Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analogue Source Turntables, Tonearms, Cartridges, Phono Stages, Tuners, Tape Recorders, etc.

Richard Lee's Ultra low Noise MC Head Amp
Richard Lee's Ultra low Noise MC Head Amp
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th October 2019, 10:21 AM   #1631
Hans Polak is offline Hans Polak  Netherlands
diyAudio Member
 
Join Date: Mar 2005
Location: Blaricum
in posting #1576, Richard Lee's Ultra low Noise MC Head Amp, I calculated the equivalent input resistance to be 3.5R based on a measured noise of -191,2dBV.

The calculation itself was correct, but the measurement can't be correct, because this is beyond what's physically possible.
When measuring a sine wave of known amplitude, the FFT is exact, but for noise, for whatever reason, the outcome is too optimistic.
Could this be the averaging proces or the used window, I have no idea.

But careful calculating gave -189.4dBV as the noise level for the ZTX devices with an Rb of resp 1.2R & 1.5R, or 1.8dB above my measurement.
That would result in a noise for the Bare Amp module of 312pV/rtHz.
The equivalent input resistance in that case would be 5.8R instead of 3.5R.

On the other hand, the more important figure is input noise after Riaa and after A-Weighting.
So without taking into account the noise contribution of the equipment behind the Head Amp, this 312pV/rtHz becomes 126pV/rtHz after Riaa and A-weighting, see images below.

This 126pV/rtHz equivalent input noise, is an equivalent input resistor of 0.95R when using the Amp for LP playback!!

Hans
Attached Images
File Type: jpg Riaa Noise.jpg (362.5 KB, 98 views)
  Reply With Quote
Old Today, 12:36 PM   #1632
Hans Polak is offline Hans Polak  Netherlands
diyAudio Member
 
Join Date: Mar 2005
Location: Blaricum
This time the Head Amp as being part of the whole audio chain, I was curious what difference it made to the noise spectrum when powering the Head Amp from either a Power Bank or from a USB mains adapter.
The two images below show the results of the measurements, with absolutely no significant difference.
Inter connections of equipment shown in the third image.


Hans
.
Attached Images
File Type: jpg Nokia Chain.jpg (257.9 KB, 33 views)
File Type: jpg Pwr Bank Chain.jpg (243.2 KB, 30 views)
File Type: jpg CONNECTION.jpg (171.5 KB, 34 views)
  Reply With Quote

Reply


Richard Lee's Ultra low Noise MC Head AmpHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
ultra low noise regulators wtnsmk Power Supplies 26 2nd May 2019 03:12 PM
ultra low noise power supply and low noise amplifier ambrosia168 Power Supplies 8 13th October 2017 02:43 PM
Matching a 1970's receiver with these Richard Allan Loudspeakers? (Richard Allen) gearu Full Range 9 23rd September 2014 03:36 AM
Ultra Low Noise - Ultra Low Impedance - Ultra big Problems! Stefan0815 Analog Line Level 2 14th January 2014 06:01 AM
Ultra low noise filters tiroth Solid State 14 21st May 2002 10:19 PM


New To Site? Need Help?

All times are GMT. The time now is 07:34 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki