| Romy the Cat wrote:|
| In here is not the value are important but the concept the you block DC not with capacitor but with an “active” resistor that backed up with positive voltage. BTW, eventually if you wish to go “kinky Milq” and have a very low impedance front end then you might do not use positive bias at all letting the excessive DC voltage on your Milq input to bias your cables (it might be a different subject and it has own “danger”) |
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Ok, since lately, going over the 6-ch Milq project I overly submerged myself into the technicality part of Audio I look forward to exhaust this subject as I am planning to close the subject up for myself. In the Melquiades circuit there is a provision do not us positive contra-bias and drive the bias over interconnect between preamps and Milq. Two conditions should be in place for this implementation:
1) Low output impedance of the preamp
2) The interconnect should not be disconnected
So, when I was experimenting with it I did the following:
1) Do not use any “kinky” positive bias supply with gas tube and have a positive bias taken just from a voltage divider sourced from B+ of the first stage.
2) Put a switch juts before a positive bias applied to the left side of the biasing resistor of 12K
3) Turn the switch on and set up the roughly 0V at input of the Milq (the exactness is not important, +/- even .5V will be fine.)
4) Connect the cable the interconnect cable to Milq and to Preamp.
5) Disengage the switch disconnecting any positive bias.
6) Fine tune the negative bias to get the operational plate voltage
7) Each time the cable need to be unplugged I juts engaged the switch.
This way of using Milq bias, I call it “Remote Biasing” has some advantages: less parts and extra DC current flows over the cables (always plus). For the most atrocious over there I would advise to change the biasing resistor and increase voltage driving over the interconnects. You can drive even 150V or higher in that configuration if you wish. The quality of the positive bias voltage will NOT affect anything as what the amps is connected and operation you will shot down or disconnect the positive bias.
Romy the caT
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