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Killer OTLs
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Old 28th December 2017, 06:13 PM   #1
kasanay is offline kasanay  United States
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Default Killer OTLs

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.
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Old 29th December 2017, 12:35 PM   #2
bonzo15011978 is offline bonzo15011978  Italy
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I think they use the same amount of energy of a small steel plant!
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Old 29th December 2017, 12:47 PM   #3
kasanay is offline kasanay  United States
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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.
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Old 29th December 2017, 05:06 PM   #4
mhouston is offline mhouston  Australia
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It apears to work. How does it sound?
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Old 29th December 2017, 08:31 PM   #5
kasanay is offline kasanay  United States
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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.
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Old 29th December 2017, 11:37 PM   #6
ProfGriff is offline ProfGriff  Canada
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Those look amazing! Out of curiosity, what's the recommended load impedance on those bad boys? GL with the re-build!
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Old 30th December 2017, 12:38 AM   #7
Refugee1 is offline Refugee1  United Kingdom
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What are the tubes?
It looks like a truck load of domestic radio pentodes in parallel.
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Old 30th December 2017, 02:38 AM   #8
kasanay is offline kasanay  United States
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Quote:
Originally Posted by ProfGriff View Post
Those look amazing! 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).
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Old 30th December 2017, 02:54 AM   #9
Carlp is offline Carlp  United States
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Killer OTLs
Pictures??? (of the Bozaks in particular)

Last edited by Carlp; 30th December 2017 at 03:05 AM.
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Old 30th December 2017, 02:54 AM   #10
kasanay is offline kasanay  United States
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Quote:
Originally Posted by Refugee1 View Post
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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