Hiraga Le Monstre 2024

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#201
ItsAllInMyHead said:
To imply that someone "should" provide you information and work for free is absolutely absurd, particularly after that person has shared a great deal. A great number of people can build this project without a kit and without paying any money. The fact that you cannot is only your personal problem.

Patrick has put out a great number of incredible designs for us to try. If you do not have the skills to build this particular project, a few options could be:

Learn
Build another project.
Click to expand...

But who told you I couldn't do it? If it was a problem for me to do it myself, I would probably have bought a kit, don't you think?

I believe that all this subjet was done for the only purpose of advertising and marketing kits. Therefore, in order to serve this purpose, it is quite possible to imagine that the comparative listenings were conducted... by deaf people.

In short, this subject no longer interests me.
 
#203
@nbvcxw8000 - I can assure you that no "sales of kits" would ever pay for the efforts that have gone into the work that has been shown in this thread. To suggest that the sole purpose of the work here is to sell kits is ludicrous and frankly, insulting. Let me just outline some of the activities it has taken to get here:

1. Years of experience and knowledge of audio electronics knowledge
2. Design of PCBs and getting them made - for modern version, but also a deluxe version for the subject of verifying sound of the original vs modern
3. Design and build of switch box to allow comparisons both on the fly and longer sessions
4. Hours and hours of building, testing, verifying, and of course listening - and financing of all parts up front.
5. Hosting of evenings with other audio fans so that the opinions you read here are not just from one set of ears, but many
6. The hours of ordering parts, and creating PDFs to explain the circuit and thinking.
7. Hours put into organising a group buy with all matched semiconductors - please sit down and match a few hundred of those, even for something as easy as hFE with a multimeter, including the labelling, sorting and storage.
8. Time spent packing and shipping, and communicating with those who would like to take part in the group buy - and solving any shipping issues that come along.

In addition, fresh gerbers made exactly of the original article for anyone to do as they please posted here.

Now tell me..... you really think there is any financial reward in this? There is not, and no groupbuy I have ever been involved in ever has the objective of profit.
 
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#209
knutn said:
One CCS (or simpler: A resistor) is connected between TP1 and TP2, and the other between TP3 and TP4. It has been explained before.
Click to expand...

Resistors connected to TP1/TP2 and TP3/TP4 will reduce the input stage gain and hence GNFB, wich is a very bad idea
since this amp has already low OLG, it will just increase the distorsion.

If CCS are connected instead this will change nothing to the amp OLG and is also useless as it wont improve anything,
you ll just get the input fets that will drain uselessly more current, overall that s a cosmetic variation that make people
think that there was something that was added while doing nothing get exactly the same result as far as we re talking
of the amp s audio characteristics.

While i m here i d like to point that this design is not from Hiraga according to his own words, actually he reproduced
a schematic that was published in the japanese audio magazine MJ a few time before he published it in the french
magazine L'Audiophile.

And last but not least this amp was good enough when vinyl discs still ruled but it s no more up to digital sources
sound precision and quality, by the time it could have been improved accordingly to be on phase with our times,
but it s certainly not with those dubbious mods that it will be better, be it by the slighest margin, worse eventually.
 
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#211
Le Monstre Text.png


Google translate :

Contrary to what its name indicates, its effective power, its work in pure class A, it is not a copy, an assembly inspired by the "Monster" I-08 of Stax. This one included no less than 42 transistors in its amplification section. Despite its performances, it was too complex a circuit. In a few words, it is in fact an assembly inspired by the (Hiraga) 20W class A......
 
#216
Bypass Current Source vs Resistor

With my very limited understanding of electronics, this is how I interpret Knut's suggestion of using a simple resistor in lieu of the bypass CCS.
It was stated that using a resistor will reduce the frontend gain, which is of course true.
The question is, by how much.

In the original Hirage circuit, with 0.6A output stage bias, target voltage across the 1k drain resistor is ~1.2V.
That means its current should be 1.2mA.
This is of course the same current through the JFETs and the cascode BJTs, as well as the 100R trimpot.
Datasheet of 2SK170 indicates that the transconductance at 1.2mA is ~16mS, or an equivalent resistance of 60R.
Assume also the trimpot is at its mid position, i.e. 50R for each half.
The input stage gain is 1K/(60+59) = ~9.

In our example of GR grade JFETs, with 50R at its source, the drain current is ~2.3mA.
Since we only want to allow 1.2mA to flow through the 1k resistor, we need to bypass 1.1mA.
Because TP2 is at the base of the cascode transistor, voltage across TP1_TP2 is ~6.6V.
We can either connect a current source of 1.1mA across TP1_TP2, or a resistor of ~6k.

The above is of course all DC.

Suppose we now apply a small AC signal to cause the JFET to swing 0.1mA.
In the original circuit, and in case of an ideal current source, all of that current wing can only go through the 1k drain resistor.
So the input stage gain is, as stated above, ~9.

But the cascode transistor also has a small emitter resistance, approximately 20R at 1.2mA.
In case of a 0.1mA ac current, TP2 will change from its DC value by 2mV.
Which means that the current through the proposed bypass resistor will also change by 0.33µA.
This has to be subtracted from the current through the 1k resistor, which now only swings 0.0997mA instead of 0.1mA.
That, if my sums are correct, corresponds to a loss in open loop gain of 0.33%.
The exact value depends also on the Idss of the JFET used.
So it is still desirable not to use, e.g. BL grade JFETs, unless you are using a very good CCS and not the resistor.

But I am sure Knut will correct me if I am talking nonsense. 😊


Patrick
 
#217
No, Patric, you are perfectly right!
As a matter of fact, a while ago, I used another approach, as seen in the attached figure. I have even made PCBs for this solution, but I have not tested it.
Here R14 and R15 will reduce the drain current, since the gate-source voltage is increased. I suspect CCSs instead of these resistors are a better solution...
 

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#218
IMHO, TP2 is a better location for bypass, because its voltage changes much less with signal.
The BJT cascode is responsible.

The advantage of your proposal above is that the resistor value can be larger (bit less than 2x).
But it swings about 2.5x compared to TP2.


Good to have you around,
Patrick
 
#219
EUVL said:
View attachment 1351919

Google translate :

Contrary to what its name indicates, its effective power, its work in pure class A, it is not a copy, an assembly inspired by the "Monster" I-08 of Stax. This one included no less than 42 transistors in its amplification section. Despite its performances, it was too complex a circuit. In a few words, it is in fact an assembly inspired by the (Hiraga) 20W class A......
Click to expand...

Only the name "Monster" is inspired by the Stax amp, but he stated that his own amp wasnt an original design but inspired by a schematic published in MJ, he said so in a follow up of the article about this amp.
EUVL said:
Are you sure ?

Not according to Spice, which shows essentially the same OLG.
Of course CCS marginally better.

But at least we are back to technical discussions. 🙂


Patrick
Click to expand...

There s no substancial difference overall, that s just adding some complexity for no big benefit, it would be much more
usefull to add a DC servo to get rid of the amp s DC output offset, as for the characteristics the VAS should be reworked
as it s actually embedded in the output stage and used as direct driver for the power transistors.

That s the typical THD of the original schematic at 2W in red and in green what could be done with a rework,
the latter case has a -100dB THD/1KHz and is within CD definition wich is about 96dB with a 16 bit DAC, rest is just
getting 0.1% instead of 0.15% and is of no interest, it s like reworking the Cx of a car without ever adressing
its engine lack of power.

Now since you re talking of Spice, could you provide some simulations of the linearity.?.
Because that s all good to say that it s better but without even simulated numbers that s a moot point
and is borderline dishonnesty.
 

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