistor the speaker becomes much easier to drive. In most of the backplates I've seen the resistor is composed of a number of smaller 20 or 25 watt resistors; the composite resistor is a 200watt device which explains where the efficiency of the speaker went. By simply removing the resistor the speaker sounds better in every way and is easily driven by MA-1s. Sound lab says that the resistor prevents saturation of the high frequency transformer but in practice with the MA-1 or MA-2 that doesn't happen. <<<<<<<<
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Mine had the toroids as an option. But they did not have the resistors, however. West offered a kit which installed the resistors. It required the removal of a cap (I recall it was a Solen....but can no longer remember what the value was. Been a few years). After removing the cap, one replaced it with the grouped ceramic resistors.

So....Are you saying to remove those resistors and not re-install the cap?



....sT

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