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Old 2nd February 2011, 01:03 PM   #461
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Quote:
Originally Posted by gaborbela View Post
You can't double the output transistors !
It is a built up darlington power stage .
Greets
If you are still around, could you post the schematic of Selectronic's Profet amp?
They sell only finished units now.
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Old 2nd February 2011, 02:25 PM   #462
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This is true, but depends on the output transistors used. I guess that you are using some of the biggest ones from on semi, which have the sweet spot around 1.1A, but also like more VOLTAGE (unless you cascode them).

I didnt check the datasheets, but I'm pretty sure that the original ones chosen by Hiraga were doing their best at 20W output power, or he would just have proposed a 30W amp
The outputs chosen were not very high powered; the maximum power depends on the heatsink thermal resistance.

Additionally: the current amplification is matched with the driver transistors, such that this becomes a combo that performs well.
Even the input pairs must be 'better than' the commonly proposed BC559 type, as the flat shelving of the amplification is needed, that reacts to a difference in the Vce-difference. Hiraga spent quite some time in matching, each choice is tricky.
albert
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Old 2nd February 2011, 02:35 PM   #463
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Old 2nd February 2011, 02:39 PM   #464
Telstar is offline Telstar  Italy
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triode_al, you're right: Hiraga "matched" all transistors.

BTW, I have found these PCB on sale, which seem good:
Leer PCB Super Class A Verstärker Hiraga "L Audiophile" su eBay.it Verstärker, High-End Audiogeräte, Audio Hi-Fi
This scheme has been posted in this thread.
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Old 2nd February 2011, 03:15 PM   #465
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Quote:
Originally Posted by Telstar View Post
I didnt check the datasheets, but I'm pretty sure that the original ones chosen by Hiraga were doing their best at 20W output power, or he would just have proposed a 30W amp
I can confirm that, as I ran a slightly higher voltage and power on my first build and killed the output transistors (and a 12" woofer). The heatsinks were big. Be careful with the bias.
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Old 3rd February 2011, 02:29 AM   #466
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Hi guys,

There is two versions of the class a you can get 30W with resistor and ps voltage changes. The original chassis will run very hot in this situation. The bias makes a big difference. 1.5A to 2A is nice from my experience with this one

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Old 3rd February 2011, 03:47 PM   #467
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Hi,
I understand some power this little monster from a 12 V regulated supply.
the original Le Monstre (which I built with the selected transistor set from the Maison de l'Audiophile) is intended to run from lead acid batteries as well. This implies that the Vb is higher than 12 V: between 12,6 and 13,2 V is useful.

This slightly more than one volt difference makes a difference in power consumption (current) and details.
albert
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Old 6th February 2011, 02:40 AM   #468
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Hi Albert, Le monstre is a different amp, this thread is for le class A

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Old 6th February 2011, 09:51 AM   #469
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Hi Albert, Le monstre is a different amp, this thread is for le class A
Daniel, You'r right. I'm shooting from the hip, apparently. albert
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Old 6th February 2011, 10:42 AM   #470
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All good al,

Have you had a listen to the Hiraga stuff before ?

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