i use this simple auto bias method but with a Mosfet CCS instead of the choke loading , 1.8R source resistor and A 6800uf output cap as i don't have a 4700uf
it seems that i have small bump at 30/40hz with my speaker that i dont' have with my other amps. perhaps the value of the "pseudo parafeed "output cap is critical. i will try with smaller ones 🙂
it is alive , my THF51S l'amp CCS with IXTH6N50D2
the B+ is 60V the THF51S is running at 30V VDS and 2.1 AMP with auto bias and a 6800uf capacitor output return to source ( western electric schema)
i have made a CLC power filter but finally get more noise than with CRC ( surely the chokes are to close of something) but nothing dramatic.
i have 1R CCS source resistor on one side and 0.8R on the other to get the same bias and vds on the VFET ( my mosfet are not matched i suppose)
sound is very good somehow very different than my alpeh min or Sony pushpull VFet. don't know if i will buy some hig power resistor to try or Chokes for the moment. it seems more powerfull than my previous build with 2SK82 but it can be a illusion of the fresh build , i will see for the next days 😀
Nice
Can you share your schematic?
sure i will , when i will stop changing it 😀
sunday version , fixed bias with 3,2V lithium battery in series with the THF51S gate . ( and 3,25A fuse on soource) now i have 32V at 2.5A .
unfortunatly too much heat for my small chassis 75° C
but what a sound 😱
Have you measured the gate current ? Any idea how long the battery will last in that application ?
i have use this method with many amps during month and never had problems with battery discharge . perhaps but my amp never last so long before being rebuilt in something else 🙂
works well with 3,6V lithium buton cell ( on the grid and not on the source !!)
somtething strange with the "wester electric bypass cap" and auto-bias the sound seems too good to be true. everything is big with an enormous soundstage and 3D effect. to compare the fixed bias with battery grid bias seems smalller and flat but more real .
the effect of the positive feedback injected by the return of the speaker directly to the source ?
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sure i will , when i will stop changing it 😀
sunday version , fixed bias with 3,2V lithium battery in series with the THF51S gate . ( and 3,25A fuse on soource) now i have 32V at 2.5A .
unfortunatly too much heat for my small chassis 75° C
but what a sound 😱
out of curiosity, what is the Pd(W) of the IXYS part?
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it is a 300W device and it run a 27W in my config , sissy biasing as someone would say 😀
i had some nasty noise on the speaker so i have tried to change the PS to a CRCRC but it doesn't change , it is more like a buzzing. as on the pictures my CCS source resistor is a wirewound type perhaps acting like an antena i will try a non indiuctive film one.. i have change my 6800uf output cap to a 4700uf and now the Bass are more real , no more bumps at 30hz.
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can you please stop doing this ! after early death of the Sony VFETs, now we can see the THF51S stock running down , next will be the other Tokins .
this forum is a tragedy and you are trés cher monsieur the devil instrument of Sit shortage 😀:
this forum is a tragedy and you are trés cher monsieur the devil instrument of Sit shortage 😀:
If SIT's disappears in Your amplifiers that is always a good reason for the sources are dry 😛
Super work on amorphous core input choke's for the PSU and nanocrystalline transformers for SIT's output stages.
I stay in tune for part 2 of the amp construction article.... ambitious high quality as usual made by Dave Slagle.
Any thoughts or Diyers comments about ?
Thanks and best regards
I stay in tune for part 2 of the amp construction article.... ambitious high quality as usual made by Dave Slagle.
Any thoughts or Diyers comments about ?
Thanks and best regards
Attachments
There was only a prototype, currently disassembled.
The dissipation of the one presented at BAF was 180 w/ch. That's
a pretty serious sink - better use two....
The dissipation of the one presented at BAF was 180 w/ch. That's
a pretty serious sink - better use two....
Thanks Mr. Pass
Look forward at final rare PL amplifier product and maybe article about.
DIGITAL DOMAIN B-1a ／全Sit／Vfet功放 - 科创
Kind regards
Look forward at final rare PL amplifier product and maybe article about.
DIGITAL DOMAIN B-1a ／全Sit／Vfet功放 - 科创
Kind regards
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