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-   -   Killer OTLs (https://www.diyaudio.com/forums/tubes-valves/316831-killer-otls.html)

kasanay 28th December 2017 06:13 PM

Killer OTLs
 
4 Attachment(s)
Here's a pair of OTL amps that were built in the early 60's by a small company named MP Concert Installations.
The system consists of 8 chassis: pre-amp, pre-amp power supply, power amp, power amp power supply and then X2 for stereo.
I acquired these about two years ago.

bonzo15011978 29th December 2017 12:35 PM

:D I think they use the same amount of energy of a small steel plant!

kasanay 29th December 2017 12:47 PM

You would think so, but check out the size of the extension cord that was used to power this bad boy up.
It's a wimpy, little lamp cord - maybe 16ga.

mhouston 29th December 2017 05:06 PM

It apears to work. How does it sound?

kasanay 29th December 2017 08:31 PM

It works, but I really can’t say how well. One of the power amps is not stable and I have not really given these guys a good run.

ProfGriff 29th December 2017 11:37 PM

Those look amazing! :eek: Out of curiosity, what's the recommended load impedance on those bad boys? GL with the re-build!

Refugee1 30th December 2017 12:38 AM

What are the tubes?
It looks like a truck load of domestic radio pentodes in parallel.

kasanay 30th December 2017 02:38 AM

Quote:

Originally Posted by ProfGriff (https://www.diyaudio.com/forums/tubes-valves/316831-killer-otls-post5291588.html#post5291588)
Those look amazing! :eek: Out of curiosity, what's the recommended load impedance on those bad boys? GL with the re-build!

32 ohm speakers work the best.
I have the original speakers that were paired with the amps.
They are custom built Bozak units (huge).

Carlp 30th December 2017 02:54 AM

Pictures??? (of the Bozaks in particular)

kasanay 30th December 2017 02:54 AM

Quote:

Originally Posted by Refugee1 (https://www.diyaudio.com/forums/tubes-valves/316831-killer-otls-post5291660.html#post5291660)
What are the tubes?
It looks like a truck load of domestic radio pentodes in parallel.

There are (30) 12B4As which have rP of 1030.
1030 / 30 = 34.4. About perfect for 32 ohm speakers.


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