#26 pre amp - Page 90 - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 13th March 2011, 09:48 PM   #891
diyAudio Member
 
Vinylsavor's Avatar
 
Join Date: Feb 2002
Location: Lindau
Hi!

Quote:
Originally Posted by Rod Coleman View Post
The type of mains trafo is also important. split bobbin type reduces noise transfer from the mains (compared to toroidal or overwound types), and high quality trafos with an Electrostatic screen can be even better still.
I fully agree with Rod on this. Using cheap power transformers is cost saving in the wrong place. Especially if the power supply changes seem to have a big impact on the sound, this could be due to a poor power trannie. I settled on power transformers with two independent screen windings. In fact the screens are not windings, but electrostatic screens made with foils. Also the core material of the power transformer has an impact.

Best regards ... Thomas
__________________
http://vinylsavor.blogspot.com/
  Reply With Quote
Old 13th March 2011, 10:11 PM   #892
diyAudio Member
 
Join Date: Sep 2003
Location: London
I found that a say 2uf film cap sounded better than smaller say .5uf Vitamin Q on Duracells. I have not tried any other caps, however a cap did sound better than no cap."

Found this comment. Is there any benefit from bypassing a grid battery?

Andy
  Reply With Quote
Old 14th March 2011, 09:13 AM   #893
работник
diyAudio Member
 
Rod Coleman's Avatar
 
Join Date: Jul 2004
Location: Warwickshire UK
DIYers that are enthusiastic about battery bias usually have favourite brands of alkaline batteries, and perform noise measurements to compare them. Using large value caps across a 9V alkaline suggests they are not quiet enough.

Other battery chemistry, especially lead-acid gel cell, and NiMH are known to be too noisy. There's measurements available on this site, to be searched out.
  Reply With Quote
Old 14th March 2011, 09:55 AM   #894
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
What about LiFePO4 battery? Supposed to be the leading edge technology nowadays.
Internal resistance down to few mOhms, probably bypassing caps not required.
Cells are 3.6 V (nominal) each and to charge them tiny smd ICs (3x3 mm!) such as MCP73123 can be used with minumum external parts.
  Reply With Quote
Old 14th March 2011, 10:07 AM   #895
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
Originally Posted by massimo View Post
What about LiFePO4 battery? Supposed to be the leading edge technology nowadays.
Internal resistance down to few mOhms, probably bypassing caps not required.
Cells are 3.6 V (nominal) each and to charge them tiny smd ICs (3x3 mm!) such as MCP73123 can be used with minumum external parts.
Good idea, suggested circuit schematic for charger?
  Reply With Quote
Old 14th March 2011, 10:14 AM   #896
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
IC Manufacturer's application note. http://ww1.microchip.com/downloads/e...tes/01276a.pdf
Two caps, two resistors, one led + one cheap wall mart p.s. (you might already have a suitable one around)
  Reply With Quote
Old 14th March 2011, 10:25 AM   #897
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
How can reach 9V with 3.6V?
  Reply With Quote
Old 14th March 2011, 11:16 AM   #898
massimo is offline massimo  Italy
diyAudio Member
 
Join Date: Dec 2002
Location: Milan, Italy
You cannot, of course, but you can eventually chose a different operating point based on -7.2V (2 cells) or -10.8V (3 cells) bias.
I'rather go with -7.2V and with two cells in series you can use the MPC73223 chip instead
  Reply With Quote
Old 14th March 2011, 12:58 PM   #899
diyAudio Member
 
merlin el mago's Avatar
 
Join Date: Sep 2009
Location: Catalonia - Europe
1st I will try with a Panasonic 9V alkaline.
  Reply With Quote
Old 14th March 2011, 03:19 PM   #900
diyAudio Member
 
Join Date: Sep 2003
Quote:
Originally Posted by merlin el mago View Post
Good idea, suggested circuit schematic for charger?
For the application discussed here, you have probaly trashed the preamp and built a new one before you will have to recharge the batteries. I suppose that the shelf life of this type of batteries are even better than with lithium batteries. Since the grid draws extremely little current, I would expect a LiFePO4 to last many years in a linestage.
__________________
Thanx!

Last edited by bequerel; 14th March 2011 at 03:21 PM.
  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



New To Site? Need Help?

All times are GMT. The time now is 01:00 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