I don't know your scope, but you'll need one with a certain bandwith (I suggest at least 20 MHz). DMM is not of much help.
Then you need a signal generator, or you can use your soundcard with REW.
Drive your amp at different levels, with sine and square wave signals, with resistive and real loudspeaker loads. If the output shows other waveforms than the input (overshoots, high frequency content, ...), that is not good and shows that the amp is not stable enough. Do a Google search on "Amplifier Oscillation" and look at the pictures in the search results....
Sanken and OnSemi are pretty much state of the art. You may also try 2SC5200 and it's PNP counterpart from Toshiba, an excellent transistor.
You need constant (high) hfe at higher currents, a fast transistor, cob as low as avialable.
There is no such thing as a "wonder-transistor", and the difference between those suggested is overrated in my opinion.
Ok so at first switch on the dc offset was:
The sankens were 919ma and the MJL's 418ma.
Stuck a timer on and after 35mins the temp was 41 degrees Sankens went down 30ma and the MJL's 35ma
It took almost an hour for both of them to get to 0V. at which point the temp was around 46degrees.
after two hours both heatsinks averaged about 47-48 degrees.
So yes it shows that dc offset is proportional to the temperature raise.
One more question do both transistors have to have equal levels of bias? For me to have it stable its like 0.60 on the npn and 0.62 on the pnp.
Last edited:
What a good day it was for testing, i was really able to put these amplifiers through their paces and they did not disappoint.
Ill keep it quick and simple.
Preamps:
Yamaha ca-600 (i like the mode function where it joins the Left and Right signals together so the preamp outputs share both signals) . This allowed me to test one amplifier at a time but getting both L/R signals coming through.
Diy Marantz 7 circuit Tube Preamp
Speakers:
Planet 10 onkens with MA alpair 7.3
Tannoy Berkeleys (i was very surprised how good it sounded with these amps)
Things really came alive when i used the big tannoys it gave a good impression of how well the amp performed and how the transistors used sounded.
Amplifer 1:
The MJL21193+MJL21194
Amplifer 2:
NJW0302G+NJW0281G
Both Amps were tested at 0.6A and 0.7A, allowed to be fully warmed and stable, i didn't want let the rail voltages drop below 16V. I will may 1A just to listen and test more, my thought was to eventually try and get a stable bias where my PSU you can handle the load and i get good measurements from my scope. I mean i tried 1.5A and it sounded strong, further tests showed no benefits cons were HEAT,PSU having a hard time and bad rms value tests from my scope. Just using 0.6 - 1A tests better for my current setup which is fine.
Ok i will continue this tomorrow as it's late!
Last edited:
Hi Vishal,
You may have seen the below photo of my amp (Jean Hiraga 30 Watts) It was a complete DIY right from the PCB's to the Enclosure.
But Now as the time has passed I too have updated my amplifier with Proper PCB's, Power Bank (4,40,000 uf Per Channel) and a Heavy Enclosure (Enclosure is a complete DIY) with More bigger Heat sinks. The Amp PCB's were made as per my layout from a PCB manufacturing company, Soft turn on & Protection PCB's were purchased as a complete assembled kits.
When i shifted to Proper power Bank there was a huge difference in the low frequency. The difference is on the better side, the low frequency is improved a lot the difference is like day & night.
When I was using Cap multiplier the lower notes were blurred and the intensity was very light. (but still it sounded very good in mids and high region)
Belive me this 30 Watter is a Real Monster. And so dose it looks now.
Sadik
You may have seen the below photo of my amp (Jean Hiraga 30 Watts) It was a complete DIY right from the PCB's to the Enclosure.
But Now as the time has passed I too have updated my amplifier with Proper PCB's, Power Bank (4,40,000 uf Per Channel) and a Heavy Enclosure (Enclosure is a complete DIY) with More bigger Heat sinks. The Amp PCB's were made as per my layout from a PCB manufacturing company, Soft turn on & Protection PCB's were purchased as a complete assembled kits.
When i shifted to Proper power Bank there was a huge difference in the low frequency. The difference is on the better side, the low frequency is improved a lot the difference is like day & night.
When I was using Cap multiplier the lower notes were blurred and the intensity was very light. (but still it sounded very good in mids and high region)
Belive me this 30 Watter is a Real Monster. And so dose it looks now.
Sadik
no!, not at all.
your earlier one is better.
I only said , All input section grounds should meet at a single point, e.g. input signal -, FB ground, i/p section 47k res gnd, R6/R7 gnd, etc.
Last edited:
That is the modified version of the Hiraga class A.
I am not a fan of the 13V diode on the front, that version.
I built that and never like her at all.
Much more the 20V Zener D type.
Keep all the resistor values, the rail voltage can be lowered, only because I am not sure the type of heatsink you got will take the heat.
May be use 15 or 16VAC transformers.
Attachments
Last edited:
Many years ago (30?) I modified the Hiraga Le Monstre schematic and built a 25 W amplifier. After having moved around a couple of times, I replaced the amplifier with new ones.
Now I have started to go back to this amplifier, following the attached schematic, but not using the pair C2922 and A1216 (I don't remember which drivers I used). I used a 2x18 V tranformer with CRC-filtering giving plus/minus 24 V (no huge power supply).
Have someone tried something like this?
Now I have started to go back to this amplifier, following the attached schematic, but not using the pair C2922 and A1216 (I don't remember which drivers I used). I used a 2x18 V tranformer with CRC-filtering giving plus/minus 24 V (no huge power supply).
Have someone tried something like this?
Attachments
Last edited: