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

My "audiophile" LM3886  approach
My "audiophile" LM3886  approach
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 October 2017, 07:13 PM   #4591
miklos is offline miklos  Hungary
diyAudio Member
 
miklos's Avatar
 
Join Date: Jul 2004
Location: Budapest/Toronto
Ideally it should be a potentiometer at the input and that terminate the input and would stop your hum.
__________________
miklos
  Reply With Quote
Old 31st October 2017, 01:12 AM   #4592
madisonears is offline madisonears  United States
diyAudio Member
 
Join Date: Sep 2007
Quote:
Originally Posted by bullittstang View Post
Ran a few more tests and I'm still perplexed by my findings.

Both RCA's plugged in - no hum
both RCA's unplugged - hum
either RCA plugged in - no hum

It is certainly AC type hum - measuring 0.002 on Left channel input and 0.006 on right channel input.
Is it possible it is picking up transformer hum? Should I try a shielded cable and see if that helps?
Also see a lot of people (Rev D version) that uses a CL60 on teh PGND connection. Would that do anything?
It'a annoying and I want to try and figure out why the hum is there, as much for learning as just to have a quiet amp at all times.
To put this in perspective, EVERY MyRef amp ever built hums with open inputs. If the hum bothers you while listening to your system with no inputs, just turn it off. No more hum.

Peace,
Tom E
  Reply With Quote
Old 31st October 2017, 02:41 AM   #4593
bullittstang is offline bullittstang  United States
diyAudio Member
 
Join Date: May 2013
Location: Mahwah, NJ
I get it, I'm being stupid...but I thought I read every page of this and the 4 other My Ref threads and never saw a single mention of this type of humming. Granted who would judge hum with an open input as a problem except me.
OCD is a disease and not understanding "why" makes it twice as irritating to my brain.

I will stop trying to figure out why and enjoy what I have when the inputs are plugged and the music is playing.
  Reply With Quote
Old 31st October 2017, 02:46 AM   #4594
madisonears is offline madisonears  United States
diyAudio Member
 
Join Date: Sep 2007
Yeah, we're all a little obsessive about our babies. You've done nothing wrong and there's nothing to fix. Hope you can relax and enjoy. You have really nice amplifiers to make it easier!
  Reply With Quote
Old 31st October 2017, 11:51 PM   #4595
ClaveFremen is offline ClaveFremen  Italy
Reality first!
diyAudio Member
 
ClaveFremen's Avatar
 
Join Date: May 2005
Location: Milan, Italy
My "audiophile" LM3886  approach
Default 11th My_Ref Fremen Edition GB is open!

My_Ref Fremen Edition GB (11th run)
__________________
Dario
ClaveFremen "Bailando Salsa en el Sietch" - For My_Ref FE 12th GB extra boards PM me.
  Reply With Quote
Old 7th November 2017, 01:47 PM   #4596
varun21 is offline varun21
diyAudio Member
 
Join Date: Dec 2013
Can the myref run tweeters? I'm planning to tri-amp since the fullrangers sound a little bit absent on the top-end. Do the tweeters still need a protection cap? I know I can use a lower power amp but I just want to use myref.
  Reply With Quote
Old 7th November 2017, 02:06 PM   #4597
bullittstang is offline bullittstang  United States
diyAudio Member
 
Join Date: May 2013
Location: Mahwah, NJ
Yes you can - but YES you will need a cap (1st order XO) at a minimum to protect your tweeters.
As long as you have an adequate (properly designed) crossover, your tweeters will be fine with the MyRef as an amp.
  Reply With Quote
Old 8th November 2017, 03:25 AM   #4598
madisonears is offline madisonears  United States
diyAudio Member
 
Join Date: Sep 2007
But use a large enough value cap that will NOT act as a 1st order XO.

Tom E
  Reply With Quote
Old 8th November 2017, 08:49 AM   #4599
AndrewT is offline AndrewT  Scotland
R.I.P.
 
Join Date: Jul 2004
Location: Scottish Borders
Or use the cap as the first one pole stage of a multi-pole filter.

If you have a natural roll-off that is at the correct frequency and is 2pole and you want 4 pole at that same frequency then you could use the capacitor to add one pole passively and add in a second one pole active but with a Q = 1 so that you end up with a Butterworth 4pole acoustic roll-off.

But it's much better to have an octave spare in the natural roll-off and then you have a 3pole active with Q=1 and the passive 1pole from the capacitor. This gives a cleaner performance at the turn-over frequency.
But that active 3pole may need to be shelved into a 1pole, where it reaches the natural roll-off of the driver.
__________________
regards Andrew T.

Last edited by AndrewT; 8th November 2017 at 08:52 AM.
  Reply With Quote
Old 12th November 2017, 04:37 AM   #4600
varun21 is offline varun21
diyAudio Member
 
Join Date: Dec 2013
My speaker protection isn't kicking in. I just noticed a DC offset of around 10V because R43 (Rev C) was 22M ohms. Although I've fixed it and there's acceptable DC offset now. One day the old speaker cables just shorted when I was twisting them straight. The 200w bulb in series went very bright for some seconds when I just turned the thing off and fixed the wires before powering on.

I think rev C has slightly modified values of the protection circuit than A. Attached are schematics and Mauro's inputs.

What's the right way to troubleshoot.

Included:
1. Original schematic
2. rev C.
3. rev A (improved speaker protection that everyone is supposed to be using in the latest version / kit ? )

Quote:
Originally Posted by mauropenasa View Post
The Voltage +VRL it's about +24V.
At start up C12 it' s discharge and determined (with R14 charge current) the ON-time delay. At VB Q1 >1,2V the darlington (Q1&Q2) close the Output relay.
If at Ampli out it's present a positive tension with time- costant > several mS (integrated on C19-R42 or R41) and Voltage > 2V (about),
Q3 discharge C12 and Relay are Open. If the status return at 0VDC, C12 are recharge with delay.
If a negative tension are present at ampli out, C12 it's discarge (from R44 or R43 and Q1 base potential are about 0V (or some negative mV) so, Relay it's off.
The Low value of C13 disable immediately the relay on power off state.

Ciao

Mauro
Quote:
Originally Posted by mauropenasa View Post
Hi, Greg

Your observation is near, but...

My description is a lot of fast, and non exact (sorry). With the components used in the circuit the threshold of intervention is +5,5VDC @ 0 , 5 sec. and -5, 5V @ 2 sec. The motive is that C12 discharge of 0,3V to stop the relay. Naturally modifying R44 R43 R42 R43 gets the constant and the threshold that is prefered.
Affair remembers that the speed of various intervention to the increase of the tension, and if an ending is spoiled usually in exit there are about tens of volt. In this conditions the intervention becomes < 0,5 sec. even on the negative thing.
Obviously this circuit not doesn't want be an absolute reference, and it is in my scheme because much compacts ( all the circuit is on a 100160mm card ). In the use daily paper has not given never problems and the breakdowns of the prototypes have not damaged never my loudspeakers.

Ciao

Mauro
Attached Files
File Type: pdf my_ampli.pdf (32.9 KB, 107 views)
File Type: pdf revc.pdf (29.7 KB, 98 views)
File Type: pdf reva.pdf (99.3 KB, 79 views)
  Reply With Quote

Reply


My &quot;audiophile&quot; LM3886  approachHide 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


New To Site? Need Help?

All times are GMT. The time now is 07:40 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki