Aleph-X builder's thread. - Page 5 - 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 21st February 2004, 04:35 PM   #41
diyAudio Member
 
Join Date: Sep 2001
Location: Salt Lake City
Yea, I was waiting for someone to recognize my idea above..... I work with alot of 3 phase rectifiers in the Motion Picture industry, some capable of 400 amps continous @ less that 5% ripple. Ripple is alot easier to deal with and inductors are physically much smaller to boot. Unfortunately not too many homes have 3 phase capabilities in them.

Lets see 400 amps at 30 volt rails....that would be one hell of a huge X amp and could probably drive loads as lows as .1 ohm at full power! I think the heat exchanger would be a tad bit larger than what you were thinking of though.......

Mark
  Reply With Quote
Old 21st February 2004, 07:08 PM   #42
diyAudio Member
 
Join Date: Sep 2001
Location: Salt Lake City
Update on the biasing resistors...
Out of 10 .25 ohm Dale 1%ers I got 8 that were .23 ohms, two @ .24 ohm. Needless to say I used the all of .23's as the stock design calls for .22 ohms. Unfortunately I saw CheffDeGaars posting after I had already ordered the components...but what the heck...I'm only building this one channel for now to understand how it all works... Now on to FET matching... then hook up the supply and see what I get.......

Mark
  Reply With Quote
Old 21st February 2004, 07:11 PM   #43
yoke is offline yoke  Croatia
diyAudio Member
 
yoke's Avatar
 
Join Date: Jan 2004
Location: Split
Default nead help, how to macth resistors

Hi all...
I need help how to match this low value resistors...I have 0.5 Ohm mills resistors and I try to match them but the curent and voltage drop was to little to measure...
I have regulated 30V 940mA from my printer power supply...I've got two multimiters, one fluke 87III and other some cheap no name , but it's working...will this work...
Any suggestion how to mach them???
How do you mach this small value resistors???

Thanks
Josip
  Reply With Quote
Old 21st February 2004, 08:25 PM   #44
diyAudio Member
 
Brian Donaldson's Avatar
 
Join Date: Jan 2003
Location: Texas, Love it or leave it
We may not have 3 phase, but most car altinators can put out 100 amps and up. the voltage is regulated by the feild current x rpm. I think a 3 hp electric motor turning a altinator 4000 rpm could get you +- 30 volt rails at 30 amps at 800 hz or so. wouldn't take much capacitance to smooth that out nicely. And it would be cheaper than 2 toriods(or about the same price)
  Reply With Quote
Old 22nd February 2004, 02:12 AM   #45
diyAudio Member
 
Join Date: Jan 2004
Location: hk
Default power of ax

would anyone please inform me the relationship
of supply voltage, no of pairs of output mosfet, idle current
speaker impendance
thanks
  Reply With Quote
Old 22nd February 2004, 05:16 AM   #46
diyAudio Member
 
Brian Donaldson's Avatar
 
Join Date: Jan 2003
Location: Texas, Love it or leave it
Let me try to run the numbers in an understandable fashion.

Lets say you want 64W RMS. That's 128 watts peak. For 8 ohms, that's Sqr(128/8) = 4 Amps , at 8 ohms, thats 32 volts.

The AX is a bridged amp, so each half needs to swing +- 16 volts at 4 amps.

Giving 4 volts to be lost in the current source at maximum swing, that means 20 volt rails, each side biased at around 3 amps. The Aleph current source will peak 4.5A at 50% gain (this is the part where I'm a little unsure about the math) Every one says more bias sound better. If your speakers dip below 8 ohms, bias to their minimum impedance at minimum.

So you have 4 banks of output devices burning 60W each. You should try to keep dissapation per device around 25 watts each to be safe. 2 devices per bank is 30W each ( a little close to the edge if your sinks aren't large enough, but should work ) or 3 devices at 20W each.

Refigure your source resistors so they drop .5V +- for the current in each fet. At 2 devices, 1.5A each is .33 ohm, at 3 devices, 1A each, .5 ohm. You may also need to adjust the current source for the diff pair so you don't burn the zener.

Going through these steps will give you a better understanding of the relations than plugging numbers into the spredsheet thats somewhere else in the forum.

All corrections are welcomed.
  Reply With Quote
Old 22nd February 2004, 06:14 AM   #47
Raka is offline Raka  Europe
diyAudio Member
 
Raka's Avatar
 
Join Date: Aug 2002
Location: Close to Oistrakh
Default Re: power of ax

Quote:
Originally posted by andrew li
would anyone please inform me the relationship
of supply voltage, no of pairs of output mosfet, idle current
speaker impendance
thanks

You haven't been to the wiki page, have you? There is a NICE excel sheet with all you need.
__________________
What is beyond the speaker?
  Reply With Quote
Old 22nd February 2004, 06:44 AM   #48
diyAudio Moderator Emeritus
 
roddyama's Avatar
 
Join Date: Jan 2002
Location: Michigan
To those getting their new AX boards or if your finally going to use the boards from last years sale, if you need parts, read on.

If you're a Cardas fan, the 2nd annual Cardas bulk purchase is well under way. If you're interested see this thread in the trading Post Forum and the WIKI Page for details.

I have started to send order confirmation emails to those that already placed their orders. I haven't processed them all yet but yours is coming soon.

I will be accepting requests for the price list up until Wednesday, the 25th at 12 midnight EST.

PS: I will delete this post after Wednesday.
__________________
Rodd Yamashita
  Reply With Quote
Old 22nd February 2004, 08:26 AM   #49
yoke is offline yoke  Croatia
diyAudio Member
 
yoke's Avatar
 
Join Date: Jan 2004
Location: Split
Default Re: nead help, how to macth resistors

Quote:
Originally posted by yoke
Hi all...
I need help how to match this low value resistors...I have 0.5 Ohm mills resistors and I try to match them but the curent and voltage drop was to little to measure...
I have regulated 30V 940mA from my printer power supply...I've got two multimiters, one fluke 87III and other some cheap no name , but it's working...will this work...
Any suggestion how to mach them???
How do you mach this small value resistors???

Thanks
Josip

any one???
  Reply With Quote
Old 22nd February 2004, 08:54 AM   #50
diyAudio Member
 
CheffDeGaar's Avatar
 
Join Date: Feb 2003
Location: This Universe, I think
Default Re: nead help, how to macth resistors

Quote:
Originally posted by yoke
Hi all...
I need help how to match this low value resistors...I have 0.5 Ohm mills resistors and I try to match them but the curent and voltage drop was to little to measure...
I have regulated 30V 940mA from my printer power supply...I've got two multimiters, one fluke 87III and other some cheap no name , but it's working...will this work...
Any suggestion how to mach them???
How do you mach this small value resistors???

Thanks
Josip
Just a silly idea I get . Not tested it, but may be worth a try Just take an opamp, preferably a fet input one, and make a non inverting amp just like the schematic attached. Hook the right supply and a AF generator, around 200Hz in frequency. Amplitude's up to you. Connect a DMM in AC voltage mode at output. Make sure the output amplitude of the generator is stable and don't touch it anymore Most of DMMs have a sufficient bandwidth in AC measurements to provide good reading at 200Hz. Just change your resistors, and note the output voltage value. Same resistors will give same readings... The feedback R on the schematic gives a voltage gain of 21 for a 0.5R "unknown" resistor. Just change it to suit your needs and your DMM sensivity.

Should work with a DC source, but the stability of supply and components should affect the readings.

Too silly to be good, but who knows...
May be this helps
Attached Images
File Type: gif image2.gif (2.8 KB, 5577 views)
__________________
/Cheff - Falling feels like flying, until you hit the ground
  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



New To Site? Need Help?

All times are GMT. The time now is 09:19 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