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Audio and Video Talk
Valves / Vacuum Tubes
Mars 5-10 stereo - update
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<blockquote data-quote="Ampdog" data-source="post: 919255" data-attributes="member: 144"><p>With passive tone controls the variable resistors would invariably be of the log taper type. A very preliminary estimate of whether the frequency response will be flat in pot middle position, can be made by checking whether he following relationships are true (referring to Karel's circuits on the left of the graphs):</p><p></p><p>R1 = 10 x R3</p><p>C2 = 10 x C1</p><p>C4 = 10 x C3</p><p></p><p>Unfortunately response at frequency extremities can never be mirror images. In the cut positions (control sliders at R3 and C4 ends) the response will flatten out more than at the opposite sides, i.e. 'boost' will be more than 'cut'.</p><p></p><p>Symmetrical responses are only possible in feedback circuits e.g. the well-known Baxandall circuit. The responses of channels in stereo would also track better. (Ganged linear pots track better than log ones.) Then R5 there is on the low side; it interferes with the symmetrical operation of the bass pot. It should be at least 6 times the pot value.</p></blockquote><p></p>
[QUOTE="Ampdog, post: 919255, member: 144"] With passive tone controls the variable resistors would invariably be of the log taper type. A very preliminary estimate of whether the frequency response will be flat in pot middle position, can be made by checking whether he following relationships are true (referring to Karel's circuits on the left of the graphs): R1 = 10 x R3 C2 = 10 x C1 C4 = 10 x C3 Unfortunately response at frequency extremities can never be mirror images. In the cut positions (control sliders at R3 and C4 ends) the response will flatten out more than at the opposite sides, i.e. 'boost' will be more than 'cut'. Symmetrical responses are only possible in feedback circuits e.g. the well-known Baxandall circuit. The responses of channels in stereo would also track better. (Ganged linear pots track better than log ones.) Then R5 there is on the low side; it interferes with the symmetrical operation of the bass pot. It should be at least 6 times the pot value. [/QUOTE]
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Audio and Video Talk
Valves / Vacuum Tubes
Mars 5-10 stereo - update
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