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I slowly get together all the parts I need and I also decided to built my own amplifier.

Since etching my own circuit board seemed like to much of a challenge for me I decided to go with an assembly kit I found at a local electronic dealer for a mono microphone pre amp which offers a 1500 fold amplification.

There are different options on how to assemble the kit depending on whether it is used with a dynamic or a  capacitor microphone. From what I understand, the way a piezo element works resembles more the way a capacitor microphone works and so I'm going to solder the kit accordingly.

What do you guys think?

 

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4 hours ago, Eland said:

I slowly get together all the parts I need and I also decided to built my own amplifier.

Since etching my own circuit board seemed like to much of a challenge for me I decided to go with an assembly kit I found at a local electronic dealer for a mono microphone pre amp which offers a 1500 fold amplification.

There are different options on how to assemble the kit depending on whether it is used with a dynamic or a  capacitor microphone. From what I understand, the way a piezo element works resembles more the way a capacitor microphone works and so I'm going to solder the kit accordingly.

What do you guys think?

 

I'm not sure, you will have to test it and let us know how it turns out :lol:
Is it easy to disassemble the kit if you want to try soldering it the other way?

I'm currently waiting for some parts for a different type of pre-amp that I ordered from China, but it is taking abnormally long to arrive...maybe the package got lost.

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5 hours ago, Eland said:

From what I understand, the way a piezo element works resembles more the way a capacitor microphone works and so I'm going to solder the kit accordingly.

It would be nice if you had a schematic diagram? The capacitive microphone requires a biased voltage. The piezo microphone and dynamic microphone do not.

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13 hours ago, JohnR725 said:

It would be nice if you had a schematic diagram? The capacitive microphone requires a biased voltage. The piezo microphone and dynamic microphone do not.

Here is the link to the operations manual as a pdf. It's only available in German but it contains all schematics.

It says that if you use a capacitive microphone you need to solder resistor R6 onto the circuit board an the electrolytic capacitor C1 needs to be in reverse voltage direction.

I also studied the manual in the meantime. To that specific issue it says that you need to make that modification if you want to use a microphone without separate power supply like e.g. a capacitor microphone.

 

14 hours ago, 24h said:

I'm currently waiting for some parts for a different type of pre-amp that I ordered from China, but it is taking abnormally long to arrive...maybe the package got lost.

What kind of pre amp did you order.

Since I only soldered together some audio cables and have absolutely no clue at all about the principles of electrical engineering it is very likely the I will need one of them as well :lol:. Really hope your package didn't get lost though!

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2 hours ago, JohnR725 said:

So as you discovered R6 is not needed for a piezo pickup.

wait, i personally came to a different conclusion. My train of thought was  that i would need R6 and C1 reverse since the piezo like a capacitor microphone does not have a separate power source an therefore I would need to pick up the power from the amp.

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58 minutes ago, Eland said:

wait, i personally came to a different conclusion. My train of thought was  that i would need R6 and C1 reverse since the piezo like a capacitor microphone does not have a separate power source an therefore I would need to pick up the power from the amp.

Unlike a capacitor microphone, a piezo doesn't need a power source. And a dynamic microphone is a power source.

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On 10/29/2018 at 1:35 AM, Eland said:

Here is the link to the operations manual as a pdf. It's only available in German but it contains all schematics.

It says that if you use a capacitive microphone you need to solder resistor R6 onto the circuit board an the electrolytic capacitor C1 needs to be in reverse voltage direction.

I also studied the manual in the meantime. To that specific issue it says that you need to make that modification if you want to use a microphone without separate power supply like e.g. a capacitor microphone.

 

What kind of pre amp did you order.

Since I only soldered together some audio cables and have absolutely no clue at all about the principles of electrical engineering it is very likely the I will need one of them as well :lol:. Really hope your package didn't get lost though!

This circuit option seems very efficient. Especially that the voltage can be from 3 volts to 25 volts.

Mono Preamp.pdf

 

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6 hours ago, guidovelasquez said:

This circuit option seems very efficient. Especially that the voltage can be from 3 volts to 25 volts.

Mono Preamp.pdf

 

The gain of that circuit is only about 100 (40dB), which probably won't be adequate, and despite what the manual says, it won't run off of 3V. At 3V, the input signal is biased at 1.5V, which is of course only 1.5V below the chip's supply voltage, a point above which it will not operate. Put another way, there is zero headroom if operated at 3V. The only thing it will amplify without severe distortion is total silence.

Edited by svorkoetter

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6 hours ago, svorkoetter said:

The gain of that circuit is only about 100 (40dB), which probably won't be adequate, and despite what the manual says, it won't run off of 3V. At 3V, the input signal is biased at 1.5V, which is of course only 1.5V below the chip's supply voltage, a point above which it will not operate. Put another way, there is zero headroom if operated at 3V. The only thing it will amplify without severe distortion is total silence.

Thanks for the clarification. The circuit has not physically tested it. And I had the suspicion that it did not work on the edge of 3 volts. But the explanation is appreciated. I only have one question left and I appreciate the help: would it work with 5 volts from a USB port?

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Guido,

beware, the input resistance of that circuit (1 k) is too low for a piezo disc!

With a bit electronic knowledge much can be adapted at this standard design. E.g. plug in a more modern OP replacing that grandfather of IC and it will work at 2V and lower.

Frank

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Thanks for the suggestions Frank. Our limitations in the electronics benefit from your experience and knowledge. On a more modern IC, I have tried to find one that can work a low voltage and that does not require a "symmetrical" source of tension that complicated.

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So far, the kit that Eland posted seems to be a good option for someone who doesn't want to start from scratch. I will pick one up when I'm in Germany later this month, and give it a try. The thing I like about it is that it doesn't use a proprietary part. The LF351 is generic, has multiple sources, and has been around for a long time. I just haven't had any experience with it before now.

Edited by svorkoetter

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Dear Sirs. I share with you a record recording of a Omega Lemania Caliber 9160A. 18000 bph stopwatch. According to my records it presents approximately 4.8 seconds of advance. The beat error is approx 0.2ms and the amplitude is 270 degrees or so. The elevation angle is adjusted by 41 degrees. I share it because someone can be useful. I also want to inform you that to pick it up I am using a caiman clamp to which I soldered a 27mm piezo electric disk with a modified PYLE PP444 preamplifier. In addition to improve the sound and filter unwanted noise I am using the applications for windows: PEACE + APO EQ I also leave a screenshot of the configuration. There are 30 seconds of recording that can be played as a loop.

https://mega.nz/#!HaQFTSxA!FATJQ6XI8FYjQBBGqtPjvdVj1i6bZp7RwI5uBgaL7ng

1844812179_MiEQ.thumb.JPG.23c32dc775d1f07b6dbb78c0831dacd4.JPG

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Hi, Frank. Thanks for the data you share. I wish to clarify that I made a mistake in indicating the breadth in my publication.

He had indicated an amplitude of 270 degrees. But it is not correct. What you publish is correct. Approximately 235 degrees. Excellent application It strikes me that in addition to indicating the value of beat error in milliseconds, the program also indicates it in degrees. According to my assessment that is very useful, because to correct it, it is necessary to pre-visualize approximately how much the collet must be turned on the balance wheel staff or how much movable stud must be moved. 

Thank you

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Hi,

in my workshop I service mainly vintage chronographs. To adjust the beat error, I always have to rotate the collet. To see the pallet position and in which direction to rotate,  I use to let down the mainspring, look, wind again.
This means, after every check there is a different state of winding and amplitude.
Beat error will show different [ms] values for the same error angle then, but beat error [deg] always shows the same value for the same error. That is why I like [deg] display for the beat error.

Frank

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Thanks for your comments and experience Frank. I also work with watches that it is necessary to move the collet. It is a very precise adjustment. And sometimes tedious because the adjustment can easily be exceeded or not knowing in which direction it should be done.

Guido

 

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I wanted to post a quick update on my timegrapher. All together I encountered a lot more difficulties then i thought. I screwed up the amplifier assembly kit  by using blunt wire cutter and thereby accidentally ripping the conducting layer of the board as i tried to clip the wire of a resistance.

I also have the hardest time soldering the brass pin onto the piezo element. I broke several piezos by applying to much heat an bringing the ceramic layer to crack .

I'll visit a good friend of mine in January who is a electrical engineer and we'll try to get it done together (using his professional equipment).

Until then I wanted to ask @24h if you have any special techniques u used to establish the connection between the pin and the piezo and also if you could elaborate why you used a rubber casting around the pin. I thought it might rather weaken the vibrations and therefore the signal.

at least I am making a little progress with my timegrapher stand. Here is a picture of my first built (which is not functional because there is no piezo on the end of the pin):

20181116-191338.jpg

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