Home Tube DIY Asylum

Do It Yourself (DIY) paradise for tube and SET project builders.

active filter : 2nd order LP HP OPA227 distortion % ARTA ...




A few people contacted me regarding active x-over filters for use with 811B horn.

Tested Sallen Key 2nd order 1.2KHz LP & HP filters for distortion at various Hz's with ARTA spectrum analyzer.

Used a 100K load to simulate the input Z of a typical tube amp.

At measurements were taken at -3dB level.

For HP filter :

@ 1.2KHz THD = .15% THD+N = .16%

@ 2.4KHz THD = .12% THD+N = .16%

@ 4.8KHz THD = .099% THD+N = .10%

@ 9.6KHz THD = .096% THD+N = .099%

@ 19.2KHz THD = N/A THD+N = .0017%

For LP filter:

@ 1.2KHz THD = .098% THD+N = .1%

@ 600Hz THD = .098% THD+N = .099%

@ 300Hz THD = .082% THD+N = .084%

@ 150Hz THD = .071% THD+N = .071%

@ 75Hz THD = .055% THD+N = .057%

@ 37.5Hz THD = .051% THD+N = .051%

The only harmonics I could see were 2nd order that were down about 80dB from the fundamental.

Edit: I added a simple bipolar power supply for the filter.

Battery supply runs down too fast to be useful for long term listening.

The prototype circuit on breadboard for evaluation.




Edits: 08/10/14

This post is made possible by the generous support of people like you and our sponsors:
  Herbie's Audio Lab  


Topic - active filter : 2nd order LP HP OPA227 distortion % ARTA ... - deathtube 667 11:27:44 08/09/14 (0)

FAQ

Post a Message!

Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.