SE OTL amp - What do you think? - diyAudio
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 14th August 2002, 05:14 PM   #1
diyAudio Member
 
Join Date: Feb 2002
Location: Roskilde, Denmark
Default SE OTL amp - What do you think?

Hi There.

I found this circuit on the web and I consider to give it a go. Have anny of you made before? What dou you think of the circuit. I was thinking of trying to use it to drive a set of Quad ELS.
Anny input is welcome

Thanks Peter Jensen

Attached Images
File Type: jpg se otl.jpg (49.5 KB, 900 views)
  Reply With Quote
Old 14th August 2002, 06:40 PM   #2
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Sofia
Peter,

A 2000uF/200v is bound to sound ugly whether you like cathode followers or not. And why a low voltage OTL for the Quad? You'll still be using it's step-up transformer which i never felt was briliant. If you really want to improve on the Quad go for either some dangerous high-voltage OTL or a custom o/p transformer which eliminates the Quad step-up.

best regards

peter
  Reply With Quote
Old 16th August 2002, 08:03 AM   #3
diyAudio Member
 
Join Date: Feb 2002
Location: Roskilde, Denmark
Hi again

Well if you study the internet, severat OTL amps are listed as good amps to drive the quad´s. I know that the capacitor in the output stage is a critical component, but i still think the amp looks interesting.
If you forget about the quads and look at it as an amp for driving a dynamic speaker, it might be interesting to use it as a mid and or tveeter amp. The capacitor in the crossover vill remove the DC and you can forget about the 2000uf 200v beast. This only geos for a 3-vay system if used for both the tveeter and mid section.

Still not anny of you that have actually build this circuit?

MVH Peter Jensen
  Reply With Quote
Old 16th August 2002, 01:37 PM   #4
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Sofia
Why don't you just try it? I doubt if a 6SN7 will properly drive a 6080, but breadbording will take you an hour or so and at least you'll be able to make up your mind if it's worth building with blackgates at the o/p And the cathode follower... at least it's choke loaded.

regards

peter
  Reply With Quote
Old 21st August 2002, 01:43 AM   #5
diyAudio Senior Member
 
fdegrove's Avatar
 
Join Date: Aug 2002
Location: Belgium
Hi,

I took a look at your circuit and have some remarks.
First of all I can say the 6SN7 will drive the 6080's with ample reserve,I have built a similar amp were it drove 8 6080's per channel.Also I 'd replace the 6SJ7 with a 12AX7.You will also need more power, 40 watts would be a good start.
A couple of years ago a well thought out OTL was offered in Glass Audio by Bruce Rosenblitt.I developped it a bit further to be used as monoblocks with twice the number of output valves,it has no dc blocking cap in the output ( you can still put it there if you're uncomfortable with the idea ) and has been working flawlessly ever since.
Also I prefer an electrostatic such as the Quads ( ESL 57's I presume ) to be driven by a push-pull amp rather than single-ended.Remember that in the very unlikely event of dc on the output (if you study the circuit and it's valves you KNOW this can not happen in the Push-pull OTL I suggest) the stepup transformer of the stats will block it nicely.
On the other hand people tend to overreact when they see such a huge electrolytic in the signal path but in this application it won't do that much harm.Moreover the Quads also have some in their signal path.Just see if you can hear the difference.

Rgds,
__________________
Frank
  Reply With Quote
Old 10th April 2003, 01:48 PM   #6
Masami is offline Masami  Hong Kong
diyAudio Member
 
Join Date: Apr 2003
Location: HK
Hi,

I also very take interested about this SE OTL Amp.
I send a e-mail to the web which post this circuit and they give me some comment :
1. use an EF86 for the input tube
2. use 4 -6 output tube. to devlep 8-12 watts
3. you can eleimate the 1mH & 600mH coil . They are used suppress RF interference

They told me it is a very good sounding amplifier.

Anyone really build it before ?

Regards,
__________________
Masami
  Reply With Quote
Old 11th April 2003, 02:38 PM   #7
Joel is offline Joel  United States
diyAudio Member
 
Joel's Avatar
 
Join Date: Oct 2002
Location: Brooklyn, NY
Quote:
Originally posted by Masami
3. you can eleimate the 1mH & 600mH coil . They are used suppress RF interference.
Actually, they are a large portion of the cathode load, and they should not be removed. A 600mH choke presents a 3,768 ohm load at 1kHz.
  Reply With Quote
Old 11th April 2003, 03:03 PM   #8
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
We will have reached Nirvana when someone builds an amp that dissipates over a kilowatt, has a source impedance of more than 20 ohms, puts out less than a watt, has more than 5% distortion, gets worse with reactive loads, and blows up on a regular basis. This is a step in the right direction.
__________________
The more you pay for it, the less inclined you are to doubt it.- George Smiley
  Reply With Quote
Old 11th April 2003, 03:12 PM   #9
Joel is offline Joel  United States
diyAudio Member
 
Joel's Avatar
 
Join Date: Oct 2002
Location: Brooklyn, NY
Sy, sounds like a good argument for transistors.
  Reply With Quote
Old 11th April 2003, 03:45 PM   #10
diyAudio Member
 
Tube_Dude's Avatar
 
Join Date: Mar 2002
Location: Aveiro-Portugal
Default The overrated capacitor...

Quote:
A 2000uF/200v is bound to sound ugly whether you like cathode followers or not
This capacitor doesn't need to be 200 Volts rated...the choke will have a very low DC resistence to ground more the 20 Ohms resistor...we will end with 21 ou less Ohms to ground!

Even if you pass 1 Amp across it they don't have more than 20 volts across it...so being even is the safe side a 50 volt rated capacitor will do the job nicely...
__________________
Jorge
  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



New To Site? Need Help?

All times are GMT. The time now is 09:26 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