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Ready to get my feet wet with OTL magic.... looking for a schemtic or 2

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Posted on June 22, 2012 at 00:13:57
Jeff Davison
Audiophile

Posts: 923
Joined: November 9, 2007
 After building a few amplifiers over the years, I'm just about skilled enough to tackle another.
This time around, I'd like to do an OTL based on the Atmosphere S30 for my 1st go at OTL's. I have not done much research into them however.
I've migrated over to this forum from the DIY Tube forum as there is a a wealth more info on OTL design, care and feeding.

I am hoping some one here could guide me to a source of schematics for the above mentioned amps?

THANKS!!!!

JD

 

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RE: Ready to get my feet wet with OTL magic.... looking for a schemtic or 2, posted on June 22, 2012 at 08:27:10
Ralph
Manufacturer

Posts: 2180
Location: Minnesota
Joined: April 24, 2002
 I'm guessing that you've not read every thread on the DIYaudio forum :)

There are thousands, no worries. Search on a thread entitled 'What tubes for a tube amp?"

BTW we are offering the M-60 in kit form once again.

 

RE: Ready to get my feet wet with OTL magic.... looking for a schemtic or 2, posted on June 22, 2012 at 08:34:34
Jeff Davison
Audiophile

Posts: 923
Joined: November 9, 2007
 Thanks... can go insane reading every thread.
I'm a "ground-up" do it yourselfer. Not so much a kit builder.
Been doing low power SETS for the last few years and my system only needs between 8 and 15 watts or so. 60 watt's is way too much power for my needs, wants and desires. 20 would do nicely.


"EDIT"..... I found it over on the "other" forum... i.e. DIYAudio


JD

 

RE: Ready to get my feet wet with OTL magic.... looking for a schemtic or 2, posted on June 22, 2012 at 08:43:40
Jeff Davison
Audiophile

Posts: 923
Joined: November 9, 2007
 no joy

"EDIT" nevermind this post...

I found it over on the "other" forum... i.e. DIYAudio


quick note.... I have a box of 12 NOS TungSol 6520's and another stash of about 12 NOS 12sx7gt's.


JD

 

RE: Ready to get my feet wet with OTL magic.... looking for a schemtic or 2, posted on June 22, 2012 at 13:19:20
Lew
Audiophile

Posts: 5289
Location: Bethesda, Maryland
Joined: December 11, 2000
 FWIW, 12SX7GT makes a nice driver tube for whatever outputs you choose. For outputs, I have a stash of selected vintage 6C33Cs, the good ones from the early 90s, if you are interested.

 

RE: Ready to get my feet wet with OTL magic.... looking for a schemtic or 2, posted on June 22, 2012 at 13:47:14
Jeff Davison
Audiophile

Posts: 923
Joined: November 9, 2007
 thanks, but no need for any more tubes. I want to use what I have on hand.


JD

 

RE: Ready to get my feet wet with OTL magic.... looking for a schemtic or 2, posted on June 25, 2012 at 11:17:16
Ralph
Manufacturer

Posts: 2180
Location: Minnesota
Joined: April 24, 2002
 Ah yes, the allure of the small OTL...

It is possible if you have the right speakers- don't expect a small OTL to driver Magnaplanars...

I routinely run my speakers at home with only 4 output tubes. That will give you about 20-30 watts, depending on the load. It should be an easy load and this gets even better if the load is higher impedance like 16 ohms (that benefits almost any amplifier, FWIW...).

 

RE: Ready to get my feet wet with OTL magic.... looking for a schemtic or 2, posted on July 2, 2012 at 11:37:55
Retsel
Audiophile

Posts: 1034
Joined: April 17, 2000
 If you want to try something wild and wooly, try Steve (Stephie) Bench's single ended OTL with the output tubes in inverted mode. I provided a link to the Web site for the schematics below. You would have one of the only in the world, and I bet it sounds really great too! I have not built it, but I intend to someday (I have 15 ohm Lowthers, a perfect match). I believe that it only draws about 150 watts per side - a modest energy draw.

http://diyaudioprojects.com/mirror/members.aol.com/sbench102/PowerAmps/se_otl.gif

You can look on Bench's webpages for more information about how this was pulled together.

Retsel

 

RE: Ready to get my feet wet with OTL magic.... looking for a schemtic or 2, posted on July 2, 2012 at 13:00:24
Ralph
Manufacturer

Posts: 2180
Location: Minnesota
Joined: April 24, 2002
 You need a lot of these tubes to make only a small amount of power. You could get more power from a single 6AS7G! I've never figured out what the advantage is. Have you heard one?

 

RE: Ready to get my feet wet with OTL magic.... looking for a schemtic or 2, posted on July 2, 2012 at 14:22:21
Retsel
Audiophile

Posts: 1034
Joined: April 17, 2000
 I haven not heard one, but Bench said that it sounds very, very good. Having seen the quality of Bench's designs over time and hearing Bench's very high regard for this design, I trust that this design would sound very good. The advantage of this design is using the tube in single ended operation while it is in its inverted mode, resulting in a very linear tube curve. Linear tube curves, of course, means very low distortion. The other advantage is very low power draw for the amp. As you point out, you would need efficient speakers for this amp to qualify, or a lot of output tubes (which are not expensive).

Bench went out of the way to avoid any iron, but I would think hard about using very high quality interstage transformers versus the coupling caps shown in this design.

 

RE: Ready to get my feet wet with OTL magic.... looking for a schemtic or 2, posted on July 2, 2012 at 19:20:31
coolhand
Audiophile

Posts: 471
Joined: June 5, 2006
 I have very efficient horns so I know which OTL amps I'll be building next.... and it'll be a great way put use to all those NOS WE300B's I've got on my shelves, no point them collecting dust is there !

The design will be in Bruce's forthcoming new book along with some other really neat stuff:

 

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