Pls help with a preamp - 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 10th March 2012, 11:23 PM   #1
kendt is offline kendt  Canada
diyAudio Member
 
Join Date: Dec 2006
Default Pls help with a preamp

I have a pair of charlize-2 amp baords from diy paradise. They will be running my speakers bi-amped.I would like to build a simple tube preamp to drive the amps. I dont think i need much gain at all so i'm just trying to add a bit of tube goodness to the sound. I would like something fairly straight forward and not too hard on the wallet.

Thanks
  Reply With Quote
Old 10th March 2012, 11:57 PM   #2
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Used properly, tubes don't add "goodness". If you want a subtle effects box, look for a badly designed 'tube buffer' - usually a poorly biased cathode follower.
  Reply With Quote
Old 11th March 2012, 03:10 AM   #3
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
Low gain and good sound sure seems like 12B4 territory to me. There are any number of decent designs available. Of course, I'm uploading the version I'm associated with.

Make the net I/P impedance presented by the "sand" amps 15 KOhms, to hold gain down.
Attached Images
File Type: jpg 12B4 Line Stage.jpg (24.4 KB, 187 views)
__________________
Eli D.
  Reply With Quote
Old 11th March 2012, 10:26 AM   #4
kendt is offline kendt  Canada
diyAudio Member
 
Join Date: Dec 2006
That looks like a nice easy build, thank you. I'm toying with the possibility of doing a four channel pre so that each channel of the amp is driven by its own pre amp channel, but that will depend of course on cost.

Last edited by kendt; 11th March 2012 at 10:30 AM.
  Reply With Quote
Old 11th March 2012, 09:57 PM   #5
diyAudio Member
 
Join Date: Apr 2004
Location: Monroe Township, NJ
IIRC, Allied sells directly in Canada. A Triad VPL24-400 (Allied stock # 70218209) takes care of providing 2X suitable "12" VAC heater windings. A Triad N-68X isolation trafo (Allied stock # 70218526) takes care of B+. Those 2 combined cost about 20 USD. Canada's own Hammond makes suitable filter chokes. A pair of Hammond 155Hs takes care of the 5 H. parts. A Hammond 193J will take care of the 1st inductor position. Use a 10 KOhm bleeder rated for at least 5 W.

A 2nd generation of high PIV SiC Schottky diodes has become available. The pricing of those parts is more favorable. Use 4X 2 A. rated 600 PIV parts in the bridge rectifier.

The rail voltage that pseudo choke I/P filter produces has to be set at the bench, with the bleeder installed. A 0.47 μF. cap. in the "fudge factor" position is a starting point. The capacitance in that position is adjusted until the voltage measured across the bleeder is > 125 V. and < 130 V.

The costly Mundorf O/P cap. can be quite comfortably replaced by a 4.7 μF. metalized polypropylene part, which is bypassed by a 0.47 μF. 716P "Orange Drop" film and foil part. The schematic was drawn, from a narrative I provided, by a fellow who uses the "moniker" Buzz and he LIKES "boutique" parts.
__________________
Eli D.
  Reply With Quote
Old 15th March 2012, 01:46 AM   #6
roline is offline roline  United States
diyAudio Member
 
roline's Avatar
 
Join Date: Sep 2010
Location: East Tennessee
Have you considered a SRPP stage with a follower?
__________________
SO many tubes, SO little time!!!
  Reply With Quote
Old 15th March 2012, 03:00 AM   #7
popilin is offline popilin  Argentina
diyAudio Member
 
popilin's Avatar
 
Join Date: Oct 2010
Location: Traslasierra
Try this

http://www.diyaudio.com/forums/tubes...ne-preamp.html

If you consider 2K is much for output impedance try with an ECC99 reducing +B to 350V and cathode resistors to 1K5.
A cathode follower isn't necessary.
  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
hi new here can some one pls help me with something lance007 Parts 3 1st January 2011 12:19 AM
Preamp suggestion required pls milen007 Tubes / Valves 4 19th September 2009 04:53 AM
help me lower the gain of this preamp pls milen007 Tubes / Valves 2 23rd January 2009 02:25 AM
Bass boosted preamp, suggestions pls... Dxvideo Chip Amps 0 10th August 2007 03:25 PM


New To Site? Need Help?

All times are GMT. The time now is 05:08 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