Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Millett Low mu Preamp help
Millett Low mu Preamp help
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 11th September 2005, 10:39 PM   #1
dsavitsk is offline dsavitsk  United States
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
Default Millett Low mu Preamp help

I am looking to build a slightly modified version of Pete Millett's low mu preamp. (originally here http://www.pmillett.com/lowmu_preamp.htm)

The primary change I am making is to use the Bottlehead C4S constant current sourse rather than the pentode based version Pete uses. As far as I can tell, the voltage drop across the C4S is just a few volts. Pete suggests running the plate voltage at about 150V, so I am planning to lower the B+ to about that.

Also, Pete biased the heaters up by 45V due to requirements of the el34 based CCS, but since I am not using this CCS, I am planning to not do this. In fact, I am intending to use a toriod (perhaps with SS rectification) for the B+, and a second small transformer for the heater.

Here is the basic schematic I am looking at. Can anyone offer any comments or suggestions before I get started? This will be one of my first tube builds, so even obvious comments and suggestions are appreciated.

Thanks,

-d
Attached Images
File Type: gif low_mu_pre.gif (4.5 KB, 285 views)
  Reply With Quote
Old 11th September 2005, 10:48 PM   #2
Zen Mod is offline Zen Mod  Serbia
Official Court Jester
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Millett Low mu Preamp help
put some 470K from pot wiper to ground-tube just don't like that grid loose ground-in case that your pot make some weird thing

elevate Uf to some DC potencial ,because you'll get less hiss and whistle from your tube ; tip-there is invisible diode between heater and cathode in every indirect heated tube and that diode is just waiting to rectify every AC gremlin near those preciouss electrodes
when you put some DC distance between Cathode and heater ,lets say that mentioned diode is removed from circuit.
if you don't believe-try......then choose
__________________
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 11th September 2005, 10:57 PM   #3
dsavitsk is offline dsavitsk  United States
diyAudio Member
 
dsavitsk's Avatar
 
Join Date: Jan 2005
Location: Hartford
Quote:
Originally posted by choky
put some 470K from pot wiper to ground-tube just don't like that grid loose ground-in case that your pot make some weird thing
Good Suggestion. I'll definitely do that. I have also seen others using input transformers, and I may look into that as well.

Quote:
elevate Uf to some DC potencial ,because you'll get less hiss and whistle from your tube ; tip-there is invisible diode between heater and cathode in every indirect heated tube and that diode is just waiting to rectify every AC gremlin near those preciouss electrodes
when you put some DC distance between Cathode and heater ,lets say that mentioned diode is removed from circuit.
if you don't believe-try......then choose
I'm not sure I understand what you are saying here. Could you explain more fully
  Reply With Quote

Reply


Millett Low mu Preamp helpHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Peter Millett's Uniamp with KT88 eeyore Tubes / Valves 27 6th March 2018 11:40 PM
Pete Millett Low-Mu Triode Preamp wirewiggler Tubes / Valves 13 8th November 2008 11:33 PM
Anyone Interested in Pete Millett Hybrid Amp PCB's? Geek Tubes / Valves 3 2nd November 2008 11:56 PM
Pete Millett's 829B amp -> monoblocks lochness Tubes / Valves 3 17th June 2008 12:30 AM


New To Site? Need Help?

All times are GMT. The time now is 03:03 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki