RumbleFX build and general guidance
Posted: Fri 03/17/23 11:10 am
Hello, everyone. I built a 18watter a few months ago based on this layout from RumbleFX[1], which seemed to be one of the coolest around (there are so many versions of these Plexi 18w that I had a hard time figuring out which one to pick).
So, besides the VVR, which I couldn't get to work, despite many tries and even help from other forums - I blew up 4 or 5 FET transistors and just gave up on damn solid state crap - everything worked fine.
But, I'm still interested in messing around with this build and would like to ask a few things.
1. I've been reading some old threads and no images or attachments are available anymore; so, I also see many MODs being mentioned, from guy X and guy Z - where can I find this stuff? I would like to explore the possible modifications for this circuit;
2. This build has a PPIMV but it cleans up a lot in lower volumes, is it really expected? I guess so, since power distortion plays an important role in this circuit, but just wanted to confirm, since stock Plexi master volume mods are also a common thing;
3. I dared to add a NFB to it, to see what would happen. Weirdly, I couldn't hear any difference until I used a very low resistor value (10k from the 8omh tap, which means a lot of feedback, with a 470R resistor added from PI tail to ground, the NFB going in between). The NFB helped a lot in reducing noise at higher volumes but didn't seem to change my tone much. I'm really not sure about this NFB setup I came up with, does it sound right?
4. I have no reference of the real thing, but I found this one to have such a glassy high-end. Is it really like this? The Plexi tone, I mean. Are there tweaks I could do to be able to tune it more. Maybe a presence control?
Thank you all in advance!
[1] https://www.ramblefx.com/diy
So, besides the VVR, which I couldn't get to work, despite many tries and even help from other forums - I blew up 4 or 5 FET transistors and just gave up on damn solid state crap - everything worked fine.
But, I'm still interested in messing around with this build and would like to ask a few things.
1. I've been reading some old threads and no images or attachments are available anymore; so, I also see many MODs being mentioned, from guy X and guy Z - where can I find this stuff? I would like to explore the possible modifications for this circuit;
2. This build has a PPIMV but it cleans up a lot in lower volumes, is it really expected? I guess so, since power distortion plays an important role in this circuit, but just wanted to confirm, since stock Plexi master volume mods are also a common thing;
3. I dared to add a NFB to it, to see what would happen. Weirdly, I couldn't hear any difference until I used a very low resistor value (10k from the 8omh tap, which means a lot of feedback, with a 470R resistor added from PI tail to ground, the NFB going in between). The NFB helped a lot in reducing noise at higher volumes but didn't seem to change my tone much. I'm really not sure about this NFB setup I came up with, does it sound right?
4. I have no reference of the real thing, but I found this one to have such a glassy high-end. Is it really like this? The Plexi tone, I mean. Are there tweaks I could do to be able to tune it more. Maybe a presence control?
Thank you all in advance!
[1] https://www.ramblefx.com/diy