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Old 31st March 2013, 03:48 PM   #37611
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Mr Curl,

looks like miniature relays with Omron pin-out survived the monolithics and your Shallco switch.
By the dozens.
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Old 31st March 2013, 03:58 PM   #37612
Bonsai is offline Bonsai  Taiwan
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Quote:
Originally Posted by john curl View Post
This is what we call a 'crowded' analog board.
That ain't crowded. Positively as open and with as much space between the components as the Serengeti plains. You want to take a look at one of the latest smart phones, or an Ultrabook notebook PCB to see what crowded is.
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Old 31st March 2013, 04:11 PM   #37613
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Quote:
Originally Posted by john curl View Post
This is what we call a 'crowded' analog board.
Nice color representation,
Marce if you been doing these for 27 years does Johns attachment remind you of triple prints?

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-Antonio
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Old 31st March 2013, 04:15 PM   #37614
1audio is online now 1audio  United States
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The latest technology is really crowded with 6 and 8 layer PCB and chip scale packages. But they have very little exposed analog. I have been working with a PCB with a Bluetooth chip and 2 full DSP's plus antenna in less than 1 square inch. We could shrink it more if we put parts on both sides but that has consequences. Despite all of the connections (6 microphones, USB and RF) there is very little analog that is not in a chip. Which also means little opportunity to make it better.

The constellation board is much denser than other discrete boards using that generation technology (really, late 80's and early 90's). Surface mount makes for much smaller footprints, but the "good" parts are unavailable in surface mount if at all.

The IC argument will pop up and it's true, the functionality of that board could be accomplished in smaller space with IC's but one real limitation on IC's is dynamic range. Even really low noise IC's are still limited in output swing. Going discrete can permit much higher voltage rails and more max out.
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Old 31st March 2013, 05:01 PM   #37615
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Thanks Demian for your input. All I know is, NEVER AGAIN! Any board that I have to troubleshoot in future will be more optimally layed out for symmetry and ease of identification of the individual components.
Don't worry Demian, I won't show the other layers or the bottom of the board, even though it has a bit of surface mount.
Demian has more experience in 'troubleshooting' this board than I do. Trust me, it is a 'headache' not just because of the schematic, but finding the individual parts and measuring voltages, as well as replacing them.
This board has been a hard lesson for me, as I only approximate the specific resistances in a design and once a prototype board is made, I optimize the entire circuit. The difficulty of changing the resistor values in this schematic, as well as the surface mount changes has caused an embarrassingly high amount of trouble.
I guess, in future, I will have to computer SPICE modeling, before making anything. I never had to, before.
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Old 31st March 2013, 11:27 PM   #37616
bcarso is offline bcarso  United States
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Quote:
Originally Posted by 1audio View Post

The IC argument will pop up and it's true, the functionality of that board could be accomplished in smaller space with IC's but one real limitation on IC's is dynamic range. Even really low noise IC's are still limited in output swing. Going discrete can permit much higher voltage rails and more max out.
Indeed. It's almost as if a cottage industry could spring up around discrete circuits for augmenting the output voltage and current swings of ICs, without fatally affecting bandwidth, slew rate, settling time, and so on.

Of course the notion of resorting to such is not a negative commentary on the skills and ingenuity of IC designers. It's just that to date at least there are no compelling applications to provide an adequate market and thus an incentive to develop such. It was interesting to see somewhere in here the query about the evaluation of the AD797 being based on sound quality, as we tend to suppose it was developed for audio, which Scott pointed out was not the case.

The pernicious effects of obsession with power consumption, coupled with the convenience of integrating analog circuitry with lower-and-lower-voltage digital hardware, have also limited our choices.

I do welcome the ubiquity of surface mount as it allows us to do low-volume designs that come near to integrated performance by reducing parasitic inductances etc. And even changing out parts, once one gets the hang of it, is in some ways easier than working with leaded parts and plated-through holes --- at least with 0805 or thereabouts. Much below that gets tough for manual assembly without specialized equipment.
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Old 1st April 2013, 01:02 AM   #37617
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Bcarso, we do it all the time. I have a new power amp here with augmented IC's. I have been augmenting IC's for more than 40 years.
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Old 1st April 2013, 10:28 AM   #37618
marce is offline marce  United Kingdom
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Magnoman, it reminds me of the tape ups I started on, firstly simple single sided boards with black tape, then up to red and blue tape ups (which I presume are similar or the same to triple prints, photographic techniques to drop one colour or another), then after a year slaving at theses and drafting the schematics (A0 plus drawing board), I was allowed on the CAD system (Racal Redacs Redboard, now Cadstar), heaven. I don't miss the old days though, a lot of exciting developments (though in some aspects negative see #37616 above) brought on a lot by the sheer market volume of hand help devices has shrunk devices to often silly levels. I now do boards where 0603 chip components look huge. The reduction in both size and voltages does add its own problems, recently did an ADC with a 1.2V swing!
Quote:
but the "good" parts are unavailable in surface mount if at all.
A problem also for redundancy, for equipment that has to run 15 years or more, trying to get a circuit to work the same today with new parts causes engineers headaches, on the same note, see a lot of older designs coming in to have EMC components added to I/O specially to cables.
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Old 1st April 2013, 01:18 PM   #37619
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Well, layout is NOT my thing. I leave it to others, people who have a proven record. We only miniaturize circuit boards when it is absolutely necessary.
Surface mount has a VERY LIMITED selection, these days, for my circuit designs, at least.
My biggest headache is CASES. It is difficult, if not impossible, to make a case that is attractive (at a world class level), cost effective, and useful as a shield, enclosure, heatsink, and stable platform for switches.
Most of the time, these days, I leave the CASES to others who I consult for. They do a pretty good job at making the tradeoffs, if necessary.
I will stick to fundamental analog design, with or without IC's, leave the board layouts to Carl, and hope to improve my troubleshooting skills, that have declined since I have aged and lost an eye. I sure wish there were some skilled techs or jr engineers who could do the things that I once had to do, when I was younger, and save myself as an overseer of the circuit design, rather than have to do the mechanics of it. I can still read test results easily enough to optimize the circuitry.
Unfortunately, there are many here, especially the vocal ones, who believe that design efforts, like my own, are redundant, and a waste of time. Fortunately, I do hear from others, who think differently, and I still hear differences in IC's, preamps, power amps and EVEN cables (at times), that tell me I am still on the right track. I'll just 'keep on truckin'. '-)
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Old 1st April 2013, 02:06 PM   #37620
rsavas is offline rsavas  Canada
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Default This is what we call a 'crowded' analog board.

Hi Guys,

Quote:
This is what we call a 'crowded' analog board.
Maybe in the days of old, but not by today's standards.
Layout is fun for me, especially if I am not under any schedule pressures.
Layout brings lots of challenges to a designer. It really sucks when you have to do it again, for one reason or another, kinda have to allow for at least two rev's before Mfg Release. I remember back at HP, the average was a between 1-2 pcb rev's, which is darn good. One design that we did had a brain dead ASIC on it, I did 6-8? pcb rev's before MR release, made lots of OTime$ on that project. A mass of FPGA's on it to fix the prob.This was done using Mentor BoardStation.
In this latest design, "Portable Media Player" I have done, as shown, a mixed signal design. Tuner(Si4735), MP3/WMA/AAC memory stick player(BU9458), USB CODEC(PCM2902B), headphone amp(MAX9729), 25W Class "D" amp(TPA3100D2). Amtel ATxmega MCU. This done in ORCAD.
It blows me a way, that I can do the same & a whole lot more in this small form factor than an ole receiver. I look at my old Pioneer SX-950, still selling on eBay for almost the same, I paid for it in 1978 and get a chuckle.Okay this portable ain't a 100W/ch Class "AB" amp, but for the majority of your listening it is fine.
Right now I am listening to Van M, playing the CD in my computer, through the USB to the portable, on to my Dynaudio Gemini's, the sound is great and this all that really matters. I am drawing about 3W idle. Maybe double if I crank it.
I am an advocate of jamming as much functionality into a small package as possible, considering this is a design for my own use.
This is what I call AudioDIY for myself at least, say compared to what I did for a college project 30+ years ago.
Anybody interested in one? Assembled or bare pcb? Just kidding, I know this ain't the commercial section. Actually I need more help with SW than HW, of late.
Rick
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