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SV1, SV2, SV-TT update
#1
Hi Guys

Back when I designed SV1, SV2 and SV-TT it seemed like "a good thing" to add some tiny caps to reduce the bandwidth of the otherwise wide-bandwidth regulator sections. The idea was that noise on the supply line that might be impressed across the Power Scale control could be amplified through the regulators and be heard through the amp. Of course, C1 across the pot output would clean this up all on its own.

In most installations these caps do not present a problem and everything works fine. However, some installations will show some oscillation and removing the small feedback cap 56-68pF will eliminate the oscillation. In SV1 and SV-TT, remove the 270pF from the bias regulator. Do this in TBS if there are issues. The bias regulator cap can cause a secondary oscillation.

Over the life of these kits, the 330k-1W feeding the Power Scale pot was split into 150k + 180k and a filter cap to ground was added at their junction. This cap helps reduce hum, ripple or other noise getting to the pot. Some installers found that C1 could be removed without any audible effect, although the main purpose for C1 is to keep DC-related pot-scratchy sounds from happening.

Techs report that he removal of these caps makes the amp sound better. It should, since these are very wide-bandwidth regulators which present a low-impedance voltage source to the amp allowing any frequency restrictions to be only those imposed by the amp itself.

I annotated the kit notes but if you have old notes or ones without the update, at least the information is accessible here on the forum.
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