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

OTL Topologies
OTL Topologies
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 12th January 2018, 10:46 PM   #21
Koonw is offline Koonw
diyAudio Member
 
Join Date: Apr 2013
The top bank would certainly needs feedback as explaint earlier. My current listen version does nothing to the bottom driver, a little NFB is fine, but excessive to the bottom will have sonic impact certainly esp. this is just one side affair, you need to test it. The SIM can tell whether symmetry conduction or not. In the sch I have with 6p12p triode has 470 ohms cathode resistor with 68k connect to cathode and output, for both drivers (the top is strapped Pentode), the SIM shows good symmetry when load is changed. I don't know yet how good it sounds compared to the current simplest version. So this is gain version (not cathode follower perhaps?) driver as the stage gain is decided by top drive gain and bottom drive follow to suit.

If you don't apply PFB then it's quite different story, it then becomes Technics version which is rare.

Btw I only reduce the cathode resistor of the top driver to increase gain. It sounds good on Pioneer CL-70.

Last edited by Koonw; 12th January 2018 at 10:53 PM.
  Reply With Quote
Old 12th January 2018, 10:46 PM   #22
banat is offline banat  Serbia
diyAudio Member
 
Join Date: Dec 2009
Location: near Belgrade
Koonw

I wonder about Sinclair-Peterson topology? his have concertina as DC coupled driver, it is characteristics the same as in on from topology from Fig.2 from my earlier post, or is something better by balancing OPS operation?

ps, maybe resistors around 6S4 tube need to be with slightly higher values, Ra=56K , Rk=41K+15K trim pot...

edit , 47uF on lower side of 6S4 cathode resistor is shown Wrong Inverse connected!
Attached Images
File Type: jpg Sinclair Peterson OTL.JPG (361.2 KB, 99 views)

Last edited by banat; 12th January 2018 at 10:55 PM.
  Reply With Quote
Old 12th January 2018, 11:00 PM   #23
Koonw is offline Koonw
diyAudio Member
 
Join Date: Apr 2013
Ah, the reverse of Tim Mellow's OTL (100% NFB),this is 100% PFB on top and 100% NFB to the bottom. It should have good current symmetry..Let me SIM later to better understand it.

Last edited by Koonw; 12th January 2018 at 11:16 PM.
  Reply With Quote
Old 12th January 2018, 11:14 PM   #24
banat is offline banat  Serbia
diyAudio Member
 
Join Date: Dec 2009
Location: near Belgrade
Thanks !
-------------------------
IMO this Sinclair Peterson based OTL amp Must also to have some sort of LS- DC protection unit, since until all tubes is not fully warm output DC offset oscillation will be significant .
  Reply With Quote
Old 13th January 2018, 03:30 AM   #25
smoking-amp is offline smoking-amp  United States
diyAudio Member
 
smoking-amp's Avatar
 
Join Date: Dec 2001
Location: Hickory, NC
I found this simplified Technics OTL design on the Web by Luca Cellai. (almost readable!) It is using separate class A drivers as Koonw suggested. Seems to be just what one would expect for the Inverted Futterman using separate drivers. Should give very close to matched tube bank gains. But there is no servo -exact- gain matching with the separate drivers. Could use a gain trim pot or some servo extension mod since the upper cathode follower tube bank will have gain slightly less than 1. (while the lower bank is servo'd to exactly one, depending on driver resistors.)

Using an LTP driver for the top tube bank (with output Fdbk to the unused grid 1) would get the top bank accurately up to gain of 1 (or matched gain with the bottom driver if they both have gain)

{and then finally, replace those tube banks with some big N channel Mosfets, they are just acting as unity gain followers}

Edit:
Two high gain feedback drivers can still mis-match by a tiny amount and produce a significant tube fight between top and bottom banks. So the gain trim has to be really closely trimmed.

If we just used a single LTP/CCS driver stage, with signal input on one grid, and the output Fdbk on the other, and the two outputs (bank gains trimmed by load resistors, or bootstrap to one load R, and a trimmed R on the other driver load R ), then the two banks would have to track exactly (no gain mis-match fighting with the single differential compare function controlling all)
Attached Images
File Type: jpg Technics_type_schematic.JPG (43.6 KB, 92 views)

Last edited by smoking-amp; 13th January 2018 at 04:00 AM.
  Reply With Quote
Old 13th January 2018, 04:22 AM   #26
smoking-amp is offline smoking-amp  United States
diyAudio Member
 
smoking-amp's Avatar
 
Join Date: Dec 2001
Location: Hickory, NC
Looking back at that TEM3200 OTL, Broskie had suggested that the first two tubes were in cascade, followed by the cathode follower to the Mosfet.

Due to the DC coupling advertised there, I'm thinking the TEM3200 has the 1st two tubes in a dissimilar LTP/CCS with input to the 1st triode and N Fdbk to the 2nd pentode tube. The pentode side providing decent gain.

The block diagram seems to indicate that. Then the follower to the Mosfet. (which is a ridiculously large 300 Amp one, gate slewing rate?) So the same LTP/CCS driver circuit essentially as evolved in the above post! (further pre-amp gain un-needed with the extreme gm Mosfet outputs)

The Mosfets are then in a Circlotron configuration for the final output. This should be really easy to build. And cheap.

With Mosfet outputs, 60V will do fine. There are these new (Chinese) switching/linear-follower power supplies lately. Only $65 0 to 60V at 0 to 5 Amps, 300 Watt. Two of them to make a 400 Watt OTL.
Attached Images
File Type: gif TEM3200.gif (18.3 KB, 86 views)
File Type: gif TEM3200_block_diag.gif (90.0 KB, 86 views)
File Type: jpg STP6005.jpg (93.2 KB, 74 views)

Last edited by smoking-amp; 13th January 2018 at 04:40 AM.
  Reply With Quote
Old 13th January 2018, 04:26 AM   #27
Koonw is offline Koonw
diyAudio Member
 
Join Date: Apr 2013
You need to control the top driver as well beside controlling the bottom so that they will stay matching even after output level or load change. You can build my version if you like to try :-), then build another version but with asymmetry driver. You only need to change out the drive board. So far I built about 5 versions, two are still in use, the rest in the drawer.
Attached Images
File Type: png 6c19p otl output current-1.png (92.3 KB, 64 views)
  Reply With Quote
Old 13th January 2018, 04:58 AM   #28
smoking-amp is offline smoking-amp  United States
diyAudio Member
 
smoking-amp's Avatar
 
Join Date: Dec 2001
Location: Hickory, NC
Thanks for posting your design!

6C19 triode tubes I see. 140 mA peak. Similar, somewhat bigger to the 12B4. What is the value of RL there? Oh, I see, 8, 16, 32.
How many 6C19 to work 8 Ohms?

I have a BIG box full of 21HB5 tubes, 800 mA peak, 18 watt, pentode.
Also 21LG6 tubes, 1100 mA peak, 28 Watt, pentode.
I even have a box of 13FM7 triodes, 175 mA, 10 Watt

A Mosfet OTL for summer, a Tube OTL for winter....

http://www.jogis-roehrenbude.de/Russian/6C19N/6s19.gif
http://www.wooaudio.com/docs/tube_data/6C19.pdf

http://tubedata.milbert.com/sheets/123/2/21HB5A.pdf
http://tubedata.milbert.com/sheets/123/6/6LG6.pdf
http://tubedata.milbert.com/sheets/123/6/6FM7.pdf

A couple of Xantrex/Sorensen XHR 150-7 power supplies should do. (got two for cheap years ago) The price is out of sight for two more of them now though. Guess I could use the two for both amps.
Attached Images
File Type: jpg Xantrex_Sorensen_XHR150.jpg (215.9 KB, 38 views)

Last edited by smoking-amp; 13th January 2018 at 05:26 AM.
  Reply With Quote
Old 13th January 2018, 05:04 AM   #29
Koonw is offline Koonw
diyAudio Member
 
Join Date: Apr 2013
RL 8-32 Ohms

Can strap the Pentode of 6f12p so you only need one pair tube.

5 pairs 6c19p for 8 Ohms, 25-30W rms.

Last edited by Koonw; 13th January 2018 at 05:15 AM.
  Reply With Quote
Old 13th January 2018, 01:43 PM   #30
Koonw is offline Koonw
diyAudio Member
 
Join Date: Apr 2013
Here is Sinclair Peterson sim plots and schematic for sharing.
There is a problem with trimmer for setting bias of driver, it's out of range. See attached.
Attached Images
File Type: png Sinclair Peterson OTL output current-1.png (89.5 KB, 24 views)
File Type: png Sinclair Peterson OTL levels-2.png (75.3 KB, 19 views)
File Type: png Sinclair Peterson OTL schematic-3.png (41.5 KB, 30 views)
Attached Files
File Type: asc Sinclair Peterson OTL-21.asc (6.8 KB, 5 views)

Last edited by Koonw; 13th January 2018 at 01:50 PM.
  Reply With Quote

Reply


OTL TopologiesHide 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
Topologies using darlingtons. beppe61 Solid State 71 13th January 2011 11:27 PM
Comparing 3 topologies hahfran Solid State 19 24th November 2008 08:33 PM


New To Site? Need Help?

All times are GMT. The time now is 08:45 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki