Hiraga amplifier

Hello Rafal,

I agree with Wim.
Also remember that its output impedance is highish (IIRC a dampening factor of about 12) so keep that in mind when using it for low frequencies only.

When buying, try to assess the condition of the PSU capacitors and look for non-original replacement output transistors.

Good luck,

Johan
 
I searched on ebay but cannot find any recently completed auctions.

Where there several versions with different power output?

If so how do you know what is the power output of the model I am looking at?

The amp has black chassis without aluminum face plate. Some photos I seen have aluminum face plate?

Thanks
Rafal
 
AKSA said:
Hi Rafalc,

I don't think I'd be using a Hiraga amp for BASS duties!! Two reasons; it's not all that powerful, and it's possible you really need about 50W for bass, and secondly, these amplifiers have a sublime, exquisite midrange and top end, and this perhaps is where it might best be utilized.

Cheers,

Hugh

I agree with Hugh. Mr Hiraga always was a fan of high-efficiency speakers and that is reflected in his amplifier designs. Normally I would not hesitate to recommend any of his designs, except for bass/subwoofer duty. You should use the Hiraga for mid/high, that's where they are unbeatable. Get a more powerfull one for the bass.

Jan Didden
 
Hi Rafalc,

The Hiraga 30 watt amp was called "Super 30 Watts". The original kit price was FF 6300.- corresponding to roughly EURO 1000.-. The original amp had a dark colored bent aluminum chassis. Very old ones from the early eighties had black rectangulare steel chassis.
Important is that the power transistors are not discolored - the green ones should not partly turn to brownish - a sign of overaged and should be replaced in this case. The types are Toshiba 2SB688-O and 2SD718-O.
It is a superb amp. I have build several ones and I'm still happy. One of them I use for the low midrange in my active system covering the frequency range of 200 - 1500 Hertz.
In the meantime I have redesigned the PSU to a regulated one with big capacities (100T mFarad each) upfront and after the regulation. This modification has again improved the clarity and transparency of the whole frequency range.
Good luck!

GKU
 
Good afternoon, Rafal,

What kind of bass horn you use? From the data I assume a Altec "Voice of Theatre" or similar. In this case there should be no major problem.
In the late eighties the team of Jean Hiraga of the journal L'Audiophile used this combination successfully, together with Japanese Iwata mid-range horns and Onken tweeter horns. A very musical system much ahead of standard audiophile systems at this time and still a reference in dynamic compared with today's standard systems.
I wish you success.

Rgds, GKU
 
GKU said:
Good afternoon, Rafal,

What kind of bass horn you use? From the data I assume a Altec "Voice of Theatre" or similar. In this case there should be no major problem.
In the late eighties the team of Jean Hiraga of the journal L'Audiophile used this combination successfully, together with Japanese Iwata mid-range horns and Onken tweeter horns. A very musical system much ahead of standard audiophile systems at this time and still a reference in dynamic compared with today's standard systems.
I wish you success.

Rgds, GKU


I have heard his system. Two Voice of the Theatre's PER SIDE. Tube amps, of course. You come out a different man. Audio will never be the same to you.....

Jan Didden
 
I got the amp today. Since the bass horns have not been build yet, I plugged them into my Azura horns with Lowthers EX4, first impression sounds quiet different to my 245 SET, very clean and transparent but not too bright, treble is very clear, less warmth in the mid range but still very very involving.

Difficult to compare with my 245 SET since system in transition using 100usd DVD player as a source which is very bright even with the SET.
 
Hi Rafal,

Glad to hear your amp is well working.
I'm not familiar with the 245SET, thus I can't judge the sound difference.
Following one remark, the Hiaraga amp suffer sometimes from DC-offset which has un influence on the dynamic. Please check first the offset level at the speaker terminals. After warming up (~20 minutes) it should be below 50 milli Volt. Little oscillating is normal. If higher than 50 milli Volt adjust it slowly with the 500Ohm trimmer located at the center of each circuit. Perhaps you have to repeate it several times before getting constant.

Hope you will be happy with this amp.
If you need any help, don't hesitate to write.

Rgds, GKU
 
Floating

In mine it floats, never is stable. And one channel effects the other because it is adjusting where the ground rail is in respect with the +/- rails.
This is temperature dependent also. But it is always around -110 mv cold and will get to 20 -30 mv after being on for many hours. Stange behavior, but sweet sound.
Check for ocillation. This thing can get unstable. I built one that gave me headaches if turned up loud. It had to be dumping a bunch out to do that.
My best luck was using the original recommended transistors. Using substitutes did not sound as good.


George