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Question of the amplifier circuit Jean Hiraga's Class-A
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Author:  caniggia [ 11 Mar 2012, 12:14 ]
Post subject:  Re: Question of the amplifier circuit Jean Hiraga's Class-A

or better this :king:

Author:  elav [ 25 Mar 2012, 20:54 ]
Post subject:  Re: Question of the amplifier circuit Jean Hiraga's Class-A

hello friend

iam a doing you jean hiraga.
when Ibias is higher better quality?

i cant find the transistor so i pick bc550/60 and bd139/140....

What can i do to improve quality???

Author:  pat93320 France [ 14 Apr 2012, 06:24 ]
Post subject:  Re: Question of the amplifier circuit Jean Hiraga's Class-A

I still have a 20W Hiraga since 30 years. I changed transistors by the first version 2SD188/2SA626 and the sounds is amazing.
I would like to increase the powzer to 30 or 50W to drive my B&W 803D.
is there a good place where to find capacitors (0,22f) and 5000VA transformers to build 50W Hiraga?
thx for any advice

Author:  gmurray618 [ 15 Apr 2012, 21:24 ]
Post subject:  Re: Question of the amplifier circuit Jean Hiraga's Class-A

Dan, this looks like an amazing and beautiful amp. I would love to build this beefy (1.2 f capacitance!) music maker. Can you give me an estimation of the difficulty and cost? I’ve never built anything like this. I’m ok with meters and soldering, but haven't ever used transistors (cant wait to learn). I’ll be poking around this site and I imagine I’ll find the transformer and capacitors. I’m very new to the site.

I’m also looking for a project to take to school for next year. I’m a physics teacher and have been given an introduction to engineering next year. Something simple. My goal beyond making a really cool project and hooking the kids is to introduce basic circuits, induction, basic concepts of V, I and R. This should be a group of intelligent motivated kids with no experience. Any recommendations?

Thanks in advance for any help and advice.
George

Author:  greatape [ 25 May 2012, 12:46 ]
Post subject:  Re: Question of the amplifier circuit Jean Hiraga's Class-A

Is the bias stable in this amp?

I have read where people have built this and experienced bias instability.

Most notably that they were unable to reach a 0Vdc offset.

Author:  pat93320 France [ 30 May 2012, 06:24 ]
Post subject:  Re: Question of the amplifier circuit Jean Hiraga's Class-A

As somebody mentioned sooner, I did not reach bias current of 1.65A in each transistor. Could anybody mention the right bias resistor replacing the 1.8K in the power circuitry? the current is about 0.6A with 1.8K and all resistors mentioned in the proposed schematic.
thanks for any advice
Pat

Author:  pat93320 France [ 30 May 2012, 06:24 ]
Post subject:  Re: Question of the amplifier circuit Jean Hiraga's Class-A

As somebody mentioned sooner, I did not reach bias current of 1.65A in each transistor. Could anybody mention the right bias resistor replacing the 1.8K in the power circuitry? the current is about 0.6A with 1.8K and all resistors mentioned in the proposed schematic.
thanks for any advice
Pat

Author:  tombapic [ 01 Jul 2012, 17:45 ]
Post subject:  Re: Question of the amplifier circuit Jean Hiraga's Class-A

pat93320 France wrote:
As somebody mentioned sooner, I did not reach bias current of 1.65A in each transistor. Could anybody mention the right bias resistor replacing the 1.8K in the power circuitry? the current is about 0.6A with 1.8K and all resistors mentioned in the proposed schematic.

Salut, tu as réussi à régler ton souci?

Author:  bubus [ 29 Nov 2012, 10:30 ]
Post subject:  Re: Question of the amplifier circuit Jean Hiraga's Class-A

Hello,
I want to build one and i have a question.
Can i use 2SA1695 instead of 2SA1943 and 2sc4468 instead of 2SC5200?

Best regards.

Author:  quochuy0202 [ 02 Dec 2012, 02:44 ]
Post subject:  Re: Question of the amplifier circuit Jean Hiraga's Class-A

I see on the pictures of the project, there are 3 circuit boards, I know that two circuits are for the left and right channel, so what is the middle circuit for? Please tell me, Thank you!

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