Lumba, I read that post a few days after you wrote it. That is why I thought you wanted to go OL and not only degenrate-
Would be interesting with a non global feedback le Monstre
(I have one in MC) and compare sonics.
My simulated OL le Monstre has 25dB gain, 100kHz BW,
and THD can be 2nd, 3rd, or a mix of your choice and THD is about 0,5% at 1W/ 8 Ohm.
Sigurd
Would be interesting with a non global feedback le Monstre
(I have one in MC) and compare sonics.
My simulated OL le Monstre has 25dB gain, 100kHz BW,
and THD can be 2nd, 3rd, or a mix of your choice and THD is about 0,5% at 1W/ 8 Ohm.
Sigurd
Lumba Ogir said:
HKC- here are some ideas:
* make the tracks that carries heavy currents MUCH wider. As wide as you can make them, ie make copper pours.
* Put the input JFETs so that they "kiss" eachother, so you can later on glue them together
* Move the power resistors to the sides and put the drivers close to the output transistors
* Move the long feedback wire more to the middle of the PCB.
* Move the cascode transistors more to the middle an d closer to the JFETs.
* Maybe a ground plane?
Hirga has a 47u cap on each rail. Did you skip that or did I miss it?
You might want to decouple the cascode resistors with a small cap (say 100n) so that the cascode voltage going in to the small BJTs is low pass filtered. It can give slighly better sonics.
Attached is my layout which has more PS decoupling (incl input section low pass filtering) than the original le Monstre and also an input filter and a feedback capacitor. I also use TO220 power resistors with a heatsink instead of the standard cylindical ones,
and have LEDs power-on indication.
Size is 160x100mm.
Sigurd
* make the tracks that carries heavy currents MUCH wider. As wide as you can make them, ie make copper pours.
* Put the input JFETs so that they "kiss" eachother, so you can later on glue them together
* Move the power resistors to the sides and put the drivers close to the output transistors
* Move the long feedback wire more to the middle of the PCB.
* Move the cascode transistors more to the middle an d closer to the JFETs.
* Maybe a ground plane?
Hirga has a 47u cap on each rail. Did you skip that or did I miss it?
You might want to decouple the cascode resistors with a small cap (say 100n) so that the cascode voltage going in to the small BJTs is low pass filtered. It can give slighly better sonics.
Attached is my layout which has more PS decoupling (incl input section low pass filtering) than the original le Monstre and also an input filter and a feedback capacitor. I also use TO220 power resistors with a heatsink instead of the standard cylindical ones,
and have LEDs power-on indication.
Size is 160x100mm.
Sigurd
HKC said:
Attachments
Sigurd,
it is a beautiful design, excellent sonics and driving capability, indicating genuine sense for audio. The feedback is probably not very harmful here.
Running the FETs at 1mA, instead of 2-3mA, I suspect Hiraga`s intention was to keep the open-loop gain low.
Emitter resistors raise THD, which does not look nice in simulations.
it is a beautiful design, excellent sonics and driving capability, indicating genuine sense for audio. The feedback is probably not very harmful here.
Running the FETs at 1mA, instead of 2-3mA, I suspect Hiraga`s intention was to keep the open-loop gain low.
Emitter resistors raise THD, which does not look nice in simulations.
Attachments
Lumba-
Zeners are too noisy in that position - add a cap to filter it out,
or do as I plan to do, and use a blue LED.
The sound of the le Monstre much depends on the power supply as with most power amps,
and also depends on the type of passive components one uses.
As I am running at approx 2.5A idle current, I have skipped the 8 Ohm series resistor in the PS and used a choke instead,
and also used a dual bridge rectifying circuit with plenty decoupling.
Sigurd
Zeners are too noisy in that position - add a cap to filter it out,
or do as I plan to do, and use a blue LED.
The sound of the le Monstre much depends on the power supply as with most power amps,
and also depends on the type of passive components one uses.
As I am running at approx 2.5A idle current, I have skipped the 8 Ohm series resistor in the PS and used a choke instead,
and also used a dual bridge rectifying circuit with plenty decoupling.
Sigurd
Lumba Ogir said:
Yes, you can. The design is rather forgiving when it comes to different types of semis.
The output devices can for ex be the very good 0281/0302 from OnSemi or the bigger brother of these.
Some even use the 2N3055 and its complementary...
But I like to use the much faster ones from Onsemi.
The cascode transistors can be 2SC2240/SA970 or smiliar,
and the JFETs can be of other types, too, but you need
to see to that the current is approx correct through them by changing the pot.
You could even use JFETs for the cascode transistors.
The drivers I have not played with as I use the original types.
Sigurd
The output devices can for ex be the very good 0281/0302 from OnSemi or the bigger brother of these.
Some even use the 2N3055 and its complementary...
But I like to use the much faster ones from Onsemi.
The cascode transistors can be 2SC2240/SA970 or smiliar,
and the JFETs can be of other types, too, but you need
to see to that the current is approx correct through them by changing the pot.
You could even use JFETs for the cascode transistors.
The drivers I have not played with as I use the original types.
Sigurd
qwad said:l'm intrigued by this design, just one question though, can other devices be used ?; i.e: outputs, or the small signal. l ask this as in one schematic l see the use of bc550/ 560 devices besides the j fets......... cheers, live long and prosper
T.C.
Lumba -
Here we disagree. JFETs work fine for cascode work. I have many amp with JFETs for cascodes. Even MOSFETs could be used.
How rock solid the cascode voltages are, can make a difference aswell as how clean they are.
I guess your 5V "Zener" is not a Zener but something else, right?
2Sj74 and 2Sk170 are still widely available in both Europe and the US - get them while the last.
Sigurd
Here we disagree. JFETs work fine for cascode work. I have many amp with JFETs for cascodes. Even MOSFETs could be used.
How rock solid the cascode voltages are, can make a difference aswell as how clean they are.
I guess your 5V "Zener" is not a Zener but something else, right?
2Sj74 and 2Sk170 are still widely available in both Europe and the US - get them while the last.
Sigurd
Lumba Ogir said: