Transiet response in low pass filter

Hi, this is my first post - I hope this is the right place to ask this question:


I'm a newbie in analog electronics. I'm building a RIAA-preamplifier and I'm stuck implemting the 75 us low pass filter. It's a passive filter implemented in between to JFET amplifiers. Well, it looks like it works just fine, the only problem is, that if i have a square wave on the input, it looks not exactly like a square wave at 1 kHz... at 10 kHz it's triangular

That tells me that the transient response of my circuit is very, very bad. What is the source of this problem and/or how can I improve it?

You don't want to improve its response. You filter is working exactly as designed. It is a 2.12KHz low pass filter and is rolling off the high frequency edges of the 10kHz square-wave, giving an output that looks more or less triangular.

The purpose of the filter is to exactly compensate for the 75µs high-pass increase in the recorded signal (the purpose of this increase in high frequency signal and subsequent roll-off during playback is to minimizes the effect of high frequency record noise). Thus a recorded square-wave would be reproduced correctly since the low-pass filter roll-off matches this high-pass recorded gain increase, giving an overall flat-response at the output.

Aha... Thank you very much!

I assume you are also implementing the 318 µs and 3180 µs roll-offs that are part of the RIAA equalization.

"Oh no! My circuit does exactly what it's supposed to!"

Yeah, I'm going to implement the 318/3180 roll-off as well. This is my first serious analog project, so I might have more questions soon - I feel so stupid about the last question... well, nobody told me it should be like that - the few books I have is either very basic or very advanced - searching the internet for explanations, formulas and so on is sometimes even more confusing.

Old vinyl records?
Before compact cassette tapes?
Before CDs?
Before MP3 players?
Before the North America was discovered?
Why?