PA200 and 8ohm load? - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 7th March 2007, 06:15 AM   #1
CJ900RR is offline CJ900RR  Sweden
diyAudio Member
 
Join Date: Jan 2006
Default PA200 and 8ohm load?

Im thinking of building a amp, or two acctualy. My plan is to base it on the PA200 in Nationals AN-1192 for 2 x 100W, but also by using the DRV134 I want to be able to bridge it into 1 X 200W.

I dont want to use the BPA200 simply because I want the option to use it as stereo-amp or to use it as a mono-block whit more power.

But I am concerned about one thing. What is the risk of using loudspeakers whit 8 ohms load when the amp is in stereo-mode (2 x PA100). According to AN-1192 it means that the amp will see the load as 16 ohm, right?

My loudspeakers is 4 ohms but I have a friend who want a amp and his speakers is 8 ohm. Can he use it whit good result anyway or do I need to rethink the concept?

Please share your knowledge

Best regards, Carl Johan...
  Reply With Quote
Old 7th March 2007, 06:32 AM   #2
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
I found PA100 but not PA200.
The PA100 is a parallel pair of chipamps to power a 4ohm load to 100W.
Each amplifier thinks it is sending just sufficient current to power an 8ohm load. The amps are each designed to produce 50W into 8ohm.
They will produce just over 25W into 16ohm possibly 30W into 16r. It depends very much on the design of the PSU.

The PA100 will give 100W into 4r and 60W into 8r.

If you separate the amps the result is 50W + 50W into 8r

Generally a solid state amp does not come to any harm driving a higher value load. Many perform better, particularly in respect of distortion.
__________________
regards Andrew T.
  Reply With Quote
Old 7th March 2007, 06:43 AM   #3
CJ900RR is offline CJ900RR  Sweden
diyAudio Member
 
Join Date: Jan 2006
Quote:
Originally posted by AndrewT
Hi,
I found PA100 but not PA200.
The PA100 is a parallel pair of chipamps to power a 4ohm load to 100W.
Each amplifier thinks it is sending just sufficient current to power an 8ohm load. The amps are each designed to produce 50W into 8ohm.
They will produce just over 25W into 16ohm possibly 30W into 16r. It depends very much on the design of the PSU.

The PA100 will give 100W into 4r and 60W into 8r.

If you separate the amps the result is 50W + 50W into 8r

Generally a solid state amp does not come to any harm driving a higher value load. Many perform better, particularly in respect of distortion.
My bad, i meant PA100

So the result would be, in 4 ohm load:

Stereo-mode (2 X PA100) = 2 X 100W
Mono-mode (bridged PA100) = 1 X 200W

and for a 8 ohm load:

Stereo-mode (2 X PA100) = 2 X 60W
Mono-mode (bridged PA100) = 1 X 120W

Is that correct? Thanks
  Reply With Quote
Old 7th March 2007, 07:00 AM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
NO!

PA100 is parallel.

BR100 & BPA200 are bridged.
__________________
regards Andrew T.
  Reply With Quote
Old 7th March 2007, 07:10 AM   #5
CJ900RR is offline CJ900RR  Sweden
diyAudio Member
 
Join Date: Jan 2006
Quote:
Originally posted by AndrewT
NO!

PA100 is parallel.

BR100 & BPA200 are bridged.

Yes I know! Sorry its to early in the morning still. By mono-mode i mean 2 PA100-boards bridged using the DRV134, so they becomes a BPA.

I want to use 2 boards, PA100s for stereo-mode, and I want to be able to use my DRV134s to bridge those 2 PA100s into one BPA.

So, in stereo-mode, one PA100/channel it would give me 100W into 4 ohm and 60W into 8 ohm.

And in mono-mode, two PA100 bridged togheter using a DRV134, it would me 200W into 4 ohm, and 120W into 8 ohm?

Or am I totally lost?

Thanks again
  Reply With Quote
Old 7th March 2007, 09:05 AM   #6
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally posted by CJ900RR
...... By mono-mode i mean 2 PA100-boards bridged using the DRV134, so they becomes a BPA.

I want to use 2 boards, PA100s for stereo-mode, and I want to be able to use my DRV134s to bridge those 2 PA100s into one BPA.

So, in stereo-mode, one PA100/channel it would give me 100W into 4 ohm and 60W into 8 ohm.
you're OK up to here.
Quote:
And in mono-mode, two PA100 bridged togheter using a DRV134, it would me 200W into 4 ohm, and 120W into 8 ohm?

Or am I totally lost?
The rule for bridged is double the power into double the impedance.
The two mono channels, pa100, each give 100W into 4r and about 55W to 60W into 8r.
When these two PA100s (4 chipamps) are bridged they will give a mono channel of 200W into 8r and about 110W to 120W into 16r.

If you adjust the voltages as detailed in the BPA200 table it can produce the same powers but into the half value loads. i.e reduced voltage allows 200W into 4r and 110W to 120W into 8r.

Notice that in all these combinations no single chipamp is ever giving more than 50W. You can squeeze a little more, 60W to 70W, some even claim to get around 80W reliably, but at the risk of the protection systems cutting in.

Is all this worth the effort when you can get at least equal performance from a discrete amplifier. 100W from a chip may save some design effort but going to 4chips and massive smoothing requirements is, I believe, going too far.
Chipamps are attractive because they are simple, you are way beyond simple with these ambitions.
__________________
regards Andrew T.
  Reply With Quote
Old 7th March 2007, 10:46 AM   #7
CJ900RR is offline CJ900RR  Sweden
diyAudio Member
 
Join Date: Jan 2006
Quote:
Originally posted by AndrewT
The rule for bridged is double the power into double the impedance.
...
When these two PA100s (4 chipamps) are bridged they will give a mono channel of 200W into 8r and about 110W to 120W into 16r.
And when you say 8r and 16r its because the parallel configuration see's the 4r speaker as 8r (4r/chip) and a 8r speaker as 16r (8r/chip)?

Quote:
Originally posted by AndrewT
Is all this worth the effort when you can get at least equal performance from a discrete amplifier. 100W from a chip may save some design effort but going to 4chips and massive smoothing requirements is, I believe, going too far.
Chipamps are attractive because they are simple, you are way beyond simple with these ambitions.

Maybee its me who has got it all wrong from the beginning. I have allways belived that, for a single chip, if you got say 50W in 8 ohm, you'll end up whit 100W in 4 ohm. And I thought that rule applied to the bridge mode. I have never tryed parallel mode before but i guess I have to do some more reading
  Reply With Quote
Old 7th March 2007, 11:08 AM   #8
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
I'm glad folk know me as patient.

A normal amplifer operates as a constant voltage source.
It's a bit like us, when you ask it to do much it starts to sweat and then gives up.

A perfect constant voltage source will put out constant voltage into any resistance you tack on as a load.

Take 20Vrms as the output and apply it to an 8r0 load, the power delivered is 50W.
Change the load to 16r and you get 25W, 4r0 and it's 100W 2r0 and it's 200W.

But no amplifier behaves as a constant voltage source into all loads.

A chipamp is usually designed to get near maximum power into a selected load value. say 50W into 8r0. that requires 20Vac and Ipk=3.536Apk.
Apply a 16r load and the voltage will probably rise above 21Vac and may rise as high as 23Vac.
In a similar vein applying a lower value load will pull the output voltage down. Let's assume 16Vac into 4r0. that is equivalent to 64W, but the peak current is now up to 5.657Apk. This makes the amplifer heat up. If the power supply were stiffer and the amplifier tried to deliver 18Vac into that 4r0 load then maximum power is now 81W and peak current is now 6.364Apk. Either the amplifier has gone into protection mode or blown up.

To avoid that you can parallel amplifiers to reduce the current delivered from each amplifier and that reduces the heat dissipated in the single chip devices. Equals increased reliability.
In a discrete amp the same is achieved by adding extra output transistors.

Bridged is a completely different animal.
Here's that rule again, it's absolute in any well designed bridged amplifier.
double the power into DOUBLE the impedance.

If you don't double the impedance you will increase the chip dissipation to way beyond anything it can manage.

I, and many others, have said this before. A pair of 50W + 50W into 4r0 amplifiers when bridged will deliver 100W into 8r.
__________________
regards Andrew T.
  Reply With Quote
Old 7th March 2007, 02:48 PM   #9
CJ900RR is offline CJ900RR  Sweden
diyAudio Member
 
Join Date: Jan 2006
Im sorry if I have pushed your patients to its limit. I dont know from where I got that crazy idea that made me belive that this site where made to help beginners like me by asking questions to people who has the answers

Anyway. Your help is truly appreciated and I would like to thank you for the time you have spend (wasted?) on me. Your last post where really helpfull.

Best regards...
  Reply With Quote
Old 7th March 2007, 04:44 PM   #10
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
only too glad to help.
Sometimes simply answering the question does not fully explain the reasons, that being why some of my answers become long winded.

In this case back to basics seems to have done the job.
__________________
regards Andrew T.
  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
Power load, dummy load (pic) luka Power Supplies 43 9th February 2012 02:50 PM
Dynamic load line analysis using music and speaker load Michael Koster Tubes / Valves 0 7th March 2008 08:47 PM
Lm3886 Pa200 mrquality Chip Amps 0 26th June 2007 04:36 PM
2 x 90w rms @ 8ohm help please djronbxs Solid State 1 1st March 2007 04:47 AM
Halving OPT's pri.imp. by connecting 8ohm load to 16ohm tap - Good/Bad? argo Tubes / Valves 16 23rd May 2005 04:33 PM


New To Site? Need Help?

All times are GMT. The time now is 05:37 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2