Tiens, j'étais sur freestompboxes.org et je lis ceci :
Jettenuator seems to have correct impedance [resistance] as a load box for dedicated 16-8-4 ohm inputs without speaker, but with the speaker connected those resistances are about 12.7, 6.6 and 1.95 ohms [with correct impedance speaker] - if my calculations are OK. Not so bad, though a little low - especially for 4 ohm input at full open setting.
16 ohm socket switch is used for connecting two parallel 15 ohm resitors to ground - lowering load impedance for 8 and 4 ohm inputs.
I have no idea why the full seen impedance [from the amp side] is assumed to be nominal at 2-3 setting of the big rheostat [according to manual].
The highest load impedance should be seen with the speaker [pot wiper] shorted to ground - speaker virtually out of circuit - and the lowest with the pot on full [speaker impedance in parallel with 15 ohm resistor and 16 ohm pot]. These settings have no meaning without speaker connected - why set pot with unconnected wiper to 2 - [ignoring line out/speaksim out signal availability] - ?
Obviously this argumentation needs to be verified and quite probably contains mistakes ...
For now I have no access to the device, but simple measuring input sockets resistances with and without speaker connected [various pot settings] should explain much.
Strangely there is no visible connection soldered to the 16 ohm socket's sleeve lug. The sleeve is probably connected via mounting washer to the conductive case/ground [if it works at all] but this is not the right way I think. A soldering mistake ...?
"Je mets les pieds où je veux Little John... Et c'est souvent dans la gueule..."
Chuck "Braddock" Norris (1987)
