Hi Dj,
As Soulsonic wrote in a previous post:
All the volume issues are due the two germanium diodes: good sound but at lower junction voltage.Soulsonic wrote: "If you replace the two germanium diodes with silicon ones, like 1N4148, and it will likely be very obviously louder. Replace them with red LEDs and it will be very loud. But this also changes the tone of the distortion, but maybe in a way that you will like.
If you remove the old diodes carefully, you can put them back and make it "original" again if you ever wanted to sell it."
Cheers,
Jose