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  1. KrisBlueNZ

    Sine Tone Generation Help!

    LOL :-) How about digitised audio that's been ripped from vinyl? Include the needle drop, groove noise, clicks and pops, etc, in the digitised version. Then ask an "expert" to compare listening to the vinyl directly, against listening to the pre-recorded, digitised version. If he couldn't tell...
  2. KrisBlueNZ

    Sine Tone Generation Help!

    Portable MP3 players would be good sources of accurate sinewaves as well, though you would still need to add an amplifier and speaker on each one. You might be able to pick up a bundle of old ones that are being thrown away because they don't have enough gigabytes of storage to be cool any more...
  3. KrisBlueNZ

    Motor control diy

    Here's my design for stall current detection as suggested by CDRIVE. I designed this more as an exercise to see whether it could be done tidily and efficiently. I personally think you should stick with limit switches and a loosely coupled drive, as in the earlier circuit drawings. If you use...
  4. KrisBlueNZ

    Motor control diy

    Isn't it amazing what you can get nowadays. A tiny, super-efficient, super-powerful module for a tiny price, that does things that just 10 or 20 years ago would have been either impossible, or extremely large and expensive. The synergy of many separate technology and process improvements enable...
  5. KrisBlueNZ

    Valve (tube) amplifier schematic help

    Under 2 hours with an Alkaline, or around 6 hours with a Lithium battery. I thought it would be even less than that, but I think most people would say even that's impractical. Exactly.
  6. KrisBlueNZ

    Motor control diy

    Ah, "zip cord". That makes sense. I have no idea what the characteristic impedance would be. I really don't know Chris. I expect there will be problems with the microswitch design, and with optos or reed switches as well. I think detecting the stall current would be workable, without needing a...
  7. KrisBlueNZ

    A challenge for you expert folks.....about tennis!!

    I think we should all reconsider the requirement for this setup to be OUTSIDE in the weather, with dirt, dust, falling leaves, polluted rain, etc. I don't know whether ANY of the suggestions made so far would be practical under those conditions. I expect there are already solutions out there...
  8. KrisBlueNZ

    Valve (tube) amplifier schematic help

    Yes, I saw that earlier. That's what I would recommend as well. Solidus, please have a look at CDRIVE's schematic. This shows everything I was trying to describe. He's even included a pi filter with a 470 ohm resistor. This should give you a very good result - almost NO ripple on the B+ rail...
  9. KrisBlueNZ

    Sine Tone Generation Help!

    I agree completely. It's a bit of a shame that MP3 is still the dominant standard for audio compression; apparently other lossy compression algorithms like AAC and others can get a much better sounding result at the same bit rate. I've gone a bit anal with my music collection: it's all...
  10. KrisBlueNZ

    Sine Tone Generation Help!

    I doubt that would be accurate enough for this application. The OP wants to be able to choose frequencies in a 1:1.04 ratio, i.e. one frequency is only 4% higher than the next lower one. With multiple frequencies being emitted in different places around a room, there will be audible beat...
  11. KrisBlueNZ

    Motor control diy

    I'd use "speaker wire". Get the "twin trurip" type. "True-rip" means two pieces of wire individually insulated and joined together, so you can rip them apart if you need single wires. Stranded (many thin pieces of wire twisted together inside the insulation, rather than a single thick wire)...
  12. KrisBlueNZ

    Sine Tone Generation Help!

    I strongly suspect that these people hear what they want to hear. If you KNOW when you're listening to analogue, and when you're listening to digital, it's easy to imagine the characteristics that you expect to hear for each, and I think it's quite possible that this will affect their perception...
  13. KrisBlueNZ

    Valve (tube) amplifier schematic help

    It ought to be possible to eliminate common-mode and differential-mode noise using inductance in series, and capacitance in parallel. I think it will depend on how _much_ noise is present. I'm interested to know whether you have a noise problem initially, and if so, what it takes to overcome it...
  14. KrisBlueNZ

    A challenge for you expert folks.....about tennis!!

    I must be missing something. If you're using a single beam reflecting back and forth, and a single receiver, how can you tell which part of the beam got broken?
  15. KrisBlueNZ

    A challenge for you expert folks.....about tennis!!

    I bow to your experience. Agreed. I would say it would be the most fun option anyway :-)
  16. KrisBlueNZ

    Valve (tube) amplifier schematic help

    Yes. The circuit has a single 9V supply so he used that for the filaments as well as the actual circuitry. Hum comes from the mains frequency and is caused by insufficient smoothing when working from a mains power supply that uses a mains transformer. The noise from a switching power supply is...
  17. KrisBlueNZ

    WD40 ok as switch cleaner

    My two cents: WD-40 and 2-26 are alright for switches, but I wouldn't use them on potentiometers. This is how I clean a potentiometer. 1. Replace it, if possible! 2. If that's impossible or infeasible, open it up and clean it. Remove the potentiometer. Find the tabs that hold it together and...
  18. KrisBlueNZ

    Sine Tone Generation Help!

    Google direct digital synthesis sinewave. Analog Devices make a range of parts. Ones that have use SPI or I2C programming will need a micro of some sort (even just a fifty cent one) to set the frequency. I don't know about prices. Get some representative part numbers and look them up on...
  19. KrisBlueNZ

    Sine Tone Generation Help!

    So you have perfect pitch for a 36-note octave? That's pretty unusual! And you want to produce sinewaves at pitches that fit with a 19-note octave? That means each tone will be related to the previous one by the 19th root of 2, which is 3.7155%, is that right? And your frequency range is 100~500...
  20. KrisBlueNZ

    Valve (tube) amplifier schematic help

    You're right, you did summarise it well. I hadn't been following the thread closely. Apologies. Re powering the filament from 12VAC or something else: No, that's just how the schematic happened to be designed. Because there was a 9V DC rail, the designer decided to power the filaments from it...
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