SOAP MKIII (Simple OpAmp Pre) With onboard PSU

[Puffin]

Zei. When it was in my main system, it had developed a worrying fizzing/buzzing noise. It was switched on when it blew the speaker.

You suggest I wire the pot in this way :-

Signal In direct to Pot.

Signal Out to SOAP IN

SOAP Out to Phono Outs

?

 

[zei]

Yes

Input> Pot>preamp>output>>

/JZ

 

[zei]

Oh. i noticed you opened another thread.
The cap on the output is a DC blocking cap. It is there to prevent any dc gettting to the power amp.

In your tests, did you try your power amp without the preamp?
Just so we can rule out that it is the power amp that is making trouble.



/JZ

 

[Puffin]

Zei. Thanks for all your replies. It is definitely not the power amp.

I will wire the SOAP as in your last post and see if this works.

 

[zei]

Ok great.

Also please reheat all solderjoints to make shure that they are ok.

/JZ

 

[Puffin]

I checked the board all over. I have added more solder to the pads at C15 - C18. I am not sure that it matters which of the 3 holes you use. However having done that and re-installed it, it all seems to be working as it should.

Incidentally should you be able to test continuity for a polarised cap (i.e between + and -) (no current flowing through cap)

 

[AndrewT]

it should read open circuit.
But it takes a while to charge up from the voltage source inside the meter. What you see is a rising resistance until the meter goes off scale as the charging current drops.

 

[wasky]

I'm interested to build this simple Pre whit OPamp mr Zei but, the link in the first post are broken or the forum bildarkiv is down now ?

if possible you can re- link the .pdf

10x

my compliment for your PCB


Roberto

 

[zei]

Sry about the dead links.

I have no place to put the files bu i could mail you?

/JZ

 

[gabanyayaya]

Hey, Get back in touch anytime, cant remember what you did with the speaker, I might fair better if I work out your real name (email) how did you get on?

Hey Mr. Blair. Remember me. I was the one in asking about Mission speaker modification based on you mod with your 753. We meet at http://forum.lowyat.net/Audiophiles

I can confirm, the calculator works for the 337, and also the negative varients as well.

Sorry to hear your preamps puzzling you puffin.

Oh and thanks for the shameless plug trip!

So it's conform that the calculator works positively for both LM337 & LM317....

What's the shameless plug trip

 

[gabanyayaya]

zei,

Is it safe to use a 1000uF 35V on the power supply section (C7 & C8)? Have these as spares from previous projects....

 

[AndrewT]

what is the worst case (high) voltage that can appear across these caps from your transformer?

 

[zei]

gabanyayaya:
With you transformer that should be fine.

The answer to AndrewT,s question is also you answer


/JZ

 

[wasky]

Sry about the dead links.

I have no place to put the files bu i could mail you?

/JZ

thank for email mr Zei you're very kind

you can send me zip at this address

roberto.vagli at gmail dot com



and 10X



Roberto

 

[wasky]

u email arrived


thanks Zei i've appreciated


Roberto

 

[gabanyayaya]

what is the worst case (high) voltage that can appear across these caps from your transformer?

explosion...!!!! I have a an allergy to high voltage curent...

gabanyayaya:
With you transformer that should be fine.

The answer to AndrewT,s question is also you answer


/JZ

Thank you zei...


Hmmm...any simple tweak can can be done to the SOAP???

 

[zei]

Using a different OpAmp would for shure alter the "sound".
If it is to the better however is another story You could always ask Tripmaster what he thinks about it.

Changing the output caps to another type/brand might also give another voicing....

Some swears by using expensive fancy pancy resistors....



Try and report back your impressions


Puffin: How are things working for you?


/JZ

 

[Puffin]

Zei. Great thanks. I did post a bit earlier on to say that I had corrected any problem I had. It seemed that soldering the whole of the pads at C15 - C18 cured the problem. It shouldn't matter which hole the caps are soldered to, but as I say I am now getting no bad noises or DC.

 

[zei]

Great news puffin

No, it should not matter what holes you used for the caps.
Might just have been a bad solderjoint.

Good that it works

/JZ

 

[mikesnowdon]

Anyone got a spare board on know if any are available to buy?