Piezo Disc Preamp

[mjf]

hello.
100nf (or 47nf,68nf.........) x - rated caps across the primary are a standard. i often use these rifa caps,they are good.
can not find pmr 209 with a quick view.........
greetings.............

[teleman]

Thank you again mjf!I have now included you in my prayers.he...he..(you don't know, how much I appreciate this)

I am able to get both these types easily from a company called https://www.elfa.se They have many branches around europe. A bit pricy though!

With regard to PMR 209, it is an anti surge cap, & reading from the data sheet it has a very low resistor in series with it. I assume it is therefore an X type cap? (Pl.let me know if you need the data...can mail it to you)

So, does it matter which way I connect these?
Supply +/- C, + R to ground or the other way around? I hope I got the question right.!

Thanks again.

[mjf]

hello.
now i have found the rifa 209 cap.these are the r-c units against arcing and sparking, for contact protection (should increase the life of contacts),e.g. relays,thyristors and the contacts of your on-off switch of your power supply.usually this unit (a res in series with a x - cap) is connected to the contacts of the switch (but sometimes they are connected to the load...........depends on the application).
i think it does not matter in which way you connect them to the rails or contacts..........it is a simple r-c network.
can not tell much,because i do not use them.............
thank you for the email.............would you like to show a foto here?
greetings..........

[mjf]

here is an example

[teleman]

Hi mjf,
Thanks for the diagram,It makes things clearer to me now.

We have 220v ac ie;110v ac on both lines here (star config?) + earth.
hence don't have a neutral line at all.

So can I use PMR209 across these live lines across the primary side of the trafo do you think? I need to use something as a mains suppressor. A thyristor perhaps?

I suppose ESR caps for the 1000uF's won't do any harm either?

PME271 is ok in the secondary side.

Ok...here's the 9 month old baby under wraps with strict orders from the Dr. Due to arrive any time soon.....but can be a bit of a "crybaby" sometimes.so been making a nice little "Cot"...i mean a metal case at the moment.

Sorry,won't allow anything larger than this file format!!

[mjf]

hello.
sorry i am no "mains expert"................norway power plants???
please do not connect the x-rated suppressor caps from mains to earth (the value is to big and you need y-rated caps -with only a few nf,e.g. 1nf ......4,7nf).
mostly i use pme caps connected to the primary mains.
yes,the 1000uf elcos should be low esr types like panasonic fc or so for better performance............
greetings..................

[teleman]

Hi mjf,
I've now decided to use this circuit (please see attachment) instead of the earlier one shown.I've also started a new thread "Small Power Regulated Power Supply" under "Power supply" as to not to deviate too much from my original posting on PIEZO DISC PREAMP"

So looking forward to your continued help & advice in the new post.

[mjf]

hello.
if you want to use a 2x12volt transformer you can reduce the output voltage of the regulators a little bit (to 13v or 12v or so),because the standard opamps work at lower supply voltages without problems .
and you can substitute the adjust res by a trim pot(e.g. 1k) and a res(500 ohm or so) in series.
if you use a bridge rectifier in place of the four diodes the number of parts will be reduced and it is easier to build.......
greetings...........

[teleman]

Yes,good thinking! why didn't i think of this before?

As I've mentioned earlier, am actually running all my circuits on 2x 9v Lithium battaries at present. Although they work quite well, i just wanted to see how much (more) headroom/dynamic range I can get by using a dual 15v supply & see if there would be any vast improvement in noise levels as well.

So I will first measure how much the the caps are outputting & then can adjust the regulaters accordingly as you've suggested.

[mjf]

[QUOTE][i]Originally posted by teleman
So I will first measure how much the the caps are outputting & then can adjust the regulaters accordingly as you've suggested.

heatsinks...............have a look at the temperature of the regulators.
perhaps you will test it with different loads (resistors).......the standard opamps need only a few ma.
greeting.................