Blogs

Your
Blog

Recent
Entries

Best
Entries

Best
Blogs

Blog List

Search Blogs

Home > Forums > Amplifiers
> Tubes /
Valves

Broskie auto bias

[log out]
Welcome, dmfraser66.
You last visited: Today at 09:35 PM

Private
Messages: Unread 0, Total 9.

Home

Forums

Rules

Articles

The
diyAudio Store

Gallery

Wiki

Blogs

User CP

Donations

FAQ

Calendar

Community

Quick Links

Search

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

Community Links

Social Groups

Contacts

Members
List

Search Forums

Show
Threads   Show Posts

Advanced
Search

Google™ Search

Search Wiki

Advanced Search

Search Blogs

Advanced Search

Quick Links

Today's
Posts

Mark Forums Read

Open
Contacts Popup

Networking

Contacts

Social Groups

User
Control Panel

Edit Signature

Edit Your Details

Edit Options

Miscellaneous

Private
Messages

Subscribed Threads

Your Profile

Who's
Online

Wiki Links

diyAudio.com Wiki (Page)

diyAudio.com Wiki (List)

Post New Article

Wiki Tools

Special pages

Books

Recent changes

Go to Page...

User Control
Panel

Private
Messages

Subscribed Threads

Edit Signature

Edit Your Details

Edit Options

Miscellaneous

Your Profile

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

Page 4 of 5

« First

<

2

3

4

5

>

Thread Tools

Search this Thread

Rate Thread

1st May 2012, 04:44 PM

#31

SY

diyAudio Moderator

Join Date: Oct 2002

Location: Chicagoland

Blog Entries: 1

Take a look at the schematic for the old
Berning/Audionics BA-150. Since this was 1977, he used a pile of logic
chips rather than a uC. It was a clever approach- the circuit acted much
like a sample and hold. When the input dropped below a certain level, the
circuit would check the idle current and adjust the bias. When the music
started, the circuit was inhibited and kept the bias constant at the last
value.

Other good analog op-amp based approaches can be found in
Morgan Jones's "Valve Amplifiers" and Menno Vanderveen's "High End Valve
Amplifiers 2." If each tube is controlled well, you don't need a
differential circuit.

__________________
“Instead of Rational Law, objective truths
perceptible to any who will undergo the necessary intellectual discipline,
Knowledge will degenerate into a riot of subjective visions. . ." - Auden

SY

View
Public Profile

Visit SY's
homepage!

Find More Posts by SY

Add SY to Your Contacts

View
Blog

2nd May 2012, 07:18 AM

#32

gingertube

diyAudio Member

Join Date: Oct 2004

Location: Adelaide South Oz

Many of these schemes for bias servos for
Class AB amps depend upon clipping the cathode signal at 2 x the idle bias
level to match the natural clipping which occurs at tube cut off, that is,
the monitored cathode signal is clipped such that is swings symmetrically
either side of the idle point.
For simplicity I like the Menno/Guido
scheme where signal is clipped in a very narrow window around the idle
voltage. They do this with a diode clamped integrator which means that you
need a enough gain after the integrator for a 0.6V max signal to achieve
the full bias voltage output. I also like their bias output amp, why?
because it is current source loaded which isolates the bias voltage output
from any residual noise on the -ve rail.

Here is a part schemo -
Mods Alert, please remove post if deemed inappropriate.
Cheers,
Ian

Attached Thumbnails

gingertube

View Public Profile

Send a private message to gingertube

Find More Posts by gingertube

Add gingertube to Your Contacts

2nd May 2012, 04:44 PM

#33

SpreadSpectrum

diyAudio Member

Join Date: Nov 2007

I realized I forgot to post a link to the
TubeCad blog article that explains the design of the master bias control.
That is here in case anyone missed it.

Microprocessors
would be a more technically perfect solution but I try to stay with simple
analog circuits if they do as good a job. The problem with microprocessors
is the development tools become obsolete. I have a chip programmer I built
in college 8 years ago and I can't run the software anymore because the
executable only runs with XP and earlier. I'll have to give it some
thought.

A clipping autobias circuit that clips within a more
linear portion of the tube's operation may be a really good approach if
there is little assymetry around the operating point in the autobias
circuit's 'window'. Might get less error all around.

I expect all
of these autobias circuits, clipping circuits or the non-clipping Broskie
circuit, to function well in this amp since the local feedback in the
output stage makes the KT88s have very linear triode-looking
characteristics with mu=2. Most of the errors in these bias circuits under
dynamic conditions come from even order distortion produced by the tube
when it is operating in the circuit's 'window'.

SpreadSpectrum

View Public Profile

Send a private message to SpreadSpectrum

Visit SpreadSpectrum's
homepage!

Find More Posts by SpreadSpectrum

Add SpreadSpectrum to Your
Contacts

2nd May 2012, 08:57 PM

#34

Merlinb

diyAudio Member

Join Date: May 2006

Location: Lancashire

Quote:

Originally Posted by SpreadSpectrum

Blumlein's circuit is very elegant
in its simplicity and offers pretty good performance, but not as
good as the circuits Broskie fleshes
out.

Hey, let's not drag poor
Blumlein's name through it. I don't know how Broskie accidentally attached
Blumlein's name to the circuit, but the garter circuit was created by
Jean-Victor Martens in patent FR64203E, not by Blumlein!

Merlinb

View Public Profile

Send a private message to Merlinb

Find More Posts by Merlinb

Add Merlinb to Your Contacts

19th January 2013, 09:46 PM

#35

tinitus

diyAudio Moderator R.I.P.

Join Date: Nov 2005

Martens or Blumlein, I don't know

regarding paralel pushpull

maybe I'm
completely wrong, but I suppose with the Blumlein you could use non
matched tubes in paralel

wouldn't both of the two tubes in paralel
try to 'allign' with the other two tubes .....not perfectly, but in a
sense be 'auto-matched'

tinitus

View Public Profile

Send a private message to tinitus

Find More Posts by tinitus

Add tinitus to Your Contacts

22nd January 2013, 01:43 PM

#36

tinitus

diyAudio Moderator R.I.P.

Join Date: Nov 2005

just another of my silly 'drawings'

Attached Thumbnails

tinitus

View Public Profile

Send a private message to tinitus

Find More Posts by tinitus

Add tinitus to Your Contacts

22nd January 2013, 09:02 PM

#37

tinitus

diyAudio Moderator R.I.P.

Join Date: Nov 2005

ups! forgot a resistor

phase
splitter, driver stage...

Attached Thumbnails

tinitus

View Public Profile

Send a private message to tinitus

Find More Posts by tinitus

Add tinitus to Your Contacts

22nd January 2014, 05:03 PM

#38

Warmsound

diyAudio Member

Join Date: Mar 2009

Hi Folks:
I know it's an old thread, but I
just found it. Here’s my board layout based on a variation of the
Vanderveen circuit found at the RMS Acoustics & Mechatronics website
Motional feedback intro. According to the site, RMS is
the brainchild of Rob Munnig Schmidt, professor in Mechatronic System
Design at Delft University of Technology. I have no affiliation but liked
the explanation and simplicity of his version so I decided to start with
it rather than one of the other versions. Thanks to Mr. Schmidt for making
it available on-line.

A couple things to note:

1. The board
includes a regulated power supply for the +- 15v OpAmp supply and a
separate adjustable regulated supply for the negative reference voltage.
Both start with AC taken from the 6.3Vac filament supply and go through a
quadrupler to get raw ~+-17.6Vdc.
2. The board includes a simple
unregulated power supply for the negative grid bias voltage. A regulator
could be squeezed in, but since I’ve seen countless schematics with just
plain CRC filtering for the bias supply I decided not to sweat it for this
round. Plus, I wanted to be able to run a variety of tubes, some with high
bias requirements (6AS7 for example), and a discrete transistor/MOSFET HV
regulator would take more fiddling to fit.
3. The board is 2”x4”,
manages two tubes and is laid out one-sided so I can make it with the
laser printer + photo paper + iron method. (After much trial and error
I’ve worked out the bugs and get reliable good looking results with this
method. The trick is to NOT overheat the toner and NOT over compress
it.)

Any comments on improvements or flaws?

Attached Files

Bias
Control PCB 3 w PS 2.pdf (34.1 KB, 120
views)

Last edited by Warmsound; 22nd January 2014 at 05:05
PM.

Warmsound

View Public Profile

Send a private message to Warmsound

Find More Posts by Warmsound

Add Warmsound to Your Contacts

12th January 2015, 11:17 PM

#39

tomlang

diyAudio Member

Join Date: Oct 2009

Location: Augusta, GA

I know it's been a year...but did you make
these boards?

tomlang

View Public Profile

Send a private message to tomlang

Find More Posts by tomlang

Add tomlang to Your Contacts

13th January 2015, 02:18 AM

#40

SpreadSpectrum

diyAudio Member

Join Date: Nov 2007

I ended up ordering a board from Guido Tent.
I had made some boards of Broskie's circuit but they had shorts and didn't
work. I have learned that you get what you pay for when you have boards
made.

SpreadSpectrum

View Public Profile

Send a private message to SpreadSpectrum

Visit SpreadSpectrum's
homepage!

Find More Posts by SpreadSpectrum

Add SpreadSpectrum to Your
Contacts

Page 4 of 5

« First

<

2

3

4

5

>

Message

Cancel
Changes

Quick Reply

The following errors occurred with your submission

Okay

Message:

Options

Show your
signature
Quote
message in reply?

Posting
Quick Reply - Please Wait

« Previous Thread | Next Thread »

Thread Tools

Enhanced Print View

Regular Print View

Subscribe to this Thread

Search this Thread

Advanced Search

Rate This Thread

Excellent

Good

Average

Bad

Terrible

Posting Rules

You may post new threads

You may post replies

You may post attachments

You may 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

Forum
Rules

Forum
Jump

User Control
Panel Private Messages
Subscriptions Who's Online Search
Forums Forums Home
Site
Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies
Headphone
Systems Source &
Line
Analogue Source
Analog Line Level     Digital Source     Digital Line
Level     PC
Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems
Instruments and
Amps Design &
Build
Parts
Equipment & Tools     Construction Tips     Software Tools
General Interest     Car Audio     diyAudio.com
Articles
Music
Everything Else Member
Areas
Introductions
The Lounge     Clubs & Events The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio
Store
Vendor Forums
Vendor's Bazaar         Sonic
Craft
Apex Jr         Audio Sector

Acoustic Fun
Chipamp         DIY HiFi Supply

Elekit
Elektor         Mains Cables R Us

Parts Connexion
Planet 10 hifi         Quanghao
Audio Design
Siliconray Online Electronics
Store
Tubelab     Manufacturers         AKSA

Audio Poutine
Musicaltech         Aussie Amplifiers

CSS
exaDevices         Feastrex
GedLee
Head 'n' HiFi - Walter         Heatsink
USA
Markaudio
miniDSP         SITO Audio
Twin
Audio
Twisted Pear         Wild Burro Audio

Similar Threads

Thread

Thread Starter

Forum

Replies

Last Post

Class
B auto bias

mchambin

Solid State

6

1st March 2012 05:59 PM

Fixed
bias vs. auto bias

HFGuy

Tubes / Valves

30

14th October 2011 09:45 AM

Auto
Bias?

lpd

Tubes / Valves

0

18th February 2007 03:33 AM

benifits
of auto bias

hacknet

Tubes / Valves

11

26th October 2004 03:04 AM

New To Site?

Need Help?

Search

Privacy Statement

Contact Us

Frequently Asked
Questions

Mark Forums Read

Log Out dmfraser66

All times are GMT. The time now is 10:25 PM.

Home - Contact Us - Advertise - Rules
- Store - Sponsors - Archive - Privacy Statement - Terms of
Service - Top
- Opt-out policy

vBulletin
Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte
Technologies Ltd.
Copyright ©1999-2015 diyAudio

Content Relevant URLs by vBSEO 3.3.2