Hiraga amplifier Mosfet insulation

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#2
You shouldn't have any mosfets if the schematic is correct - I assume you mean bipolar power transistors. Yes, they must be insulated or you'll short the power rails together through the heatsink and possibly to ground if the heatsink is grounded. If you are really stuck, can you put each power device on it's own heatsink and keep the heatsink insulated from ground and other signals ?
 
#3
Thank you Bigun ,
Sorry my bad yes i meant the power transistors ,,

cutting the HS and bolting to wood is too much of work .I will order few insulator pads
instead ... just boring wait game by free airmail!!

edit: got local vendor 🙂
 
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#4
It is important that you check with a meter that the output devices are fully insulated from the heatsink. Don't just rely upon the parts themselves.

Also remember that the heatsink compound should only be smeared very slightly on both sides of the insulator (again only if mica or keratherm), if you are using silicon rubber pads, you don't need heatsink compound.
 
#9
destroyer X said:
I have never assembled this one...what do you think about it?
Click to expand...

I'm sad to say that like you, I never heard it, never built it. But I like the topology. I believe it requires a very clean power supply to make it quiet when it's supposed to be quiet.

I never made a Class A solid state amplifier yet - the closest I came so far is the JLH 10W which is still under construction - well actually it's not, it was doing well and is at least half done but it sits on a shelf due to many other projects that are also not quite finished :xeye:

But Hiraga was very careful with his designs, if he said it sounded good then I believe him. But his care extended to details of the transistor type, I don't know how easily the original can be created with substitutes. He looked at the current-gain curves and many other things when he created his amplifier. It might be necessary to do some level of matching between p-type and n-type ?? I think he also used some unusual power supply made from car batteries. Because of all the details he looked at and the way he chose parts, I'm not sure it is easy to simulate it accurately.

It looks to me, to be a design that is worth the care and attention to get a very nice sounding amplifier at the end.
 
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#10
I see what you mean...i understood

I do feel some empathy about Hiraga amplifiers.....they look nice..in special the first one that uses BJTs... symmetric is nice... we all love that... this is connected to beauty and harmony in the shape .

I see i have assembled in the past....and i knew reading Hiraga old thread that i said no good for it.

Then i found the old simulation..and i could make it a little it better....made it today..some improvement...but efficiency still 20 percent and this all i could have.

Reducing voltage and current, to reduce dissipation, then i have lost power...naturally..now 8 watts is 0.1 percent distortion (THD) and 5.5 watts with low distortion of 0.045%... you know.... even higher distortion i had in the first amplifier, the Dx Amplifier...seems to me to go backwards alike a crab... mine amplifiers, now a days are 0.002%... some are 0.00167%.... i will not tollerate to listen all these harmonics...you see... no crossover distortion to clean the sound that will be plenty of annoying harmonics...you know..looks bad business...bad solution...then i always give up to make it once again.... will be waste of time.... alike all other Class A i have build.

To make it again...well...this does not mean progress .. this is a return to a kind of old .. performance far outweighed nowadays.

To zener diode hatters.... this one will not produce noise because the huge electrolitic will "eat" the noise generated.

Performance of this one is alike the toy i have made a couple of days ago... a 555 chip together a BD139 and a BD140... a class D unit...power consumption ridiculous.... 1.2 watt to produce 1 watt of audio..and distortion is almost the same of the Hiraga...you see..how crazy this stuff is?

This Hiraga i have tweaked is 45 watts of consumption to generate 5.5 watts at 0.045% or 8 watts RMS at 0.1 percent...you see the difference...the ratio of consumption versus effective audio.

You see the trimpot, it is there to adjust the off set..but if you increase pot value, then you current will also increase...if you remove the 560 parallel resistor your stand by current will jump from 868 mA to each rail to almost 1.7A per rail.... heat will be huge...and power will jump to 19 watts RMS if i can remember....but imagine...each rail with 46 watts of heat...transistor gonna melt..you will need 2 pairs....and if you increase the voltage the hell gonna be even worse!

Carlos
 

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#11
I have also been making very clean amplifiers. My TGM8 is relatively high feedback and it sounds superb, I don't know how to make a better high power amplifier.

So Hiraga....

Well this is not about large powers. It is not about how clear and strong is the beer with near infinite supply. It is about the small barrel with the carefully brewed ale. It isn't full off gas and pressure, but instead sits atop the bar and gravity feeds the beer into your glass. It doesn't taste clean and sparkly like the supermarket beer, rather it has a unique body, taste and texture which the sunlight penetrates with difficulty. It's not a party beer, it's for the time when you are sitting in your favourite chair. A lot of effort was spent making these few pints of ale, not good for business efficiency, but very good for the few lucky drinkers who know.
 
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#15
any product's schematic, circuit topology is fair game for discussion - as long as you redraw it, don't make a exact optical/mechanical/digital copy you aren't violating copyright - copyright only protects the exact image - not the ideas, transistor types, parts values...

only active patents can restrict your use of circuit topology/idea - and the patent is explicitly public to spark examination/discussion/experimentation "to promote advancement of the useful arts"


proper attribution of the source is nice - but avoid violating Trademark - and promoting "Clones" of active commercial product is socially discouraged here
 
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