Fresh F5 Build - 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 24th June 2012, 08:13 PM   #1
willamp is offline willamp  United States
diyAudio Member
 
willamp's Avatar
 
Join Date: Dec 2011
Location: Austin, Texas
Default Fresh F5 Build

Hi All,

Almost finished with my first F5. Spent over 4 hours listening to it last night. It sounds great! Much more detail than the tube amp I've been using for the last four years. It's like a vail has been removed from the music. Soundstage is much more detailed and precise. Bass is much more controlled. Which makes sense considering the drastic increase in damping factor. My tube amp has on output impedence of 4.5 Ohm so really bad damping factor.

My build seems to be performing as expected. Gain is 15.4db. I wanted to check THD but alas it is lower than what my old HP distortion analyzer can measure. Measuring the internal oscillator I am starting out at 0.0068%. Higher than the 0.002% Mr Pass mentions for the F5. I took some measurements at different wattage ratings anyway but there are some inconsistencies in the numbers and nothing to really say the F5 is anything other than <0.002%. The only thing I saw is one channel seems to have slightly higher distortion than the other. Odd think is the one with higher distortion is biased slightly lower than the other.

Currently I'm running only around 1 amp of current but will increase to 1.3 after I replace the R11/12 and re-bias. I did a stupid thing of not zero-ing the trim pots before powering on and beginning biasing. They were set to around 2k Ohm so I was probably running around 2 amps for a short while. The resistors turned a bit brown so I ordered some replacements. Everything else seems to have survived the abuse OK.

My heat sinks only reach ~42 degrees C when things stabilize so things seem OK there. I do wonder how things will fare with the case top installed. This case has no venting which I didn't think about earlier. Does anyone think this will be a problem? I just now turned the unit on with the case top in place and a temperature probe inside. I'll report back where it ends up. I would think it would be the same as my heat sink measurement but that was with the top off, so maybe it will be higher too.

I'm currently missing the 0.0033uf cap across the mains input indicated in the PSU schematic. I have one on order now though. Can someone tell me the function of this cap? Is it a high freq filter by any chance?

Anyway I'd like to thank Mr Pass and all of you diy'ers who share your knowledge and experience. As it was I spent many months researching and gathering parts and can't imagine how long that would have taken without all of your help (unwitting, and otherwise).

Sorry for the fuzzy pictures, my wife's out of town with the good camera.
Attached Images
File Type: jpg P1010002.JPG (777.8 KB, 610 views)
File Type: jpg P1010001.JPG (693.3 KB, 566 views)
File Type: jpg P1010001 (2).JPG (617.1 KB, 550 views)
  Reply With Quote
Old 24th June 2012, 09:09 PM   #2
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
you need vents on both bottom and top

source resistors are still fine , after conducting 2A for some time

function of 3n3 cap across mains is filtering of mains crap ; you can live without it
__________________
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 24th June 2012, 09:26 PM   #3
willamp is offline willamp  United States
diyAudio Member
 
willamp's Avatar
 
Join Date: Dec 2011
Location: Austin, Texas
Quote:
Originally Posted by Zen Mod View Post
you need vents on both bottom and top
Thanks for your input. As much as I don't want to take everything apart again I believe you're right. Looking at my layout can you make a suggestion of the best way to add them? I can only think of drilling many holes on the drill press. Or, maybe cutting out some openings with a coping saw or a nibbler and attaching a metal screen over them.

Thanks in advance for any suggestions
  Reply With Quote
Old 25th June 2012, 01:36 AM   #4
diyAudio Member
 
Join Date: Mar 2003
Location: midwest
Quote:
Originally Posted by willamp View Post
Thanks for your input. As much as I don't want to take everything apart again I believe you're right. Looking at my layout can you make a suggestion of the best way to add them? I can only think of drilling many holes on the drill press. Or, maybe cutting out some openings with a coping saw or a nibbler and attaching a metal screen over them.

Thanks in advance for any suggestions
For the top, I just "spacered" mine so it floats about 1/2 high...1/2 space all the way around ventilates well. At least for the top.

Russellc
__________________
Pass DIY B-1, Pass DIY F-5
  Reply With Quote
Old 25th June 2012, 01:45 AM   #5
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
yup - spacers are effective and certainly most easier solution

but - only if you can make same for both top and bottom plates

no use of making escape way for air , if not making inlet way
__________________
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 25th June 2012, 02:05 AM   #6
diyAudio Member
 
Join Date: Mar 2003
Location: midwest
Oh well, at least holes drilled in the bottom plate dont show as badly as in the top plate!

Russellc
__________________
Pass DIY B-1, Pass DIY F-5
  Reply With Quote
Old 25th June 2012, 01:39 PM   #7
willamp is offline willamp  United States
diyAudio Member
 
willamp's Avatar
 
Join Date: Dec 2011
Location: Austin, Texas
I think I'll contact my case supplier and ask them to make a ventilated top. Then I'll modify the bottom cover myself. Not sure why they didn't have the case ventilated in the first place.

Thanks for your input guys.
  Reply With Quote
Old 25th June 2012, 01:45 PM   #8
diyAudio Member
 
Join Date: Feb 2009
i gues this is a par-metal chassis?
  Reply With Quote
Old 25th June 2012, 02:23 PM   #9
willamp is offline willamp  United States
diyAudio Member
 
willamp's Avatar
 
Join Date: Dec 2011
Location: Austin, Texas
Quote:
Originally Posted by AudioSan View Post
i gues this is a par-metal chassis?
Yes, that's right.

It's ironic, I used one of their chassis for my passive pre-amp which has no active components.....and it has major ventilation on top and bottom...just to let dust in on my expensive auto-former attenuators
  Reply With Quote
Old 25th June 2012, 03:16 PM   #10
diyAudio Member
 
Join Date: Feb 2009
hehe but they do machine part on demand don't them?
  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
How to build the F5 6L6 Pass Labs 1133 23rd January 2014 06:32 PM
oneplustwo F5 build thread oneplustwo Pass Labs 251 30th May 2012 10:36 PM
FS: Parts for F5 build Jimmy D. Swap Meet 2 5th July 2011 05:33 PM
Next suggested build after F5 anilva Pass Labs 36 3rd December 2010 05:11 AM
F5 Build Instructions 1108 Pass Labs 4 12th May 2009 11:58 PM


New To Site? Need Help?

All times are GMT. The time now is 01:28 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