Just sold my new Gamma,I really liked how the vdi locked on at depth,a really deep and accurate detector. The reason I sold it is the tone for coins was weak and volume low.The operators manual stated ths to be normal. I do have some hearing loss but I hear my other detectors fine.My old F4 tones are sharp and clear. My question is. Are all tecknetics like this.I really want to upgrade the F4 but need more info.Can any one offer some advice?