Hello dear colleagues,
I'm collecting parts for this wonderful amplifier (to build one) and I want to ask you guys (from your experience) wich transistor pair from the ones listed bellow do you think that suits better for this amp (30w@1.2A@+-25V):
1)2sd718/2sb688 (obsolete)
2)2sc5200/2sa1943 (by ON SEMI)
3)mjl4281/mjl4302
4)mjl3281/mjl1302
5)2stc5242/2sta1962 (by ST )
1)http://www.radiomods.co.nz/transistors/2sd718.pdf
2)http://www.tme.eu/en/Document/cf5dd35f638dd8ed180bd72300b3c766/7890.pdf
3)http://www.cordellaudio.com/book/datasheets/MJL4281.pdf
4)http://www.onsemi.com/pub_link/Collateral/MJL3281A-D.PDF
5)http://www.tme.eu/en/Document/53cf3b34ff283c6f437e3abc346921b3/6398412.pdf
I have styudied the pdf's and my money is for the STC pair for the great linearity and Cob and i think that they are better than the Toshiba's sc/sa.
What do you think about the rest of the transistors? They have bigger Cobs but how do they react in this amp ? How do they sound? Do we need compensation for them?
Please help!
Thanks in advance.
Sergiu
I'm collecting parts for this wonderful amplifier (to build one) and I want to ask you guys (from your experience) wich transistor pair from the ones listed bellow do you think that suits better for this amp (30w@1.2A@+-25V):
1)2sd718/2sb688 (obsolete)
2)2sc5200/2sa1943 (by ON SEMI)
3)mjl4281/mjl4302
4)mjl3281/mjl1302
5)2stc5242/2sta1962 (by ST )
1)http://www.radiomods.co.nz/transistors/2sd718.pdf
2)http://www.tme.eu/en/Document/cf5dd35f638dd8ed180bd72300b3c766/7890.pdf
3)http://www.cordellaudio.com/book/datasheets/MJL4281.pdf
4)http://www.onsemi.com/pub_link/Collateral/MJL3281A-D.PDF
5)http://www.tme.eu/en/Document/53cf3b34ff283c6f437e3abc346921b3/6398412.pdf
I have styudied the pdf's and my money is for the STC pair for the great linearity and Cob and i think that they are better than the Toshiba's sc/sa.
What do you think about the rest of the transistors? They have bigger Cobs but how do they react in this amp ? How do they sound? Do we need compensation for them?
Please help!
Thanks in advance.
Sergiu
Hi Jacques
I see, but the STC's looks better on paper then the SC series.. The kits on Ebay are with mjl outputs but they have higher Cob even than the 2sa/2sc..
Did you matched the outputs?
Hiraga did mention about matching the transistors on hot air. How is that? What are the results, perfect matching?
Do you use another psu for the input?
I see, but the STC's looks better on paper then the SC series.. The kits on Ebay are with mjl outputs but they have higher Cob even than the 2sa/2sc..
Did you matched the outputs?
Hiraga did mention about matching the transistors on hot air. How is that? What are the results, perfect matching?
Do you use another psu for the input?
I have no idea what the hot air matching means. I have not matched the outputs on two separate experimental builds and they worked fine.
If I remember well, Hiraga recommended instead to match the input pair, which I did. The same psu was used for all stages.
Beware, this amp runs quite hot: better use it in the winter! Wifey calls it the 'barbecue grill'
I used the original 2SC1775A/2SA872A since my local shop still carries them.
Out of 15 of each, it was quite easy to find several close input pairs.
I only matched the differential pair at the input, not the others.
With 100 pieces, it should be very straightforward.
Thank you.
I have another problem and thinking right now at it.........
I have two 2x25v trafo for a stereo pair and wanted to make a CM just for the inputs and a classic CrC (the same as in the original article)for the outputs and the prefinals. The problem is that with 2x25vac i should obtain approx 2x35vdc and that means more power from this amp and i dont have sufficent cooling for keeping the trannies cooler..
What do you recomend to do: lower the bias or increase the R value from the CrC?
Lowering the bias would affect sound fidelity on this amp?
I have another problem and thinking right now at it.........
I have two 2x25v trafo for a stereo pair and wanted to make a CM just for the inputs and a classic CrC (the same as in the original article)for the outputs and the prefinals. The problem is that with 2x25vac i should obtain approx 2x35vdc and that means more power from this amp and i dont have sufficent cooling for keeping the trannies cooler..
What do you recomend to do: lower the bias or increase the R value from the CrC?
Lowering the bias would affect sound fidelity on this amp?
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I would not exceed 30V/rail as 25V makes it run quite hot already.
If you have separate secondaries, you might get the 25-30V you want by the means of LM338 regulators
(2 for each amp) or some other regulator circuitry as suggested by members here who built the Hiraga amp.
You probably want to keep the amp biased in classA so lowering the biais in not the best option.
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