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Old 31st December 2012, 03:45 PM   #1
MINER is offline MINER  Serbia
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Default TUBE/MOSFET/BJT hibrid amp

Sorry -___- looks like dont know how to post smaller pics with the enlargement option.................

I`ve read thru part of the moskido thread, and few others, and there are some good ideas, and some not so good but i would like help for some of the designes, i havent seen in those threads I`ve made a few modifications to some projects, i have found., but i`m not experienced designer, nor so knowledgeable about suitable elements for the design, i want to achive/make So i want to present, design idea by design idea, and to finish it with your help
I`ll upload the original design(s) that inspired me, and the resulting one, to polish&finish it without blunders of type "ooooupss i didnt know that" with your help ^___^
I`m new to spice, so i`ll TRY to do something on my own, but dont hold your hopes to much for that XDDD


I will start with the design i saw/found in Elektor 1997 september
This is the tube section of the amp
Click the image to open in full size.

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this is the original current section

Click the image to open in full size.

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and this is the modified current section

Click the image to open in full size.

For cheaper version up to +47/0/-47V i consider BD912 T6-T13 / BD911 T14-T21 with R20-R35=100ohms, and R36-R51=0,27ohm

For better option(and higher voltages), i consider 2SC2992/2SA1216 pairs and MJL15024/MJL15025

Last edited by MINER; 31st December 2012 at 07:22 PM.
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Old 31st December 2012, 03:59 PM   #2
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Elektor output stage, a bit more complicated than necessary.
My suggestions helped improve the output of this one.

Tube(6N8P/6SN7) + MOSFET Hybrid Hifi Amplifier Kit/Board

One BJT watches over current sum of two resistors, insuring linear
class A. Makes all that other bias spread junk and CCS unnecessary.
In your modified output, perhaps watch over the sum of R40 R44?

Also makes no sense Elektor got two CCS pulling opposite ways with no
mechanism to insure those two currents are forced equal. It will tend
to pull the cap couplings toward one rail or the other, and huge offset.

----

Just as with Elektor, SR's SRPP still has to drive the full Miller
non-linear gate to drain capacitance of both output MOSFETS.
My BJT bias spreader scheme is only that, not driving outputs...

Elector adds a relay that shuts down output bias, I do like that!
Who knows what happens while power supplies come up or down?
I would surely graft that much of the Elektor to your final design.

Last edited by kenpeter; 31st December 2012 at 04:26 PM.
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Old 31st December 2012, 05:27 PM   #3
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I've outstOOpid'd myself again. Forgot how my own circuit worked...

Used one output to drive the other (solid state SRPP turned upside down),
so only 1 MOSFET's Miller is loading down the tube SRPP, a bonus...
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Old 1st January 2013, 04:26 PM   #4
MINER is offline MINER  Serbia
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I started this thread because i didnt want to bury my posts under 200+ pages of posts in the moskido thread .......
Also i`m gona post some other moskido, and non moskido designs that i have modified, and in need of help for finishing them.
Can someone help me with sugestion about usable BJT-s, R20-R35 best values for the sugested BJT-s, and with boucherot-s network values, because i supose the old ones are not suitable for new design.
And how much smaller values can i use for resistors R18&R19???
Or should i open a new thread i solid state part of the forum???

@kenpeter: - CCS is not a junk, and has a good role i CMRR, and preventing the oscilation in mosfets.

Last edited by MINER; 1st January 2013 at 04:37 PM.
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Old 1st January 2013, 06:51 PM   #5
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Blind battle of two CCS with no guidance toward center is junk.
You can't tweak both CCS equal and expect will stay that way.
Expect to pull toward the stronger CCS til output pegs the rail.

Choices: Choke to GND, DC couple, DC servo, get rid one CSS, or better yet both...

Prevents oscillation??? How you figure?

Last edited by kenpeter; 1st January 2013 at 07:12 PM.
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Old 2nd January 2013, 01:09 PM   #6
MINER is offline MINER  Serbia
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Ripple, and all the junk that passes thru PS filtering can cause/trigger oscilations in mosfets. That`s how i figure ^___^ Thats why i put in LM317/337 as an option for higher voltages(the + is aditional filtering) , not only for lowering the voltage + i dont have to change the transistors in CCS, and retweak the CCS because i dont have the knowledge/experience for that.
In this design, i can easily add DC servo between R11 and R12, together with the rest of DC protection.

Last edited by MINER; 2nd January 2013 at 01:17 PM.
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Old 9th January 2013, 12:55 PM   #7
MINER is offline MINER  Serbia
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This is one more hibrid design for which i need help finishing and i`ll post some more designs(as i stated in the first post) in a 2-3 days.

http://img689.imageshack.us/img689/6858/hibridpr2.jpg

Last edited by MINER; 9th January 2013 at 12:59 PM.
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Old 17th January 2013, 11:49 PM   #8
MINER is offline MINER  Serbia
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The link in previous post is invalid now. Here is the new one, and new three more schemmatics :-)
All schenatics in this post are UNFINISHED designes for which i need help with, from the people on this forum :-)
These is the original starting point design for the schematics after this one.
Click the image to open in full size.



Click the image to open in full size.

hibrid project 2
http://imageshack.us/a/img560/1467/hibridpr21.jpg

hibrid project 3
http://imageshack.us/a/img407/1474/hibridpr3.jpg

hibrid project 4
http://imageshack.us/a/img90/3663/hibridpr4.jpg

hibrid project 5
http://imageshack.us/a/img266/1162/hibridpr5.jpg

Last edited by MINER; 17th January 2013 at 11:58 PM.
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Old 18th January 2013, 09:21 PM   #9
nikwal is offline nikwal  Sweden
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on the srpp, you might want to try maybe a 40k resistor from suppy to lower anode and the same to earth from the anode. exact value will vary depending on the rest of the circuit and it has to be just right..
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