TI Active volume control board...tipd136 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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 11th February 2015, 02:49 PM   #1
diyAudio Member
 
Join Date: Jan 2012
Location: Limousin
Default TI Active volume control board...tipd136

Hi !

What do you think about texas instrument tipd136 design ?
Active Volume Control for Professional Audio - TIPD136 - TI Tool Folder

I haven't got the knowledge now, but those TI design doc and board files make a very interesting package to start learning and tweaking safely.

Is it worth a try, and lauch a batch of pcbs ?
Am i wrong calculating a input impedance of 68,75k=1/ (1/r6 + 1/r7) ?

Didn't found reference to this design on the forum.

Thanks for help !
  Reply With Quote
Old 11th February 2015, 07:51 PM   #2
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
The circuit is based on a Peter Baxandall circuit/design/idea from many years ago. I've used these and Doug Self did a similar highly developed design for his 'Precision Preamp' from 1996 and also a later design.

There is some controversy however. You will have to read posts before and after this,

New Doug Self pre-amp design...
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 11th February 2015, 08:56 PM   #3
diyAudio Member
 
Join Date: Jan 2012
Location: Limousin
Thanks ! Even if i don't have the clues to understand all, but it help me a lot linking/"conceptualizing" effects each others (impedance/load/current/distortion/loop...).
So if i understand a bit, the TI doc lack of attenuated setting distortion measurement.
  Reply With Quote
Old 12th February 2015, 08:12 AM   #4
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
That's right, I don't think they quote it at very low output levels. Its a very clever idea and it does work well... you need to try it yourself.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 12th February 2015, 10:02 AM   #5
diyAudio Member
 
Join Date: Jan 2012
Location: Limousin
so, let's try it ! 10 pcb batch launched, 9 in swap meet in few weeks/month
  Reply With Quote
Old 12th February 2015, 11:13 AM   #6
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
OK Good luck, and let us know what you think of it.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 14th February 2015, 02:49 AM   #7
diyAudio Member
 
Join Date: Jan 2006
Location: Tucson, AZ
Quote:
Originally Posted by papasteack View Post
so, let's try it ! 10 pcb batch launched, 9 in swap meet in few weeks/month
Enjoy! I can ask the author (Ian, who sits 15 feet away) if he has one of the boards laying around and I can measure the distortion at lower levels if you're still interested.

It's good to see people are looking at the TI designs docs. We started them with the idea that the traditional app notes of old didn't go far enough. Some of us distrust a circuit unless it's actually been built, put on the bench and run through its paces. If you're going to do all that, you might as well give the reader all of the simulation files, pcb files, and measured data to duplicate your results!
  Reply With Quote
Old 14th February 2015, 02:04 PM   #8
diyAudio Member
 
Join Date: Jan 2012
Location: Limousin
Wow, of course i would be really really interested ! Thanks a lot for this generous offer !
Waiting for result :-)
  Reply With Quote
Old 14th February 2015, 02:18 PM   #9
diyAudio Member
 
Join Date: Jan 2006
Location: Tucson, AZ
Quote:
Originally Posted by papasteack View Post
Wow, of course i would be really really interested ! Thanks a lot for this generous offer !
Waiting for result :-)
You're welcome. It's really a selfish offer because right now I'm looking for any excuse I can find to use our new APx555.
  Reply With Quote
Old Yesterday, 06:08 PM   #10
diyAudio Member
 
Join Date: Jan 2006
Location: Tucson, AZ
Hey guys, sorry for the slow reply on this. I did some reading on the original thread above to understand Mr. Cordell's concern and found that in that thread the potentiometer used was 1kOhm. I orignally tested the pcb from TIPD136 with a higher impedance potentiometer and didn't see much in the way of distortion, so I ordered a 1kOhm potentiometer and swapped it into the board. I took FFTs of the output signal for a 1kHz sinusoid at 2Vrms. The FFTs are taken at attenuation levels of 0dB, 40dB and 75 dB. The y-axis in these FFTs are dB relative to 2Vrms for ease of comparison. I also measured the frequency response at a these attenuation levels.

For 0dB attenuation and a 2Vrms signal, the 3rd harmonic is dominate at -117dB, the other harmonics are down 130dB or more. At 40dB of attenuation the 3rd harmonic is still dominant and is -103dB below the fundamental. At 75dB of attenuation the 3rd harmonic is 70 dB below the fundamental.

Frequency response only changed in the case of 75dB of attenuation, where there is about a 10dB loss in attenuation at 100kHz.

Overall I feel that if this performance concerns you, a good option would be to use a higher impedance potentiometer.
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Active volume control - Be quiet please. Buehgemeiste Analog Line Level 11 5th November 2014 12:46 PM
CS3318 Volume Control board with IR? mikealanlee Analog Line Level 27 11th October 2014 11:45 AM
Volume control for class D audio TI-600 amp subwerker Class D 2 13th June 2011 10:11 PM
Need volume control on active filter Buzzy Analog Line Level 5 29th December 2009 04:40 AM
Aleph P 1.0 volume control board question? tomchaoda Pass Labs 31 21st July 2004 04:24 PM


New To Site? Need Help?

All times are GMT. The time now is 05:38 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.
Copyright 1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2