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Old 14th April 2008, 10:56 PM   #81
Pano is offline Pano  United States
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Nice job Daniel!

Be careful not to stress those output transistors too much - bring the bias down. If run too hot they will eventualy fail and send DC right thru your voice coil.
(Guess how I know).

This is a fine amp that is stable into even very difficult loads. You'll enjoy it!
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Old 14th April 2008, 11:27 PM   #82
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Thanks Panomaniac,

I am thinking i will reduce the bias to about 1.5A,
the amplifier runs at a more reasonable temperature and i did not notice a difference on the scope or the test speaker.

something like 20-30 watts will still be in class A anyhow.

(if i understand correctly.)


-Dan
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Old 27th April 2008, 09:22 AM   #83
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couple of pics of the build....

(painful chassis to make...)
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Old 27th April 2008, 09:23 AM   #84
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chassis mock up
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Old 27th April 2008, 11:30 AM   #85
eduard is online now eduard  Netherlands
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Hello,
Long time ago the company that did sell the stuff necessary to make these circuits published in a french magazine by jean hiraga did also sell 200mhenry chokes to replace the resistor in the power circuit. This is more then 20 years ago. This choke was constructed for a single ended transistor design with one powerfet and an output transformer. So people begin asking could i use this choke for the 20 or 30 watts hiraga design? The two models available in the shops would use a double c- core transformer. For the kit of the 30 watt hiraga a 500va ordinary transformer was available. The model i did buy did use 68000mf in front of the choke and four 330000MF (2 for+ 2 for_) All six were 25 volts and after a few years one of the 68000mf did start leaking. They were used very close to their max. working voltage The 330000 were especially made for the hiraga design and were very expensive. The chokes did look very ordinary and were cheap for the improvement they did offer. Their dc resistance was about 1 ohm. Maybe if i would still be in my hiraga era i would try to go for a choke input version but that should be done with an impregnated or potted and shielded choke probably because of the hig current involved( 1.5A for the 30 watt) Maybe there are companies that have a choke in their list that could be used for running a small comparison and after that one could ask them to make one perfect for this design. Greetings, eduard
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Old 27th April 2008, 10:04 PM   #86
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Thanks for the info Eduard !!

I haver seen another design from france similar to the "Kaneda" which used two small chokes I am considering this as an option too

-Dan
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Old 27th April 2008, 11:42 PM   #87
eduard is online now eduard  Netherlands
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Hello,There has been a 50 watt kaneda design that did use the same choke 200mhenry 2,5A as my old 30 watt hiraga It is a pity that you probably have to adjust your chassis to use these coils.
Because you have some extra voltage maybe you could make a choke-input with a choke with more mhenry to get the voltage down. I never did try that with a transistor design but i did gain a lot with tube circuits. But it has to be a potted one because it will probably vibrate a lot when there is so much current running. If you did not actually listen to it you can do some things in advance to make the use of chokes easier.
I remember that replacing the two 1800 ohm 0,5 watt resistors supplied in Paris by 2 watt Allen Bradleys or was it Mills did make a big improvement.
Hiraga did pay a lot of attention to chosing the right components
But it is long time ago that i did spend time reading about it. It is a pity that outside Europe there aren't many people that can read his articles. The first ones on this hiraga amp were published in 1979. there has also been a cd rom available with copies of the magazines called l'audiophile. The original magazines were allready hard to find when i did start collecting them. Nice to see that this design still draws a lot of global attention. Greetings Eduard
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Old 28th April 2008, 03:22 AM   #88
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Yes i have the full CDrom set it i think it is well worth getting if you want to build some hiraga stuff.

I cant read french but the diagrams and pics are useful.

the link to a translated version with most of the info is here:

http://www.tcaas.btinternet.co.uk/hiraga.htm

-Dan
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Old 28th April 2008, 10:34 AM   #89
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Hello,
I have both the magazines and the cd-rom. Both contain loads of information on some very good designs. I think the shop in Paris still exist but because of the internet people did start buying their stuff elsewhere. The diy scene in France is still alive but i think it is less vivid and enthousiastic compared to the era when i did discover it.
The l'' audiophile magazine did cease to exist long time ago and the other magazines were getting more and more commercial.
Allthough i did start using tube amps now i am still curious about the opinions about using chokes in a hiraga amp. I remember that there were 2 groups of people in france . One would say it is better to get the biggest transformer and smaller electrolytics . The other group would state the opposite. I would say 500va and 2 big chokes. If i am right the dc resistance of the chokes i did use was just below 1 ohm. I think using a choke with a resistance of a few ohms may be not giving a big advantage. Maybe a special order BIG choke can do a good job. I would certainly try that if i was still playing with this amp., This kind of choke would not be to expensive to make but i think it has to be potted and shielded.
The original Hiraga did use sic safco for the 20 watt version and cef ( special order) for the 30 watt version which did have very low internal resistance, capable of delivering lots of amperes and constructed more rigidly then the usual mallory stuff. Nowadays these parts are getting smaller so maybe using a big number of small ones might be a good idea.
The sic safco had series like the co38/co39 ( long life) tfrs ( tres faible resistance serie) The cef were ufrs ( ultra faible resistance serie) ( faible means low in this context and tres is very )
greetings, Eduard
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Old 28th April 2008, 10:51 AM   #90
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is it possible to purchase that CD somewhere ?

it will be nice to have and learn from piece of history
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