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

Headphone Systems Everything to do with Headphones

Universal buffer/headamp based on OPA1622
Universal buffer/headamp based on OPA1622
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 23rd November 2017, 08:48 AM   #291
AndrewT is offline AndrewT  Scotland
R.I.P.
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by OlegSh View Post
Today I finally received the OPA2140 and tried it immediately in the headamp. The result is the same, the small pop is still there. I conclude that this family of op-amps simply has such a turn-on transient... or there is something else going on which I don't understand.

In principle it is possible to delay the unmute of OPA1622 further by changing D3 (LED) to a resistor and using a capacitor instead of R15. Since the internal impedance of the enable network of the OPA1622 is around 700k (see p.16 of the datasheet for details), resistor can probably be as high as 1M which in combination with 1u capacitor should give a long enough unmute delay.

Regards,
Oleg
Have you read John Caldwell's and others paper on developing the opa1622?
Which of these 4 opamps for headphone amp/preamp?
Part5 is about start up and shut down pops.
__________________
regards Andrew T.

Last edited by AndrewT; 23rd November 2017 at 08:53 AM.
  Reply With Quote
Old 23rd November 2017, 08:52 AM   #292
OlegSh is offline OlegSh
diyAudio Member
 
Join Date: Dec 2010
Location: Germany
Universal buffer/headamp based on OPA1622
Thanks for looking at my project, Patrick! The entire idea of using the OPA1622 was its "convenience" as an all-in-one solution which soon proved to be not so trivial to implement. Since there are tons of projects on this forum dealing with all kinds of amps topologies I took this route for myself to avoid interfering with the efforts of others. Since I am not skilled enough to come up with a better discrete design than already exists I use a pragmatic approach and use the best measurable spec op-amp solution.

Regards,
Oleg
  Reply With Quote
Old 23rd November 2017, 08:59 AM   #293
OlegSh is offline OlegSh
diyAudio Member
 
Join Date: Dec 2010
Location: Germany
Universal buffer/headamp based on OPA1622
Quote:
Originally Posted by AndrewT View Post
Have you read John Caldwell's and others paper on developing the opa1622?
Which of these 4 opamps for headphone amp/preamp?
Yes Andrew, I did. The difficult part in using the OPA1622 is its enormous bias currents and sensitivity to input impedance and RF interferebce. The IC was meant to be used after the voltage output DAC in portable applications (the reason for small size of the IC). Trying to interface the OPA1622 with the volume pot, input RF filter and AC coupling cap proved troublesome which lead to adding a buffer/gain stage using the FET input op-amp... And so things started to add up... endlessly But I like the process of designing the whole thing and the sound I hear in the end.., except this tiny pop since I'm a perfectionist and it steps a bit on my nerves
  Reply With Quote
Old 23rd November 2017, 09:02 AM   #294
OlegSh is offline OlegSh
diyAudio Member
 
Join Date: Dec 2010
Location: Germany
Universal buffer/headamp based on OPA1622
Regarding the Part 5 of John Caldwell's series of papers, it deals with the start-up transient of the OPA1622 itself which is a non-issue, while in my case the pop originates from the buffer op-amp - OPA2140/OPA1642.
  Reply With Quote
Old 28th November 2017, 09:58 AM   #295
Joseph K is offline Joseph K  Hungary
diyAudio Member
 
Join Date: Dec 2004
Location: gran sasso
Quote:
Originally Posted by EUVL View Post
I admire your endless effort with the OPA1622.
For me it is not worth the while.
Maybe one day you should try some discrete Class A circuit, just to compare (subjectively).


Patrick
Patrick, I don't know if a Cavalli amp satisfies your acceptance threshold..
But we compared and simply no contest, subjectively.
And let's forget about measurement-wise..

Last edited by Joseph K; 28th November 2017 at 10:01 AM.
  Reply With Quote
Old 2nd December 2017, 03:31 PM   #296
johnc124 is offline johnc124  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Tucson, AZ
Quote:
Originally Posted by DPH View Post
1642 and 2140 are the same chip in different bins (offset), no?
Not exactly. OPA1642 uses a very slight change in compensation to improve distortion. OPAx140 devices are trimmed in production for excellent DC precision.
__________________
Product Line Manager - Texas Instruments High Speed Amplifiers
  Reply With Quote
Old 2nd December 2017, 03:42 PM   #297
johnc124 is offline johnc124  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Tucson, AZ
Quote:
Originally Posted by OlegSh View Post
Yes Andrew, I did. The difficult part in using the OPA1622 is its enormous bias currents and sensitivity to input impedance and RF interferebce. The IC was meant to be used after the voltage output DAC in portable applications (the reason for small size of the IC). Trying to interface the OPA1622 with the volume pot, input RF filter and AC coupling cap proved troublesome which lead to adding a buffer/gain stage using the FET input op-amp... And so things started to add up... endlessly But I like the process of designing the whole thing and the sound I hear in the end.., except this tiny pop since I'm a perfectionist and it steps a bit on my nerves
I still debate about the decisions we made in the input stage of OPA1622, even though the chip has been very successful. Some compromises had to be made to allow for a wider input voltage range and low supply operation, and they resulted in higher input bias current. Improving EMI sensitivity on the other hand normally involves a trade-off with input voltage noise. There's always the next chip to make!

In the future I would also like to incorporate some of the technology we developed on the new OPA1692: OPA1692 SoundPlus Low-Power, Low-Noise, High-Performance Dual Bipolar-Input Audio Op Amp | TI.com into other products. We had to get clever to reduce distortion with only 650uA of power supply current and 5-6 MHz of bandwidth without totally giving up all stability with capacitive loads.
__________________
Product Line Manager - Texas Instruments High Speed Amplifiers
  Reply With Quote
Old 2nd December 2017, 03:56 PM   #298
OlegSh is offline OlegSh
diyAudio Member
 
Join Date: Dec 2010
Location: Germany
Universal buffer/headamp based on OPA1622
Wow! Thanks for the teaser, John! The OPA1692 looks really interesting. I am looking forward for the new parts you are designing. I hope to finish my current projects by the time you release them
  Reply With Quote
Old 3rd December 2017, 04:14 PM   #299
johnc124 is offline johnc124  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Tucson, AZ
Quote:
Originally Posted by OlegSh View Post
Wow! Thanks for the teaser, John! The OPA1692 looks really interesting. I am looking forward for the new parts you are designing. I hope to finish my current projects by the time you release them
The MSOP package version of the OPA1692 will release this week. SOIC will follow-on early next year. It was designed for low power applications, but the distortion cancellation technique we developed is applicable across many other applications. This coming year I'll be releasing some fun new parts!
__________________
Product Line Manager - Texas Instruments High Speed Amplifiers
  Reply With Quote
Old 3rd December 2017, 04:16 PM   #300
OlegSh is offline OlegSh
diyAudio Member
 
Join Date: Dec 2010
Location: Germany
Universal buffer/headamp based on OPA1622
I should hurry up then
  Reply With Quote

Reply


Universal buffer/headamp based on OPA1622Hide 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
Universal Buffer/HP Amplifer Bonsai Headphone Systems 20 30th August 2014 06:06 PM
Universal FET buffer / preamplifier veteran Analog Line Level 31 21st May 2013 09:42 PM
LME498xx Based Headamp panson_hk Chip Amps 20 9th April 2013 10:20 PM
FS: Mini headamp/preamp/buffer boards theAnonymous1 Swap Meet 1 26th November 2008 12:39 AM
AD8610 and HA5002 Buffer/HeadAmp rehanabid Chip Amps 8 28th January 2006 12:20 PM


New To Site? Need Help?

All times are GMT. The time now is 03:35 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki