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

Digital Line Level DACs, Digital Crossovers, Equalizers, etc.

Using the AD844 as an I/V
Using the AD844 as an I/V
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
Thread Tools Search this Thread
Old 11th February 2019, 09:24 AM   #2241
diyiggy is offline diyiggy
diyAudio Member
Join Date: Jan 2019
wow ! And seems also abble to drive headphones.

C4 & C6 with a foilded styren cap (or a silver mica) or a less good 5 mm pitch MKP (avoiding XR7) should be usefull to preserve the clarity of the previous stage.

And for the same purpose : C4+R10 / C7+R18 could be removed if one has an input cap on the pre or amp... (but headphone?)

Btw, just has been looking at your Lingdac shematic. Is this AD8017arz a sort of AD844/OPA860(/1) transconductance IC ? Or why do you prefer it over these last ones to stay in the thread topic (whether an embeded feedbackloop in it?)

Anyway, many thanks for that.
  Reply With Quote
Old 11th February 2019, 09:52 AM   #2242
abraxalito is offline abraxalito  United Kingdom
diyAudio Member
abraxalito's Avatar
Join Date: Sep 2007
Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though...
Send a message via Yahoo to abraxalito
Headphones can be driven yes - just need to check that the bias current is set (via R8 & R16) in accord with the impedance of the 'phones. Also since its classA there's a fair amount of power being dissipated in Q1/Q2/Q4/Q5 - the PCB layout (found on the lingDAC thread) has areas of copper on both sides to act as heat spreaders. One point I just noticed - the PSU is shown as +9V but in fact this buffer only needs 7V to swing 2VRMS at the output, so to keep the FETs as cool as possible its best to run only as high on the rail as needed to swing the full signal.

C4 and C6 are NP0 types, not X7R so no need to swap them out. NP0 are quite blameless as caps. Yes you could remove output coupling caps if you know the next stage has them - definitely do not remove when feeding headphones.

AD8017 is a current feedback amp with high output drive capability. I chose it mainly because its very cheap on Taobao, excellent bang-for-the-buck. AD811 performs slightly better SQ-wise but is more difficult to employ as its output doesn't swing as close to the rails, demanding more volts on the supply. It also runs very, very hot. Incidentally lingDAC only uses discretes in the OPS, its PhiDAC which uses the ADs.
I know you think you understand what you thought I said but I'm not sure you realize that what you heard is not what I meant - Alan Greenspan

Last edited by abraxalito; 11th February 2019 at 10:00 AM.
  Reply With Quote
Old 11th February 2019, 10:02 AM   #2243
pistollero is offline pistollero  Portugal
diyAudio Member
Join Date: Apr 2016
Location: portugal
Originally Posted by georgehifi View Post
Forget the AD844's own buffer it's not very good sounding. Come off the 844's pin5 to your own buffer, I found a "genuine" OPA627 to be exemplary, make sure it's genuine by getting it from an authorized TI distributor, as there are many fakes of these.

Forget the BUF03 in the pic that's the first one I tried, too dirty sounding great bass though.

Cheers George
Hello George, could i use this schematic for the pcm1702 instead of 1704?
are all the component values ok? use 3x ad844 or only 1?
i īm using lt1028 as i/v but i would like to try this alternative.
  Reply With Quote
Old 11th February 2019, 10:52 AM   #2244
diyiggy is offline diyiggy
diyAudio Member
Join Date: Jan 2019
With good layouts I noticed NP0 in the final direct signal path gives subjectivly something not so neutral at ears (so in the listen frenquency range) : often too thin and a little brighty. Although it depends on the width of the traces on the pcb as well ! When I have choice I swap them for Panasonic PPS if SMD designs where the capicitance is notof an importance (serie signal)- Wima FKP2 (non metalized) are good too. or foilded styrens if vias (silver mica being a little too much brighty and thin as NP0 and not tin foilded styrens less good either). YMMV. I like AWG30 (or more little)width and short length output traces for some reasons before RCAs or any gears output stage (trying to have low mass serie contacts). As for the serie resistors I try to use cheap metalized Yageo which are very low noise or RD if not better RS Sussumu in the digital stage AND after.

Again YMMV, all being subjective at ears in the last details (but the Devil often in its for sure)
  Reply With Quote


Using the AD844 as an I/VHide 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
AD844 as a common base stage in the I/V converter Pedja Digital Source 44 14th September 2015 11:10 AM
WTB AD844 Opamps apassgear Swap Meet 6 31st January 2007 03:57 PM

New To Site? Need Help?

All times are GMT. The time now is 09:49 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