Hiraga 20W class A

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masag1

Member
Joined 2008
Hello to you all.

A friend of mine recently did a new PCB Layout for the 30W Hiraga.
On the board is a 12V automotive relay with two pair of contacts and the DC-protection circuit with and switch on delay.

I have posted the top view as pdf

I love the Hiraga amps!

Regards

Sam
 

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M

megaymir

Member
Joined 2008
Try KSC2690A/KSA1220A as driver. I have some of them and the hfe is about 250, but some of them goes up to 300.
Click to expand...

Sajti!

Where can I get those transistors? Via internet?
What do you think, could make the high fT value (155 MHz) any trouble in this circuitry?
Other idea: MJE340/350. But it's fT is only 10 MHz.
Is the rule true, that the previorus stage always must have wider bandwidth?
At this moment the first two stage is about 100 MHz, the output stage is 30 MHz.
 
sajti

sajti

Member
Joined 2003
megaymir said:
Sajti!

Where can I get those transistors? Via internet?
What do you think, could make the high fT value (155 MHz) any trouble in this circuitry?
Other idea: MJE340/350. But it's fT is only 10 MHz.
Is the rule true, that the previorus stage always must have wider bandwidth?
At this moment the first two stage is about 100 MHz, the output stage is 30 MHz.
Click to expand...

Drop me some private message on the hungarian forum, and we can meet somewhere. I have about 200 pcs. from Mouser.
I can't tell You anything about the speed. But the BD139 has ft about 50-100MHz depended by the manufacturer, and there was no problem.

Sajti
 
M

megaymir

Member
Joined 2008
audio-grade types
Click to expand...

E.g.? Source?

It makes me wonder, even the mentioned mediocre elements are hard to get in adequate quality. I tryed a number of local shops (I got 5-5 piece from every type), and I realised, that the store of this shops are from random source. E.g. I asked for Philips BC559C/549C, but the PNP-NPN pairs were always different products. Almost impossible to maching the complementers in this manner...
 
L

Lumba Ogir

Banned
Joined 2005
Hi Sajti,
here are some types designed for voltage amplification:
2SC2911/2SA1209
2SC3953/2SA1538
2SC3600/2SA1406
2SD1609/2SB1109
2SC3423/2SA1360

megaymir,
the BC559/549 is somewhat better, otherwise the 2SC2240/2SA970 is a good general purpose pair for audio.
the PNP-NPN pairs were always different products.
Click to expand...
It´s necessarily so. Japanese devices are more closely matched.
 
sajti

sajti

Member
Joined 2003
Lumba Ogir said:
Sajti,
"driver" is an exceedingly loose designation. It is about topology, determining the nature of operation, that requires different device characteristics.
Click to expand...

OK, then use the common sense only. This transistor gives the base current of the output devices. Using 100-200mA max collector current devices is not the safe side for me.
What is Your real problem with the KSC2690A/KSA1220A? They are slow? Low Hfe? Wrong hfe characteristics? High internal capacitance? Any other?

Sajti
 
L

Lumba Ogir

Banned
Joined 2005
Sajti,
I`m talking about the common-emitter stages, directly driving the output devices, where you prefer triple Darlington, considerable distortion as a result. Voltage amplifier transistors have small Icmax, wide bandwidth, small Cob and small conduction losses, essential for large, fast moving voltage swings. The coarse types in question are meant neither for voltage nor current amplification, but for switching, and are pretty bad at linearly amplifying anything. They were around for thirty years ago, but Hiraga avoided them like the plague. It`s more than common sense, it`s deep insight.
 
G

Glogov_Kolac

Member
Joined 2008
Does somebody can tell me which PSU is adequate for 20W Hiraga. My configuration is: 1.3 bias current,15VAC (about 18 VDC) PSU, 80000uF capacitors and BD250/249 output transistors. Why I get only 18V from 15VAC (15*1.41-1,4V is suppose to be about 19.5V). Is there anybody who built the 20W Hiraga vith the PSU which is published in the L'audiophile magasine:http://www.tcaas.btinternet.co.uk/hiraga1fig10.gif
 
sajti

sajti

Member
Joined 2003
Lumba,

Generally I agree with You. I would never use the KSC2690/KSA1220 as VAS in common amplifier. 3503/1381 is a way better for VAS. But this amplifier has different requirements, because that stage has to provide the base current of the output devices. The low Ic max types has significant beta drop with high Ic. The 2SC2911/2SA1209 B drops from 250 down to 100 at 100mA. KSA2690/KSA1220 has no significant B drop up to 1A. The speed is equal. Only the capacitances are higher (19pF vs 4pF). This is the only drawback.
I don't know what do You mean with coarse types? The types I recommend is not for switching.

Sajti
 
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