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Hiraga 20W class A
Hiraga 20W class A
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Old 28th January 2009, 08:24 PM   #321
danieljw is offline danieljw  Australia
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wow thats a great find !!!

put it in a good chassis with more bias and heatsinks !!!!!!

i am sure you wont be dissapointed !!!!

0.5A is a bit low i found a big difference in sound (obviously) when i cranked the bias to about 1.6-1.8 amps the only downside i can see with this amp is wasted heat !!!!

-Dan
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Old 1st March 2009, 01:54 AM   #322
Dr.X is offline Dr.X  United Kingdom
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Default Alternative output transistors?

Hi guys,
I'd like to build an amp based on the Hiraga 20W design and I've managed to find some of the originally spec'd input/driver transistors but what are your recommendations for the "best" replacements for the output devices?

How about OnSemi's MJ15003/4 or MJL0281/0302 or MJL1302/3281?

Any advice would be much appreciated!

Thanks,
Steve
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Old 1st March 2009, 02:21 AM   #323
danieljw is offline danieljw  Australia
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Hi Steve,

I would suggest that MJ15003 istoo slow (fT 2.0MHz) andthe capacitance is 1000pF,

The MJL0281 and MJL3281 are better choices the MJL0281 is the best out of the three in terms of speed / capacitance.

I would suggest using the toshiba 2SC5200/2SA1943 pair as the capacitance is much lower. another option would be Sanken 2SC3264/2SA1295

Hope this helps

-Dan
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Old 1st March 2009, 07:05 AM   #324
Boxmaster is offline Boxmaster  Netherlands
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Hi Dan,

First time for me on this forum, but i am also planning to build an Hiraga on stero´ds like yours. Allready have almost all the parts.
I have a question about the 1K8 biasresistors.
On the Class-A amp site they mention that you should increase the value of it by a couple of hundred ohms when the voltage rises. In case of the 30 watt Hiraga 2K4 max instead of 1K8.
In your case whe go from 21 volts to (+/-)34 volts.
Shouldn't the resistor be much bigger than 1K8 ?

Jurjen.
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Old 1st March 2009, 07:29 AM   #325
JohanH is offline JohanH  Netherlands
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Quote:
Originally posted by danieljw
Hi Steve,

I would suggest that MJ15003 istoo slow (fT 2.0MHz) andthe capacitance is 1000pF,

The MJL0281 and MJL3281 are better choices the MJL0281 is the best out of the three in terms of speed / capacitance.

I would suggest using the toshiba 2SC5200/2SA1943 pair as the capacitance is much lower. another option would be Sanken 2SC3264/2SA1295

Hope this helps

-Dan
Slow could be good to prevent oscillation.

To original question poster: there's a lot of info here on substituting the transistor. Do a search.

Johan
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Old 1st March 2009, 10:58 AM   #326
danieljw is offline danieljw  Australia
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Quote:
Originally posted by Boxmaster
Hi Dan,

First time for me on this forum, but i am also planning to build an Hiraga on stero´ds like yours. Allready have almost all the parts.
I have a question about the 1K8 biasresistors.
On the Class-A amp site they mention that you should increase the value of it by a couple of hundred ohms when the voltage rises. In case of the 30 watt Hiraga 2K4 max instead of 1K8.
In your case whe go from 21 volts to (+/-)34 volts.
Shouldn't the resistor be much bigger than 1K8 ?

Jurjen.
Hi Jurjen,

In my signature line there is a link which has details of what i changed and also the performance measurements.

Quote:
Originally posted by JohanH


Slow could be good to prevent oscillation.

To original question poster: there's a lot of info here on substituting the transistor. Do a search.

Johan

In this design the transistors should relatively fast 2.0MHz will not be sufficient. the circuit has inherant roll of much lower than this however faster transistors tend to have lower capacitance resulting in better/faster performance and they are easier to drive

- hope this helps and makes sense.

-Dan
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Old 3rd March 2009, 01:46 AM   #327
Dr.X is offline Dr.X  United Kingdom
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Hi Dan,
Many thanks for your reply! Yup it helps a lot

Cheers,
Steve


Quote:
Originally posted by danieljw
Hi Steve,

I would suggest that MJ15003 is too slow (fT 2.0MHz) and the capacitance is 1000pF,

The MJL0281 and MJL3281 are better choices the MJL0281 is the best out of the three in terms of speed / capacitance.

I would suggest using the toshiba 2SC5200/2SA1943 pair as the capacitance is much lower. another option would be Sanken 2SC3264/2SA1295

Hope this helps

-Dan
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Old 20th April 2009, 05:21 PM   #328
taotao is offline taotao  Germany
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Default Driving Apogees Ribbons?

Hello members,

I would like to build this amp for my mid/ High Range Ribbon (Apogee Duetta).
It's crossed over at 450 Hz, with a slope of 24 dB.
I guess concerning power, this amp would suit fine. But what about the ribbons` Z; It's around 2,6 ohm, so quiet on the low side.

Do you think the Hiagra can handle this load?

Thanx for clarification.

Olaf

Oh, Dan, your amp looks great, hope you don't mind me doing copy cat. I like to see this big towers on the top :-) Maybe in red, like le monstre...
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Old 20th April 2009, 10:26 PM   #329
danieljw is offline danieljw  Australia
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Hi Olaf,

is the impedance consistantly 2.6 Ohm or is 2.6 ohm the lowest point ?


feel free to copy i copied a little off the original layout anyhow

-Dan
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Old 21st April 2009, 06:35 AM   #330
taotao is offline taotao  Germany
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Hello Dan,

no it's constant (it's a ribbon and R is nearly equal Z)
For an amp with low damping factor, this linearity in impedance is an easy load (no dips ore peaks).
Might be the problem, that it is so low.

I hope le class a is able to drive this, 'cause I really like to build one :-)

Have a nice time

Olaf
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