The No.1 Website for Pro Audio
API 1608 Mix Buss - Op Amp Blind Listening Test - API 2520, 990C, Rogue 5, GAR 2520, VF600, Red Dot
Old 1 week ago | Show parent
  #271
Gear Maniac
 
dogears's Avatar
 
1 Review written
🎧 5 years
Quote:
Originally Posted by johannburkard ➡️
I'm not sure I understand the context of that test. Pass does power amps doesn't he? He might be talking about very large voltages.

A slew rate is a function of frequency and voltage. You can convert a peak voltage + frequency into a slew rate required to faithfully reproduce it.

Its just 2pifV = slew rate.

To reproduce a 55V peak signal at 20 kHz you need a slew rate of just under 7V / uS.

2V / uS gives you 100kHz at +4 dBu.

As I said, I don't see the practical benefit.

This is well worth a read, if you haven't read it before.
http://hifisonix.com/wordpress/wp-co...Jung_77-79.pdf

Walt set out long ago that you want 0.5 to 1 V/uS slew rate per peak output volt to minimize slew rate induced distortion.
Old 1 week ago
  #272
One benefit of a high slew rate along with high open loop gain at 10k hz is no increase in THD at higher frequencies. Examine most opamps at 1k hz and they look great. Test at 20k hz and they drop off, even some of the better audio IC opamps also do this.

If an opamp can pass 20k hz at full power without any errors everything below that frequency will be equally clear. Run CCIF twin tone IMD tests and you will see "the rest of the story" along with fft's.
Old 1 week ago | Show parent
  #273
Quote:
Originally Posted by Jim Williams ➡️
Run CCIF twin tone IMD tests and you will see "the rest of the story" along with fft's.
That is 19 kHz and 20 kHz, equal amplitude?
Old 6 days ago
  #274
A 1k hz spacing is typical but the AP allows for 80, 100, 120, 200, 250, 500 and 1k spacing. Sweep ranges go from 4K hz to 20k hz. DIM tests include a fixed 3.15K square wave. These are punishing twin tone IMD tests, closer to actual musical waveforms than a simple sine wave test, the easiest to reproduce. Analyzer residuals are around 1.2 ppm as the noise floor included in traditional THD + noise tests are factored out of the measurements.
📝 Reply

Similar Threads

Thread / Thread Starter Replies / Views Last Post
replies: 87 views: 43043
Avatar for 12tone
12tone 4th May 2017
replies: 295 views: 70992
Avatar for anguswoodhead
anguswoodhead 26th March 2013
replies: 1296 views: 176178
Avatar for heraldo_jones
heraldo_jones 1st February 2016
replies: 28162 views: 2962737
Avatar for synesthetic
synesthetic 21 minutes ago
Post Reply

Welcome to the Gearspace Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…

Forum Jump
Forum Jump