Hiraga "Le Monstre"

I tried to understand the monster DF so i took some measurements using signal generator and micro-voltmeter. Load - 8 ohm speakers.

gain2.jpg


spice simulation with speaker equivalent (with higher value Rs)

spice2.jpg


Theory meets practice.
I am also try to measure DF in spice - I got that with original value Rs 50 ohm DF is aprox. 10 or so and with Rs 100 ohm about 7 or 8 its mean output impedance of Monster about 1 ohm. it is correct?

I myself personally do not care about DF because monster sounds divine :sing:
 
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Hi,

I measured the DF with bridged amp ( one input shorted) and input signal was fed in to one channel and output measured on resistor. Like described in Pass citation 12 article.I do not know how precise my measurements but Spice simulation shows similar picture.
Yes i like a lot this little amp - sounds like a tube amplifier or so !
 
spice file and models:

*2SJ74
*Toshiba Dep-Mode 20mA 400mW LowNoise pkg:TO-92B 2,1,3
.MODEL 2SJ74 PJF(Beta=92.12m Rs=7.748 Rd=7.748 Lambda=4.464m
+Vto=-.5428 Cgd=85.67p Pb=.3905 Fc=.5
+Cgs=78.27p Is=12.98p
+Kf=26.64E-18 Af=1)

*2SK170
* 20mA 400mW LowNoise Dep-Mode pkg:TO-92B 3,1,2
.MODEL 2SK170 NJF(Beta=59.86m Rs=4.151 Rd=4.151 Lambda=1.923m
+Vto=-.5024 Cgd=20p Pb=.4746 Fc=.5
+Cgs=25.48p Is=8.477p
+Kf=111.3E-18 Af=1)

*.model TIP3055 ako:NSC_4A NPN() ; case TO-220 (s)
.MODEL TIP3055 NPN(Is=457.5f Xti=3 Eg=1.11 Vaf=50 Bf=156.7 Ise=1.346p Ne=1.34
+ Ikf=3.296 Nk=.5961 Xtb=2.2 Br=7.639 Isc=604.1f Nc=2.168
+ Ikr=8.131m Rc=91.29m Cjc=278.7p Mjc=.385 Vjc=.75 Fc=.5 Cje=433p
+ Mje=.5 Vje=.75 Tr=1.412u Tf=37.34n Itf=35.68 Xtf=1.163 Vtf=10
+ Rb=.1)
*.model TIP2955 ako:NSC_5A PNP() ; case TO-220 (s)
.MODEL TIP2955 PNP(Is=66.19f Xti=3 Eg=1.11 Vaf=100 Bf=137.6 Ise=862.2f
+ Ne=1.481 Ikf=1.642 Nk=.5695 Xtb=2 Br=5.88 Isc=273.5f Nc=1.24
+ Ikr=3.555 Rc=79.39m Cjc=870.4p Mjc=.6481 Vjc=.75 Fc=.5
+ Cje=390.1p Mje=.4343 Vje=.75 Tr=235.4n Tf=23.21n Itf=71.33
+ Xtf=5.982 Vtf=10 Rb=.1)


.MODEL BD135_137_139 NPN ( IS=2.3985E-13 BF=244.9 NF=1.0 BR=78.11 NR=1.007 ISE=1.0471E-14 NE=1.2 ISC=1.9314E-11
+ NC=1.45 VAF=98.5 VAR=7.46 IKF=1.1863 IKR=0.1445 RB=2.14 RBM=0.001 IRB=0.031 RE=0.0832 RC=0.01 CJE=2.92702E-10
+ VJE=0.67412 MJE=0.3300 FC=0.5 CJC=4.8831E-11 VJC=0.5258 MJC=0.3928 XCJC=0.5287 XTB=1.1398 EG=1.2105 XTI=3.0)

.MODEL BD136_138_140 PNP ( IS=2.9537E-13 BF=201.4 NF=1.0 BR=23.765 NR=1.021 ISE=1.8002E-13 NE=1.5 ISC=7.0433E-12
+ NC=1.38 VAF=137.0 VAR=8.41 IKF=1.0993 IKR=0.10 RB=1.98 RBM=0.01 IRB=0.011 RE=0.1109 RC=0.01 CJE=2.1982E-10
+ VJE=0.7211 MJE=0.3685 FC=0.5 CJC=6.8291E-11 VJC=0.5499 MJC=0.3668 XCJC=0.5287 XTB=1.4883 EG=1.2343 XTI=3.0)


.MODEL BC550 NPN IS =1.8E-14 ISE=5.0E-14 NF =.9955 NE =1.46 BF =400
+BR =35.5 IKF=.14 IKR=.03 ISC=1.72E-13 NC =1.27 NR =1.005 RB =.56 RE =.6
+RC =.25 VAF=80 VAR=12.5 CJE=13E-12 TF =.64E-9 CJC=4E-12 TR =50.72E-9
+VJC=.54 MJC=.33
.MODEL BC560 PNP IS =1.149E-14 ISE=5E-14 NF =.9872 NE =1.4 BF =330
+BR =13 IKF=.1 IKR=.012 ISC=1.43E-14 NC =1.1 NR =.996 RB =.2 RE =.4
+RC =.95 VAR=8.15 VAF=84.56 CJE=16E-12 TF =.493E-9 CJC=10.5E-12
+TR =73.55E-9 MJC=.415 VJC=.565
 

Attachments

  • le_monstre.zip
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I made some changes to my Le Monstre (such as a 'star ground' and a hybrid powersupply.). I have the original transistors bought at W. Walthers's shop in Paris: (noir et vert).

Reason: I noticed the output resistors of 1 ohm were taking more than 1 Amp (1,15 and 1,20 Amp) from 750 mA I had a fifteen ago. I parralled extra resistors to get 840 ohms on the cascodes (from previous 910) and this gave 950 mA bias. Not the big reduction I had hoped for.

So I decided to change things a bit.
My builds:
divers 02'11 2353Kerst 2010.jpg
I changed the transformer, now a Metalimphy 214 (bifilar wound!), used a new 40V/30Amp bridge. And I inserted a current sink (TIP142/TL431) along the power supply. Plus I added a set of 100.000.000 microfarad "super capa's" from NEC, these are specially advised by Hiraga.

Then I noticed a strange effect. The bias current dropped. Bias current is now 750 mA in cold state and 850 hot. Power supply is both plus and minus 12,99. Conclusion: the power supply matters.

Distortion:
divers 02'11 2357Kerst 2010.jpg
The amp shows a nice 2nd Harmonic at just 2,05 V RMS, with a 8 ohms load, of less than 0,2%.
Without a load it is 2,45 volt RMS. Now Osscar, this will allow you to calculate a Damping Factor (DF) calculation with this configuration . . .

The amp will give 7,2 V RMS on 8 ohms just before clipping. The distortion is then still about 1% - but now complex. With a higher bias of 1 amp and a slightly higher voltage of 13,7 volt I got a max. 7,8 Volt output.

Bandwidth: without a load: from less than 1 Hz to above 500 kHz; with load (non inductive) it is up to more than 350 kHz, but I have to reduce output to 4 volt RMS to see the upper limit.

Sound:
I notice very subtle vocals on my 'nasty and difficult' Quad ESL.

albert
 
I took the time to drop the values in the DF formula
DF = V1 / (V2-V1)
V1 = output voltage of the amplifier with load resistor connected (2,45V)
V2 = output voltage of amplifier without a load (2,05V).​

This is a very solid 1,0 at 8 ohms. And it sounds gorgeous!!!

PS - You can see the TIP146 on the housing in the second picture. It gets luke warm. Is there interest in the shunted power supply I developed?

albert
 
Sorry, just out of curiosity. Do You REALLY mean 100 Farad ? I've never seen one of these.
In cars, i have often seen a few Farads hooked up close to these huge amplifiers all those young guys use to destroy their hearing.
Best regards
Ebbe

Sorry Ebbe, typo, it's 100.000 microFarad in a small box - 2cm high and 2,7 cm dia. It comes with a flat ESR (non-inductive by nature). It is a 10V version that can withstand 13,5 volt without a problem.
divers 02'11 2358Kerst 2010 1.jpg I found my components in the local surplus market.

There is a 1 Farad version too of 10V, that Hiraga used himself in his design.
[There exist 100 F types for 3,3 volt on the market by the way too for power-supply backup purposes.].
albert