hi..we build mj amps with friend..they are risky amps because of high bias and balance risk..the mosfets can burn if there is sth is wrong.for example not quite matched small transistors..
some audophiles says mj amp is a very good amp.
as Nelson says the best amp is a piece of wire with gain i decided to build jfet version.it only has 4transistors.2 less pieces than mj amp
do you have any idea of differences between these amps?which one can sound better?what are the advantages and disadvantages of these amps?
thank you
some audophiles says mj amp is a very good amp.
as Nelson says the best amp is a piece of wire with gain i decided to build jfet version.it only has 4transistors.2 less pieces than mj amp
do you have any idea of differences between these amps?which one can sound better?what are the advantages and disadvantages of these amps?
thank you
Attachments
difference
between your one and what?
I need at least two (2) Class A to compare
mj amp .. what is?
Regards, Lineup
between your one and what?
I need at least two (2) Class A to compare
mj amp .. what is?
Regards, Lineup
Okay.
Now you have posted 2 circuits.
I say there is not much difference, in basic idea.
Apart from one has got bipolar and the other jfet input.
( Which can make a great difference, really, when comes to distortions harmonics spectra. )
Both are complementary with similar output stage (output from DRAINS).
Generally these drain output power amplifiers require some care
to watch the BIAS CURRENT in output.
As you are using Class A operation, this is less of a problem.
The output temperature and current will stabilize after some time after switch ON.
I recommend good & big heatsinks, as this further makes the output power transistors
run with less temerature differences at different output levels
and different room temperatures.
Regards, Lineup
Now you have posted 2 circuits.
I say there is not much difference, in basic idea.
Apart from one has got bipolar and the other jfet input.
( Which can make a great difference, really, when comes to distortions harmonics spectra. )
Both are complementary with similar output stage (output from DRAINS).
Generally these drain output power amplifiers require some care
to watch the BIAS CURRENT in output.
As you are using Class A operation, this is less of a problem.
The output temperature and current will stabilize after some time after switch ON.
I recommend good & big heatsinks, as this further makes the output power transistors
run with less temerature differences at different output levels
and different room temperatures.
Regards, Lineup
ok i see..but is it good to feed the output transistors with only 2little jfets? someone says its not good to get much gain with only one transistor..they say its better to cascade the small transistors..but nelson says less parts is better..i dont know what to do :S
umut1001 said:
Cascoding will NOT make more gain. But can reduce distortion quite a bit, if you make the cascode in a good way. Sometimes is not much to improve by cascoding. Other times it is.
Nelson Pass has designed so many cascode amplifiers.
He is the one that knows better than ANYONE else here WHEN to cascode and WHEN NOT. Cascoding makes more parts (less simple) but changes not the number of gain stages or the gain.
I say you try to get Nelson Pass to advice you.
Hope this topic will get his attention 😉
Because there is almost no other to better give you advice on:
1. Class A
2. MOSFET
3. Cascode
============================
About using 'only' two jfets to drive those lateral MOSFET,
2SK1058 and 2SJ62.
1. Use 2SK170BL & 2SJ74BL
The BL will have higher current operation = more gain!
2. When using less gain we get less feedback to correct the output signal.
Another way to say it, less open loop gain gives less negative feedback and a bit higher THD distortion
Now, the Grandmos Silver Design is one Low Global Feedback amplifier. ( It is not a ZERO Global Feedback (no feedback))
It is done on purpose!
Using Low Global Feedback, is something I often do. And also Nelson Pass 😉
This can give another (more pleasant)sound and change types of distortions,
even if this distortion is at a higher level, than for a normal High Level GNFB amplifier ( Global Negative FeedBack ).
Lineup
thanks for interest Lineup!i am an electronics engineer and my proffesor said that cascading reduces distortion i remember now🙂we listened to mj amp(cascaded one) it sounds really good..but i want to make simpler and not loosing any details 🙂 i bought 12pairs of 2sk170bl and 2sj74bl matched transistors today..i hope i receive them in 2weeks..
i hope Nelson comes and reads this thread..and says advantages and disadvantages.
thanks a lot
i hope Nelson comes and reads this thread..and says advantages and disadvantages.
thanks a lot
Zen Mod said:
well worth a try, umut1001
... 100-reds and 100-reds of F5 builders can not be all wrong. Can they?
🙂
Schematic and instructions by Nelson Pass:
http://www.firstwatt.com/downloads/F5-om_sm-080527.pdf
http://www.firstwatt.com/downloads/F5-om_sm-080527.pdf
Schematic:
Attachments
yes it seems good.but seems not simplier 🙂.of course F5can sound good..i want to try all of these circuits but not have enough time..can anyone send me single sided pcbs of F5?i want to make them and discuss something.. thanks
Re: this is i want to build
Since you ask me, you will note that it is quite similar to the F5 circuit
as a concept, but it uses Lateral Mosfets and the F5 uses Vertical Mosfets.
Some prefer the Laterals, some don't. It's easy enough to try both and
see what you like.
😎
umut1001 said:
Since you ask me, you will note that it is quite similar to the F5 circuit
as a concept, but it uses Lateral Mosfets and the F5 uses Vertical Mosfets.
Some prefer the Laterals, some don't. It's easy enough to try both and
see what you like.
😎
ok.i wanna ask differences between mj amp and grandmos design.. what are the differences between driving mos with only two jfets or cascading two bjt transistors to drive mosfets ? you say simpler is better.but at the other hand- someone says distortion will increase when getting much gain with one pair of transistors? thanks
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