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01-25-2026, 09:10 PM
It took me more than a year but I finally got the SV2 working in my VHT Special 12/20RT.
It works exactly as advertised, and sounds great!
This is a unique amp. In spite of being advertised as mod-friendly, the reverb and tremolo circuitry combine with my noobishness negated this friendliness. This bell and whistle combo need to be considered separately.
The tremolo shares the dual-ganged 1MΩ pot used to control WATTS but this inevitably fails due to the high voltage from B+ across it (probably accelerated by heat from my nooby soldering technique.) I never wanted the tremolo anyway so I replaced it with a single pot 1MΩ pot instead, and just disconnected the tremolo but since its in the path of the concertina phase inverter, this meant I had to jumper the grids to ground get any sound!
Removing the tremolo may be more overkill but the bigger issue is the reverb that sharing the same voltage supply node as the critical screen grids. KoC recommended I "cascade" the power supply nodes. To understand this, I ordered TUT1.
The stock circuit supplies the power tubes and preamp tubes in parallel so that WATTS does not drop the voltage to the latter. (Enter VCK!) Eventually we concurred that adding a dedicated supply node for reverb was the best solution. So I added a fat green 10KΩ resistor from the B+ mains to a fat black capacitor to ground, and spliced some wire from the new node to reverb. This node is parallel (not cascaded) but it works for now.
Along the way I made lots of other noob mistakes that blew several fuses requiring me to rebuild the rectifier, and that required a bottle of 99.9% isopropyl alcohol to clean the glue off of it.
Hum specifically from the reverb also stalled the project until I realized it the two ends of a coax wire to the pot were touching each other! So I feared that that the kit might not compatible with this amp but I knew that was more likely my ignorance rather than anyone else's.
That didn't stop me from removing all the components for the tremolo, though. Now I have an unused triode in the amp, and three holes to fill...
It works exactly as advertised, and sounds great!
This is a unique amp. In spite of being advertised as mod-friendly, the reverb and tremolo circuitry combine with my noobishness negated this friendliness. This bell and whistle combo need to be considered separately.
The tremolo shares the dual-ganged 1MΩ pot used to control WATTS but this inevitably fails due to the high voltage from B+ across it (probably accelerated by heat from my nooby soldering technique.) I never wanted the tremolo anyway so I replaced it with a single pot 1MΩ pot instead, and just disconnected the tremolo but since its in the path of the concertina phase inverter, this meant I had to jumper the grids to ground get any sound!
Removing the tremolo may be more overkill but the bigger issue is the reverb that sharing the same voltage supply node as the critical screen grids. KoC recommended I "cascade" the power supply nodes. To understand this, I ordered TUT1.
The stock circuit supplies the power tubes and preamp tubes in parallel so that WATTS does not drop the voltage to the latter. (Enter VCK!) Eventually we concurred that adding a dedicated supply node for reverb was the best solution. So I added a fat green 10KΩ resistor from the B+ mains to a fat black capacitor to ground, and spliced some wire from the new node to reverb. This node is parallel (not cascaded) but it works for now.
Along the way I made lots of other noob mistakes that blew several fuses requiring me to rebuild the rectifier, and that required a bottle of 99.9% isopropyl alcohol to clean the glue off of it.
Hum specifically from the reverb also stalled the project until I realized it the two ends of a coax wire to the pot were touching each other! So I feared that that the kit might not compatible with this amp but I knew that was more likely my ignorance rather than anyone else's.
That didn't stop me from removing all the components for the tremolo, though. Now I have an unused triode in the amp, and three holes to fill...
