B1 Buffer Preamp - Page 380 - 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 2nd August 2013, 10:49 AM   #3791
Rixsta is offline Rixsta  United Kingdom
diyAudio Member
 
Join Date: Feb 2004
Location: Barrow-In-Furness, Cumbria
Send a message via Skype™ to Rixsta
everything's from Hong Kong and the Diyaudio board might take a long time to get here.
Im not actually worried about the B1 having a turn on thump I just don't like that thump going right into the input of the F5turbo!
__________________
www.Rixsta.co.uk Free music recorded by me/DIY pics Currently Selling, amps=Zen V4, Zen-lightenment‎, Jean Hiraga 20w, F5, F5T
  Reply With Quote
Old 2nd August 2013, 11:22 AM   #3792
Itsmee is online now Itsmee  England
diyAudio Member
 
Itsmee's Avatar
 
Join Date: Feb 2009
Because the B1 is a single supply, there will always be a turn on thump due to the output coupling cap charging up, there are a couple of ways around the problem,
1. use a muting relay with a turn on delay to short the output to ground for a few seconds.
2. use a slow ramping supply as in post 2 of help LM317/337 Slow-on design.
3. turn the B1 on 5 seconds before the F5
4. leave the B1 permanently powered up

My choice would be for No 3 or 4
  Reply With Quote
Old 2nd August 2013, 11:51 AM   #3793
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
The B1 doesn't need a soft start. Soft start is aimed at high power amplifiers with KVA of transformers.

Sounds like your FETs are not well matched and you are getting a DC offset. A correctly functioning B1 will exhibit very little turn-on thump. It's always wise to turn on power amp after the pre amp anyway.
  Reply With Quote
Old 2nd August 2013, 12:27 PM   #3794
Rixsta is offline Rixsta  United Kingdom
diyAudio Member
 
Join Date: Feb 2004
Location: Barrow-In-Furness, Cumbria
Send a message via Skype™ to Rixsta
I see your Point, thanks well I noticed just now that when i Turn the B1 off the power Led takes about 30 seconds to dim out. and im using 2x 15,000uf caps.
Don't know if thats normal ?

Thanks for the Info itsme I was thinking along the lines of Regulator Initially.

Katieanddad
I kind of just like the idea of Power rising slowly when the amps turned on but I see your point
Ill check for DC-offset

Btw, the B1 is built inside the massive F5 chassis so both use the same transformer but different windings!
__________________
www.Rixsta.co.uk Free music recorded by me/DIY pics Currently Selling, amps=Zen V4, Zen-lightenment‎, Jean Hiraga 20w, F5, F5T
  Reply With Quote
Old 2nd August 2013, 12:29 PM   #3795
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
When you turn OFF the power, the B1 is pulling so little current that it is largely the LED that is discharging the 30mF of capacitance - Quite Normal.

I hate relays - especially in high quality audio. But you could arrange a pair of relays to (1) apply the B1 output to the F5 after say 5 seconds and (2) to apply a significant load to the B1 power supply to discharge it more quickly and/or remove the B1 output from the F5 at power down.

Last edited by KatieandDad; 2nd August 2013 at 12:31 PM.
  Reply With Quote
Old 2nd August 2013, 12:39 PM   #3796
Rixsta is offline Rixsta  United Kingdom
diyAudio Member
 
Join Date: Feb 2004
Location: Barrow-In-Furness, Cumbria
Send a message via Skype™ to Rixsta
Another thing is my PSU for B1 is 22v but when B1 (load) connected is showing as 33v, as I don't have much knowledge on the subject I don't know why this is.
So which is the real voltage ?
Dc offset
Left = 0.01v
Right = 0.34v (slowly decreases over a minute or two)

Hows that for DC-offset ?
__________________
www.Rixsta.co.uk Free music recorded by me/DIY pics Currently Selling, amps=Zen V4, Zen-lightenment‎, Jean Hiraga 20w, F5, F5T

Last edited by Rixsta; 2nd August 2013 at 12:53 PM.
  Reply With Quote
Old 2nd August 2013, 12:43 PM   #3797
Mihan is offline Mihan  New Zealand
diyAudio Member
 
Join Date: Aug 2008
Quote:
Originally Posted by Rixsta View Post

there's a turn on thump on the B1 which id prefer to get rid of!

im thinking Just get a soft start for the whole amp
Get in to the habit of turning on the B1 before the power amp and turning off the power amp first when you power off. It's never a good idea turning a preamp on, after the power amp. (sorry for the lecture)
  Reply With Quote
Old 2nd August 2013, 12:43 PM   #3798
Rixsta is offline Rixsta  United Kingdom
diyAudio Member
 
Join Date: Feb 2004
Location: Barrow-In-Furness, Cumbria
Send a message via Skype™ to Rixsta
Quote:
Originally Posted by KatieandDad View Post
When you turn OFF the power, the B1 is pulling so little current that it is largely the LED that is discharging the 30mF of capacitance - Quite Normal.

I hate relays - especially in high quality audio. But you could arrange a pair of relays to (1) apply the B1 output to the F5 after say 5 seconds and (2) to apply a significant load to the B1 power supply to discharge it more quickly and/or remove the B1 output from the F5 at power down.
Ahh ok I see, Im used to the power of the F5 and so On which will drain the PSU rather fast but of course B1 only draws 0.02A and 15,000uf I suppose would be large capacitance in that respect.

Sounds like a good idea, The relay thing is nice but a bit of a hassle and also wouldn't want to degrade the sound.

I actualy just put a 12v Light bulb in series of PSU to see what it will do, it lights briefly on turn on then dims, probably not a good idea but im experimenting

Well Im actualy thinking of getting some kind of Pre-amp to replace the B1 as it would give more gain.
__________________
www.Rixsta.co.uk Free music recorded by me/DIY pics Currently Selling, amps=Zen V4, Zen-lightenment‎, Jean Hiraga 20w, F5, F5T
  Reply With Quote
Old 2nd August 2013, 12:45 PM   #3799
Rixsta is offline Rixsta  United Kingdom
diyAudio Member
 
Join Date: Feb 2004
Location: Barrow-In-Furness, Cumbria
Send a message via Skype™ to Rixsta
Quote:
Originally Posted by Mihan View Post
Get in to the habit of turning on the B1 before the power amp and turning off the power amp first when you power off. It's never a good idea turning a preamp on, after the power amp. (sorry for the lecture)
Can't B1 shares same transformer and chassis, I could add a Switch for it.
__________________
www.Rixsta.co.uk Free music recorded by me/DIY pics Currently Selling, amps=Zen V4, Zen-lightenment‎, Jean Hiraga 20w, F5, F5T
  Reply With Quote
Old 2nd August 2013, 12:45 PM   #3800
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Dc offset
Left = 0.01v
Right = 0.34v (slowly decreases over a minute or two)
This seems broken.
Most properly built B1 have zero Output offset. The DC blocking cap and the leakage to signal ground resistor ensure the output offset is zero.

0.01Vdc = 10mVdc is wrong.
0.34Vdc = 340mVdc is broken.
__________________
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
buffer/preamp? TheDriver41 Chip Amps 2 3rd October 2004 08:40 AM


New To Site? Need Help?

All times are GMT. The time now is 12:26 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