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

Pass Labs This forum is dedicated to Pass Labs discussion.

A possible approach to adding a silent start/shutdown to the ACA
A possible approach to adding a silent start/shutdown to the ACA
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 14th September 2018, 07:55 PM   #11
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
A possible approach to adding a silent start/shutdown to the ACA
Quote:
Originally Posted by takitaj View Post
Hi Mooly. I'm still deep in the learning stage so forgive me if this is a dumb question.

I was wondering if the delay in the mosfets shutting off could be due to the capacitance charge of the mosfets themselves? Could that be why it improved when you added the resistor between gate and source? Would a resistor to ground somewhere help at all?
I've just run the simulations and looked into this and I think your reasoning is sound in that retained charge on the gate is responsible for a big part of the switch off glitch. The opto used in the simulation seems critical to deciding on the value of resistor that could be used to shunt the gate and source of both FET's. A 100k stops the relay turning on whereas 1meg seems to work reasonably well.

If anyone were to use the real deal (the photovoltaic coupler) then I think the problem would vanish due to the active turn off circuitry within the package.

I'll tidy the simulations up tomorrow hopefully and add them to the thread so that anyone can have a play around.
  Reply With Quote
Old 14th September 2018, 11:19 PM   #12
RafaPolit is offline RafaPolit  Ecuador
diyAudio Member
 
RafaPolit's Avatar
 
Join Date: Dec 2016
Location: Quito, Ecuador
This is really interesting theoretical information.

I for one am very interested in the conceptual side of this (mostly because the on and off noises do not bother me at all). But this is way, waaaay, above my knowledge level to comprehend.

As an owner of an previews version of ACA, would there be any adjustments if the circuit where fed by 19V and biased to 10v?

Thanks,
Rafa.

Last edited by RafaPolit; 14th September 2018 at 11:22 PM.
  Reply With Quote
Old 15th September 2018, 12:33 AM   #13
Old'n'Cranky is offline Old'n'Cranky  Australia
diyAudio Member
 
Join Date: Aug 2009
Hmmm.
I was going to install a speaker protector (purely for start up / power off noises) but I think I will wait and see what happens with this
  Reply With Quote
Old 15th September 2018, 07:19 AM   #14
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
A possible approach to adding a silent start/shutdown to the ACA
Quote:
Originally Posted by RafaPolit View Post
This is really interesting theoretical information.

I for one am very interested in the conceptual side of this (mostly because the on and off noises do not bother me at all). But this is way, waaaay, above my knowledge level to comprehend.

As an owner of an previews version of ACA, would there be any adjustments if the circuit where fed by 19V and biased to 10v?

Thanks,
Rafa.
A 19 volt supply would need the reference voltage (the Zener) for the comparator altering to perhaps a 17 volt one. Zener's are just one easy way to create a moderately stable reference.
  Reply With Quote
Old 15th September 2018, 09:22 AM   #15
albertNL is offline albertNL  Australia
diyAudio Member
 
Join Date: Sep 2011
Location: Brisbane area
A possible approach to adding a silent start/shutdown to the ACA
They say a carpenter thinks with his hammer. More generally, you solve a problem with the tools you are used to. After more than 35 years of writing software I think you can appreciate what my hammer looks like , so I hope you will forgive me for using a digital rather than analog attempt to solve the problem.

The problem, as I see it, is that you do not want output to the speakers during unstable phases. In other words, you only want output when (you know) there is stability.

With little theoretical electronics knowledge, I assume that a suitably low-ohm high-power resistor parallel to the speaker will provide an alternative path for the spike and make it inaudible. Left in place, this resistor would also make our music inaudible, so we only want the resistor to be connected to the circuit during the unstable phases.

According to the simulations in posts 1 and 2, spikes occur during start-up (ca. 2 sec after power is switched on) and during shutdown (it takes about 200ms for the supply voltage to drop from 24V to 0V; in the simulation the spike occurs when voltage has dropped from 24V to 15V).


When I started working in software, computer were expensive. Nowadays, a small arduino computer (credit card sized) costs next to nothing (€ 2.50 from Aliexpress, including shipping). It is powered by 7-20VDC (it has its own inbuilt regulator to drop this to 5VDC). By placing a few diodes (under € 1 for a lot of 100 from Aliexpress) in series with the ACA PSU, the voltage can be brought down to under 20V, so no extra power source is needed to power the arduino. A suitable 24V relay could also come from Aliexpress for under € 1.

If the resistor is placed into the ACA output circuit as shown below, the resistor is always in the circuit unless the relay is turned on. We now need a program that will leave the relay off for a few seconds after powerup.
Although programming can seem difficult, programming an arduino is easier than learning LTSpice! The example below takes care of the start-up thump:
Code:
// Switch relay on 3 after seconds after startup
// Relay switching signal (+5V) is provided on digital pin 8

void setup()
{
  // setup digital pin 8 for output
  pinMode(8, OUTPUT);
   
  // make sure the relay is off by forcing the pin low
  digitalWrite(8, LOW);

  // wait for the power supply to stabilise, so do nothing for 3s
  delay(3000);
  
  // turn relay on
  digitalWrite(8, HIGH);
}

void loop() 
{
   // we have nothing to run here
}

The powerdown thump is slightly more difficult. We need to make sure that as soon as the voltage drops (let's say below 22V but before it reaches 15V) the relay is turned off.

The arduino also has analog pins that can measure voltage. We can continuously measure the psu voltage and switch off the relay when the voltage drops below a set value.
Note that arduino cannot handle >5V so we must use 2 resistors to make a suitable voltage divider. Using a 30k and a 7k5 resistor would be suitable.

The program above becomes a little more complicated, but not much:
Code:
// Switch relay on 3 seconds after startup
// Monitor voltage and switch relay off when voltage < 22V
// Relay switching signal (+5V) is provided on digital pin 8
// Voltage measurement using analog pin 1

void setup()
{
  // setup digital pin 8 for output
  pinMode(8, OUTPUT);
  
  // make sure the relay is off by forcing the pin low
  digitalWrite(8, LOW);

  // setup analog pin 1 for input
  pinMode(A1, INPUT);
   
  // wait for the power supply to stabilise
  // do nothing for 3 seconds
  delay(3000);
  
  // turn relay on
  digitalWrite(8, HIGH);
}


void loop() 
{
  // The analog pin provides a digital value of 0-1024 for 0-5V
  // Our voltage divider reduced the voltage by a factor 5
  // To work out what the measured voltage is we multiply by 5
  // and divide by 1024

  // check voltage and turn the relay off when it is low
  if (analogRead(A1) * 5.0 / 1024) < 22)
    digitalWrite(8, LOW);

  // we now wait for the power to drop low enough so the arduino is 
  // switched off due to lack of power
  while(true)
    delay(1000);
}
Disclaimer: I do not have an ACA and have not built this spike-diverter (yet).
Attached Images
File Type: jpg aca relay.jpg (88.3 KB, 145 views)
File Type: png Arduino-Voltage-Sensor-Module-Schematic.png (3.0 KB, 146 views)

Last edited by albertNL; 15th September 2018 at 09:27 AM. Reason: typos
  Reply With Quote
Old 15th September 2018, 11:51 AM   #16
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
A possible approach to adding a silent start/shutdown to the ACA
Post #4 now has two LTspice .asc files attached for anyone wishing to try these.
  Reply With Quote
Old 15th September 2018, 11:55 AM   #17
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
A possible approach to adding a silent start/shutdown to the ACA
Quote:
Originally Posted by albertNL View Post
They say a carpenter thinks with his hammer. More generally, you solve a problem with the tools you are used to. After more than 35 years of writing software I think you can appreciate what my hammer looks like , so I hope you will forgive me for using a digital rather than analog attempt to solve the problem.
Thanks Albert Using a uP based approach is pretty much alien to me (my programming skills might just about reach to getting an LED to flash given enough time) but I agree its a valid approach for those that can make it work.
  Reply With Quote
Old 15th September 2018, 02:02 PM   #18
RafaPolit is offline RafaPolit  Ecuador
diyAudio Member
 
RafaPolit's Avatar
 
Join Date: Dec 2016
Location: Quito, Ecuador
Albert, that is 'my type of hammer' also!

I have been contemplating something similar to create the standard 12V trigger on the ACA.

Wouldn't you be afraid that the 'noisy' arduino could affect the highly-sought-after clean supply?

As for the trigger, I will not hijack this nice initiative with any details, this is just form thumps and weeeeeps.

Rafa.
  Reply With Quote
Old 15th September 2018, 03:13 PM   #19
Mark Johnson is offline Mark Johnson  United States
diyAudio Member
 
Mark Johnson's Avatar
 
Join Date: May 2011
Location: Silicon Valley
A possible approach to adding a silent start/shutdown to the ACA
Use the NC contacts of an SPDT or DPDT relay, to connect a 1 ohm resistor in parallel with the speaker terminals. Arrange the relay to pull-in "X seconds" after power on, which disconnects the 1 ohm resistor from the speaker terminals.

This shrinks the output thump by a factor of nine. 8/9ths of the thump goes into the 1 ohm resistor, and 1/9th of the thump goes into the 8 ohm loudspeaker.

You could imagine different choices of resistor value too.
  Reply With Quote
Old 15th September 2018, 04:13 PM   #20
Alan4411 is online now Alan4411  Wales
diyAudio Member
 
Alan4411's Avatar
 
Join Date: Oct 2011
Location: West Wales
Quote:
Originally Posted by Mark Johnson View Post
Use the NC contacts of an SPDT or DPDT relay, to connect a 1 ohm resistor in parallel with the speaker terminals. Arrange the relay to pull-in "X seconds" after power on, which disconnects the 1 ohm resistor from the speaker terminals.

This shrinks the output thump by a factor of nine. 8/9ths of the thump goes into the 1 ohm resistor, and 1/9th of the thump goes into the 8 ohm loudspeaker.

You could imagine different choices of resistor value too.
Then why not do it this way? 8R to charge C1 once 'stable' the relay pulls and swaps to the speaker. Better still if one could make the relay pull in at switch on and drop once stable, then it would 'fail safe'.
Attached Images
File Type: jpg aca relay2.jpg (133.4 KB, 125 views)
  Reply With Quote

Reply


A possible approach to adding a silent start/shutdown to the ACAHide 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
P3A amp shutdown 'plop' jacques antoine Solid State 11 28th May 2015 07:23 AM
NTC thermal shutdown lazzer408 Power Supplies 36 14th March 2015 05:59 PM
Squeal on shutdown famousmockingbird Tubes / Valves 48 11th February 2014 06:55 AM
OPA548 and shutdown kafka Chip Amps 9 5th September 2004 04:26 PM
Shutdown noise energyandair Solid State 3 10th May 2003 10:52 AM


New To Site? Need Help?

All times are GMT. The time now is 08:04 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki