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02-13-2024, 02:06 PM
Hi Guys
Looeselectron: The VHT1220 has trem which needs to be controlled. The Watts control is a dual with one section controlling power and the other section keeping the trem modulation of the grids in proportion. To have a one-knob Power Scale solution here requires a 3-section 1MA pot.
Your SV2 has been modified to use a 1M for Power Scale to accommodate use of the stock pot.
The MV is 250kA just like the usual Power Scale and DriveComp pots are in the SV kits. If you could find a triple or 4-section 250kA that might work for you - with a caveat.
The VHT schematic shows the 1MA in series with the ground-referenced 250kB Depth control, forming a voltage divider. The 1MA is wired as a rheostat and can look like any value between zero and 1M. At the extreme end, there is a voltage division of 5:1, where the modulation signal amplitude comes out at 1/5 of what went in. With 1MA replaced by 250kA, the minimum signal is much higher at 1/2. This would cause the trem depth to increase as you dial down power.. This suggests that changing the Depth control itself to 62k5 would keep everything proportioned as it should be. Of course, you won't find such a value of pot but you can use a 100kA paralleled across pot-X to pot-0 by 167k.
The loading on the tremolo circuit ranges from 1M25 to 250k as stock. In the modified form with the triple 250kA for Power Scale, the loading would range from 500k to 250k. This likely would not effect things too noticeably.
Note that the SP-MV referred to is only for Schmitt splitters. It is not really a preferred MV type and is meant to be the proper form of such MVs if one wishes to use it.
Looeselectron: The VHT1220 has trem which needs to be controlled. The Watts control is a dual with one section controlling power and the other section keeping the trem modulation of the grids in proportion. To have a one-knob Power Scale solution here requires a 3-section 1MA pot.
Your SV2 has been modified to use a 1M for Power Scale to accommodate use of the stock pot.
The MV is 250kA just like the usual Power Scale and DriveComp pots are in the SV kits. If you could find a triple or 4-section 250kA that might work for you - with a caveat.
The VHT schematic shows the 1MA in series with the ground-referenced 250kB Depth control, forming a voltage divider. The 1MA is wired as a rheostat and can look like any value between zero and 1M. At the extreme end, there is a voltage division of 5:1, where the modulation signal amplitude comes out at 1/5 of what went in. With 1MA replaced by 250kA, the minimum signal is much higher at 1/2. This would cause the trem depth to increase as you dial down power.. This suggests that changing the Depth control itself to 62k5 would keep everything proportioned as it should be. Of course, you won't find such a value of pot but you can use a 100kA paralleled across pot-X to pot-0 by 167k.
The loading on the tremolo circuit ranges from 1M25 to 250k as stock. In the modified form with the triple 250kA for Power Scale, the loading would range from 500k to 250k. This likely would not effect things too noticeably.
Note that the SP-MV referred to is only for Schmitt splitters. It is not really a preferred MV type and is meant to be the proper form of such MVs if one wishes to use it.
