Hiraga Le Monstre 2024

[Nico Ras]

Slight deviation of the original, maybe worth a look.

 

[EUVL]

From Borbely :

Patrick

 

[EUVL]

Slight deviation of the original, maybe worth a look.

The object of our exercise was to find out how close you need to get to the original if you want to build it today.

It was never meant to be any attempt to modify or improve.
Only the bare minimum of changes were introduced because of unavailable parts, etc.


Patrick

 

[Nico Ras]

Any change deviates from the original, so what is the point of all these posts? Is it even relevant? Not really all regurgitated stuff from the past.

 

[Nico Ras]

BTW Patrick, if you never heard or seen the original, what contribution can you really make, if anything? Or can you only simulate and guess what it would sound like. Even changing track width or layout can have repercussions.

 

[EUVL]

Ich merely stated what we tried to set out to investigate.
Nothing personal.


Best regards,
Patrick

 

[PMA]

It has taken us some extra time, but we finally got round to measure the Le Monstre Deluxe as well.
This has original transistors, all TaN resistors, including Shinkoh for the 220R in the feedback network, RA12P trimmer, Riedon 1R 35W thin film, etc.
As described in the article.

View attachment 1317284

The surprising thing is, that H2 & H4 are ~20dB lower than the previous prototype using same active devices.
So what has changed ? 20dB less even harmonics cannot be just due to the passives.

Well, the JFETs used in this were matched at Id with 50R source resistors, instead of at Idss.
They also happened to have quite close Yfs at that current.
On top of that, we used the current source bypass to keep the 1k drain resistors and 0.7A bias.
So the trimmer was almost at its mid-point when DC offset is trimmed.
And now you get near perfect even harmonics cancellation from top and bottom halves.
And maybe the higher bias with the original output devices also contribute to some extra distortion.

Just tells you that no two Le Monstre's can be exactly the same, unless you measured every active component upfront.


Cheers,
Patrick

Why there is no level mentioned? What is the voltage or power at which you have made the measurement? Why the noise floor is so very high? Why SNR is as low as about 80dB?

Cheers, Pavel

 

[EUVL]

1W into 8R at 1kHz, using Viktor and Autoranger / E1DA Cosmos.
My apologies.

I read the fundamental at -3 dB on the plot, and the noise floor at ~ -116dB.
Measurement was done with lab supply and the amp is not properly cased.
Also no LP filter used.


Patrick

 

[lineup]

How much bias in the output of the Monstre original?
@EUVL

 

[EUVL]

https://sound-au.com/tcaas/monster31.htm

"One should not lose sight of the fact that the 8W functions in class A. The quiescent current therefore has a prime importance. Its value should not be too low otherwise the amplifier will pass into class AB on strong signals, nor too high because it would impose too great a dissipation on the power transistors which, in addition to the fact of limiting their lifespan, can lead to thermal runaway. Indeed, the characteristics of the power transistors are related to the temperature of the junctions and beyond a certain threshold there is runaway, that is to say the more the temperature rises the more the current increases. The optimal value lies between 0.5 and 0.6A."


Patrick

 

[lineup]

thanks

 

[Mooly]

I am on both threads, now you know what intermodulation distortion is. Two threads mixing and producing a third with no relevance to either just a mix up. Sincere apologies.

Posts on JLH69 vs Hiraga split off to here:

https://www.diyaudio.com/community/threads/jlh69-vs-hiraga-le-monstre-2024.417128/

 

[PMA]

The optimal value lies between 0.5 and 0.6A."

for 0.5A, you get 4W in class A into 8ohm and only 2W into 4ohm. Not many speakers have Z >= 8ohm through 20Hz-20kHz. The amp would not work at class A at higher power.

 

[EUVL]

I was merely quoting Mr. Hiraga in his original article.
Not my circuit, not my design.
I only tried to build as close to what he described as possible today.

But I do agree that the 8W as quoted by him is certainly not RMS.


Regards,
Patrick

 

[Icareabout Whatsright]

Not my circuit, not my design.

Have you ever made a circuit or designed anything yourself?

 

[hbtaudio]

The mystery is quickly solved: 1^2 * 8 = sine peak power!

2 times Iq=0,5Adc equals 1A_peak

 

[EUVL]

You might also say square wave power.


Patrick

 

[gijser]

Have you ever made a circuit or designed anything yourself?

I think he did. You could go visit his website.

 

[hbtaudio]

Why don't you try it out on an original?

16Vpp sine to 8Ohm and then switch to square, oscilloscope the current function (i(t)).