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Old 12th March 2009, 10:48 PM   #131
Salas is online now Salas  Greece
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Default Mosfet Cascode Loaded

Designed some Mosfet cascode anode CCS sinks with parts I had, for the 6V6 line preamp.
Initial impressions and THD measurements are very positive.

Click the image to open in full size.
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Old 14th March 2009, 04:37 PM   #132
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here is a preamp I builded use 5686 pentode.

the 5686 pentode is similar to 6V6/EL84.

the DIY report are post to my homepage below:

http://my.coolala.net/showpost.php?b...2907609&page=1
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Old 14th March 2009, 04:49 PM   #133
Salas is online now Salas  Greece
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Making a small tube out of a bigger tube... How does it compare to normally anode loaded with much more current?

P.S. Waiting for some IXYS 10M45 kindly sent by an Italian DIY member (guglielmope) so I will test this Jung sink with high hopes for even better results.
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Old 11th April 2009, 09:50 AM   #134
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Hello Salas----
How good is the 6v6 pre compared to Conrad Johnson act2 pre-
i have try that --in my system--but it vas to boring---is there good life sound in yours??
is the pre easy to build for a man there only have made fet build-eks. Erno Borbely-?
best regards
Bjarne

ps---it is first time, i post something on forum.so i hope i do it right.
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Old 11th April 2009, 10:30 AM   #135
Zen Mod is offline Zen Mod  Serbia
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Salas - I'm just curious ..... you obviously are trying to find best CCS for your purpose , but - did you tried yet to cascode 6V6 itself ..... to ensure constant voltage operation of triode ?

bjt+mosfet wil suffice for that purpose , if not mosfet alone ....
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Old 11th April 2009, 01:46 PM   #136
Salas is online now Salas  Greece
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Quote:
Originally posted by beardman
Hello Salas----
How good is the 6v6 pre compared to Conrad Johnson act2 pre-
i have try that --in my system--but it vas to boring---is there good life sound in yours??
is the pre easy to build for a man there only have made fet build-eks. Erno Borbely-?
best regards
Bjarne

ps---it is first time, i post something on forum.so i hope i do it right.
Don't know about CJ.

Lifelike sound there is in it, but handling 6V6 in a line pre without false enthusiasm in its sound takes caution in its mounting. Needs to be mechanically decoupled especially when actively loaded in full mu (gain=9.4). Its not a difficult concept to grasp at all, but it takes work. It has to be made with quality parts, and silent transformer if on same chassis. The chassis plays significant role. One general remark for a pre not to sound boring or aggressive in your system, is gain structure. There is just right or less or too much. Happily, the 6V6 trioded sounds excellent from cathode follower buffer arrangement, or medium gain with resistor loading, up to full tilt with active anode loading.
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Old 11th April 2009, 02:03 PM   #137
Salas is online now Salas  Greece
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Quote:
Originally posted by Zen Mod
Salas - I'm just curious ..... you obviously are trying to find best CCS for your purpose , but - did you tried yet to cascode 6V6 itself ..... to ensure constant voltage operation of triode ?

bjt+mosfet wil suffice for that purpose , if not mosfet alone ....
Won't this increase the output impedance? If it remains acceptable, I can try.

*I really wanted to do that with valves and OPT, but the chassis is too nice and heavy so to hack and experiment. I will have to do experiments with 4 6V6s and the assorted psu and heating arrangements given the chance of making another new one and most probably with an HV shunt too.

**Meantime, THE BEST active loading to my ears is an electronic choke. Recommend you to try on some project of yours. Alas, I have too sensitive speakers for the gain I get...
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Old 11th April 2009, 02:39 PM   #138
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Salas


Won't this increase the output impedance? If it remains acceptable, I can try.
.......
not really - you can look at mosfet cascode as on follower

sort of ....

point is that properly biased cascode is invisible , sound wise ....

Quote:
Originally posted by Salas


.........

*I really wanted to do that with valves and OPT, but the chassis is too nice and heavy so to hack and experiment. I will have to do experiments with 4 6V6s and the assorted psu and heating arrangements given the chance of making another new one and most probably with an HV shunt too.

.......
yup - but you already know for my opinion about shunt regs ... you'll have benefits , even with all those CCS-es everywhere


Quote:
Originally posted by Salas


.......

**Meantime, THE BEST active loading to my ears is an electronic choke. Recommend you to try on some project of yours. Alas, I have too sensitive speakers for the gain I get...
principle is ( at least on that schematic , where you forgot to draw point between 3. and 4. led ... hehe) same as with Geek/P10/forgivemeifIforgotsomeone "generic universal CCS-es" , where you have one current setting active element , cascoded with another one ....

look at my LTP tail ....

overall - fugly! , what else ?




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Old 11th April 2009, 02:55 PM   #139
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Quote:
Originally posted by Zen Mod
( at least on that schematic , where you forgot to draw point between 3. and 4. led ... hehe)
Naah, I did not forget. There has to be no connection there. 6LEDS turn on the lower Mosfet. The upper one has the top divider's resistor. If you connect, the voltage on anode will latch up at B+ level.

*This is constant voltage on DC, not constant current. Its a gyrator. Gives the benefit of the constant voltage anode by electronically simulating a large choke (e-choky? ).
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Old 1st July 2009, 12:30 AM   #140
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Salas ,

Any more thoughts or comments on the Russian 6V6 equivalent ?


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