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PostPosted: 07 Feb 2014, 11:11 
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Joined: 04 Feb 2014, 08:20
Posts: 10
I have just completed a pair of these Hiraga amplifiers and was amazed with the sound. Was never an advocate of class A but after completing a regulated power supply and using transistors that i had available i can confirm that this simple amp is one of the very best as far as sound quality is concerned.

For those who want to give it a try and cannot get the specified original transistors here is what i used and its working fine with no problem in setting the bias current and the DC offset. I do not want to get into a debate about the characteristics of the transistors i used. I can only say that they complement the circuit and they do the job. Just bear in mind that you might have to adjust the 47k bias resistor to give around 380 mV measured across the 0.33R resistors at 30V. I got it right at around 34.3k.

  • The use of a regulated power supply is highly recommended as with it, the amp is extremely quiet, no hum etc.
  • Transistors used for the output is the 2SA1942 and 2SC5200
  • Drivers BD237 and BD238
  • Inputs BC258 and BC639.

Give it a try its worth the effort.


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PostPosted: 07 Feb 2014, 17:52 
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Joined: 28 May 2008, 21:53
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Location: Winnipeg, CANADA
Hi suztek and welcome to the forum.

Thanks for sharing your results. I've linked your other posts back to this one to help others looking for alternate transistors. Feel free to posts photos of your build.

Cheers

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PostPosted: 13 Feb 2014, 06:01 
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Joined: 04 Feb 2014, 08:20
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I have been a DIY audio fanatic since i was 18 years old and though i rate my DIY Mosftes amps highly, i must admit that audio quality of the Class A amp based on a 30 year old Hiraga design is just unbelievable. The design is simple and yet the music is so clear, with every instrument so detailed and the low frequency so powerful ,all that from only a 30 watter. With a proper regulated power supply it is very quiet with no hum. I am now experiencing a new era of listening to my music collection, Vynil and CD's.

Attached is a photo of the completed amplifier.
Attachment:
Class-A 30W Hiraga Amplifier Transistor Equivalents.jpg

Regards
William


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PostPosted: 18 Feb 2014, 19:08 
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Location: Winnipeg, CANADA
Very nice work William. Looks great and I'm glad to hear you are so pleased with the results. Congrats and enjoy the amp.

PS - I fixed the transistor typo

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PostPosted: 31 Dec 2014, 03:50 
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Joined: 31 Dec 2014, 01:44
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Well now it must surely be time for me to come with my version of "Le-Monster"
In 2001 I built that project a power amplifier. HE HE.
The goal was to make a "100 Watts of pure Class-A" Amplifier.
PIX 1
I had 2 1000VA traffo 45 Volt output. 100.000uF 80V per channel
PIX 2
I used the same input stage that in the original AMP. However, as a driver I used (2SA3298A and 2SC1306A) to drive and now comes the 4 Sanken transistors.
Paired 2 x and 2 x 2SA1216 2SC2922 per channel.

I used 1 meter heat sink per channel and about temp was 70 degrees Celsius on the heat sink
PIX 4
I solved the problem with the 22 Volt input as needed by removing the zener diode and the resistor of 1 Kohm. I added a 22 Volt supply
then there were control of the input stage
.................................................. ..........................
I have never heard an amplifier it could catch up with this Monster. Which ended up with a weight of 50kg :-)
I Was a Very Happy Man When I heard it play
.........................


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PostPosted: 09 Aug 2015, 17:32 
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Joined: 09 Aug 2015, 16:58
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There is much interest in the newer amplifiers which follow the Hiraga and Nelson Pass philosophies.
I am most curious to look at the harmonic spectrum (FFT) of this Hiraga build, which may explain why the listener satisfaction
is so convincing.
I am the proud owner of a Naksa 125 designed and made by my close friend Hugh Dean (Melbourne Australia)
I have been a practicing pro musician (jazz trumpet) audiophile, engineer, and CD collector all my life (am 64) and am on the local AES committee.
Dean's LTSPICE simulations show a pleasing harmonic profile, and he runs 150 mA quiescent current so the amp is class A
for low to average listening levels.
If you would prefer compromise in the bulk and expense of the power supply (and your power bill !) then the Naksa 125 is for you.
To defray international shipping costs (heavy toroids) Dean will sell the tested boards.
The boards contain many surface mount devices so cannot be a DIY project.
Check out Hugh and AKSA at aksaonline.com.
Hugh has an interesting thread on the pros and cons of global feedback at diyaudio.com right now.
Lots of healthy and contrarian opinion.


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PostPosted: 09 Sep 2015, 07:54 
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Joined: 06 Jun 2008, 18:23
Posts: 5144
Location: Australia
So where are you? Hugh is a member of the Melbourne Audio Club of which I am a member to.

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