High-rails Passlabs amplifier design ? - Page 2 - 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 22nd April 2009, 05:24 PM   #11
diyAudio Member
 
Join Date: Jan 2002
Location: Tyrone Ga. U.S.A.
Chokes seem like a good idea till you figure in the cost of a pair
of sutiable chokes.
  Reply With Quote
Old 22nd April 2009, 08:29 PM   #12
Magura is offline Magura  Denmark
diyAudio Member
 
Magura's Avatar
 
Join Date: Oct 2003
Location: Denmark, Viborg
Quote:
Originally posted by flg
I think an L input filter will give you .9 Vrms and 1.41 Irms
Wiki Who?

Please explain.


I've used this trick before.....I have even had this working against me once, I had forgotten about a removed cap.


Magura


EDIT: I have not read that particular Wiki page, so if it's dodgy, don't look at me
__________________
Everything is possible....to do the impossible just takes a little while longer.
www.class-a-labs.com
  Reply With Quote
Old 22nd April 2009, 08:30 PM   #13
Magura is offline Magura  Denmark
diyAudio Member
 
Magura's Avatar
 
Join Date: Oct 2003
Location: Denmark, Viborg
Quote:
Originally posted by woody
Chokes seem like a good idea till you figure in the cost of a pair
of sutiable chokes.

That's not so bad these days.

If you're on a low budget, wind your own.


Magura
__________________
Everything is possible....to do the impossible just takes a little while longer.
www.class-a-labs.com
  Reply With Quote
Old 22nd April 2009, 09:09 PM   #14
Bønna is offline Bønna  Norway
diyAudio Member
 
Join Date: Mar 2009
I was also wondering about the cost of such a choke.

However a very interesting and useful tip that will be tested Magura ! Thanks !

Regards,
Bjørn
  Reply With Quote
Old 23rd April 2009, 02:15 AM   #15
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East

I might be a little off on the I suggestion
Attached Files
File Type: pdf xfrmr supply topologies.pdf (37.9 KB, 56 views)
__________________
"It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.
  Reply With Quote
Old 23rd April 2009, 08:02 AM   #16
Bønna is offline Bønna  Norway
diyAudio Member
 
Join Date: Mar 2009
Thanks flg !

These figures explains the topologies well.

It seems to me that all the choke topologies that gives a substantial reduction in Vdc utilises the centre tap of the transformer.

My trannie is 55-0-55 (0 on the centre tap).

My quick conclusion is that only the full bridge choke topologies (0,9xVac) will be of any use. Does it sound correct ?

Regards,
Bjørn
  Reply With Quote
Old 23rd April 2009, 12:38 PM   #17
john65b is offline john65b  United States
diyAudio Member
 
john65b's Avatar
 
Join Date: Jan 2005
Location: Chicago
I have successfully utilized a choke input on a tube amp. I am considering it on a SS amp for the exact same reasons as the poster.

Putting a small cap (.01uf to 3uf) in front of the choke will vary to output voltage from .9vac to 1.4vac. I know this is not what you are seeking, but its cool to be able to "dial in" a required voltage with a cap on a choke input filter. Use PSUdesigner to check your design.

Is there a way to physically check your output voltage rails on a choke input without having the amp board connected? I know the Lcrit current is key here.

A load resistor of value X and wattage Y would be what I am requesting to test a desired +/-35VDC rails @ 6A Choke input power supply??
__________________
All right, but apart from the sanitation, medicine, education, wine, public order, irrigation, roads, the fresh water system and public health, what have the Romans ever done for us? Life of Brian
  Reply With Quote
Old 24th April 2009, 10:05 AM   #18
Bønna is offline Bønna  Norway
diyAudio Member
 
Join Date: Mar 2009
Hi John65b !

Isnt it a matter just applying ohms law ?

R=V/I=35V/6A=5,83ohm so you should look for a 5,6 or safer 6,8 ohm resistor from each rail to ground.

of wattage: P=V x I=35VX6A= 210W i.e. 250W

This will be a maxiumum load test of the supply, and for prolonged testing a more relaxed (higher) value of R must be chosen.

Please take reservation for my possible misunderstanding of your specs.

NB! Dont forget to attach your dummy load resistors to a big piece of aluminium, if testing for a long duration.
  Reply With Quote
Old 24th April 2009, 10:35 AM   #19
diyAudio Member
 
Join Date: Apr 2007
Bonna,
You have 6 transformers. You could parallel a couple of them to increase the current capacity. This is not a common practice but should work O.K. You could make several combinations from the 6 units or use one per channel.
Tad
  Reply With Quote
Old 24th April 2009, 12:55 PM   #20
john65b is offline john65b  United States
diyAudio Member
 
john65b's Avatar
 
Join Date: Jan 2005
Location: Chicago
Bonna,

Maybe I left out a little more info in my post -

I was wanting to ask if that test load resistor needs to be designed with respect to Critical Inductance, and not the 6A. The 6A was just the amp rating of the tranny. The amp draw of the eventual amp should be quite a bit less than the 6A...maybe half? I really don't know which amp it will be going into yet (but will be high current Class A)

From what I understand, the LC PS needs a minimum current that the at all times, or all hell supposedly breaks loose - really don't know what exactly happens - the choke starts to smoke, or the PS sees the choke as a short and your back to a C filter and the 1.414*Vac outputs.

Anyway, the bleeder resistor is supposed to flow this minimal current, and drain the cap at shut down.

So my question should have been, what minimum load resistor is required be to test a LC input PS, as I don't have a 250W resistor anywhere...?


BTW -

Lcrit = Vdc / Ima

where Lcrit is the minimum (critical) choke inductance, Vdc is the supply DC output voltage (35VDC), and Ima is the load current in milliamperes (guessing 3A).

So in operation:

Lcrit=35/3000=.0166mh, and I will be doing at least a 2mh choke, so for 3A draw, Lcrit is not an issue.
__________________
All right, but apart from the sanitation, medicine, education, wine, public order, irrigation, roads, the fresh water system and public health, what have the Romans ever done for us? Life of Brian
  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
Help with amplifier design (high quality) CrazyChipMan Solid State 20 10th July 2012 07:25 PM
Does anyone know a bridged design for 12v rails? mpmarino Solid State 3 16th June 2007 11:37 AM
6BY5 High Voltage & High Current Choke Input Design P.S. snoopyma Tubes / Valves 7 28th June 2006 01:32 PM
Active lowpass filter + high rails Firebug24k Solid State 4 19th September 2004 07:47 PM
Suggestions for high efficiency high SPL kit/design Kanga Multi-Way 50 23rd May 2003 12:52 AM


New To Site? Need Help?

All times are GMT. The time now is 03:35 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