# Promethium 1u5 Electrolytic Cap swap question



## Danbieranowski (Feb 3, 2021)

Hey all,

Quick question for the team here. The Promethium calls for a 1u5 electrolytic in C16, but I can't seem to get ahold of one of these through Tayda, and I don't want to make an order elsewhere for a single silly cap. Is this value necessary here? Could I maybe accomplish this by pairing a 1uf electrolytic with a 470n film (like you can combine resistors in series to reach a specific total)?

It looks like it's part of the Low knob circuit, so could I just use a 1uf which I'm assuming would allow more low end through and the Low knob could just roll that off to taste?

Any assistance would be appreciated as always!


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## Nostradoomus (Feb 3, 2021)

The 1.5uf is definitely necessary for it to sound like a proper HM2. With the 1.5uf cap the low Q is at about 86hz, with 1uf it bumps it up to around 106hz. Doesn’t sound like much but that 86hz just rustles ya right in the jimmies. Use piggybacked caps to make it up, I’ve done it before haha.


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## Danbieranowski (Feb 3, 2021)

Nostradoomus said:


> The 1.5uf is definitely necessary for it to sound like a proper HM2. With the 1.5uf cap the low Q is at about 86hz, with 1uf it bumps it up to around 106hz. Doesn’t sound like much but that 86hz just rustles ya right in the jimmies. Use piggybacked caps to make it up, I’ve done it before haha.


If I were using "piggybacked" caps, would I just do them in series like resistors? For example, 1uf electrolytic has the positive leg in the positive pad of C16 on the PCB. The negative leg is soldered to one of the legs of a 470n film cap. The other leg of the 470n film cap is soldered into the negative pad of C16 on the PCB? Or is there some other magic that must be done?


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## Robert (Feb 3, 2021)

You'd need to install them in parallel.

(eg: positive of 1uF and positive of 470nF into the positive pad,   negative of 1uF and negative of 470nF into the negative pad)

It might be easier if you use 1uF and 470nF MLCC (0.47uF), that's what I've used in the past.


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## Danbieranowski (Feb 3, 2021)

Robert said:


> You'd need to install them in parallel.
> 
> (eg: positive of 1uF and positive of 470nF into the positive pad,   negative of 1uF and negative of 470nF into the negative pad)
> 
> It might be easier if you use 1uF and 470nF MLCC (0.47uF), that's what I've used in the past.


I'll check that out for sure. Since my MLCC and film box caps are non-polarized, it wouldn't matter which leg I use where correct?


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## Betty Wont (Feb 3, 2021)

I prefer a tantalum there and I've found it much easier to source in that value for this purpose. I agree that is a critical value for the HM-2.


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## manfesto (Feb 4, 2021)

I’ve used paralleled box caps for this, but it’s big and ugly. But if it’s what you have on hand, it’ll work!

Like @Torgoslayer I also found sourcing tantalum easier for that value:









						16pcs Roederstein Tantalum Radial Capacitor 1.5uF 35v    | eBay
					

Find many great new & used options and get the best deals for 16pcs Roederstein Tantalum Radial Capacitor 1.5uF 35v   at the best online prices at eBay! Free shipping for many products!



					www.ebay.com


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## manfesto (Feb 4, 2021)

Oh, Smallbear has 1.5uF box caps!









						Topmay TMCF07 5mm Box, .68 μF - 1.5 μF
					

Small Bear Electronics DIY Parts




					smallbear-electronics.mybigcommerce.com


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## twebb6778 (Feb 4, 2021)

Here in Australia 1.5uF electrolytic caps are available at an electronics chain called Jaycar. I made sure to stock up while they still have them!


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## Robert (Feb 4, 2021)

Danbieranowski said:


> I'll check that out for sure. Since my MLCC and film box caps are non-polarized, it wouldn't matter which leg I use where correct?



Correct.  I just used positive/negative for reference.


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## Danbieranowski (Feb 4, 2021)

Thank you everyone! You’re all fantastic.


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## Danbieranowski (Feb 4, 2021)

One other confirmation: I have 1u MLCCs. I could use one of these in place of the polar 1u electrolytic as well to save space correct? So parallel 1u MLCC + film box 470n would be relatively small and get me close to my 1.5u value.


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## Nostradoomus (Feb 4, 2021)

Yup, go for it.


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## Danbieranowski (Feb 4, 2021)

Thanks everyone for your help. Trying to combine this with the Buff N Blend so we’ll see if it works and how it all shakes out. Hopefully there’s no serious phase issues introduced and it works! Will post a build report at the end.


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## fig (Feb 4, 2021)

Danbieranowski said:


> Hey all,
> 
> Quick question for the team here. The Promethium calls for a 1u5 electrolytic in C16, but I can't seem to get ahold of one of these through Tayda, and I don't want to make an order elsewhere for a single silly cap.


That's coincidental. I have some in my cart at Mouser for a tremolo experiment. Just waiting to build the order to offset shipping. 

JIC, here's a link;
https://www.mouser.com/ProductDetail/505-MKS2C041501H00KO/

Look forward to the build report!


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## twebb6778 (Feb 4, 2021)

Another sneaky trick you can do is to solder 1uF cap as normal and clip the leads. Then on the other side of the board, solder your 470n to the leads you just clipped.

Ba da bing ba da boom - the extra parallel cap is totally hidden.

Also, if you're looking for an easy switchable phase inverter, this has worked really well for me: http://guitar-fx-layouts.42897.x6.nabble.com/file/n24347/Phase.png


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## Danbieranowski (Feb 6, 2021)

twebb6778 said:


> Another sneaky trick you can do is to solder 1uF cap as normal and clip the leads. Then on the other side of the board, solder your 470n to the leads you just clipped.
> 
> Ba da bing ba da boom - the extra parallel cap is totally hidden.
> 
> Also, if you're looking for an easy switchable phase inverter, this has worked really well for me: http://guitar-fx-layouts.42897.x6.nabble.com/file/n24347/Phase.png


I actually didn’t run into a phase issue as the blend works well. What I DID run into is if I dime the high knob I get some oscillation/squealing. It’s only in the last like 5% of the knob too. Total bummer. I think it’s related to wiring being too close but I haven’t sorted out a fix.


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## giovanni (Jan 29, 2022)

I am also struggling to find the 1u5 cap for the Powder Blue (which actually calls for one electrolytic and one MLCC), are the values there just as critical?


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## Robert (Jan 29, 2022)

Those should both be MLCC,  I've corrected the text.

I used a 1uF and 0.47uF in parallel for the prototype.


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## giovanni (Jan 29, 2022)

Alright thank you!

Edit: actually those seem like very high values for ceramic? Can I use box film or metal film?


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## Robert (Jan 29, 2022)

You certainly could, that's just not what was in the original.   Film is going to be pretty large in those values.

These are what I used:








						1uF 50V Multilayer Monolithic Ceramic Capacitor
					

Tayda Electronics - Get It Fast - Same Day Shipping




					www.taydaelectronics.com
				











						0.47uF 50V Multilayer Monolithic Ceramic Capacitor
					

AEC - Get It Fast - Same Day Shipping




					www.taydaelectronics.com


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## fig (Jan 29, 2022)

tantalum


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