This is un-tested, theory only, USE AT YOUR OWN RISK!
CAUTION; this mod requires PC board soldering skills!
BEFORE STARTING ANY MOD;
Unplug the amp’s power cable from the power source it is plugged into and remove the power cable from the rear of the amp. Set the power cable aside away from the amp, being absolutely sure the power cable is disconnected from the amp.
*WARNING!! The power must be disconnected from the amp, failure to comply could result in serious injury or death!
WHAT WE ARE DOING
C63 capacitor (C53 0n the AC30VR) controls the time of the switching (latency) on U3 NJM2120 dual OP amp/with output switch (the AC30VR has two, U2 & U6, doesn’t matter).
The existing value is 2.2uf, lowering the value of this capacitor will lesson the latency of the switching (time it takes to change). The capacitor stores voltage as the switch is turned on, then releases the stored voltage back when the switch is turned off (slows the switching).
The latency of the switch is designed to eliminate switching noise, so be careful, the less switching time the greater the risk for noise being introduced during switching (pops, exc.).
Material List;
1 - 1UF Electrolytic capacitor @ 50 volt
1 - .05UF Polypropylene capacitor @ 50 volt
HOW TO DO IT
Start with C63 capacitor (C53 0n the AC30VR);
Paying close attention to the polarity of this capacitor (mark the negative side on the board, if not already), carefully remove the existing capacitor and replace it with a 1uf. Test the amp, if the switching speed and noise level is exceptable you will not need to do anything else.
You can experiment with different capacitors value up or down slightly to change the speed of switching to taste.
Additionally;
There are two Jfets on the OD channel that may be effected by the above changes, if noise is introduced (pop when switching) try lowering the value of capacitor C58 (C74 on the AC30VR). This capacitor controls the latency for the Jfets, the existing value is 100nf (.1uf), lowering this capacitor to .05uf may help eliminate pops when switching.
- VR Switching time.jpg (855.75 KiB) Viewed 254 times
