F5 power amplifier - Page 1023 - 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 1st February 2011, 10:20 PM   #10221
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
Quote:
Originally Posted by Nevohteeb View Post

Hmm, actually, I was first thinking about taking a 4U 400mm.
each heatsink on the 400mm design is made from two pieces, and best avoided

from what I can see the price difference between 4U and 5U in 300mm is only 30EUR
I would definately choose 5U, no doubt about it
5U is the one you want, and need

actually, prices on 4U/400mm and 5U/300mm are exactly the same, so I dont understand your argument
no question about it, heatsinks are not where you want to save money

if only the 400mm had properly designed heatsinks
  Reply With Quote
Old 1st February 2011, 10:51 PM   #10222
ramallo is offline ramallo  Europe
diyAudio Member
 
ramallo's Avatar
 
Join Date: Nov 2004
Location: Madrid
Send a message via Skype™ to ramallo
Quote:
Originally Posted by Nevohteeb View Post
Hi everyone,

I plan to finalyse my BoM and then purchase the last little things I need.
Nevertheless, I have 2 questions about 1) the transformer 2) the case.
  1. according to several threads on several forums I read, it seems that a 400VA instead of a 300VA would be better. Is that true?
  2. I plan to buy either a HiFi2000 4U 300mm or a 4U 400mm. According to the attached file, a 4U 300mm should be ok, but isn't it a little bit too tight?
Thank you very much in advance.
I'm using the 4U 300mm chassis and is perfect for the amp, enough dissipation for the Madrid summer.

3U is too small
  Reply With Quote
Old 2nd February 2011, 12:37 AM   #10223
lhquam is offline lhquam  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
Default Adjust R15/R16 for better thermal stability?

Does anybody know if the F5 bias thermal stability can be improved by adjusting the values of R15 and R16 which are in series with the thermistors.
  Reply With Quote
Old 2nd February 2011, 02:52 AM   #10224
ichiban is offline ichiban  United States
space charged
diyAudio Member
 
ichiban's Avatar
 
Join Date: Oct 2004
Location: Tonawanda
Quote:
Originally Posted by nigelwright7557 View Post
Just make sure the trafo bolt does touch the top of the chassis as well or you will have a shorted turn.
__________________

  Reply With Quote
Old 2nd February 2011, 08:18 AM   #10225
diyAudio Member
 
Join Date: Jan 2010
What should be changed in F5 schematics , that I could replace irfp240, irfp9240 to 2sk1530,2sj201
  Reply With Quote
Old 2nd February 2011, 08:36 AM   #10226
diyAudio Member
 
Join Date: Mar 2010
Location: Lille
Quote:
Originally Posted by tinitus View Post
from what I can see the price difference between 4U and 5U in 300mm is only 30EUR
I would definately choose 5U, no doubt about it 5U is the one you want, and need

actually, prices on 4U/400mm and 5U/300mm are exactly the same, so I dont understand your argument
no question about it, heatsinks are not where you want to save money

if only the 400mm had properly designed heatsinks
Hello,

first of all, my mistake, I did not use the proper word. By "tight", I wasn't talking about the dimensions of the case, but I was talking about its power dissipation capacity.

Here is the website I will order the case. I can see :
  • 4U 300mm = 119,50 (0.31 /W and 165W Max total power dissipation for 2xTO3-P transistors on each sink)
  • 4U 400mm = 154,00 (0.23 /W and 175W Max total power dissipation for 2xTO3-P transistors on each sink)
  • I don't see any 5U 300mm on that shop, and the cheapest 5U is 200.
So, according to this shop, the difference between those cases is not unimportant, specially about a 5U.
Moreover, it seems that the 4U 300mm fills all the required conditions. All I wanted is the be sure I can chose it

Anyway, again, my mistake.

Quote:
Originally Posted by ramallo View Post
I'm using the 4U 300mm chassis and is perfect for the amp, enough dissipation for the Madrid summer.
Good to hear.
Thx a lot.
  Reply With Quote
Old 2nd February 2011, 09:59 AM   #10227
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Default transformer VA

Normally a ClassA amplifier has a transformer rated ~ 6 to 10 times the maximum ClassA output power.
300VA would provide adequate power for 30W to 50W of total ClassA power.
400VA would provide adequate power for 40W to 65W of total ClassA power.

There is an alternative method of assessing the required transformer rating.
300VA 18+18Vac gives a current rating of 8.33Aac. This reduces to ~4.17Adc after the capacitor input filter. The 400VA would be rated at 5.55Adc.
The 1.3Adc of a single channel of F5 would use ~31% of the 300VA transformer capability. and use ~23% of the 400VA transformer capability.

A 400VA should be able to power two channels of F5, whereas the 300VA is more than enough for a single channel of F5.

Both assessments show that there is no technical reason for using bigger transformers.

There is the possibility/probability that sound quality might change, but is 33% bigger going to show that effect when both sizes are already bigger than needed for a single F5.

If you were to compare 200VA to 400VA powering a single channel F5, I would expect a difference, even though technically both are big enough.
__________________
regards Andrew T.
  Reply With Quote
Old 2nd February 2011, 10:20 AM   #10228
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
http://www.firstwatt.com/pdf/art_power_supplies.pdf
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  Reply With Quote
Old 2nd February 2011, 10:32 AM   #10229
anilva is offline anilva  India
diyAudio Member
 
Join Date: Mar 2004
Location: Bangalore
Quote:
Originally Posted by mancubus View Post
What should be changed in F5 schematics , that I could replace irfp240, irfp9240 to 2sk1530,2sj201
F5 power amplifier
__________________
DIY F5, F5T, F6, Aleph J, Fostex 206 based BLH, Altec Onken with 515B LF & 288H HF, Technics SP10 MKII & EMT938 turntables
  Reply With Quote
Old 2nd February 2011, 12:03 PM   #10230
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
Quote:
Originally Posted by anilva View Post
This link I don't believe answers the question It only talks about getting better complementary behaviour from the input stage.
The major difference in setting up the output for Toshiba's is in the Vgs. The IR FETs and most of the other mfg's we typically use have to have 4Vgs or so to get turned on to 1.3A + or -. The Toshiba MOSFETs are going to want to have maybe 2V or so. This means that the drain Rs of the JFETs needs to be smaller. Or, the pot will be adjusted to a very low value swamping out the paralell fixed resister. I don't like pots. I would take it out once I found the necessary value of the Input drain R's. But, it might be best to just reduce the value of the fixed Rs to 1k or so, so more current goes through them than the pot. If you read through this thread and/or the balanced F5 Question thread, you will find JFET drain R values that have actually been used with Toshiba outputs. You would probably have found an expanation similar to this and you wouln't be asking. If you are interested in changing the output Source resistors to a lower value you will need an even smaller JFET drain R value.
__________________
"It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.
  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
Rockford Fosgate Power 20001 bd amplifier power rating?? pachoorion Car Audio 8 8th May 2011 10:49 PM
Power transformers versus amplifier output power..what is your option? destroyer X Solid State 38 9th May 2009 05:23 PM
McIntosh Power Amplifier Power Guard johnnyrt Solid State 2 23rd August 2007 10:22 PM
Output power for a power amplifier Progg70 Solid State 33 10th September 2006 08:44 AM
Amplifier 3000 Wats Rms Power + Smps Higcht Power Bestiality MARAVILLASAUDIO Class D 1 5th November 2004 04:06 PM


New To Site? Need Help?

All times are GMT. The time now is 08:22 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