If you want to boost the signal to overdrive the amp ant lower volume, just turn the LEVEL knob to max (10/10) and leave the tone and drive at 0 so it will stay the same almost.. . You can do that with almost any pedal, most common are probably Boss DS1 or SD1, Dod 250(or YJMmodel) obviously and many more. If you do not want to add even a little more drive to your solo, then there's no other way than just buying a volume pedal. Which would still have some influence on the drive. (if you have valve amp)