What's going on in this V1 pic?

[JamesO]

Hi everyone

I was just wondering what's going on here? This is a pic of V1 from a Two-Rock Custom Rev. Sig. The same values are used in the D Lite. What are these components doing?

500pf/220k in parallel to pin 7 of V1

22M/.047uf/22M from pin 6 to pin 7 of V1

[img:640:480]http://www.languagepool.net/amp/IMG_0906.jpg[/img]

[heisthl]

The 500pf/220K to pin 7 is just passing the signal from the volume pot to the second tube stage(grid resistor) - the 500pf lets some more highs through and balances out the tone.
The 22M/.047/22M is known as a LNFB (local negative feedback) it's purpose is also tone shaping - in this case to limit the extreme highs that might get passed to the first overdrive stage. When I use this circuit in a build my ear hears little difference in the clean sound, but can hear an improvement in the OD sound.

[dogears]

The .047uf cap allows much more than highs to feedback. There is a noticeable loss of gain across much of the frequency spectrum. There is noticeably more bass without the FB. This is very evident if you have the low gain HRM circuit. Less evident in a build like the Hybrid A style Sig.

The 22M/.047/22M is known as a LNFB (local negative feedback) it's purpose is also tone shaping - in this case to limit the extreme highs that might get passed to the first overdrive stage. When I use this circuit in a build my ear hears little difference in the clean sound, but can hear an improvement in the OD sound.

[drz400]

The .047uf cap allows much more than highs to feedback. There is a noticeable loss of gain across much of the frequency spectrum. There is noticeably more bass without the FB. This is very evident if you have the low gain HRM circuit. Less evident in a build like the Hybrid A style Sig.

The 22M/.047/22M is known as a LNFB (local negative feedback) it's purpose is also tone shaping - in this case to limit the extreme highs that might get passed to the first overdrive stage. When I use this circuit in a build my ear hears little difference in the clean sound, but can hear an improvement in the OD sound.

I have seen in a few schematics the pre EQ filter
Where does that go and what is it good for ? says something about Dogears likes it with the boost HRM I think?
does it replace the trim gain and the 220k feeding it or something?
some slices on the schematic where it belongs would be nice

[JamesO]

That's really interesting guys, thanks. Haha, I think it's one of those things that could be interesting to try. It's not going to break the bank, you know?

[glasman]

That's really interesting guys, thanks. Haha, I think it's one of those things that could be interesting to try. It's not going to break the bank, you know?

The LFB network is best applied to a non-HRM type of build. It really helps to smooth out the overdrive. The downside is that it does add a bit of compression. I find that the network robs too much gain from a low gain HRM circuit.

Early Dumbles used 20M with a .047uf. Later ones used 44M with a .047uf. The later Dumble HRM amps did not use this circuit (there are a couple of exceptions).

Gary