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

Chip Amps Amplifiers based on integrated circuits

Building a massively parallel op amp power amplifier
Building a massively parallel op amp power amplifier
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 30th November 2017, 12:22 AM   #41
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Building a massively parallel op amp power amplifier
Nice work Idiosyncrasy!


The “choir” comment was aimed at discrete output transistors. It’s a real effect - that’s why we have load sharing resistors to take up the small differences. If totally unmatched, even load sharing resistors can’t help.

With opamps in a buffer config, each one has local feedback to make it match its neighbors. But one thing to consider is that a feedback free amp sounds better from an imaging standpoint - phase is very flat and with great margin. Listen to a single opamp based amp and then 40 in parallel - with tracks that rely on stereo imaging. Now you have 40 feedback loops going on. See in your minds eye which is better or more clear.
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote
Old 4th December 2017, 12:52 PM   #42
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
Default listening with your imagination does give 'different' results from 'ears only'

Quote:
Listen to a single opamp based amp and then 40 in parallel - with tracks that rely on stereo imaging. Now you have 40 feedback loops going on. See in your minds eye which is better or more clear.
of course you can inform your imagination

try comparing unity gain vs 2x gain with fast opamps for difference in group delay, essentailly the same as batch GBW variation of 2:1

result: ~ 130 ps @ 20 KHz - yes that's picoseconds
Attached Images
File Type: png grp_dly.PNG (34.8 KB, 306 views)
  Reply With Quote
Old 5th December 2017, 06:00 PM   #43
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Building a massively parallel op amp power amplifier
JCX,
That’s cool if you don’t believe ZGF amps make a difference in imaging. It makes a difference for live recorded minimally produced ambient music. I don’t want to clog up this thread with that debate. It’s in a way similar to people who argue that speakers without transient perfect response crossovers are indistinguishable from those that are because they think LR2 XO’s sound fine with a tweeter signal that’s 180deg out of phase. It’s the most popular XO in multi ways.
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio

Last edited by xrk971; 5th December 2017 at 06:03 PM.
  Reply With Quote
Old 8th December 2017, 04:15 PM   #44
70s Veteran is offline 70s Veteran
diyAudio Member
 
Join Date: Sep 2017
Utter nonsense. Doug Self is not The guru of Audio design nor is Nelson Pass. But I must admit his Camp Amp with lateral MOSFETS is very good indeed. Especially when driven by a EF86 pentode configured as a triode with an MJE340 buffer transistor for 0.003% distortion. Maybe you like Opamp sound I don't. In my opinion the best web site I have found is Elliot Sound Products.
  Reply With Quote
Old 8th December 2017, 04:25 PM   #45
scottjoplin is offline scottjoplin  Wales
diyAudio Member
 
scottjoplin's Avatar
 
Join Date: Dec 2015
Location: Penrhyndeudraeth
Quote:
Originally Posted by xrk971 View Post
The ďchoirĒ comment was aimed at discrete output transistors. Itís a real effect - thatís why we have load sharing resistors to take up the small differences. If totally unmatched, even load sharing resistors canít help.
Any literature on this? I can't find any
__________________
Woofer Assisted Wideband is the New Testament renounce the anachronistic acronym FAST
  Reply With Quote
Old 8th December 2017, 05:14 PM   #46
Decker is offline Decker  United States
diyAudio Member
 
Join Date: Jun 2004
Location: San Francisco
Hey 70s Veteran, can you post a schematic of the triode/MJE340 circuit? I have a couple of Amp Camp boards that I haven't used yet. Been thinking of a project with them and would love to see your ideas.
  Reply With Quote
Old 8th December 2017, 06:52 PM   #47
traderbam is offline traderbam  Europe
diyAudio Member
 
traderbam's Avatar
 
Join Date: Jan 2002
Location: Earth
Each of the 80 op-amps in a channel is different. If they were all exactly the same then there would still be variance in resistor values, connection trace resistances and reactances, and noise. Any individual op-amp output target voltage that's different from the average (sort of average) of the herd will be driven into a 1 ohm resistor. How large are these differential currents likely to be when playing music?
__________________
Everything matters.
  Reply With Quote
Old 9th December 2017, 07:07 AM   #48
palstanturhin is offline palstanturhin  Finland
diyAudio Member
 
palstanturhin's Avatar
 
Join Date: Jun 2011
Quote:
Originally Posted by traderbam View Post
Any individual op-amp output target voltage that's different from the average (sort of average) of the herd will be driven into a 1 ohm resistor. How large are these differential currents likely to be when playing music?
Each opamp will also sink the error voltage any opamp produces, so paralleling a million should create quite good average. Starting from 80 for example.
  Reply With Quote
Old 10th May 2018, 03:33 PM   #49
Idiosyncrasy is offline Idiosyncrasy  Netherlands
Megahurtz
diyAudio Member
 
Join Date: Jan 2015
Building a massively parallel op amp power amplifier
Thumbs up Finishing things up properly

After going through a couple of iterations for the power supply for this amplifier, I finally managed to finish this project. I re-used the aluminum enclosure my previous amplifier resided in to house this new one (it's originally an HTPC computer case).

Anyway, here are a couple of pics showing the end result:

20180510 Amplifier guts.jpg

20180510 Full frontal nude shot.jpg

The 90mm fans can be controlled dynamically using a temperature sensor mounted underneath the op amp array.

I'm quite happy with how this build turned out; thanks again to D. Self for the inspiration!
  Reply With Quote
Old 10th May 2018, 04:54 PM   #50
tomchr is offline tomchr  Canada
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Calgary
Quote:
Originally Posted by palstanturhin View Post
Each opamp will also sink the error voltage any opamp produces, so paralleling a million should create quite good average. Starting from 80 for example.
Unfortunately, all these error currents eat into your output current budget, so the overall output power is less than you'd think. I've also seen such error currents wreck the THD of a parallel amp, so it usually pays to minimize the offset first, then put the amps in parallel.

Tom
__________________
MOD686: Up to 240W/8Ω, <0.00025% THD. MOD86: 40W/8Ω, 0.000054% THD. HP-1: 3W/20Ω, -130dBc THD, 128dB DNR.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
  Reply With Quote

Reply


Building a massively parallel op amp power amplifierHide 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
Massively parallel LME49990 headamp agdr Headphone Systems 26 1st July 2014 04:22 AM
DIY AMP Three parallel LM3886 power amplifier board 150W Current fever #868 nelnar Chip Amps 24 29th May 2012 11:51 AM
Building an amplifier power supply using a voltage doubler and LM317? hornloaded Solid State 22 31st March 2010 04:50 PM
Building first tube power amplifier, reccomendations? rhysh Tubes / Valves 81 20th December 2009 05:12 PM
building an high power amplifier selector valvol4 Solid State 3 24th November 2005 01:47 PM


New To Site? Need Help?

All times are GMT. The time now is 01:51 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