tantalum capacitors in Tubescreamer

[tauscj55]

I am currently working on a tubescreamer clone project from the generalguitargadgets.com website.  I have a question about the tantalum caps... They are polarized but the parts lay out doesn't specify which way to orient the cap in the board:  Could anyone please help me as to which way the positive/negative of these capacitors go?  I was going to use film capactitors instead, which I did... sort of.. I put in .022µF caps instead of .22µF caps.  So, I am thinking about just using the tantalum caps I originally purchased for this project instead, but I am wondering which way to put the leads in.  By the way, what would the wrong caps in this circuit do?

Thanks

Josh

[hawkeye2u]

Hi Mate!
U can NOT subst a 0.022 cap instead of a 0.22 tantalum (I DONT like Tant, but app in dist boxes they are OK) Subst a 0.22 with a 0.022 will have VAST frequency differences, its 10 to 1 ratio !!
U can however replace the 0.22 Tant with a 0.22 Electrolytic ( then again, I've been told that the Tant are fine in dist boxes)
To polarise it-- look at the circuit- is one end conn to ground or earth?
If so thats where the neg on the cap goes!
If its in series with another amp, have a close look at the circuit, my guess is that it doesnt matter as these circuits seemes to be biased at 4.5v at the inputs and the output will bias at the same voltage
By looking at a scem I've got U are looking at the capacitor JUST after the first OP amp??? output to a 1k series resistor, cap to ground?
If so the pos has to be to the 1k resistor- neg to ground
Good luck

[tauscj55]

I think I understand you correctly... I am looking at this parts layout: http://www.generalguitargadgets.com/v2/diagrams/ts_lo_808.gif

The caps in question at C5 and C9.  I am new to all this electronic stuff (the only things I can say I really know is Ohm's law and how resistors and capacitors work in both series and parallel ) so I am not quite sure how a schematic gets convertered into the parts lay out but I do know what the ground symbol is.  So would the + lead for C5 be the one closest to the op amp and, for C9, would the negative lead be the one going to the 220ohm resistor in series with it?

Thanks again

Josh

[Steve C]

So would the + lead for C5 be the one closest to the op amp for C9, would the negative lead be the one going to the 220ohm resistor in series with it?

Thanks again

Josh

Yes to both.

[Mark Hammer]

Look at any power supply schematic, and you will see a large value capacitor between the hot lead and ground.  Itr is there to *filter* the ripple from the AC supply.  In effect, it is a "treble cut" filter, except that "treble" in this instance is anything above 15hz or so.

In the same way, the tantalum caps in the TS are there to provide filtering of the signal.  The "-" side therefore goes to ground, excatly the way it would in a power supply.

BTW, I doubt there is anything necessary about use of tantalum caps.  These were often used in pedals of that era because they were small in size for the capacitance values, and could be easily bent over to facilitate a lowprofile parts side to the board.  If you aren't planning on aiming for a perfect fit inside some just-enough-room chassis, feel free to use other cap types.  I can assure you that the individual tolerance-related variation in all the other components in the circuit will have enough impact to obscure whatever it is that the tantalum "does".