Friday, March 24, 2023

Try these

  1. What’s the primary ingredient in hummus?
  2. Seqenenre Tao opened the revanchism against whom?
  3. Current tallest building on earth?
  4. What did the letters of Segretti’s CREEP stand for?
  5. Heptadecagon - how many sides?
  6. Why is the pre-amplifier important to the sound?

21 comments:

  1. 3. Khalifa skyscraper? in Dubai
    5.17?
    6. A pre amplifier is where any filters 'shape'the sound wave - add bass or treble - remove hiss etc before the final stage boosts the whole signal

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    1. JH: 3, 5, 6 all good.

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    2. 6 - The preamp boosts the audio waveform, compresses the amplitude of noise using filters, then adjusts the waveform amplitude to RIAA standard. This means that when the amplitude is reduced, the noise is much lower. It is not a hi-fi component as such, being just a small circuit board attached to one of the inputs to the tone controls. Nevertheless it has become habit to refer to the tone control section as the preamp.

      After the preamp comes the tone control section, which does not change the amplitude (unity gain). The preamp is only connected to the record deck input, the rest of the inputs bypass it, going straight to the tone control section via the input selector switch(es). The tone control's job is to boost/cut bass and treble (later to become 5 or sometimes 10 sliders) and balance left/right channels whilst maintaining audio waveform amplitude at a constant level.

      Then the audio goes to the power amplifier which has the gain or volume control on its single input. The power amp feeds the speakers.

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    3. Indeed it does. It also amplifies the low level signal from a turntable cartridge to match the amplitude of the line inputs so all inputs all have equivalent amplitude when they feed into the tone control circuit (which is also 'pre' the main power amplifier and may even be a quite separate unit - hence often called the preamp)

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    4. The amplitude and filtering curve in the preamp was to a standard set by the RIAA (Recording Industry Association of America (the same org that went on a rampage against piracy. The first case was RIAA/Metallica vs Napster around 2001 and it snowballed from there). Not only did the preamp match line amplitudes but also the input impedance of the tone control unit/section. I struggle to recall, but I believe that was to DIN standard. The preamp existed only for one reason, and that was for a record deck fitted with a moving coil cartridge, often called a 'magnetic' cartridge.

      There were all manner of configurations in audio equipment, some of the higher end separate systems (eg. Pioneer, Rotel) had the preamp built into the record deck, so that all inputs to the tone control unit or integrated amplifier were all the same. Location of the preamp was a marketing strategy, it deterred mixing/matching of different brands. Cheaper systems had a piezo cartridge in the record deck with a higher voltage output than the moving coil type (eg. Goldring) so didn't need a preamp at all (eg. BSR record decks). Piezo cartridges (sometimes referred to as 'crystal' cartridges) were noisy.

      The tone control unit was always referred to by the wrong name, when the bass/treble knobs began to be replaced by multiple sliders (equalizer) the 'preamp' unit started to be called the 'graphic equalizer'. There is no such thing, but that's a different story.

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    5. Thank you Ripper and woodsy - my limited technical knowledge has been shown up! You have also given me an idea for linking my old turntable to my new(er) receiver - first find a pre-amp!

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    6. About £20 from places like Ebay Ian.Plenty around with the surge in vinyl use. Designed to take a magnetic cartridge input and output a standard level for the amp's line/aux or tape in socket. Probably cheaper if you look around.

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    7. Happy that my ramblings helped someone Ian. Like Woodsy says you can get these preamps very cheap and will adapt your turntable. I'm stating the obvious here I know, but check first that there isn't already a preamp built into your old turntable. A lot of turntable manufacturers started doing that. Secondly, if your receiver has a designated Phono input (the rest being labelled 'AUX'), it is more than likely that there is a preamp built in. The thing to do is link up the turntable (it will do no harm), play a record and if a) the sound is extremely low, or b) distorted then you need a preamp. Your instruction booklets may also tell you. Here is an example I searched out for you on fleabay. It comes with a mains adapter but will also work on a 9v PP3 battery if you don't like the extra wires or run out of sockets, price £14.99.

      https://www.ebay.co.uk/itm/183484453783

      If you want to do your own search, use the term "RIAA preamp".

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    8. Thanks again Woodsy and Ripper, I've just found one on **ay. Back in the day I'd have bought a kit in Maplin (?) and got the soldering iron out!

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    9. Long before fleabay, I used to build most things from scratch on Veroboard (strip board), getting my components from a mixture of Maplin, Tandy and a local electronics shop (all gone now). I did repairs for friends and family, and sometimes neighbours would give me unwanted, outdated and non functioning items that would otherwise be thrown away. I would sit for hours de-soldering circuit board components which got used in repairs, making it much cheaper for my clients. Some audio circuits demanded a specific component layout where noise/feedback was a problem, in which case I used to etch my own printed circuit boards in ferric chloride. That kind of thing has become far too expensive, nowadays you can get pre-made circuit boards which only need boxing/wiring. I was able to learn as I went along over the years by being an avid reader of Practical Electronics and Everyday Electronics. One of the contributors of that mag was an author, R.A.Penfold, who specialised in audio, and I still have a few of his books.

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    10. Didn't Alan Sugar start out by selling electronics kits? I started at the beginnig of the IC era - at one time, the TTL cookbook and CMOS cookbook were by my side constantly!

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    11. Grief yes - wax resist eching and circuit mock-ups on blocks with little socket holes for the component legs prior to building on stripboard. Been there, done that. Once had to build a timer board and response system on a plug in board for a - then very early - Apple II Feels like a lifetime ago! Now you just buy something from China. I have a couple of 60s radios which I intended to repair and some bits and pieces in a cupboard but to be honest I have probably forgotten too much to get back into it. My mate had a hi-fi amp years ago that was made from DIY plans in PE by his Dad. I suspect that was an R.A. Penfold design?

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    12. Ian - perhaps, I don't really know, but what I can tell you is that Sugar founded Amstrad (Alan Michael Sugar Trading) in 1968 (everyone seemed to think that the brand was Swedish). He was 21 at the time. It wasn't until the early 80s that he got ahead in the market with a 'hi-fi' unit that was in fact a cheap ghetto blaster made to look like hi-fi separates. Clearly rubbish but a lot of people fell for it and it was a lot for its money. Then came the Amstrad CPC464 which competed with the Spectrum and C64 and things took off from there. I never bothered with TTL myself, went straight for CMOS because those were more resistant to static damage and more forgiving with input voltage fluctuations. When I started out, colour TV was a new thing and transistorised equipment ran on germanium transistors rather than silicon. About the early 70's I'd say, and its been a main hobby to this day.

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    13. Woodsy - It most likely was one of his designs, though he contributed mostly to Everyday Electronics. The projects in PE were a little more advanced but my favourite was EE, I found that easier to learn from and the projects were more ingenious. He wrote about power supplies too, and one of the books I mentioned earlier is on power supplies.

      Those radios you have - I would get them repaired and working, since now they are classic/vintage and you would be surprised to find out their value. Iconic ones like the old Bush with the big round dial were selling like hot cakes, so much so that Bush bought the design back to market a few years ago, upgraded of course. Same with those old portable record players that resembled a suitcase such as the Dansette.

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  2. JH: 1, 3 and 5 all good.

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  3. JH: 2: Certain kings were pushed out; 4: think Watergate.

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  4. 4; Committee to Re-Elect the President

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    1. Eggsellent. Those kings … name started with Hy.

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    2. whatever the question was the answer is Hyksos

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    3. JH: And that wraps it up. Thx.

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Comments need a moniker of your choosing before or after ... no moniker, not posted, sorry.