Sunn Beta Preamp Capacitor orientation

[Guzz]

Hello,

Would it be possible to replace some, or even better, all the 2.2uF film capacitors in this layout with polarized electrolytic caps? Can you guys help me figure out which ones can be replaced and what their orientation should be ?

Thanks !

[GrooveChampion]

I think it would be easier to buy a tantalum capacitor kit.

[rocket88]

definitely would not replace them with electrolytics or tantalum caps. tantalum caps are notoriously a pain in the ass and can explode if they receive the wrong polarity. electrolytics would be a pain in the ass due to size. just grab some 2.2uf multilayer ceramic caps. they're small, non-microphonic, and non-polarized.

[Guzz]

the 2.2uF electrolytics I have are pretty small (they're only 50V). I was hoping to use them because this is a time sensitive issue.

[Guzz]

Is there at least some I can replace ?

[Mulekicker]

Do you have any 1uf film caps? You could parallel em and at least get in the ballpark.

[induction]

Most of them are coupling caps, and this is a dual-rail circuit, which means there will be no DC offset across the coupling caps. That's why those caps are specified as bipolar. The only way to use polar caps would be to modify the circuit to single-rail supply or modify the layout to accept caps in series.

[Guzz]

Are you sure about that ? I'm only  asking because people on the freestompboxes thread about this preamp seem to think polarized capacitors can be used as long as I respect the polarity (anode to +15v and cathode to -15v).

[rocket88]

Looking at the schematic I believe induction is correct. But, just saying you probably could have ordered and received the nonpolatized caps by now.

[induction]

Guzz wrote

people on the freestompboxes thread about this preamp seem to think polarized capacitors can be used as long as I respect the polarity (anode to +15v and cathode to -15v).

There are no nonpolar caps in this schematic that connect between +15V  and -15V.

The advice on FSB was general advice for replacing nonpolar caps. It's mostly accurate, but the part you mentioned requires there to be DC offset scross the cap. In this case, you don't have DC offset, so you can't use this method. Those caps are specified nonpolar for this reason.

[Guzz]

I did, but since I'm planning on building one more of these things, and my usual supplier doesn't carry unpolarized 2.2uF caps, it was still good to know.

Also thanks Induction!

Last question for this layout, do I need the mixer daughterboard If I want to build the dual channel version ? Or can I use footswitches to go a/b/y ? I don't see why not, but I'd rather be sure.

[rocket88]

You can do 2 inputs, 1 for each board, and have an A/B/Y switch pedal to go between the different option. You could also simply add a 3rd input jack that connects to both boards so you have 3 separate inputs, 1 for each option.

[Guzz]

How about using the switching method used below ? The "I/O" jack would be my input, A would go to board #1 instead of a jack, B would go to board #2 instead of a jack, then both board go into the daughter board mixer.

The idea is that I can select either channel with my foot, as well as both at the same time with only one input jack.

Thanks for your time Rocket !

[rocket88]

I wouldn’t do a simple switch. I would use a buffer splitter like the AMZ splitter on the main page.

[Guzz]

Last question about this layout, can a 470uF be used in place of the 680uF ? Thanks.