OPEN SOURCE DIY Mic Project - ORS 87 - Stripped Down u87
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Exactly!
Please put the correspondence scheme of version v1.1 one more time
homero.leal
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I'm thinking about creating two versions, one with multiple options (as V1 and V1.1), and the other one with no open options, even R* won't be there. Makes sense?
I would make GND present all around, up to the edge and as extended as possible inwards, close to the other traces, except for the jFET input area. Thus the PCB would connect its GND to the body with the help of screws.
...more to come
homero.leal
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My attempt to PCB Star Grounding
Not quite sure what the benefit of that might be, with currents well under 10mA involved... But hey, if you prefer to make things more difficult for yourself "just because"...
Yes, but...
You could create even more confusion among beginners.
If you let someone uninitiated make a decision on their own, they will most likely make the worst decision.
Then @Khron has to 'fight' with them, to explain clearly and quickly things learned over the years.
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mrchapp
Active member
Very much this is what I see. I sent a PCB (for BM-800 with these footprints) to JLCPCB and it cost me US$3.50 with shipping included to Mexico, whereas with @homero.leal's shared project on PCBWay it would cost me US$10.11, almost three times as much. Neither option is bad, but JLCPCB is definitely a better option for some.
That's with their $2-first-order promotion, and the cheapest / slowest shipping option, I'm guessing?
mrchapp
Active member
Yes: Their cheapest shipping option (10-12 business days) is US$1.50; next is US$17.80 (3-5, 4-6 business days); and then US$18.60 (4-7 business days).
What's interesting is that it's a "special offer" that just appears there all the time with small boards. This was not my first order, and now that I'm trying to order the same Gerber files it also applies the "special offer". I don't know the dynamics of their offers, but I'll gladly take the discount.
Another thing to add is that this option (US$2.00) is cheaper than buying 5 perf boards from Ali (US$2.13) with similar shipping time frames. Oh, the economics.
On subject, thanks to all who have shared so many insightful comments on their builds. This build has been a fantastic learning experience!
homero.leal
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Ok. What coupling cap (between FET and Transformer) do you think will be the best for beginners?
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Probably a box film cap - lasts virtually forever (electrolytics are so-and-so, and are +/-20% tolerance to begin with; 5% films are the same price as 10% ones).
Later edit: Oh, and you can't install them the wrong way around, either!
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As I said, it also works with the Drain and Source inverted, but not optimally and there are problems with the correct BIAS of the jFETView attachment 131428
Regarding this drawing for almost 20minutes, I've just realized I've had pinned reversed my JFET from the beginning..
I can't believe it !!!
In the upper right corner are the candidates with the best measured esr and loss.
They all sound very good, with extremely
small differences,flavors, probably imperceptible in the mix.
The winner is the one left in the test circuit.
He is a repeat offender.
He won in several tests/circuits.
Doesn't measure the best, but sounds exceptional with all transformers tested (huge or tiny core)
I made numerous comparisons, repeated on different days, having different moods.
Attachments
homero.leal
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What about the big 1uf cylindrical film?Probably a box film cap - lasts virtually forever (electrolytics are so-and-so, and are +/-20% tolerance to begin with; 5% films are the same price as 10% ones).
Later edit: Oh, and you can't install them the wrong way around, either!
homero.leal
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Ok, this will be the one! Thank you very much @micolas!In the upper right corner are the candidates with the best measured esr and loss.
They all sound very good, with extremely
small differences,flavors, probably imperceptible in the mix.
The winner is the one left in the test circuit.
He is a repeat offender.
He won in several tests/circuits.
Doesn't measure the best, but sounds exceptional with all transformers tested (huge or tiny core)
I made numerous comparisons, repeated on different days, having different moods.
So, as a summary:
- Remove HI-Z traces
- Add ground plane connecting to body using the screws
- Remove redundant/multiple options
- Use WIMA MKS-4 1uf cap
. They do make a difference.Ugly coupling pads will remain
If you say so...
Doesn't make the rest of the routing any less chaotic though (and on TWO layers, no less)... 
The yellow cylindrical film capacitor (probably polypropylene) offered the most Hi-Fi sound in the test, a little more 'smile', very clean, but slightly reducing the mids, mid-highs specific to U87.
I would use it in C800, C12.
The electrolytics produced a more nice pronounced saturation, a U87 for Rod Stewart
.The tantalum sounds nice, balanced, but I removed it for personal reasons.
