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 30th May 2007, 02:15 PM   #1
diyAudio Member
 
croccodillo's Avatar
 
Join Date: Mar 2005
Location: Bergamo
Default 6as/ Otl

Hello,

I have a bunch of 6N13S (6AS7G) tubes, I'm thinikng to realise an OTL amplifier.
What about THIS ? it seems quite critical to me...
Any other good, tested circuit for me?
I have 8 tubes, so I can use 4 of them for each channel.

Ciao,
Giovanni
__________________
In Nomine Libertatis Vincula Edificamus,
In Nomine Veritatis Mendacia Efferimus.
  Reply With Quote
Old 30th May 2007, 04:28 PM   #2
Klimon is offline Klimon  Belgium
diyAudio Member
 
Join Date: Apr 2005
Location: Leuven
There was an elaborate website from an Italian builder with layout diagrams and a treasure of info on this amp, it seems to have been removed from the net though. I've seen this schematic recommended in an old thread on this forum, it seems to be a well-tested and respected older circuit of the OTL guru behind 'Transcendent sound'. Here's another builder: http://www.ptsoundlab.com/tubes/otl/.../6as7gtaga.htm

Simon
  Reply With Quote
Old 30th May 2007, 05:20 PM   #3
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
I have so many doubts about balancing that it scares me rigid. 6AS7 are very variable valves.

Shoog
  Reply With Quote
Old 31st May 2007, 12:28 AM   #4
diyAudio Member
 
Miles Prower's Avatar
 
Join Date: May 2005
Location: USA
Blog Entries: 6
Default Re: 6as/ Otl

Quote:
Originally posted by croccodillo
I have a bunch of 6N13S (6AS7G) tubes, I'm thinikng to realise an OTL amplifier.
What about THIS ? it seems quite critical to me...
Any other good, tested circuit for me?
I have 8 tubes, so I can use 4 of them for each channel.
For hollow state OTLs, you might want to check into the "circlotron" or "inverted Futterman" topologies (the schemo you linked is a straight Futterman). The inverted Futterman has the advantage of having the lowest Zo, and it doesn't require floating power supplies. The circlotron topology has the advantage of being more "poof proof".

For either design, the 6AS7 isn't a bad choice at all, even if the balance between sections isn't quite what it would otherwise be if this type had actually been intended as an audio final (it wasn't: series pass regulator).

See Here for a good overview of OTL design.
__________________
There are no foxes in atheistholes
www.dolphin-hsl.com
  Reply With Quote
Old 31st May 2007, 05:01 AM   #5
diyAudio Member
 
Join Date: Jan 2003
Location: Sweden
Quote:
The circlotron topology has the advantage of being more "poof proof".
Where did you get that from? I think it depends more on actual implementation which design is more reliable, e.g Transcendant designs are reported to be very reliable.

For some comparison on different output topologies see here http://members.aol.com/aria3/otlpaper/otlhist.htm

BR Hans
  Reply With Quote
Old 31st May 2007, 06:15 AM   #6
diyAudio Member
 
soundbrigade's Avatar
 
Join Date: Feb 2006
Location: Vaenersborg, Sweden
Send a message via MSN to soundbrigade
You can get Bruce Rozenblit's book "Audio Reality" för 20 bucks from his company (Audio Reality .
It gives you yet another design.

This design is published in his book Tube Audio Design. Get it and you get the design ideas as well.
__________________
/Magnus
  Reply With Quote
Old 3rd June 2007, 01:29 PM   #7
diyAudio Member
 
Alastair E's Avatar
 
Join Date: Feb 2004
Location: South Wales
Whatever design of OTL you go for, remember to carefully 'Burn-In' the O/P bottles well before you run them in the OTL.

Hans (TubeTVR) has an excellent section on his Website dealing with the 6C33C-B, and advice on burning-in before use and although a different tube the same precautions I think will serve well....

Basically, the recommendation is to run the tubes with heaters only for a couple of days. Other guys recommend also after this to run at a low Plate-Volts, the maximum rated current through the tube but not exceeding the plate dissipation, for a couple of hours, then all will be well when powered up in the OTL....

The only issues I ever had with O/P tubes in my OTL happened when I used a couple of brand-new 'virgin' tubes straight in the OTL, which after half-hour or so arced over and blew fuses--The tubes were alsom damaged when this happened.....

The 6AS7/Russian 6C13s has rather fragile cathode-connections that serve as 'fuses' should they arc-over, which then destroys the tube when they fail.--Or so Im told, I may be wrong here though..

As to the choice of topology, that is a rather 'personal' thing often dictated by what parts/transformers/experience you have. My personal choice was the Circlotron, which although hideously complicated the way I did it, as I adapted an already complicated design to use the 6C33C where it originally used the EL509 tube, but it works nicely in my opinion.

Hans I believe likes the SRPP type design and has had great results and few problems with his
__________________
Das Beste Oder Nichts
  Reply With Quote
Old 14th August 2007, 10:31 AM   #8
max29 is offline max29  Netherlands
diyAudio Member
 
Join Date: Nov 2005
Location: oosterhout
Schematics of M 60 MK II somewhere to find.

Any one knows because they used to be in a kit form available.


Thanks
Max
  Reply With Quote
Old 14th August 2007, 10:52 PM   #9
diyAudio Member
 
Zero Cool's Avatar
 
Join Date: Sep 2004
Location: MN
I am currently rebuilding an Atma-Sphere prototype amp that uses 8 6AS7G tubes per channel, 4 In parallel per phase. This is a very very early Atma- Proto type. but it runs great sound very good.

I have not seen many Atma schematics anywhere. I dont know how Ralph would feel about posting his schematics online. I will ask him when he gets back in town.


Zc
  Reply With Quote
Old 15th August 2007, 01:44 AM   #10
diyAudio Member
 
HollowState's Avatar
 
Join Date: Aug 2006
Location: Taxland, New Jersey
"I have not seen many Atma schematics anywhere. I dont know how Ralph would feel about posting his schematics online. I will ask him when he gets back in town."

I was going to attach the schematic I made of the MA-1 in another thread. Since I have no scanner, I photographed it. But in order to see it clearly the file is necessarily big and this site would not accept it's size. Since I have no website of my own, I'd have to use a host like photobucket or something. I may try it later in a different format to see if it works.

As far as sharing it, I have no qualms or problems with doing so. It is not illegal to post it since it is my drawing, not their's. I am not manufacturing the amplifier nor am I profiting from showing my diagram. Also, one needs no special permission to build a clone for their own personal use.

Not wanting to post it out of respect for a friend is perfectly understandable. But I have no relationship with Atma Sphere and owe them no allegiance. Besides, it's an 18 year old design.

In the meantime, I've set my options to accept emails from members. If someone wants a peek, send me a request and I'll send it via email.

Victor
__________________
"It is hard to imagine a more stupid or more dangerous way of making decisions than by putting those decisions in the hands of people who pay no price for being wrong." ~Thomas Sowell
  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
6AS7 ppp whitelabrat Tubes / Valves 12 15th May 2008 11:33 AM
6as7 Pse croccodillo Tubes / Valves 4 19th May 2007 04:36 PM
6AS7 OTL mr l Tubes / Valves 7 8th March 2007 01:36 AM
6as7 MlinarS Tubes / Valves 2 12th March 2005 12:37 AM
pre-amp with 6as7?? AudioGeek Tubes / Valves 3 23rd January 2005 09:55 PM


New To Site? Need Help?

All times are GMT. The time now is 08:07 AM.


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