[slowpogo]

Interesting, amb, thanks. I realize this is just showing my ignorance, but I can't fathom how a geometrical value like pi factors into electrical equations...fascinating.

I may try those MKP 1837 caps that people seem to really like, as bypass to my Black Gate NX's. The largest capacitance that would fit is only 0.022uf. Is that too small to have sufficient effect against the 47uf Black Gates?

 

[JamesL]

Quote:

Originally Posted by amb /img/forum/go_quote.gif You can do the math yourself. The corner frequency is:

hmm.. I've been wondering.

If the amplifier has a input capacitor, would that act as a second capacitor in series with the first, or does r9/r16 (y2 schematic) change the behavior?

 

[K3cT]

Quote:

Originally Posted by amb /img/forum/go_quote.gif You can do the math yourself. The corner frequency is: fc = 1 / (2 * pi * R * C) where, R = the load impedance in ohms C = The coupling capacitance in Farads (you need to apply 10^-6 for uF) pi = 3.1416 I would like fc < 10Hz, maybe 5Hz if feasible. For example, if you are planning to drive a 10K ohm load (i.e., the input of Mini³ amp), and you use a 1uF MKS cap only, plugging the numbers into the formula gets you fc = ~16Hz. I would be happier with a 2.2uF or 3.3uF instead which will drop fc down to ~7Hz or ~5Hz, respectively. On the other hand, if you plan to drive 32 ohm headphones directly out of the DAC, you'll need hundreds of uF to attain the goal. 470uF will get you fc = ~11Hz.

Thanks, Ti! That's very interesting. Learning never stops indeed.

Just one thing, I'm mirroring JamesL's question. How does one determine the load impedance of an amplifier? Via its volume pot?

 

[K3cT]

OK, I just did a rough calculation assuming that load impedance is 50K (is that even right?), the value of C needs to be at least 0.33uF to make fc < 10Hz. That makes it insanely difficult to find a matching MKP cap that will fit size-wise.

 

[slowpogo]

Quote:

Originally Posted by K3cT /img/forum/go_quote.gif OK, I just did a rough calculation assuming that load impedance is 50K (is that even right?), the value of C needs to be at least 0.33uF to make fc < 10Hz. That makes it insanely difficult to find a matching MKP cap that will fit size-wise.

I believe 'C' is the capacitance of any and all output caps on that channel...meaning C19+C20, or C25+C26.

So assuming your math is correct, it means C19+C20 needs to be 0.33uf or greater. So you could do it like:

C19: small MKP, 0.022uf or whatever
C20: 10uf electrolytic, for example

The total is 10.022uf, which is obviously greater than 0.33uf, so it's all good

 

[K3cT]

That makes more sense, slowpogo. Thanks, man.

EDIT1: Still, the load input resistance is such a huge value that it's more significant than the others. I'm still unclear what's the "correct" value for this one.

EDIT2: It's tricky to get the fc close to 5Hz using commonly available capacitance values.

 

[amb]

Quote:

Originally Posted by K3cT /img/forum/go_quote.gif Just one thing, I'm mirroring JamesL's question. How does one determine the load impedance of an amplifier? Via its volume pot?

Most of the time, yes. The volume pot's resistance usually dominates the input impedance of a non-inverting amplifier, especially those with FET inputs (or tube). BJT-input amps may have slightly lower input impedance than the pot when the pot is turned up to maximum.

 

[amb]

Quote:

Originally Posted by JamesL /img/forum/go_quote.gif If the amplifier has a input capacitor, would that act as a second capacitor in series with the first, or does r9/r16 (y2 schematic) change the behavior?

When two caps are in series, then their equivalent capacitance is reduced. The formula is:

Ctotal = 1 / ((1 / C1) + (1 / C2))

R9 and R16 does add complication to the total response because instead of one single high-pass filter, now it's two of them in series, and they influence each other's response.

 

[m1abrams]

Quote:

Originally Posted by slowpogo /img/forum/go_quote.gif Interesting, amb, thanks. I realize this is just showing my ignorance, but I can't fathom how a geometrical value like pi factors into electrical equations...fascinating.

Because we are dealing with wave forms not constant values. Everything non-DC electrical is based in the trig world. Heck wait til you try to understand power factors and dealing with imaginary numbers which makes imaginary power that funny enough the power company will not accept imaginary money for!

 

[K3cT]

Quote:

Originally Posted by amb /img/forum/go_quote.gif When two caps are in series, then their equivalent capacitance is reduced. The formula is: Ctotal = 1 / ((1 / C1) + (1 / C2)) R9 and R16 does add complication to the total response because instead of one single high-pass filter, now it's two of them in series, and they influence each other's response.

Well, this is turning out to be a tricky affair. Ignoring R9 and R16, it's still difficult to find a matching C1 and C2 values using commonly available capacitors that can fit inside the y2 to get a corner frequency below 10Hz. Assuming input resistance is 50K Ohm, the recommended values of C1 = 22uF and C2 = 1uF seems to work well in most cases.

 

[JamesL]

Quote:

Originally Posted by K3cT /img/forum/go_quote.gif Well, this is turning out to be a tricky affair. Ignoring R9 and R16, it's still difficult to find a matching C1 and C2 values using commonly available capacitors that can fit inside the y2 to get a corner frequency below 10Hz. Assuming input resistance is 50K Ohm, the recommended values of C1 = 22uF and C2 = 1uF seems to work well in most cases.

He was referring to my question, where c1 and c2 are the output coupling capacitor of the source, and the protection cap on the amplifier.

In the case of g2's output capacitors, they are in parallel and therefore additive. ct=c1+c2

 

[K3cT]

Quote:

Originally Posted by JamesL /img/forum/go_quote.gif He was referring to my question, where c1 and c2 are the output coupling capacitor of the source, and the protection cap on the amplifier. In the case of g2's output capacitors, they are in parallel and therefore additive. ct=c1+c2

You're right, a quick look at the schematic proves that. *facepalm* Thanks for the heads-up, man.

 

[slowpogo]

I got my panel today...I wanted the front to be silver to match my other stuff, so I made my own template. I basically copied amb's design, except I stylized the logo a little and made it green, and counter-sunk the screw holes. The back is the exact same as amb's but the bottom "Designed by..." part is green. It turned out perfectly, though I wish I had made the panel a little wider. It's just barely as wide as the case, but it looks fine.

The picture doesn't quite do it justice...the green is more vivid, and overall it's quite handsome if I do say so myself.

 

[K3cT]

That's very nice looking, slowpogo. Where do you customize your faceplate?

 

[slowpogo]

Thanks. I should have mentioned, it's from Front Panel Express.

I just used the technical drawing and measurements on the y2 website to create the template. It was quite a bit more expensive than those that amb offers...but sometimes you can't put a price on customization.