Zobel question

[spaceludwig]

I accidentally bought polarized (instead of bipolar) capacitors to replace the 1uF capacitor in the zobel network - outlined in blue, see image below - after the input transformer.

Is it possible for me to put two 1uF caps in parallel to give me the equivalent circuit? Or would the value then be doubled (i.e. 2 uF)?  Any workarounds or do I need to order some new caps?

Thanks in advance for the help/info.

 

[PRR]

It isn't a "Zobel", it's a simple coupling network.

If you don't want to do it twice, get a bi-polar cap.

 

[spaceludwig]

Ok, sorry for my ignorance, I thought those filter networks after a transformer was called a zobel.

Anyhow, I'll buy the proper capacitors. Thanks for the advice.

 

[gemini86]

If you look close, you'll notice that all the signal passes through that cap to get to the input of the amp. A zobel would just be shunting some of the signal to ground.

 

[spaceludwig]

Yeah, you're right. I wonder why in the rest of the circuit the signal is passing through 10uF bipolar or 47uF and here it is passing through 1uF? Perhaps someone could shed some light...?

 

[PRR]

> why in the rest of the circuit the signal is

Why do you use smaller wood for a shelf bracket, bigger wood for a house frame?

Depends on the load.

The 1uFd is only driving the 47K and the opamp (nearly infinite).

The 10uFd are probably driving multiple loads, effective 10K or less. The 47uFd are probably driving heavy loads under 2K.

The bass-cutoff is related to the C and the R.

1uFd 100K = 1.7Hz
1uFd 10K  = 17Hz
10uFd 10K = 1.7Hz
50uFd 2K = 1.7Hz
50uFd 600 = 5.3Hz
10uFd 1K = 17Hz
0.01uFd 1Meg = 17Hz

While there isn't much "audio" below 20Hz, in large systems with multiple couplings, we aim the coupling bass-cutoffs lower. The "corner" is soft, a 1.7Hz cutoff is -3db at 1.7Hz, -1db at 3.4Hz, -0.5db at 7Hz, (about) -0.25db at 14Hz. Ten such -0.25db shavings would be a significant -2.5db loss at 14Hz.

 

[spaceludwig]

Thanks for the explanation, PRR. The wood analogy was a good one and helped make the idea less abstract.

I guess the logical follow up question would be why not use an amount smaller than 1uF? Shelf brackets made of toothpicks can't hold big volumes?