First of all congratulatios for this great forum with those wonderful threads and ideas . I would like to introduce to you , my new tube power amplifier ( its not complete yet , but soon it will be ) , wich is an OTL Circlotron topology with the PL36 tubes . I use the following tubes for each channel , one EF184 or EF183 for the input stage / phase spliter following by one PCC85 as first differential gain stage following by two PCL82 as second differential gain stage ( the triode sections ) and the pentode sections as cathode follower to drive easely the output tubes wich is 10 PL36 five per each rail . Here is some fotos .
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Nice job. I like the use of the PC card as a strip line for the outputs. If you run this in or near class A I hope it doesn't oscillate on you. You may have to move the stopper resistors closer to the socket connections. Also the filaments might do a little better powered from the center tube, or even end-to-end, to equalize voltage.
Yes you have right , the grid stopper resistors its better to be closer to the tubes , but in this case the driver stage have very low output resistance because it is a cathode follower and will minimeze any unwanted effect . The filaments of the PL36 is 25V 0,3A for each one and the 5 tubes need 1,5 A wich is not heavy current , but i agree with you that it is better to connect it like you say if we have tubes like EL36 or El509 or other tubes wich have big reguirements of currents . In the past i use to connect every tube filaments with sepsrate cables , in this amp i do it for simplicity because there is too many tubes .
I don't think it will oscilate i have built another one OTL amp with 12 PL36 per channel , futterman topology with the same build philosophy and dosen't oscilate at all , the frequency response was high 195 Khz -3db .
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Is this you?
otl amp.handmade with 12 PL36 tubes per channel . - YouTube
If it is, then its very nice ,,,
Regards
M. Gregg
otl amp.handmade with 12 PL36 tubes per channel . - YouTube
If it is, then its very nice ,,,
Regards
M. Gregg
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Yes it is my first OTL , i build it back in 2004 , still playing good right now with many modifications over the years . I dont't use any kind of protections , I DON'T recomend this to anyone for safety reasons , but the amp has no proplem till now .
Well I hope you are arround here for a while because I like the amp..
What kind of coupling capacitors do you use or do you DC couple?
Welcome to the forum...
Regards
M. Gregg
Thank you a lot Gregg , I use Philips / BC MKP capacitors , sounds good to my ears , MKP 378 or 379 series , maby the 336 2 too .
This is the second video . PL36 Handmade Output transformerless tube amplifier by D.Argiannis - YouTube
Sounds very clear..what power output do you get from these tubes..?
In the comments to the video you say this is a variation of the futterman..what is the variation from the scheme?
Regards
M. Gregg