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Phono Preamp Project |
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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Yes, this is true, and please inform president Obama that we received Winston Churchill's statue back in good condition after spending near on 60 years in the Whitehouse.... But when it comes to electronics, Silicon Valley and NASA speaks the same language, just that I try to make it more layman. The problem with any tiny company like ours showing the world how to design, is that I have to be exact and methodical or some individuals who think they run companies to similar standards, may just be able to trip me up. I suppose I could just say that it sounds out-of-this-world or mind-blowingly-good, which incidentally it does, but I'd be stealing everybody else's line... |
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That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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So far so good...
The left hand screen is the design copied into the windows software because I cannot get a hardware compatible MS DOS 5 printer these days. Even with the disadvantage of having to do transfers on floppy disc, the "machine-code" version of this software is mega-fast compared. Time for checking, final tweaking, then generating the gerber and drill files before emailing to the PCB manufacturer for some prototype PCBs. |
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That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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discrete badger
Senior Member Joined: 14 Jul 2009 Status: Offline Points: 479 |
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Graham, when drawing out the board like that, how much are you thinking about the sound quality effects of your decisions versus the more obvious task of getting everything to just fit onto the board and be connected in the right way?
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leo
Moderator Group Joined: 13 Jan 2008 Location: uk Status: Offline Points: 53 |
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looking great, its giving me itchy fingers would love a go at this, may even knock it up on vero (if Graham don't mind) until the kit is released, better have a trip to Craplins to see what bits they don't have
Its nice to see a diy phono stage, don't seem to be many of these about, anybody else having a bash? |
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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Like the Avatar! "Twas twillig and the slithy tove..." Graham don't mind! Looking forward to your findings - hope craplins has some veroboard - wish I had some left too! |
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That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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Good question! Did you know that when you are listening to music you are actually listening to the power supply? Here is how... (Transistor Man picture from "Art of...": points B and E is the input signal and points C and E are in-effect the amp controlling the power into the speakers, headphones, a preamp driving a power amp etc) We will assume the power supply is nice and quiet with enough current to prevent it "wobbling" in sympathy with the music. What else could go wrong? Even with short and reasonably thick PCB traces, a "dot to dot" will have sufficient impedance for one thing drawing power to affect another thing drawing power (like the headlights dimming when you switch on the rear window demister, or that recurrent "MOT-pass because they don't test them together" Ford earth fault which turns the rear indicators off when the brake lights come on). And the thing many designers forget: currents flowing into and out of the same point at the same time - it can't be done - that point cancels out completely when the currents are the same and in direct opposition - a case of a piece of wire that is solid, it is there, you can see it, you can even "bleep it out", but it's not connected! Therefore, you may be able to make out a number of tracks all going to the same place by different traces? That place is the lowest impedance point of whatever current we are wanting to connect to. Often the star earth is the only thing considered, and often the star earth is just a "pretty flower picture" with a silly thin track then leading back to the common "ground" connection - so all those currents still modulate one another (search the internet if you want a good laugh). In our case the PCB is routed to avoid one thing modulating another. We may only be talking about pico-amp differences, but those are sufficient to confuse the picture as the all-important "clues" are contained in the micro-information. Some designers adopt the ground-plane approach, but the current still takes its own path as if the rest of the ground plane didn't exist. So yes, I'm thinking most of the time about sound quality effects of my decisions, and often miss a connection because of it . So right now I'm correcting things like that, doing print-outs, checking again etc. |
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That none should be able to buy or sell without a smartphone and the knowledge in how to use apps
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RobW
New Member Joined: 10 Jan 2010 Location: Canada Status: Offline Points: 24 |
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Hey - I was just reading about "Transistor Man" on the weekend. Thanks for the tie in.
I very much like the thought-shift provoked by the idea that listening to music is basically listening to the power supply. So is the source signal then just the mechanism that controls a "rheostat" between the power supply and the transducer? And all the other bits and pieces in the signal path are just about ... what ... balancing, filtering, controlling ... ? I need to look over your schematic closely to see if I can see what you're talking about re PCB routing to avoid modulation. So many questions. |
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