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Old 5th February 2004, 01:17 PM   #1
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Default Possible to make a KT88 PP UL schemat OTL ?

I was thinking of a coupling capacitor to drive 8ohm, 16 ohm is my limit??

Any ideas on this schemat?
http://www.plitron.com/pages/Products/Audio/vtvkt88.htm

I know i've been knocking this schematic in many threads for the past month but I was considering removing the fact that I may have to import /all/ of my trannies and components just because local supply doesn't have /exactly/ what I need aswell as having a sweet-tooth for low-cost and good-sounding transistor OTL amps :P

I know I can source a local PT for the B+ of either side but I'll have to scratch my own 70v Bias supply and I would have to use a completely different filament supply as I couldn't use the single 6.3v 5a winding from the proposed centre-tapped modification that I've recently planned..as the transformer is supplying 'two' channels and is only wound for about 5a..not 10amp :P

Okay i'll promise not to post for 2 full weeks unless I have a reeely good explaination :P

OH and I'll make this thread a free-for-all for anyone to add their suggestions...

I've already got down a few from the last thread so I know not to use Carbon based resistors and that 8uF caps in place of the 10uF ones "won't matter" and that I can feed two amps B+ with only one power transformer with a CT...

Add your suggestions! reguardless of what they are and I'll fly them past a local (not to be disturbed unless via appointment) veteran to make sure I aint going to blow things up :P, besides I learn much faster from him explaining and sometimes demonstrating! infront of me than I could ever do reading... at least reading allows for writing which in turn allows me to remember some things :P

The best thing although I have found is to have a really thick yet portable notebook!!! I can't stress that enough!
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Old 5th February 2004, 01:36 PM   #2
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My suggestion is that if you want to build an OTL, build an OTL. Trying to adapt a circuit made for a totally different application will be quite frustrating- and at the end, you'll have something expensive, inefficient, and poorly performing for all the labor you put in.
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Old 5th February 2004, 02:00 PM   #3
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Ok then so this thread is to be used for suggestions for modifications to the original transformer amplifier design...

Is this circuit running the KT88's Class-A ? if not how can it be done with this schemat?
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Old 5th February 2004, 02:59 PM   #4
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For class A, you need to drop the B+ significantly- about 350 volts would work- and increase the idle current to about 90-100 ma per tube. You'll shorten the tube life, increase the heat output, and greatly reduce the power, but you'll have Class A, fwiw.
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