My_Ref Fremen Edition - Beta build/Fine tuning

[ClaveFremen]

Actually Dario's build thread answers this nicely:
(...)
Didn't see it until now. Duh. Very nice thread Dario!

I'm happy you found it useful

 

[lehmanhill]

Philbrick Op Amp from the 50's

Not too far off topic; its historical. Post a proper picture of it

Sorry it took so long. I was having trouble getting pictures to upload.

 

[No 4]

Thanks for posting. It is amazing how new it looks, other than the design elements you would have never known it was from the fifties. Neat!

 

[marcus1]

Caddocks

I'm ordering my Caddocks from partsconnexion (25% off sale at the moment) but for R104, R204 they don't have MK132 200R but only 220R or 180R.
How critical is the value of this resistor - will either 180R or 200R do?

Thanks

 

[bcmbob]

Today I sent some caddocks all the way to Jordan and it only cost $3.00. Let me know if I can help.

 

[ClaveFremen]

How critical is the value of this resistor - will either 180R or 200R do?

Better 180R

 

[marcus1]

Thanks Bob.
What I do need a hand with is buying C1 & C2 (220uf 50V Elna RJH). The BOM says "Can be ordered from Elfa-Distrelec" but they want 45 Euros for shipping! Did you use these or something else?

Thanks

P.S.
Just read that there was a elna and ero capacitor kit available. Dario: do you have any left?

Today I sent some caddocks all the way to Jordan and it only cost $3.00. Let me know if I can help.

 

[bcmbob]

A possibility - 6PCS ELNA 220uF 50V SILMIC II RFS Silk Hi-Fi Audio CAPS | eBay

 

[atupi]

Or maybe this one: 4x 470uF 63V 105C ELNA RJH series radial capacitors | eBay

 

[ClaveFremen]

Just read that there was a elna and ero capacitor kit available. Dario: do you have any left?

You have a PM

 

[bcmbob]

WARNING - Dario pointed out the caps in post #1488 are not the correct spec. Those are Silmic II and not RJK. Not sure how much difference there is but, be aware they are not what is in the BOM. They are quite usable in those positions, just not the same. I ordered some so I'll try them out and report back.

 

[soongsc]

One thing I can't understand is that why people choose polarized caps for a position that does not have DC offset? We don't to that in speaker XOs, why do we do it here?

 

[bcmbob]

I believe that is one of the topics proposed for experimentation during the RC process. There will probably be several more.

 

[AndrewT]

Soon,
the input DC blocking capacitor and the negative feedback, DC blocking capacitor locations, both have a DC offset. This is usually checked for during design and checked again at assembly time.

Have you never bothered to measure the offset on your polarised capacitors?

 

[soongsc]

Andrew, I think you are referring to something different from what I am talking about.

 

[AndrewT]

polarized caps for a position that does not have DC offset

Which polarised (electrolytic) capacitors are you referring to?
PSU, Decoupling, Coupling, DC blocking?
As far as I can see, all of these locations in the MyRef have a polarisng voltage applied to the capacitor.

 

[soongsc]

DC voltage needs to be such that polarized caps are never reverse polarized in operation. In MyRef, C9 really has no such voltage. Many chip amp applications implement the same way as well. Very curious about the considerations behind this.

 

[AndrewT]

DC voltage needs to be such that polarized caps are never reverse polarized in operation.

that is not a requirement.
Prevention of excessive reverse polarity is a requirement.

As far as I know electrolytics can tolerate 1000mVk to 1500mVpk of reverse polarity without suffering any degradation.

If you apply a 1Vac signal to an electrolytic coupling cap and it has 200mVdc offset then the worst case short term reverse polarity is ~1200mVpk.

But the capacitance of the capacitor does it's best to drag the undriven plate along with the voltage on the driven plate. That 1Vac signal can't actually apply anything like a 1200mVpk reverse polarity between the plates.

 

[soongsc]

So what about asymmetric leakage current?

 

[AndrewT]

Would that appear as different from the AC signal that is coupled across the capacitor?

I don't know because I have never heard of that before.