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About Bespav

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  1. Bespav

    The Multi Amp aka Dynalo Mk2

    Hi, Kevin! Your site is down or moved somewhere?
  2. Yes, i have buyed 2SK163/2SJ44 pairs from this seller, they was original and very well matched. Matching checked with PEAK Atlas DCA75 And gate capacitances checked with simple transistor tester (as a marker of datasheet specs): Combination of the transconductance and gate capacitance are unable to be counterfeited together. It would be great to check intrinsic device noise, but i'm too lazy for that. So i hope, those 2SK369's are original too.
  3. Are you have plans to do this in a temperature-controlled environment? If no - just label bins with desired precision step like this: But be informed, hFE (beta) and Vbe have sensible tempco, so the more precise step you want - the more precise temperature must be controlled. SMD cases can be sorted and stored straight on the two-sided scotch like this:
  4. Bespav

    SEN I/V stage for BIII

    Not clearly so. We need higher transconductance, just because it straightly defines input impedance. And latter preferably to be as lower as possible. It doesn't have huge amplification as common opamps, so noise factor are less matter than higher transconductance.
  5. Bespav

    SEN I/V stage for BIII

    Exact hmmm! I can't forgive and keep in mind my first time i have heard an amp with +-150 Volts VAS supply. Truly different from common and usual +-15 V opamp-based and something like +-40-70 V discrete ones.
  6. Bespav

    SEN I/V stage for BIII

    Corner idea was posted much more earlier: http://myelectrons.com/hotfet-pre-j-fet-audio-preamp/ Just tie it's input to the ground and blow your DAC's current to it's output.
  7. Bespav

    SEN I/V stage for BIII

    Yes. LSK170D + Cascode 2SC3503. Increase I/V supply to about +- 100-150 Volts. And you just need to simply bufferize I/V output via some kind of good follower.You can even take well known Pass F5 and realign it's input and ground like this: Let your DAC output current to flow there.
  8. Bespav

    SEN I/V stage for BIII

    Multisim + Ultiboard (simplest way to begin) Eagle Diptrace KiCAD Pulsonix Protel Altium Designer Cadence Mentor graphics Just start to try! Even by curiosity!
  9. Bespav

    SEN I/V stage for BIII

    Any JFET with preferably lower noise, higher Idss and higher transconductance. Say, LSK170 grade C or D You can tie upper transistor gate to a potentiometer and correct DC shift at the output. Yeah, nice joke. Please let me use it from time to time! Since when layouting of 2/4 transistors became a problem? 1. Cascode. 2. Mount from bottom and thermalgrease to case panel 3. 2-3-oz PCB with thick traces and ground plane 4. 3/8" air conditioner copper pipe 5. Just bend JFET case to a ground copper plane and add some thermalgrease.
  10. Bespav

    SEN I/V stage for BIII

    @sbelyo: You can even add cascode:
  11. Bespav

    Technical Assistance/Advice Thread

    Hey, man's, 200-300 VA trafos can be used without inrush limiters, especially with 20-30 mF caps after them. Primary and secondary windings active resistance and inductance would effectively limit inrush currents. Try to turn-on something bigger, say 1,3 kWt trafo with 200 mF and i have no doubt you would hear "click" from your 25 A protective breaker. MWL168, let's speak about different question. How much Joules of stored electrical energy we actually need per 1 Watt of output power? 2? 10? 50?
  12. Bespav

    Technical Assistance/Advice Thread

    The more powerful your trafo is - the more care about inrush you must take. Simple NTC is not a good choice, why heat around components? You can better provide relay shunt with 2-3 sec lag. Based on your home mains quality you must take care about DC component too. Powerful toroids can provide 50/60 Hz hum even with 0,2-0,3 Volts of DC in your mains. If you aren't familiar with AC mains - be absolutely careful and better take good known PCB/Kit like this: https://www.ebay.com/itm/132036677853 First turn-on must be made with 40-60 Wt incandescent lamp in series with your circuit. Continuous glow will tell you about errors.
  13. Bespav

    Technical Assistance/Advice Thread

  14. Bespav

    Balanced to unbalanced board

    Amb alpha24 Or you can use simple THS4131+LM6171 if your source can work with something like 2-10 kOhm load.
  15. Bespav

    what is the right Forward Voltage of LEDs?

    Different kinds of LEDs have different forward voltage requirements. Non-bright LEDs tend to require less voltage than bright LEDs, since bright LEDs need more power to work. Typical VLED values are 1.7V for non-high-brightness red, 1.9V for high-brightness high-efficiency low-current red, 2V for orange and yellow, 2.1V for green, and 3.4 to 3.6V for bright white and most blue types.