F5 Turbo Circuit Boards - Page 102 - 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 12th March 2012, 02:06 PM   #1011
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
In case i talk mystery game again.

Easy way out for high rail versions would be to scale the feedback resistor rating for peak output level.
But in the case of a V3, that would lead to unpractical resistor sizes, or TO-220 types with heatsinks.

Resistor rating is the continuous power they handle, for short periods they can cope with a multitude of that.
(e.g., short term overload for a wirewound can be five to ten times higher, for up to a 5 second period)
The resistors are heated by an average continuous load, on top of which come peak impulses.
If the resistor rating is sized to max continuous level, one would have to check if the specific ohmic value can handle the occasional peak voltage burst, in the heated condition, requires a datasheet.
(idle dissipation of the 10R is negligible, of course)
__________________
The buck stops Here
  Reply With Quote
Old 12th March 2012, 02:16 PM   #1012
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by AndrewT View Post
.................
Do the sums.
eg
Max V Output ~ 40Vpk (100W into 8r0 or 200W into 4r0 per half channel).
total voltage across 10r + 220//220 = 40Vpk
Ipk ~333mApk

10r resistor instantaneous peak dissipation ~ .333^2 * 10r = 1.1Wpk.............
Quote:
Originally Posted by jacco vermeulen View Post
...........idle dissipation of the 10R is negligible.........
1.1W instantaneous peak is not negligible, even for a big F5turbo.

Even more so when we are considering resistance stability of the NFB circuit.
__________________
regards Andrew T.
  Reply With Quote
Old 13th March 2012, 01:04 AM   #1013
a.wayne is offline a.wayne  United States
Sin Bin
 
Join Date: May 2008
Location: Front Row Center
So where are we with this ... 2 /3/5/ watter ...?
  Reply With Quote
Old 13th March 2012, 07:30 AM   #1014
diyAudio Member
 
Join Date: Jan 2010
Location: Harrow, UK
I'm changing the resistor pattern to accomodate the same resistor pad patterns as the other power resistors.
  Reply With Quote
Old 13th March 2012, 11:17 AM   #1015
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by a.wayne View Post
So where are we with this ... 2 /3/5/ watter ...?
do the sums for your amplifier.
__________________
regards Andrew T.
  Reply With Quote
Old 13th March 2012, 02:07 PM   #1016
diyAudio Member
 
Join Date: Jan 2010
Location: Harrow, UK
Quote:
Originally Posted by AndrewT View Post
do the sums for your amplifier.
Andrew,

If the constant dissipation at 100W is 1.1W then would you agree that a 'safe' rule of thumb would be 1% of output power x2 for overhead or is the relationship non-linear?

If it is then;

1W for 50W
2W for 100W
3W for 150W etc etc.......

Andy
  Reply With Quote
Old 13th March 2012, 02:16 PM   #1017
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
No.
For 40Vpk output signal, the maximum instantaneous peak dissipation is 1.1W

To get 40Vpk from an F5T you would need supply rails ~+-45Vdc.
That single amp would be capable of 100W into 8r0 and 200W into 4r0.

If you bridge a pair to make a balanced F5T then you are in the 400W into 8r0 power range.

You must do the sums for your supply rails. Post1004 shows that a bit of multiplying and dividing gets the answers you need.
__________________
regards Andrew T.
  Reply With Quote
Old 13th March 2012, 02:23 PM   #1018
diyAudio Member
 
Join Date: Jan 2010
Location: Harrow, UK
Quote:
Originally Posted by AndrewT View Post
No.
For 40Vpk output signal, the maximum instantaneous peak dissipation is 1.1W

To get 40Vpk from an F5T you would need supply rails ~+-45Vdc.
That single amp would be capable of 100W into 8r0 and 200W into 4r0.

If you bridge a pair to make a balanced F5T then you are in the 400W into 8r0 power range.

You must do the sums for your supply rails. Post1004 shows that a bit of multiplying and dividing gets the answers you need.

Andrew,

thanks.
I've just gone back to 1004 and I understand.

I was working on the assumption that running in class A and having a set level of NFB (always the same proportion) would make the relationship a linear one.

Andy
  Reply With Quote
Old 13th March 2012, 02:52 PM   #1019
diyAudio Member
 
Join Date: Jan 2010
Location: Harrow, UK
OK,

Using the formulae resistor dissipation would be as follows;

Pk Voltage Calculated Value Value to use

25V 0.433W 1W
30V 0.625W 1W
35V 0.853W 2W
40V 1.11W 2W
45V 1.41W 3W
50V 1.74W 3W
55V 2.1W 4W
60V 2.5W 5W

Last edited by UKToecutter; 13th March 2012 at 02:55 PM. Reason: data missed
  Reply With Quote
Old 13th March 2012, 03:05 PM   #1020
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
That seems like a reasonable table of values to minimise the resistance variation due to temperature induced effects when very high transient signals pass through.
A normal F5 runs on +-25Vdc supply rails so the table could be completed by adding in a 20Vpk output and using a 600mW resistor. We are back to the original now.
__________________
regards Andrew T.
  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
F5 clone boards (inc PSU boards) Tazzz Swap Meet 39 7th June 2014 07:02 AM
F5 Turbo is posted Nelson Pass Pass Labs 635 6th April 2014 10:51 AM
F5 turbo problems Rob Dingen Pass Labs 17 11th January 2013 08:38 PM
F5 Turbo ............. if only !!!!!! a.wayne Pass Labs 23 21st January 2012 02:24 AM
UGS Boards and F5 boards DUC985 Swap Meet 0 7th January 2009 07:21 PM


New To Site? Need Help?

All times are GMT. The time now is 06:30 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