Blogs

Your
Blog

Recent
Entries

Best
Entries

Best
Blogs

Blog List

Search Blogs

Home > Forums > Amplifiers
> Tubes /
Valves

Hafler/Keroes 6L6 UL

[log out]
Welcome, dmfraser66.
You last visited: 10th April 2015
at 05:57 PM

Private
Messages: Unread 0, Total 6.

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 & Friends

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 & Friends

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 1 of 13

1

2

3

11

>

Last
»

Thread Tools

Search this Thread

Rate Thread

9th August 2006, 08:55 PM

#1

sorenj07

diyAudio Member

Join Date: May 2006

Hafler/Keroes 6L6 UL

I'd picked a schematic to build, and lo and
behold it's one of the earliest (if not the original) incarnations of
Ultra-Linear topology, as invented by Hafler and Keroes of later Dynaco
and Acrosound fame.

Here's a nice copy of the schematic:
http://www.dc-daylight.ltd.uk/Valve-Audio-Interest/Schematics/UL-H&K-Fig3.pdf

I've
got a matched quad of Sovs (the WXT+ kind), and matched pairs of Sov
6SN7GT's and 6SL7GT's. My power supply is a well-regulated (~10mV) CLC,
where the C's are two 200uF sections of a big 500V LCR can cap, and the L
is a Hammond 193K for 2.6H and 21 ohms. I also stuck a 470uF 400V Rubycon
cap parellel to the first C. I get about 364V 1/2A out of this (I have a
beefy AnTek 300VA toroid at 275-0-275). Chassis is a Hammond aluminum
16x8x3.

Anyway, the output transformer that should arrive sometime
next week is from Edcor, 6600 primary impedance and a nice healthy 60W
power tolerance, only has an 8-ohm tap, besides ground. Seeing as the NFB
on this amp is connected to the 16-ohm tap, what should I do? What effect
would connecting the NFB to the 8-ohm tap do? I'll post pics of my layout
as all the stuff arrives.

sorenj07

View Public Profile

Send a private message to sorenj07

Find More Posts by sorenj07

Add sorenj07 to Your Contacts

9th August 2006, 09:07 PM

#2

EC8010

diyAudio Moderator Emeritus

Join Date: Jan 2003

Location: Near London. UK

Hafler and Keroes published their "An
Ultra-Linear Amplifier" paper in Audio Engineering November 1951, but the
topology had already been patented by Alan Blumlein in BP 496,883 (1937).

__________________
The loudspeaker: The only commercial Hi-Fi item
where a disproportionate part of the budget isn't spent on the box. And
the one where it would make a difference...

EC8010

View Public Profile

Send a private message to EC8010

Find More Posts by EC8010

Add EC8010 to Your Contacts

9th August 2006, 09:49 PM

#3

sorenj07

diyAudio Member

Join Date: May 2006

well yes, but blumlein's patent was close to
running out by the time our friends hafler and keroes got to work, and
besides, he doesn't seem to have built any amplifiers that used it. i'll
keep y'all posted on how things work out when i start building it.

sorenj07

View Public Profile

Send a private message to sorenj07

Find More Posts by sorenj07

Add sorenj07 to Your Contacts

9th August 2006, 09:51 PM

#4

SY

diyAudio Moderator

Join Date: Oct 2002

Location: Chicagoland

Blog Entries: 1

The NFB resistor value will set the gain. Most
"classic" amps have gain that is much too high, so you might think about
reducing that resistor's value. Now, you'll probably have to adjust the
compensation cap value to make up for this, but with a new output
transformer, you'd have needed to do that anyway.

Double-check that
this schematic is accurate. The coupling RC time constants don't look
right- they should be staggered at least 5:1, if not 10:1, for stability.

__________________
"Pity, wrath, heroism, filled them, but the
power of putting two and two together was annihilated."- EM Forster

SY

View
Public Profile

Send email to SY

Visit SY's
homepage!

Find More Posts by SY

Add SY to Your Contacts

View
Blog

10th August 2006, 01:06 AM

#5

sorenj07

diyAudio Member

Join Date: May 2006

What I'd heard about the NFB was that with an
8-ohm tap, I should use about 8.5K instead of 12, and raise the
capacitance to about 170pF. I have no clue what you mean by the coupling
contants, though .

sorenj07

View Public Profile

Send a private message to sorenj07

Find More Posts by sorenj07

Add sorenj07 to Your Contacts

10th August 2006, 02:28 AM

#6

SY

diyAudio Moderator

Join Date: Oct 2002

Location: Chicagoland

Blog Entries: 1

Quote:

Originally
posted by sorenj07
What I'd heard about the NFB was that
with an 8-ohm tap, I should use about 8.5K instead of 12, and raise
the capacitance to about 170pF. I have no clue what you mean by the
coupling contants, though .

That will get you in the ballpark- in
reality, the exact gain is not that important. That's why you have a
volume control. The capacitor value will not scale- since you're using a
different output transformer, you'll have to adjust that value on the
bench.

Without getting into the Mysterious Bode and his Imaginary
Poles, stability with feedback depends very much on how the open loop gain
rolls off on each end, most especially the slope.

Now C2 and R6
(also C3 and R7) form a high pass filter (i.e., roll off low frequencies).
The time constant is C2*R6, in this case about 0.1 s. Likewise, C4 and R13
form a time constant, C4*R13, about 0.067 s. That's a 1.33 ratio. If there
are no other time constants around, that would be stable. A third rolloff
nearby would cause things to get rather tipsy. But unfortunately there are
a bunch of other LF rolloffs: the output transformer, the bypass cap on
the input stage cathode, the power supply decoupling... you really want
the RC time constants to be further apart.

The best way, IMO, to
do this is to reduce C4 (and C5), to perhaps 0u047 or 0u033. This will
restrict the bottom end, but the feedback will partially make up for this.
And you've got no business using a 25 watt amp to drive a subwoofer
anyway.

A perfectly acceptable alternative would be to bring C2(3) up by a
factor of 2 or 3, then reducing C4(5) by a factor of 2 or 3. That might
also require stiffening the supply a bit, but you ought to have a good
solid supply regardless.

__________________
"Pity, wrath, heroism, filled them, but the
power of putting two and two together was annihilated."- EM Forster

SY

View
Public Profile

Send email to SY

Visit SY's
homepage!

Find More Posts by SY

Add SY to Your Contacts

View
Blog

10th August 2006, 03:44 AM

#7

sorenj07

diyAudio Member

Join Date: May 2006

Hmm. First off, if I were to stick a volume
control in there, what rating should it be? I have a smallish 6SN7-based
SRPP linestage that I could use to adjust volume (it has 4 input selection
too) but I wonder if it'd be too much gain with what I assume to be an
integrated amp. I don't suppose I could could simplify things by cutting
out one of the gain/phase split stages? Anyway probably the easiest
solution for me would be to slap another .22uF cap alongside c2 and c3 as
I have a couple left over. It _is_ all right that I'm using .22 and not
.2, right? I couldn't really find any of those.

Thanks for the
info on the filtering, however, as it's provided me with some sweet
insight into how schematics work. They used to look like random lines and
symbols a few months ago, and already I'm beginning to make sense of them
.

sorenj07

View Public Profile

Send a private message to sorenj07

Find More Posts by sorenj07

Add sorenj07 to Your Contacts

10th August 2006, 04:42 AM

#8

sorenj07

diyAudio Member

Join Date: May 2006

updated schematic:

sorenj07

View Public Profile

Send a private message to sorenj07

Find More Posts by sorenj07

Add sorenj07 to Your Contacts

10th August 2006, 12:15 PM

#9

SY

diyAudio Moderator

Join Date: Oct 2002

Location: Chicagoland

Blog Entries: 1

A few things.

First, a general note-
you might want to use one of Hafler's later designs as your starting
point.

Specifics: the LF rolloffs from the RC coupling are still
only spaced by a factor of 3. You really want them much further apart.
Five times should be a minimum, ten times is best. For my first shot, I'd
set the second rolloff at 20-30 Hz, the first one at 2-3 Hz. It's better
to make the second rolloff the dominant one because of the way this phase
splitter operates.

Also, you've got almost 700u as the input to the
pi filter in the power supply. That will cause unneccessarily large ripple
currents, and very likely cause the 4007s to pop. Something like 60u would
be more appropriate.

You'll likely have to revisit the decoupling.
The time constants are too short for comfort. Bigger decoupling caps would
help; regulation would be even better.

Check out the later Hafler
article for his adaption of the Williamson. It's a much better starting
point.

BTW, my volume control comment was directed at your preamp.

__________________
"Pity, wrath, heroism, filled them, but the
power of putting two and two together was annihilated."- EM Forster

SY

View
Public Profile

Send email to SY

Visit SY's
homepage!

Find More Posts by SY

Add SY to Your Contacts

View
Blog

10th August 2006, 12:46 PM

#10

corbato

diyAudio Member

Join Date: Jan 2003

Location: India

Quote:

Originally
posted by sorenj07
updated schematic:

Ouch...I would move that stand-by
switch before the PSU caps.

corbato

View Public Profile

Send a private message to corbato

Find More Posts by corbato

Add corbato to Your Contacts

Page 1 of 13

1

2

3

11

>

Last
»

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

Email this Page

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

What
to do with Hafler XL-280?

JWK

Solid State

3

1st May 2008 04:51 PM

Hafler...

tomtt

Everything Else

0

11th May 2006 02:34 AM

Hafler
PC-10 help.....

burntfingers

Solid State

5

22nd March 2006 12:33 AM

hafler
amp or pre-amp

larryg

Solid State

2

9th March 2004 10:39 PM

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 04:26 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