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  1. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    If I were using that MicroPre unit then, rather than use the post #57 circuit, I'd revert to the post #22 circuit but, now that we know the preamp output impedance is 3.5k, with R1 and R2 omitted and with the blend lin pot value increased to 25k to give a wider blend range.
  2. Alec_t

    Isolating electric shower

    Exactly what I would expect from the physics of the system. A single 15mm feed to the house at a given pressure can only sustain a certain flow rate. I too live near the top of a hill and have the same problem of water pressure dropping when other members of the household or the neighbours draw...
  3. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    I don't see why not. Does the Fishman already have a volume control that you use during a gig? If so, that would be the master volume control. I doubt it. From what I read, guitar piezo pickups can put out several mV.
  4. Alec_t

    Isolating electric shower

    That's basically what the TS already has, if it's a typical 'electric shower'. The problem is this type of shower includes a water-pressure sensor which cuts off the electrical supply to the shower's internal heating element (for safety, to prevent scalding) when the water pressure drops below...
  5. Alec_t

    Isolating electric shower

    Yebbut, if the solenoid valves are mains-voltage operated the setup ought to comply with IEE regs (as you are UK based). At a minimum that means a safety enclosure for the solenoid, and earth bonding of pipework. Since the electrical installation would presumably be in a kitchen or bathroom I...
  6. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    Give the post #55 arrangement a try. Use screened connecting cable to minimise noise pick-up.
  7. Alec_t

    Isolating electric shower

    Your proposed solenoid valve system sounds doable, provided it complied with local water and electrical regulations. Have you checked?
  8. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    Any setting of the blend pot would be safe. I'm thinking that IF each preamp has a level setting control built in, and you don't want to change the blend setting during a gig, then the blend pot is redundant and you could simply mix the two preamp outputs as shown in Audioguru's third circuit...
  9. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    It's wherever the sound blend suits you best. Since the preamps each seem to include a level control pot, set those for maximum level (volume).
  10. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    If the pots have metal cases then those should both be connected electrically (by soldering or with tags) to the circuit ground, which pin 1 of the log pot (NOT the lin pot) also connects to. A 10k blend pot will be safe, but with preamp output impedances of ~3.5k the blend adjustment range...
  11. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    Perhaps these frequency response traces will help to explain. The yellow and blue solid line traces for a magnetic pickup respectively show how amplitude drops away from 1kHz onward with a 50k load but from 10kHz onward for a 500k load. This is because the pickup has a high inductance whose...
  12. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    Here's how they would be connected. Now that we know the output impedances of the preamps, the 1k resistors aren't needed.
  13. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    That sounds like a dual-ganged pot. Why use that? The 10k pot and the 50k pot would not be ganged. Presumably you want both accessible for individual adjustments during a performance?
  14. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    If the pickups are magnetic and connected directly to the pot then 500k or more is required to avoid loss of the higher frequencies. If they are fed to the pot via a preamp then 500k would work, but so would a lower impedance. I'm no musician, but won't piezo pickups on an electric guitar sense...
  15. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    Without knowing the output impedances of the preamps and the input impedance of the power amp it's difficult to specify the optimum value of the pot(s). Assuming the preamps each have an output impedance < 1k and the power amp has an input impedance >500k, here's what I would try :- There's no...
  16. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    Post a sketch of exactly how you connected it.
  17. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    Piezo pickups have a source impedance which is very high at low frequencies but reduces as frequency increases. Their output voltage is small even when unloaded, but is made even smaller by the loading which the pot resistances place on them. Piezo pickups should normally be working into a 10...
  18. Alec_t

    2-channel passive mixer-independent volume control for each pickup

    So where do these voltages come from, if not from the pickups, bearing in mind that this is supposedly a passive mixer?
  19. Alec_t

    Can a low side driver control three N-type MOSFETs connected in series?

    LTspice suggests it's possible, but unpredictable, if the FETs aren't perfectly matched, but the FETs would need to be logic-level types and the individual Vds experienced by the FETs will be quite different.
  20. Alec_t

    Can a low side driver control three N-type MOSFETs connected in series?

    Do you have the MOSFETS configured like that to perform an AND function? If so, there's surely a simpler solution.
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