I have just completed a pair of these Hiraga amplifiers and was amazed with the sound. Was never an advocate of class A but after completing a regulated power supply and using transistors that i had available i can confirm that this simple amp,designed some 30 years ago, is one of the very best as far as sound quality is concerned .For those who want to give it a try and cannot get the specified original transistors here is what i used and its working fine with no problem in setting the bias current and the DC offset. I do not want to get into a debate about the characteristics of the transistors i used. I can only say that they complement the circuit and they do the job. Just bear in mind that you might have to adjust the 47 k bias resistor to give around 380 mv measured across the 0.33 R resistors at 30 v. I got it right at around 34.3 k.
The use of a regulated power supply is highly recommended as with it,the amp is extremely quiet,no hum etc.
Transistors used for the output is the 2SA 1942 and 2SC5200
Drivers BD237 and BD238
Inputs BC 258 and BC630. (TYPING ERROR CORRECTED SHOULD BE BC 639)
The use of a regulated power supply is highly recommended as with it,the amp is extremely quiet,no hum etc.
Transistors used for the output is the 2SA 1942 and 2SC5200
Drivers BD237 and BD238
Inputs BC 258 and BC630. (TYPING ERROR CORRECTED SHOULD BE BC 639)
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Bonjour Jacques, i used the 30 w version as per the one in the link below.
Jean Hiraga's Super Class-A Amplifier
Jean Hiraga's Super Class-A Amplifier
SUZTEK, it would be useful if you listed an equivalent list just to make sure that everyone is aware of what transistors you used where.
By comparing Hiraga's original schematics to the updated one, I noticed that the bottom zener in oriented differently. Which is the correct orientation?
Link to schematics
Jacques
Link to schematics
Jacques
The revised updated 30 w drawing shows the correct orientation of the zener (cathode to the ov) in the negative supply.
As mentioned in my earlier post, the transistors used were available from my spares because the specified originals were just impossible to get. Bear in mind the replacment transistors are not "direct equivalent" to the originals. I did try a few other transistors, but the one listed below allowed me to set both the bias current and the DC offset very easily. I cannot argue that the original specified transistors will sound better but the ones listed below, do the job very well and the result is a real wonderful sound with clear mids and highs and a surprisingly powerful bass.
The list 2SA872 used BC258B
2CS 1775A used BC 639
2SA634 used BD237
2SC1096 used BD238
Outputs used 2SC 5200 and 2SA1943
The list 2SA872 used BC258B
2CS 1775A used BC 639
2SA634 used BD237
2SC1096 used BD238
Outputs used 2SC 5200 and 2SA1943
The sound is very detailed with clear mid's and high's and a surprisingly powerful bass.
A worhwhile project as i am now rediscovering my Vinyl and Cd collection.
A worhwhile project as i am now rediscovering my Vinyl and Cd collection.
Very nice work Suztek!
How does it perform temperature-wise?
Would you mind sharing the regulated psu schematics?
Thanks,
Jacques
How does it perform temperature-wise?
Would you mind sharing the regulated psu schematics?
Thanks,
Jacques
Hi Jacques, the heatsink temperature is stable at 65 to 68 degrees c with ambient temperature being 27 degrees c. Send me your email address and will pdf the drawing of the regulated supply as i am not sure how to do it using this forum.
Regards
Regards
You got a winner! Nice layout, clean wiring. Thx for sharing the project with us. Your gonna have a thousand questions of where, what & how.....Congradulations!