SOAP MKIII (Simple OpAmp Pre) With onboard PSU

Thanx Kanifee!!:) It looks great.!
Regarding the rectifier, The choice of rectifer dios is your of course, If you want to use fancy nancy superfast diod then why not. :) However, "normal standard" rectifier diods also work ;)

Regarding the BOM. You will al get an "up to date" BOM and i,ll see if i can add partnumber from Farnell or something like that.

Deadhead, You got mail as well.

Thanx,

I,ll order the boards this weekend

/JZ
 
Here's my effort on the SOAP MKIII, based on the files kindly given by Zei. Thanks a lot.... I will test it this weekend, if time permits.

However, I noticed (after construction) that the design does not have a low pass filter at the input, instead it has a high pass filter (formed by C1 and R1, R2 and R3. What would happen if the position of C1 and R1 is reversed (and values adjusted accordingly) so that a low pass filter is formed? Feedback from the original designer and/or Zei will be much appreciated.

I want to use the SOAP as a pre-preamp for my el-cheapo MP3 player (powered by a single AAA battery) as the MP3 player's output is too low to drive a preamp (gain of 3) directly.
 

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Hi

I have just started putting together a Farnell parts order now that I have received the latest BOM spreadsheet.


I have a few questions for the experienced amongst you…


Resistors

I currently have a wide range of 0.25w metal film resistors in my parts bin. Which resistors need to be of a higher wattage and what would you recommend?


Capacitors

C11- C14 = 100uf

Should I use a general purpose cap here or would I benefit from a ‘Low ESR’ cap like the Panasonic FC?
The reason I ask is I have heard OPAMPs can become unstable if the ESR is to low. I assume its best to stick with a rating of between 35/50v in this circuit.

C15 – C18

Can anyone recommend a good quality capacitor that can be sourced from Farnell?


Transformer

What is the recommended voltage secondary value? Is 18v to high before rectification?


Thanks for your help

Richard
 

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Hi Richard :)

I heard the Pin. !:)

For C11- C14 = 100uf - You can use Pana FC.

For C15 - C18. You can get away with Wimas, Or more cool ones like BG, Paper in Oil etc.. I would have started with something cheap :) And then maybe maybe upgrade with fancier stuff.....

35-50V for caps works..

18V transformer is also ok :)

/JZ
 
zei said:
Hi Richard :)

I heard the Pin. !:)

For C11- C14 = 100uf - You can use Pana FC.

For C15 - C18. You can get away with Wimas, Or more cool ones like BG, Paper in Oil etc.. I would have started with something cheap :) And then maybe maybe upgrade with fancier stuff.....

35-50V for caps works..

18V transformer is also ok :)

/JZ

Thanks Zei

What about the resistors and Trim pots? What wattage should I use? What, what, what?