Scaling the Aleph-X
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Pass Labs This forum is dedicated to Pass Labs discussion.

 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
jwb
diyAudio Member

Join Date: Mar 2002
Location: San Francisco, USA
The short explanation is this: the amplifier's power is limited by two curves: Irms^2*R and Vrms^2/R. If you plot these two curves, the amplifier must be operating in the area under the curves. Where the curves intersect is the maximum power.

Here is the plot for my Aleph-X amps with 14V rails and 1.54A idle current per side. The blue line is the current limit, the red line is the voltage limit. If you can replicate this plot, you will have a good understanding of amplifier power and load impedance.

PS: I consider this a 40W amplifier.
Attached Images
 aleph-x-power.png (2.1 KB, 583 views)

 9th January 2004, 04:31 PM #12 Zapped diyAudio Member   Join Date: Jul 2002 Location: Seattle Thanks to panelhead and to jwb for the explanations. It is a tough row to hoe, but some of this stuff is beginning to make sense to me! As Harry Connick, Jr. (and maybe Bobby Darin before him) sang: "I'm beginning to see the light". From jwb's graph I infer that any given amp/setting has a well defined operating area, if that's what you call it. Panelheads arithmetic leads me to conclude that amps designed to stay tough into low impedances must have prodigious bias current (current capability?). I am reminded of a statement that Nelson made in the A-75 article, something like: 'we know that about a hundred of you will write in and ask how to bias the amplifier for class A in 1 ohm'. Larry Wright Seattle area
diyAudio Member

Join Date: Dec 2002
Location: Houston
Quote:
 Originally posted by Zapped Thanks to panelhead and to jwb for the explanations. It is a tough row to hoe, but some of this stuff is beginning to make sense to me! As Harry Connick, Jr. (and maybe Bobby Darin before him) sang: "I'm beginning to see the light". From jwb's graph I infer that any given amp/setting has a well defined operating area, if that's what you call it. Panelheads arithmetic leads me to conclude that amps designed to stay tough into low impedances must have prodigious bias current (current capability?). I am reminded of a statement that Nelson made in the A-75 article, something like: 'we know that about a hundred of you will write in and ask how to bias the amplifier for class A in 1 ohm'. Larry Wright Seattle area

There is an even bigger issue here also. A 4 ohm rated speaker usually has the impedance vary from 2.8 ohms to 20 ohms or so across the audio spectrum.
Plugging all those real impedances into the equations make the math worse than my confusing examples.

George

 9th January 2004, 05:27 PM #14 Zapped diyAudio Member   Join Date: Jul 2002 Location: Seattle For me, its easier. I have one set of Maggie MG II-A's with 6 ohm purely resistive impedance, and one set of Maggie MG-12's, with 4 ohm purely resistive impedance. So your equations have made things much easier for me to figure out which way to go. ( Both systems are bi-amped with a subwoofer, so power in the deep base regions is not a big issue either. ) Larry Wright Seattle area
 9th January 2004, 06:10 PM #15 Nelson Pass   The one and only     Join Date: Mar 2001 In many systems, the lowest impedances are found in areas where the audio power is likely to be quite low, for example below 20 Hz and above 10 KHz, and so this is not usually a real problem.
 10th January 2004, 02:03 PM #16 AudioAngel   diyAudio Member   Join Date: Dec 2003 Location: Small City in North Germany Ok, thank you all for your help. Now I'll try to make a schematic. AudioAngel

 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 Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Aussie Amplifiers         CSS         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post AudioAngel Pass Labs 3 29th December 2006 09:59 AM Harderror Full Range 2 2nd May 2006 08:03 PM dantwomey Pass Labs 7 8th November 2003 12:08 PM

 New To Site? Need Help?

All times are GMT. The time now is 09:24 PM.