Greer Amps have taken the Lightspeed overdrive and have made a few mods to give us the Southland Harmonic Overdrive.
- added a set of hard clippers after the first gain stage
- boosted the gain of the output to make up for the BAT41 hard clippers
- increase the drive pot value
Could try germanium diodes instead of the BATs, but it will probably sound about the same.
GREER AMPS SOUTHLAND HARMONIC OVERDRIVE - VERO LAYOUT
Two 1n4148s connect to nothing.
ReplyDeleteGood spotting - there’s a cut that shouldn’t be there under the 470n cap. I’ll fix that today
DeleteIt still doesn't work. I get maybe .25% of the bypass level when engaged.
ReplyDeleteOK - do you have an audio probe to trace the signal flow, and what kind of voltages are you getting on the IC?
DeleteI checked the layout, and I also had the hard clippers running to ground instead of vref, but that should not have caused the lack of output (layout updated, just had to flip them up to vref)
feel free to email pics to guitarverop2p at gmail dot com
DeleteHey Markie - move the 3.9k resistor from pin five to pin six in the IC. This should fix it. Sorry, I had it going to positive instead of negative input.
DeleteShould Southland's op amp be a TL072 ?
ReplyDeleteThey’re both dual op amps, so it doesn’t really matter - the OPA is a rather expensive TL702. I’ll update the layout to make that clear.
ReplyDelete