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Old 2nd October 2007, 01:08 PM   #1
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Default HELP PLEASE - with preamp design

hello, i am trying to design a single ended valve amp for a college project. i have decided on a cathode biased kt88 output stage coupled to a james js-6123hs output transformer. but i am unsure what would be the best preamp method. so all help would be very much apreciated.
i have looked at many designs but i am unsure.
i have looked at mikael's 6n1p based preamp but am not sure

i was thinking about a 12au7 running both parts either in parallel, cascade, cascode or srpp. i have been reading a lot to try and understand the best uses for each but help would be good.

also what sort of voltage swing should i be looking to send in to the kt88 i was thinking about 50v pk-pk. but again this is just based on what i learned in the past 3 weeks.

any help would be very much appreciated,,,,

soundbadger
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Old 2nd October 2007, 02:24 PM   #2
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Hi Soundbadger

If yoy really want to design your own amplifier I recommend some thorough reading of 'valve amplifiers' by Morgan Jones, available at amazon, and of the stuff available at this thread

Good luck, Erik
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Old 2nd October 2007, 03:15 PM   #3
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already got it and have been reading it ,,
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Old 2nd October 2007, 04:19 PM   #4
Sheldon is offline Sheldon  United States
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If you need some gain you could go with with a grounded cathode 5687 or ECC99. If you don't need as much gain, a 12B4 in the same configuration - many examples of that one here if you search.

Sheldon
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Old 2nd October 2007, 04:47 PM   #5
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Your terminology is throwing people off. By your project description, it sounds like you are not looking to build a preamp but instead to build the driver stage for your KT88's.

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Originally posted by soundbadger
already got it and have been reading it ,,
Then read up on where he discusses driver stages. Especially where he discusses trioded 6EJ7 and EF86.
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Old 2nd October 2007, 06:38 PM   #6
Conta is offline Conta  Europe
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Quote:
also what sort of voltage swing should i be looking to send in to the kt88 i was thinking about 50v pk-pk.
Yes, you need swing about 40-45V. This preamp can drive KT88 directly:
http://audio.ring.lt/pre/pre_en.htm
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