Why dont home systems have an outboard cap, like cars? - diyAudio
Go Back   Home > Forums > General Interest > Everything Else
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

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 12th January 2016, 09:46 PM   #1
diyAudio Member
 
Join Date: Nov 2015
Default Why dont home systems have an outboard cap, like cars?

Is there a reason why it is safe in cars, but not done in homes?
  Reply With Quote
Old 12th January 2016, 09:50 PM   #2
diyAudio Member
 
JonSnell Electronic's Avatar
 
Join Date: Dec 2012
Location: The Jurassic Coast, England. GB
Send a message via Skype™ to JonSnell Electronic
What do you mean?
__________________
Support for Flying Mole Class D, Valve Equipment and designs both new and old. www.jonsnell.co.uk
  Reply With Quote
Old 13th January 2016, 12:05 AM   #3
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
The 12v power in autos is the source for the car audio amps. Some systems add huge caps called "stiffening caps". Huge as in a farad or two. A quick google saw them as large as 6 farads a moment ago. Google "stiffening caps" for examples and some FAQ pages.

In cars it isn't about safety, it is for competitive sound pressure level reasons. Holds up the voltage for low frequency peaks. In a home system where the power for audio is essentially unlimited as it comes from the AC mains, they would be totally unnecessary. Plus the storage caps in a home system are on the main power rails, not a 12v power supply.
  Reply With Quote
Old 13th January 2016, 02:38 AM   #4
diyAudio Member
 
zigzagflux's Avatar
 
Join Date: Oct 2006
Location: Charlotte, NC
If by "outboard" you mean outside the amp chassis, then extra capacitors will not function in the same manner they do in cars. Auto systems are based on DC, which capacitors are able to store energy in a static manner, ready to be used when needed. This has some benefit in car audio (although it is worth noting that car audio amps have internal SMPS, so there is a practical limit to the effectiveness of outboard storage caps).

In the home environment, your power in the wall is AC, not DC. Capacitors do not behave with the same storage mechanism with AC as they do with DC. I could explain what really happens in the AC environment, but it probably would not help much. Suffice it say, with AC, capacitors do not store energy (in the way you might think).
  Reply With Quote
Old 13th January 2016, 03:23 AM   #5
diyAudio Member
 
Join Date: Nov 2015
Then perhaps a loop from the va plus and minus? So, that the Caps can see DC? Of course, you can simply add Caps inside of case if there is room.
  Reply With Quote
Old 13th January 2016, 09:21 AM   #6
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
A domestic mains-powered amplifier design will include the appropriate capacitors in the power supply. There is no need for anything extra, and this could cause extra buzz if grounded badly.
  Reply With Quote
Old 13th January 2016, 01:02 PM   #7
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
A domestic mains-powered amplifier design will include the appropriate capacitors in the power supply.
A properly designed modern amp should not need additional help. Any amp, even a high quality amp should have sufficient reservoir capacitance inside to supply its needs even while cranking big bass through inefficient low impedance speakers. Large capacitors in small packages are now quite common and reasonably priced.

This was not always the case. Back in the early 70's electrolytics were not as good or as small as they are now. I had a Fisher 500TX, which was their top model at the time. It did benefit from a large pint sized "computer grade" cap across the single positive power supply. I had it TY-Rapped to the back of the unit.

A car amp should not need a stiffening cap either if there is a direct run of fat wire to the car's battery to power it. That is not always the case, and some of these big amps can draw hundreds of amps on peaks, mount that in the trunk, along with a few other amps, and you could benefit from a big cap......if the cap is really low in ESR and can really source 100 amp peaks.

I have seen competition setups with a dozen or so caps AND two extra boat batteries in the bed of the truck. There was a separate alternator to power it all, and the trucks engine had to be revved up to reach max SPL.
__________________
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
  Reply With Quote
Old 13th January 2016, 02:37 PM   #8
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
And those high power car audio systems that are used in competitions are not playing music, they are playing test signals. In other words, those amps are not made to listen to, just made to win competitions for sound pressure levels.
  Reply With Quote
Old 14th January 2016, 04:42 PM   #9
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
In the case I was referring to, you are right. The entire "race" was about how far the needle on the SPL meter could be pushed. There was some other criteria that had to be met to "qualify" for the race, like a frequency response and distortion test. The vehicle had to actually be capable of being driven. I have no idea what the required numbers were.

I was out riding my bicycle near a large shopping mall when I heard a very LOUD, unnatural sounding buzz coming from a crowd in the parking lot, so I rode up for a look. I had stumbled on what was called the "dB drags" event. This was at least 10 years ago in Florida.

The vehicle I remember was the champion in this event. It was a small truck. The entire bed was filled with amps, speakers, batteries, caps, and other electronics. It was all contained in a large wood and fiberglass enclosure that funneled the sound into the cab through the area where the rear window should have been. All of the glass in the truck had been replaced with thick Lexan and some reinforcement had been added to the doors. The truck was called MTX Thunder, built by the speaker company of the same name....and that's about all it did.

I asked if it would play music, and the MTX guy replied "of course" and pushed a few buttons on his remote. I guess you could call it music.......I have heard worse come out of some of the cars in my neighborhood.

There was so much of that in south Florida that you could buy the supplies including the monster caps at the Walmart in that mall. I got the speaker wire for my home system in that WM's car audio department. Rolls of #14, #12 and bigger if you desired, for reasonable prices, and the caps.....the "cool" ones have LED's all over them. That WM also had amps and subs, but not of the caliber needed to enter one of those competitions.
__________________
Tubelab, it's 5 year mission. To explore strange new tubes, to seek out new circuits and topologies, to boldly go where no tube has gone before......
  Reply With Quote

Reply


Hide 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Home sub: trying to replicate that sharp 'kick' feel, common in great PA systems creyc Subwoofers 72 11th November 2015 11:48 PM
outboard xover henrylrjr Multi-Way 7 10th February 2014 01:12 AM
"Loudspeaker Management Systems" for home? sprinter Digital Source 1 5th March 2011 11:04 PM
Wiring high Watt sub woofers into home audio systems. Broken_Sight Digital Source 1 7th January 2004 11:28 PM
home units for cars YCLee Multi-Way 4 22nd January 2003 10:22 PM


New To Site? Need Help?

All times are GMT. The time now is 04:25 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki