George,
DC-offset floating from +20 to -30mv is so far ok and based on my personal experience and many discussions with Jean Hiraga a base problem of the DC-coupled design. The best is to use star ground for all ground wires including the income ground.
DC-offset is also temperature dependent as you have recognized too.
The original Japanese transistors are required according to the research made by Jean in the eighties, switching to replacements had significant impact on the sound and the circuit stability too.
End of last year I have spend some time to rebuild the amps from stereo to mono and by changing the PSU from passive to an active version with big capacitors (100T uF) before and after the regulation as proposed by Pierre Johannet of the L'Audiophile team for the Kaneda 50+50W. The new design results in more transparency in the lower mids and more bass-punch.
One more remark I have to add, the Class-A configuration with a power transistor bias current of about 1 Ampere result in a long term degradation of the power transistors due to termal fatique caused from operating close to the maximum junction temperature. Thus it is recommented to have spare transistors to replace them after about 2-3 years to avoid sound degradation.
Rgds, GKU
DC-offset floating from +20 to -30mv is so far ok and based on my personal experience and many discussions with Jean Hiraga a base problem of the DC-coupled design. The best is to use star ground for all ground wires including the income ground.
DC-offset is also temperature dependent as you have recognized too.
The original Japanese transistors are required according to the research made by Jean in the eighties, switching to replacements had significant impact on the sound and the circuit stability too.
End of last year I have spend some time to rebuild the amps from stereo to mono and by changing the PSU from passive to an active version with big capacitors (100T uF) before and after the regulation as proposed by Pierre Johannet of the L'Audiophile team for the Kaneda 50+50W. The new design results in more transparency in the lower mids and more bass-punch.
One more remark I have to add, the Class-A configuration with a power transistor bias current of about 1 Ampere result in a long term degradation of the power transistors due to termal fatique caused from operating close to the maximum junction temperature. Thus it is recommented to have spare transistors to replace them after about 2-3 years to avoid sound degradation.
Rgds, GKU
Power Supply
I use a CLCLC filter in mine. It has 350,000 ufd of Jensen 4 pole caps.
Mine runs at 800 ma bias. It barely heats the sinks. Hope it lasts for more than 2 -3 years.
Never heard an amp that I like better overall. Several are better in one or two areas.
Speaker matching is critical. Mine are full range drivers, 100 dB efficient and 15 ohm. The Hirega sounds good on more normal speakers also. Tried it on a 91 dB two way a while back. The owner said it was overall better than his 300B amp. I know it is better on my speakers than my 300B amp.
George
I use a CLCLC filter in mine. It has 350,000 ufd of Jensen 4 pole caps.
Mine runs at 800 ma bias. It barely heats the sinks. Hope it lasts for more than 2 -3 years.
Never heard an amp that I like better overall. Several are better in one or two areas.
Speaker matching is critical. Mine are full range drivers, 100 dB efficient and 15 ohm. The Hirega sounds good on more normal speakers also. Tried it on a 91 dB two way a while back. The owner said it was overall better than his 300B amp. I know it is better on my speakers than my 300B amp.
George
Hiraga
Hiraga is very good amplifier ( I got 20W and 30w version) but if you want to Hiraga sound good you must have very good preamplifer. If pre amp is not good you have problem with bass etc. Hiraga need good Cd source and cable and if you respect this conditions you are always listen to Hiraga amplifers!
Hiraga is very good amplifier ( I got 20W and 30w version) but if you want to Hiraga sound good you must have very good preamplifer. If pre amp is not good you have problem with bass etc. Hiraga need good Cd source and cable and if you respect this conditions you are always listen to Hiraga amplifers!
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