I just picked up a second plitron pat-4070-cfb output tx.. (got very good deals on both).
Specs are 70 watts, 4k pri and 5 sec, CFB and UL taps. So, that's 6400 pri w/ 8ohm sec.
Plitron's posted designs w/ these tx's have them w/ kt88's(or equiv) and being used w/ 4 ohm speakers, so 3.2k primary... I'm going to assume they'll be used w/ 8ohm speakers, 6400 primary.
What would you do w/ them? I'm thinking kt88(or equiv), simply due to cost and availability. Run them at as high a voltage possible and with a driver capable of ab2 (probably based off tubelabs 6l6 octal driver).
I don't know exactly what to plan for, as I see people saying they get no more than 20 watts out of a triode pair, to mentions of getting 75 watts out of a triode pair in ab2.
Should I be thinking about parallel tubes to get the most out of this TX? Or, is 60-70 watts for a pair in ab2 actually realistic?
Let me know what you'd do w/ them... at this point the only design criteria is finding a good use for these transformers.
Specs are 70 watts, 4k pri and 5 sec, CFB and UL taps. So, that's 6400 pri w/ 8ohm sec.
Plitron's posted designs w/ these tx's have them w/ kt88's(or equiv) and being used w/ 4 ohm speakers, so 3.2k primary... I'm going to assume they'll be used w/ 8ohm speakers, 6400 primary.
What would you do w/ them? I'm thinking kt88(or equiv), simply due to cost and availability. Run them at as high a voltage possible and with a driver capable of ab2 (probably based off tubelabs 6l6 octal driver).
I don't know exactly what to plan for, as I see people saying they get no more than 20 watts out of a triode pair, to mentions of getting 75 watts out of a triode pair in ab2.
Should I be thinking about parallel tubes to get the most out of this TX? Or, is 60-70 watts for a pair in ab2 actually realistic?
Let me know what you'd do w/ them... at this point the only design criteria is finding a good use for these transformers.
There are just a handful of typical topologies available.
Most notably - Mullard 520, Williamson, floating paraphase - push pull (also known es GEC 88-50 amplifier), Hegeman CTII.
I built first 3, prefer GEC KT88-50.
Others, like twin coupled, aren't suitable for your particular transformer.
Additionally, there are very simple variants, which, due to very generic nature, can't be "branded", for example Dynaco 6AN8 based pre-driver + concertina splitter (or similar) / PP. Such topology was used by hundreds of mid-class amps in 60th.
BTW, you can take any KT88/6550/KT120 amp schematic you like and switch its output stage to UL+CFB mode, yielding (IMHO) best sonic qualities available.
With CFB you don't need triode connection, CFB gives characteristics very close to triode.
A pair of KT88 with 6.4K primary connection (which is your case with 8 Ohm load) will produce about 35 - 40W in UL+CFB. Building quad KT88 doesn't make any sense - you will need 1.9 - 2.2K output transformer for full power.
Most notably - Mullard 520, Williamson, floating paraphase - push pull (also known es GEC 88-50 amplifier), Hegeman CTII.
I built first 3, prefer GEC KT88-50.
Others, like twin coupled, aren't suitable for your particular transformer.
Additionally, there are very simple variants, which, due to very generic nature, can't be "branded", for example Dynaco 6AN8 based pre-driver + concertina splitter (or similar) / PP. Such topology was used by hundreds of mid-class amps in 60th.
BTW, you can take any KT88/6550/KT120 amp schematic you like and switch its output stage to UL+CFB mode, yielding (IMHO) best sonic qualities available.
With CFB you don't need triode connection, CFB gives characteristics very close to triode.
A pair of KT88 with 6.4K primary connection (which is your case with 8 Ohm load) will produce about 35 - 40W in UL+CFB. Building quad KT88 doesn't make any sense - you will need 1.9 - 2.2K output transformer for full power.
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