How about this 12au7 pre? - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs 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

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
Thread Tools Search this Thread
Old 13th April 2004, 07:27 PM   #1
sith is offline sith  Croatia
diyAudio Member
Join Date: Nov 2003
Location: Split
Default How about this 12au7 pre?

Hi guys,
I found this one over the internet , so, is it good , bad? Something like foreplay, or Bruce Rosenbilts pre, or Berman, or 'something completely different'
Attached Images
File Type: jpg fb12au7a.jpg (22.7 KB, 318 views)
  Reply With Quote
Old 13th April 2004, 08:02 PM   #2
diyAudio Member
analog_sa's Avatar
Join Date: Aug 2002
Location: Cascais
Depends on your sound preferences. To me it's a horrendous, badly designed high-feedback circuit. But some like the way it sounds.
  Reply With Quote
Old 13th April 2004, 08:27 PM   #3
diyAudio Member
richwalters's Avatar
Join Date: Sep 2003
Location: Alps:Tube amp designs over 150W, SMPS guru.
Hi there.........the way to the <bootstrap> concept is a good one, a little modification and one has a real bootstrap (far better than using two single R/C coupled stages) the dummy nicely raising the input impedance...and can take a good overload.
I currently use 2 xEF86's (1st in triode config and second pent). This circuit config has excellent overload capacity with high inp Z and high feedback of about 35dB. THD is very low throughout audio pass band as is noise <75dB below 1volt. Sim results with ECC83's except noise is higher. As gain/perfomance /BW is vastly improved there can be the risk of HF positive feedback if gain is too high or from crummy layout . Best results, use screened pentodes instead of naked triodes as HF response is much higher.

The 20KHz perfmance with a good layout should expect av <0.1% THD at the 10V rms output level, then into cathode follower. At lower levels the THD drops proportionally.

keep at it

  Reply With Quote


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
Cycline3 on the 12AU7 Cycline3 Tubes / Valves 24 28th October 2007 04:20 PM
12AU7 instead of 6C4 Dr ZEE Tubes / Valves 9 3rd August 2007 02:25 AM
Question about 12AU7 pho_boi Tubes / Valves 3 3rd October 2005 06:00 AM
Wiring a 12au7 A3rd.Zero Tubes / Valves 14 1st April 2004 11:07 PM

New To Site? Need Help?

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

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2