Hiraga Le Monstre 2024

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#221
Slight deviation of the original, maybe worth a look.

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#227
EUVL said:
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
Click to expand...
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
 
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#228
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
 
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#230
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
 
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#240
Folks,

Just posting here as I know some may not have turned on notifications for the group buy thread - there are a few people who need to pass me their details for the GB

W

Post in thread 'GB for Hiraga Le Monstre 2024'

Hi all

There's a few people who need to send me on their details:

@pcgab
@Oracle1
@ixix
@rtan



Cheers and thanks all

Fran


Sorry for the cross post here - just trying to get everything lined up.


fran
 
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