Understanding Toneking integrated ironman2 schematic

[janou195]

Hello all (and merry christmas!),

I retro-engineered the integrated ironman2 attenuator of my Toneking Gremlin. The schematic I've came up with is attached to this message.

I do not really understand how this works, why it is designed this way and so on. What troubles me the most is that I feel that when an attenuation level is selected with the rotary knob, the part of the circuit related to other settings still have effects on the circuit (which would mean that if I replicate this attenuator with only a subset of the attenuation levels, it would not behave the same for the attenuation level that I keep). Do you confirm that?

I would be very glad if someone which understand this attenuator could give me the outline of how it works!

Many thanks!

[shooter]

might get you started on understanding, then add capacitance n re-do the math 


https://www.circuitdiagram.co/complex-series-and-parallel-circuits-problems/

[Merlin]

What troubles me the most is that I feel that when an attenuation level is selected with the rotary knob, the part of the circuit related to other settings still have effects on the circuit (which would mean that if I replicate this attenuator with only a subset of the attenuation levels, it would not behave the same for the attenuation level that I keep). Do you confirm that?

Correct. Assuming your drawing is accurate, at its core you have several dividers connected across the amp output, and the switch just selects which one to use. If you want to produce a subset of options, it would be easy enough to re-jig the values to get the same result with fewer dividers. R61 and R62 soak most of the power anyway, at any setting, so even if you leave out some of the dividers the end result won't be much different.

[janou195]

I clearly see how a divider works as a voltage divider when the load has a high input impedance, but here this is not that clear to me... How is the attenuation level determined?

Thanks for the answers!

[Merlin]

How is the attenuation level determined?

The loudspeaker is in parallel with the lower arm of the divider, so it must be included in calculations (or more likely, use a circuit simulator!)