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Old 19th April 2001, 01:34 AM   #11
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look also at this site:
http://invalid.ed.unit.no/~kentj/prosj.html
he made several interesting project and a 8w class power amp design based on hiraga 8W
PCB design and layout also included

Is there any consensus for the best (based on sound quality), medium power 50-100W
DIY solid state power amplifier?

regards,
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Old 23rd April 2001, 08:40 AM   #12
rmgvs is offline rmgvs  Netherlands
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Hiraga-people,

please also look at the forum tubes under 'Linsley Hood' amplifier (actually it is a transistoramp...). There now is a easy-to-build Linsley-Hood amplifier that is called the JLH evolution. It is based on the original 1969 schematics bus has a symmetrical power supply and consequently no blocking capacitor. The design is in many respects comparable (from a user's point of view) to the Hiraga:

* same power supply voltage (around + and - 21 Volts).
* both are class A (Linsley Hood has greater current through the output transistors)
* very simple and easy to build (Linsley Hood has only 4 transistors where the Hiraga has 8)
* apart from the power supply and cooling facilities very cheap to build
* Both have great sound (probably a matter of taste or of components used which of the two sounds best).
* The Linsley-Hood has a slight turn-on offset problem of around 1 Volt during 1-2 seconds. Not a serious problem for most people, but be warned.

Schematics can be found on home.wish.net/~tinholt
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Old 23rd April 2001, 04:25 PM   #13
grataku is offline grataku  United States
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rmgvs,
are you saying that the Hiraga design has no DC-offset problem whatsoever? I already liked the design, if it is also free of transient DC offset I like it even more!
Speaking of DC, I am going to have to add an input decoupling cap. In fact, I am going to feed the amp with a signal form a crossover that spits out some DC (Ask Rod Elliot why that is). So the Hiraga philosophy of DC coupled amps is going out the window.
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Old 23rd April 2001, 06:03 PM   #14
tvi is offline tvi  Australia
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Location: Moonee Ponds, Vic, Australia
Haven't built the 20 watter but have built 3 pairs of 30 Watt Hiraga class A amps.

The First used a salvaged NAD 3020 transformer and about 16kuf of capacitance for both channels and was spooky quiet, the transformer got dam warm after about an hour but never made a noise.

The second had a 300VA toroid and about the same capacitance, the toroid hummed 75% of the time from switch on but never got that warm.

The third is sitting 3 feet from me waiting to have the PSU wired up.

TP9634 was originally 2SA634/2SC1096, you should be able to pick these up still at CB radio spare parts shop as they were used in the Audio amps in a few old CB radios.

The original outputs where 2SA627/2SD188 now discontinued.

For TP2788 I have used 2SB686/2SD716 with no problems

and Semelab SM3159S/SM3160S 200W/Tc=25C/15A/10-30hfe in a TO3 package, the bass seemed to be deeper and more controlled than the B686/D716.

I have 2 pair of Fujitsu 2SA1077/2SD2527 but haven't tried them yet, these have an ft of 60Mhz & Cob = 300pF

Check out:
http://www.jls-info.com/julien/audio/index1.htm
not sure about the wirewound resistors, I use 5W Metal plate

Might change the simple Zener shunt reg on the input stage to a TL431 eventually.

From looking at French websites the MOSquito/BUZquito seems to be the successor to the 20/30 Watt Hiraga, check out
http://perso.wanadoo.fr/jm.plantefeve/
this site has lots of schematics/ideas v.interesting

also http://perso.club-internet.fr/ndavid.../mosquito.html

I have a copy of the original PCB but no scanner at the moment, I also have the original Kaneda design that inspired the Hiragas', if anyone wants I can post an ascii schematic?

This 30Watt amp sound amazing on my speakers (94db/w). the sound stage fill the room not just left/right but top/bottom almost surround.
The Vangelis/Antarctica JPN CD leaves most people speechless.


Regards James
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Old 23rd April 2001, 06:43 PM   #15
rmgvs is offline rmgvs  Netherlands
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In answer to DC offset problems:

The Hiraga has no turn-on offset problems whatsoever.

The offset is not very stable in time, it shifts very slowly between - 100 and + 100 mV, not a problem at all. The monstre however (also a Hiraga design) stays put at whatever DC offset there is (preferably less than 10 mV).

Yes, the lack of an input cap can be a problem if your source has DC at the output, but that's the problem of your source (or cross-over) and has to be fixed at that point and not in the Hiraga.

Rudy
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Old 27th April 2001, 09:12 AM   #16
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Exclamation power supply schematics

Well I'm a French guy interessted in High fidelity and of course DIY projects.
I'm going to build Hiraga's 20w Class A amplifier. I found many schematics on the net for the amplifier part but not so many schematics for the power supply.
Does anyone know where I would find it?
Thanks.
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Old 27th April 2001, 11:13 AM   #17
rmgvs is offline rmgvs  Netherlands
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Maybe there is none because of its simplicity. The original Hiraga has a transformer of 2 x 15 Volts AC around 250 Watts for stereo operation (16 Volts works fine). It is no toroidal transformer, differences here between transformers clearly can be heard. Then there is a massive bridge rectificer, 25 Amperes. Then in total 6 capacitors are used, 68.000 mF 25 Volts, Sic Safco. Also here applies: good quality can be heard. The arrangement of the 6 is as follows: after the bridge 2 are used, one in the minus and one in the plus line. Then there are 2 R's in the supplylines of 0,47Ohm/25 Watts. The remaining 4 caps follow after the R's.

The caps are connected with big copper strips in between them.

2 small caps of brand ERO MKC 2,2mF 250 Volt are used to give the supply more 'speed' in the highs. The can be mounted on the circuit board.

Hiraga chooses to use a simple passive power supply with big amounts of mF. A active power supply is not recommended here (I believe that many people have tried this nonetheless).

Rudy
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Old 27th April 2001, 12:12 PM   #18
argo is offline argo  Estonia
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Default Re: power supply schematics

babarceles

You said that you have found many schematics on the net for the Hiraga's 20W-amplifier part.
So far I have only seen one or two.
Founding the transistors is another matter. Does any of these schematics you found use more modern devices?
Anyhow I'm interested in URLs you have gathered so far.

Argo

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Old 27th April 2001, 12:29 PM   #19
argo is offline argo  Estonia
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Default Re: Re: power supply schematics

Arghh. Forgot to add PSU schematic URL.
There it is together with the original (I pressume) amp schematic: http://www.infomaniak.ch/~bonavolt/hir20.htm

Argo

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Old 27th April 2001, 02:10 PM   #20
tvi is offline tvi  Australia
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http://www.infomaniak.ch/~bonavolt/hir20.htm

Thats the Schematic for the 30W
the 20 watt output onlhy draws 0.8A to 1A at 21V

Audiolab of Georgia http://www.audiolabga.com/
have both drivers and the output devices I mentioned earlier.
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