Aleph 2 ac current setting ? - diyAudio
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 9th May 2007, 03:06 PM   #1
diyAudio Member
 
Join Date: Apr 2002
Location: Lille (France)
Default Aleph 2 ac current setting ?

Well, after 2 years of service I have decided to adjust R19 and R21 to be sure to have the best of my babies (especially now that I have 2 brand new DIY speakers that really deserve it (JP3 ribbon tweeter with audiotechnology 18H52 and audiotechnology 10C102 : a sarastro like speaker ! ))

What I found is that I had only 2.3 as bias value. And this is a maximum value I think as the heatsinks temperature is about 60°C (despite the fact that my heatsinks are huge, but...).
The DC after the filter is 44.7V.
My speaker are 4 ohms. And I think they are something like 89db.
What current gain should I choose then ? I know nelson recommand 50%, but then with my low bias and according to the well known excel file for calculating power, the power at 8 ohms is 84.6 W and at 4 ohms it is only 42.3 W !
At 70% I would have 105,1 W at 8 ohms and 117,6 W at 4 ohms
At 60%, 105 W 8 R; 66 W 4 R

I don't know what to choose on the paper, as a starting point. Do you have any idea on the side effects of setting the AC current gain as high as 70% ??
  Reply With Quote
Old 9th May 2007, 04:39 PM   #2
Manu is offline Manu  Europe
diyAudio Member
 
Manu's Avatar
 
Join Date: Nov 2002
Location: Vienna, Ostrich
http://www.diyaudio.com/forums/showt...053#post107053

Cordialement
Manuel
  Reply With Quote
Old 9th May 2007, 07:01 PM   #3
diyAudio Member
 
wuffwaff's Avatar
 
Join Date: Aug 2001
Location: Ingolstadt Germany
Hi,

I wouldn´t go higher than 60-65%. Just try as it´s an easy adjustment.
I´ve put some sockets in the resistor holes so I can swap ac-current-gain resistors very fast. This way you can listen for what you like best.
It really depends on the load what sounds best.

The other (more expensive) option would be to lower the supply voltage as it is a bit too high for the bias your running. 35V would be more than enough in your case.

William
__________________
een ooievaar is geen konijn want zijn oren zijn te klein!
  Reply With Quote
Old 9th May 2007, 07:22 PM   #4
diyAudio Member
 
Join Date: Feb 2001
Location: Columbia, SC
If I'm understanding the question correctly, I think the better solution would be to increase the overall bias rather than monkey with the ratio of the current source.

Grey
  Reply With Quote
Old 9th May 2007, 07:28 PM   #5
diyAudio Member
 
Join Date: Apr 2002
Location: Lille (France)
But to increase the bias, I would need to increase the heatsinks....This is complex as the one I am using are allready big (not big enough though...)
  Reply With Quote
Old 9th May 2007, 08:48 PM   #6
diyAudio Member
 
Join Date: Feb 2001
Location: Columbia, SC
There's no such thing as a free lunch.
If you want a class A amp, you're going to bump into the heat problem sooner or later.
Try fans.
I went water cooled. Cheap. Effective. Quiet.

Grey
  Reply With Quote
Old 9th May 2007, 09:35 PM   #7
diyAudio Member
 
Join Date: Apr 2002
Location: Lille (France)
I was also thinking about water cooling.
What solution did you use ? do you have any website where I could see what it looks like and the way you implement it ?
  Reply With Quote
Old 9th May 2007, 09:43 PM   #8
diyAudio Member
 
Join Date: Apr 2002
Location: Lille (France)
I will make a search tomorrow : from what I have seen you have built your own system with an old pump you had. I will have to study this...
  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
biasing or quescient current setting djronbxs Solid State 4 11th August 2006 11:38 PM
need help setting bias current... SkinnyBoy Solid State 10 6th May 2005 12:17 AM
sam's 300W or eti-466 :setting quiescent current bigpanda Solid State 6 20th April 2005 07:32 AM
having trouble setting quiesent current? tinkerbell Solid State 35 11th April 2005 11:34 PM
Setting bias current of Aleph 5 billy Pass Labs 1 8th August 2002 04:16 AM


New To Site? Need Help?

All times are GMT. The time now is 09:30 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