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  • 2 weeks later...

 Fair play Stefan, I think you will find my mistakes a bit more amusing and basic, for instance have you heard the one about the guy who put the heat shrink tubing on shrunk it to perfection and then peering throught the plastic noticed that there was no amp chip in the DIL socket - Doh

 

Cheers,

 

Vic

@Vic - I finally got round to building the amp and guess what, managed to do the exact same thing...... plugged it in, powered it up, could hear only a very faint ticking through the headphones. Flicked the switch a couple of times which made no difference........ and the spotted the chip on the bench!!!  Fortunately I hadn't heat shrunk the board yet so it was easily corrected :-) I'm now just waiting for the arrival of an aluminium enclosure to complete the build.

 

@Svorkoetter - I have been testing your amp with a Japanese program called Biburo. The signal quality is excellent but I'm having problems with Biburo. The values I'm getting are way off (I also have a Timegrapher which I'm comparing with) with Biburo reporting amplitude of 100 deg against 270 deg on the Timergrapher, and a rate of -240s/d against -2s/d. I think that there must be some kind of calibration issue with Biburo.

Does your software require any calibration before it can be used or is it set to go straight out of the box?

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Marc, there are two aspects to calibrating any timing machine software.

 

One is setting the thresholds for tick detection correctly, which my software does automatically, although there is the option to adjust it manually when the software occasionally gets it wrong.

 

The other is correction for error in the sound card's sampling rate. A sound card is supposed to sample at 44,100kHz per second (most have other rates too, but that's the highest rate that's guaranteed to be there, and is what my software uses). However, the actual sample rate can easily be off by +/- a few Hz. Every Hz error represents about 2s/d reported error in the rate of the watch.

 

Rather than repeat all the details here, here's a link to the section of the manual describing what's involved in this process my software: Calibrating Your Sound Card Clock.

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Hi Stefan,

 

thanks for the response re: calibration. I like flexibility of the approach you have adopted whereby pretty much anything can be used as a calibration reference so long as you know its rate. As I don't have access to a signal generator or HAQ watch the option to use an ordinary quartz whose rate I can measure against a radio controlled clock over a suitably long timebase (at constant temp) makes this very easy.

I had a brief look the rest of the Manual and have to say that I am impressed with the feature set.

 

The Biburo software does look as though it has some user calibration function in it but it's not at all clear how you go about using it.

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  • 4 weeks later...

Just a quick update, since I haven't posted in a while.

 

All the parts have come in for the new amplifier design, and I hope to put a few of them together in the next few weeks for testing. I've determined that I made a few design mistakes in the original which allows a lot of mains hum to get in, but I was lucky in my house that it wasn't an issue. But everyone who has built one, and a watchmaker that I sent mine to, has had problems, hence the need for a redesign. Another flaw with the original design is a high level of noise injected by the high-valued resistors. The new design uses more amplification stages with lower amplification per stage.

 

Anyway, that's all for now. I'll post an update once the new amplifiers have been tested.

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  • 2 weeks later...

Last night, I drilled two circuit boards for the new preamps, and tonight, I marked them for etching. I did the one on the left first, and then made some small improvements to the layout (all horizontal and vertical lines) and did the one on the right. I hope to etch them on the weekend, and get the preamps done early next week (I'm making two initially).

 

post-140-0-69913500-1418954408_thumb.jpg

 

For those interested, here's an overview of the process I use to make circuit boards: http://www.stefanv.com/electronics/etching.htm

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Hi Watch enthusiast.  I just thought that you may be interested in a company that I use for PCB's  Here is the link:

 

http://www.expresspcb.com/ExpressPCBHtm/Specs.htm

 

From your photo, you probably could have used their "miniboard" service.  If you make the boards 2.5" X 3.8" the cost for 3, 2-layer boards is $51 including solder mask and silkscreen.  The big advantage for your project (I think) is that for $98 you could get 3 four layer boards.  You may not need the other 2 layers because the circuit is not that complicated, but the extra ground and +5 planes may help with noise rejection.  You possibly could get 2 of you circuits on each board if you don't mind cutting them in half, because typical trace width is .010" (can't cut 4-layer boards, only 2-layer)

 

Their PCB design software is really nice and has NEVER given me even one problem in the last 4 years.  The only downside is that if you go into high production with another PCB company, you have to pay $75 for the Gerber files.

 

John

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  • 1 month later...

I've been busy with a new geothermal heating system that we had installed over the holidays (we like to say that we now heat with dirt), but finally got around to finishing the prototypes of the new preamp design:

 

post-140-0-84700800-1422155405_thumb.jpg

 

The preamp is now fully enclosed in aluminum.

 

post-140-0-98690700-1422155447_thumb.jpg

 

For me, performance of the new preamp isn't that much better than the old one, but I'm hoping it will work out better in electrically noisy environments.

 

I've also done some tweaking on the software, and am implementing the free vs. pro mode. As part of this, the program now has a so-called splash screen. Here's the artwork I came up with:

 

post-140-0-11291800-1422155586_thumb.png

 

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Hello Stefan,

 

Been a tad busy of late but its good to get a chance of seeing how far you have come.  I found out a long time ago that there is always room for improvement in most things and you seem to have really taken that principle to heart.  The new design seems less cramped but still quite compact.  I enjoyed building the first amp which as the sound bite I posted shows, seems to work ok but you are right about the interference it took some playing round to get it right.  Logo looks good to me.

All the best,

 

Vic

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  • 4 weeks later...

So the indicated amplitude in the software didn't quite match what you saw on your timegrapher?

What about the other parameter like rate and beat error?

 

I think clockboy is referring to Graham Baxter's timing software rather than the one created by "svorkoetter" in this thread - Graham's software does not require a circuit as he provides the ability to use any converted timing machine microphone, the one I have is a converted Greiner microphone and it works brilliantly.

 

The timegrapher I have does not allow for adjustment of the lift angle and this will affect the amplitude reading with some watches. I believe other Timegraphers do have this ability so...

 

As for your circuit board enquiry, I am sure svorkoetter will have more to say shortly.

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My timegrapher allows for lift angle adjustment and as Mark says it gives a more accurate amplitude reading.

Probably very useful for the dynamic poising.

 

Indeed, with dynamic poising it is recommended to wind the watch only until the amp is between 150º and 180º

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Hi there. Would you be willing to share the latest design for the preamp? I'm thinking of building one and giving it a whirl.

 

Sure. First the schematic:

 

post-140-0-62257500-1424197452_thumb.png

 

There is only a single chip, a TL074 quad op-amp. R7 is a trimpot, since you really should only need to set it once, but you can use a panel-mounted pot if you want. Just be sure to use shielded cable from the board to the panel.

 

The main differences between this circuit and my previous one are that this one uses a stabilized and filtered virtual ground in an effort at further hum rejection, and it uses three stages of amplification instead of two. There's also more high-pass filtering, but at a lower cut-off, so hum rejection from that should be about the same, while allowing more low-end sound from the watch through.

 

Here's the circuit board component layout, as viewed from the component side:

 

post-140-0-61927600-1424197477_thumb.png

 

And circuit board artwork, as viewed from the copper side:

 

post-140-0-20276500-1424197552_thumb.png

 

Note that I have built two of these. C1 was originally omitted, so it won't appear in the photos I posted earlier, so technically I have not built this latest version which adds C1 to the board layout, but I did retrofit C1 onto the existing boards.

 

EDIT: The locations for C2, C4, and C6 have three holes each, to allow use of capacitors with either 0.1" or 0.2" lead spacing. If using the former, be sure to use the correct pair of holes.

Edited by svorkoetter
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Graham's software does not require a circuit as he provides the ability to use any converted timing machine microphone.

 

Depending on the characteristics of the microphone, it probably does require a circuit, but that's part of what he adds during the conversion process.

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Thank you for the schematics/board print/component values... all the info served under our noses - electronics for dummies (still too hard for some of us).

 

Just to be sure, is it a +/-18V (like in TL0074 specs)? Meaning 4x9V batteries?

 

Thank you,

Bogdan

 

p.s. I built the first "model", with the help of a friend, and it works just fine when I listen to it using some headphones. When I input the signal into PC or laptop, the entire hell breaks loose - although I put a 10K variable resistor at the output, like you put at the second model) and the noise is also too high. The microphone is also listening to the laptop, desktop... things I say...

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+/-18V is the maximum that the chip can work with, but you don't need to go that high. The minimum is +/-3.5V, which is a 7V range (and thus a single 9V battery is sufficient).

 

Note that ligangyi is not proposing to simply increase the voltage, but to remove the virtual ground part of the circuit, and use a dual polarity power supply (i.e. two 9V batteries).

 

Regarding the noise, I'm not sure what's going on. A watchmaker in the UK who I've sent one of each of my amplifier models to is having the same problems. It seems like some PCs (and especially laptops) inject noise into the amplifier, which then gets amplified and sent back to the PC. Other PCs (like all of the desktop ones I've tried) work fine. With many (but not all) laptops, the problem goes away if you run the laptop on batteries instead of the AC adaptor.

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