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JohanH 29th February 2004 07:09 PM

Hiraga 30W vs. Le Monstre
Today I listened to my Hiraga 30 W class A against my Le Monstre.
I am using them on hybrid electrostatics from 350 Hz upwards. The electrostatics have a sensitivity of around 90 dB so power is sufficient on both. I use a parallel notch filter in series with the ELS for impedance correction around 20 kHz as the Monstre didn’t liked the impedance at high frequencies; resulting in no highs without the filter.

Good points are:

Hiraga: better imaging and greater depth of sound
Monstre: sounds more ‘natural’, less sharp edges on female vocals and some solo instruments

Both are very good but I’d like to know what I have to do to get the best of both worlds.

So are there modifications I can do on either to improve the shortcomings or do I have to build something like the JLH for ESL?

Thanks in advance for your input.

PMA 29th February 2004 09:20 PM

I have designed an output stage that is inspired by Jean Hiraga's circuits. It both sounds and measures very well. You can have a look at , if you like.

JohanH 29th February 2004 09:29 PM

Thanks a lot!!!

It looks even more simple than the original circuit (except of course for the capacitor on the input)

Did you have a chance to compare it to the original?
How would it behave on an ESL?


Dang it, I knew posting this question here would make things more complicated.

PMA 29th February 2004 10:27 PM


the capacitor is not a necessity, depends on the whole circuit. Please take to the account that my circuit is a power follower (voltage gain =+1), so you need voltage amplification stage before it.

I have not heard and have not build the original Hiraga, as my aim was a little bit different.


jazz 2nd March 2004 08:41 AM


I've build both but in the end stayed with the monster. I like it's sound slightly better but that's highly subjective. A change to the monster that really helps imho is bypassing the 'bias' cicuit of the input cascodes with some good quality caps. Also both circuits sound best without any bandwith limiting in my experience but given you're load that might not work for you. I played around with resistors somewhat and settled on tantalums for the input resistors and kiwame for the others. With these changes i think i reached a nice midpoint between the le classe and the monster, in my situation at least.

hope this helps


JohanH 2nd March 2004 09:06 AM


Thanks for your answer. My feeling also is that modding the Monstre would be more awarding than modding the class A..

Where did you put the bypassing caps and what values did you use?

The filter I use fortunately does not limit the amps bandwidth but adds a couple of ohms to the ESLs impedance around 20 kHz. Especially the Monstre did not like the low impedance in the highs and responded by not giving any power to the highs at all. The class A does not suffer from this; if it means I can keep my Monstre I can live with the filter.

Do you know of a local source for the resistors you mention?

Thanks again,

jazz 2nd March 2004 10:10 AM


I bought the resistors from, located in Breda but they only sell via internet.
The input cascodes have two resistors (2k value) tied to the base of the upper transistor. One resistor from the power supply line to the base of the upper transistor and one resistor from the base of the upper transistor to ground. These resistors form a voltage divider. It is the last one you'd want to bypass with a cap. Have a look at for the schematic. the upper transistors are the 2sa872 and 2sc1775 ones.

As for the sort of cap I suggest you first buy four cheap (phillips electrolytics or something like that) electro's of about 100 uf 35 v. Make sure the leads on these caps are long enough so you can solder them directly over the resistors. First try these and see if you like the effect. Then if you like the effect you can try something esotheric like a solen 1uf mkp or something like that. My experiments didn't indicate that value or quality where really important though so i simply settled for roederstein eke 100 uf 63 v bypassed with an additional 10nf multilayer ceramic. This has done it for me but i don't exclude that a better type such as the solen will be better (probably a matter of taste as well).

sorry i don't have a schematic editor right now or i'd give a pic.


Teo 2nd March 2004 03:48 PM


Your schematic is very similar in topology to the minimalist MJAMP, the main difference beeing the current feeback loop of the MJAMP, have you tried it?


PMA 2nd March 2004 06:26 PM


I know the topology mentioned, but I have not tried it.


JohanH 13th March 2004 06:30 PM


do you remember what the difference were between the kiwame and the tantalum resistors?

I have decided to build another Monstre or two and have finalised my choices on resistors between the two mentioned.

I'm assuming you've built the Monstre with both type of resistors and would like to know how you ended up with tantalum as input resistors and kiwames for the rest.

PS any other suggestions are welcome as well

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