OTL amplifier

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OTL amplifier

Postby Tubeamp » Wed May 09, 2012 2:54 pm

Hello,

I have build lately this OTL amplifier, any improvement suggestions?

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Postby Geek » Wed May 09, 2012 7:42 pm

Ten 6080's (???)

Chokes instead of 820R, too.

Cheers!
-= Gregg =-
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Postby Tubeamp » Thu May 10, 2012 12:06 am

Hi Geek, how are you doing?

Geek wrote:
Ten 6080's



Do you suggest to use ten 6080 per channel? That's a lot of stuff and... heat !!!

I get 18W into 16 ohms speakers with 3 tubes/channel. The frequency response is flat from 10 Hz (-0.5db) to 60kHz (-3db)
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Postby Geek » Thu May 10, 2012 12:41 am

Doing well, thanks. And you? ;)

That's awesome you're getting that. I am concerned about transconductance, etc. with only three.

If I were to build one for myself, I'd use 8/channel. Hence my reccommendation.

And heat and big 6.3V iron is just par for the course with these. A 6080 OTL is like driving a Hummer - if you're going to add to global warming, may as well do it right! (lol)

Cheers!
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Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
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Postby Tubeamp » Thu May 10, 2012 1:53 am

I'm doing well too...hm.. except that I'm a bit short of $) (lol)

You are right as regards transconductance and 8/channel would be great, but I don't want my OTL to contribute much in the global warming.....not to mention the thousand of the daily plane flights and the billion of cars and a/c units!!!! ;)
Last edited by Tubeamp on Thu May 10, 2012 1:58 am, edited 1 time in total.
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Postby Tubeamp » Thu May 10, 2012 1:57 am

Hey Geek, I forgot to ask you, what chokes do you have in mind ?
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Postby battradio » Thu May 10, 2012 5:50 am

Something that will handel the current , a push pull output transformer would work as a choke . Its freqincy reponce wouldn't matter just its inductace ,the higher the beter
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Postby soundbrigade » Thu May 10, 2012 12:10 pm

Have you checekd Bruce Rozenblit's OTL that looks like yours? I think he added over-current protection somehow on the PSUs.
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Postby Geek » Thu May 10, 2012 11:11 pm

Tubeamp wrote:Hey Geek, I forgot to ask you, what chokes do you have in mind ?


Mark's right on the current. I had my eye on some larger Hammond reactor types (XL = ZL @ lowest freq... preferrably XL=4*ZL).

On holidays at the moment, so I'll recommend something more specific if you need when I get home.

Cheers!
-= Gregg =-
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Postby Tubeamp » Fri May 11, 2012 6:00 am

Thanks for your suggestions!

soundbrigade wrote:
Have you checekd Bruce Rozenblit's OTL that looks like yours? I think he added over-current protection somehow on the PSUs.



Do you mean this circuit?

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Postby Tubeamp » Fri May 11, 2012 6:03 am

I wonder though, how the choke will improve the amplifier's performance?
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Postby Geek » Sun May 13, 2012 7:38 pm

Back home now.

I'd check out a Hammond 159ZA, good for 1A - it'll give 18 ohms reactance at 10Hz. Good for an 8 or 16 ohm speaker.

Chokes are nice because you get twice the swing of an active load for the same current.

Cheers!
-= Gregg =-
Fine wine comes in glass bottles, not plastic sacks. Therefore the finer electrons are also found in glass bottles.
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Postby Tubeamp » Mon May 14, 2012 12:04 pm

Hi Geek, welcome back home, hope you had a great time!!

I assume I have to use 2 of those chokes per channel, right?
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Postby Geek » Mon May 14, 2012 1:25 pm

I had a great time, thanks! :D

Yup! 2 per channel.

Cheers!
-= Gregg =-
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Postby Tubeamp » Wed May 16, 2012 1:06 am

Thanks Geek ! I will try the chokes as soon as I have some in hand.
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