Go Back   Home > Forums > Amplifiers > Pass Labs

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
Reply
 
Thread Tools Search this Thread
Old 15th February 2006, 08:07 PM   #1
diyAudio Member
 
Join Date: Jan 2002
Location: Cleveland ohio
Default Does a really big PS in an Aleph 30 help drive low impendence loads?

I just finished an Aleph 30. Because I had at hand two Signal 28v by 12a transformers, I used them in the power supply. Since the transformers’ voltages were so high, I implemented a choke input filter which bucks the voltage down to 26.5v rails under load of the Aleph 30. The inductors are 2.5 mh followed by 400,000uf of capacitance.

I took the amp over to a friend’s house and connected it to four pairs of 1970’s vintage (and refurbished) Advent two way speakers. These were the large speakers. To my delight, the Aleph 30 drove all eight speakers effortlessly and to concert hall levels in the small living room. The Aleph 30 was driven by a Norm Tracy X-DAC whose AD811 output buffers were set to a gain of 5. Four speakers were connected in parallel to each channel.

I note that the 60 watt Mcintosh amp which my friend had been using on these speakers was not nearly up to the task…no volume, distortion, out of control speaker cones and thermal cutoff after 15 minutes.


I am wondering if the larger than necessary power supply helped in the driving of four pairs of speakers. Would I have gotten the same results if the power supply was only just adequate to power the Aleph 30?


Thanx Nelson for giving us the plans, what an amp!!
  Reply With Quote
Old 15th February 2006, 08:19 PM   #2
tja is offline tja  Netherlands
diyAudio Member
 
Join Date: Feb 2004
Location: Leiden
I don't know what impedance these speakers have, but wouldn't it have been better to parallel two series pairs per channel?

Take
  Reply With Quote
Old 15th February 2006, 08:53 PM   #3
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Both of those approaches will improve the performance,
the caveat being that as you parallel lots of outputs, the
character of the amp shifts a bit of emphasis to the bottom
from the upper mid and top.
  Reply With Quote
Old 15th February 2006, 09:20 PM   #4
diyAudio Member
 
Join Date: Jan 2002
Location: Cleveland ohio
thanx for your replies...

but did the large power supply help drive these loads? or do I have a lot of excess power supply capacity.
  Reply With Quote
Old 15th February 2006, 10:18 PM   #5
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Quote:
Originally posted by audionut
thanx for your replies...

but did the large power supply help drive these loads? or do I have a lot of excess power supply capacity.

when you do something like this to your amp-there is no "excess power supply capacity".

answer is pretty obvious,or you just like to boast ?

__________________
my Papa is smarter than your Nelson !
tnx to clean thread ; Cook Book ; PSM LS Cook Book ; Baby Diyaudio FORUM ; Mighty ZM's Bloggg;I'm dumb
  Reply With Quote
Old 15th February 2006, 10:38 PM   #6
diyAudio Member
 
Stuart Easson's Avatar
 
Join Date: Oct 2002
Location: Santa Cruz, CA
Send a message via MSN to Stuart Easson Send a message via Yahoo to Stuart Easson
Default excess?

Audionut,

You have excess power supply capacity for sure, the nature of these amps is to naturally limit the maximum output current, hence they can't trivially be damaged by driving very low impedance loads, they just don't double up their output power as the load impedance halves. For sane speaker loads this is not a problem, and makes the amps more or less bulletproof.

If you wanted to be able to use more of your huge current reserve you'd need to 'tune' your amps differently. This could be achieved, as previously mentioned, by paralleling more output FETs and then adjusting the idle current and perhaps the AC gain. Of course even bigger heatsinks are then necessary...or perhaps fans...

You don't mention if your amp was already overbuilt, but if you already have large numbers of output FETs on a massive heatsink, you may not need to do more than increase the idle current and AC gain.

HTH

Stuart
  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
How can LM1875 drive loads lesser than 4ohm? goldyrathore Chip Amps 11 15th April 2009 02:49 PM
Can Aleph 3 drive 15" 97dB woofer? Sony Pass Labs 4 15th January 2008 06:23 PM
Choke Loads for Zen/Aleph Amps Kashmire Pass Labs 137 13th October 2007 11:16 PM
Best amp for hard loads - Aleph 0 or X350? Sony Pass Labs 6 25th October 2005 06:06 PM
About the wire impendence audioart Solid State 2 10th February 2004 12:44 PM


New To Site? Need Help?

All times are GMT. The time now is 08:31 PM.


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