3pr of 1943/5200 will be OK for ~200W into 8r0. But, you must keep them cool !!!!
1943/5200 have a pretty poor SOAR when Vce gets high, as in this amplifier.
BTW, how did you arrive @ +-61Vdc? If that is from a 115/230:40+40Vac transformer, you will not get anywhere near 200W into 8r0. and don't be tempted to use 45+45Vac to get to your 200W target. The 1943/5200 will not like it.
1943/5200 have a pretty poor SOAR when Vce gets high, as in this amplifier.
BTW, how did you arrive @ +-61Vdc? If that is from a 115/230:40+40Vac transformer, you will not get anywhere near 200W into 8r0. and don't be tempted to use 45+45Vac to get to your 200W target. The 1943/5200 will not like it.
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Thanks, do you advice more pairs or other transistors.
Any Transistors you would advise.
This pair are not to expensive. (MG6330-R, MG9410-R)
http://docs-europe.electrocomponents.com/webdocs/0f8a/0900766b80f8a10b.pdf
This pair cost 50% more than pair above. (MG6331-R, MG9411-R)
http://docs-europe.electrocomponents.com/webdocs/0f8a/0900766b80f8a11c.pdf
Yeah I was thinking 45+45Vac 500VA transformer,
A local supplier has stock of two left at equiv. to 70U.S. dollars.
They are decent quality toroidals, I don't think Ill get them at this price
in my country again.
thanks.
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My amp used three pairs of 2SD2155 and the complement 2SB1429 and ran off 2x60V supplies from a "800VA" transformer that in reality based on possible power output from the amp in 4 ohms seemed more like 350-400VA, i got 240WRMS from this amp in 4 ohms before the sinewave started getting clipped.
This amp even took a dead short for several seconds several times as i increased and decreased volume and survived, it got real hot in a hurry though. This caused by a overheated voice coil shorting out during a power test at low frequency around 10Hz.
I guess what kept the amp alive was that the transistors are mounted directly onto the heatsink with nothing but thermal paste between the heatsink and the transistors, instead the heatsinks are electrically insulated from each other and from the chassi mounting points.
This amp even took a dead short for several seconds several times as i increased and decreased volume and survived, it got real hot in a hurry though. This caused by a overheated voice coil shorting out during a power test at low frequency around 10Hz.
I guess what kept the amp alive was that the transistors are mounted directly onto the heatsink with nothing but thermal paste between the heatsink and the transistors, instead the heatsinks are electrically insulated from each other and from the chassi mounting points.
You could also consider TO-3 package transistors which have better thermal capability. Look for MJ21193/4 transistors from Onsemi.
If you prefer flat packs, then the MJL4281/4302 or MJL21193/4 transistors from Onsemi are good, rugged devices. The Semelab devices you mentioned are also good devices from specification - the important part is good cooling. I'd probably suggest at least 4 pairs of transistors, though.
Also for your predriver transistors (Q15/Q16), try to find some TO-126 type transistor that can handle ~1A, while still being fairly fast. For example spec 2SC2690/2SA1220 or 2SD669/2SB649 type devices work well there.
If you prefer flat packs, then the MJL4281/4302 or MJL21193/4 transistors from Onsemi are good, rugged devices. The Semelab devices you mentioned are also good devices from specification - the important part is good cooling. I'd probably suggest at least 4 pairs of transistors, though.
Also for your predriver transistors (Q15/Q16), try to find some TO-126 type transistor that can handle ~1A, while still being fairly fast. For example spec 2SC2690/2SA1220 or 2SD669/2SB649 type devices work well there.
Miller cap is mandatory with amps having LTP input stages, however,somewhat larger value than normal is at expense of slew rate and limited power at HF.
PLEASE
@Andrew lebon and sergio DS
Stop reproducing this circuit by YIROSHI it is simply a ticking bomb especially if made with this type and style of pcb
For starts this pcb has never been tested ( to my understanding ) and if put to test it will blow with in a few minutes of full power
If you like me to explain the reasons i am willing to but i don't see the reason to do so since this is told almost a million times already in numerous posts threads ..
Kind regards
Sakis
@Andrew lebon and sergio DS
Stop reproducing this circuit by YIROSHI it is simply a ticking bomb especially if made with this type and style of pcb
For starts this pcb has never been tested ( to my understanding ) and if put to test it will blow with in a few minutes of full power
If you like me to explain the reasons i am willing to but i don't see the reason to do so since this is told almost a million times already in numerous posts threads ..
Kind regards
Sakis
Yeah I guess thermal compensation sux 
Might as well link a nice pimped amplifier is you like this type of amplifier.
thanks to Mr Mile from Apexaudio
http://www.diyaudio.com/forums/solid-state/173462-studio-reference-amplifier.html
Its not a simple amp but it is fantastic
Regards
Might as well link a nice pimped amplifier is you like this type of amplifier.
thanks to Mr Mile from Apexaudio
http://www.diyaudio.com/forums/solid-state/173462-studio-reference-amplifier.html
Its not a simple amp but it is fantastic
Regards
NO !!!
The LIN topology amp with the LTP as input stage can and does operate properly without any added capacitance across the CB junction of the second stage.
That "Yiroshi" amplifier will never never never never provide 200W into 8 ohms.
Besides being horribly underbiased : 2 diodes + 10 ohms to forward bias 4 (four) BE junctions?
And unstable (no Zobel network) to the point of self destroying with any real world speaker load at the end of any real world speaker cable.
Maybe that's why those 470pF caps had to be added, but that's not the right place or value.
Did I mention no short protection?
Just because the link was provided, I checked other "Yiroshi" schematics at Scribd.
Ouch !!!
Besides being horribly underbiased : 2 diodes + 10 ohms to forward bias 4 (four) BE junctions?
And unstable (no Zobel network) to the point of self destroying with any real world speaker load at the end of any real world speaker cable.
Maybe that's why those 470pF caps had to be added, but that's not the right place or value.
Did I mention no short protection?
Just because the link was provided, I checked other "Yiroshi" schematics at Scribd.
Ouch !!!
That "Yiroshi" amplifier will never never never never provide 200W into 8 ohms.
Besides being horribly underbiased : 2 diodes + 10 ohms to forward bias 4 (four) BE junctions?
And unstable (no Zobel network) to the point of self destroying with any real world speaker load at the end of any real world speaker cable.
Maybe that's why those 470pF caps had to be added, but that's not the right place or value.
Did I mention no short protection?
Just because the link was provided, I checked other "Yiroshi" schematics at Scribd.
Ouch !!!
I agree with you.
This amplifier used Otala - Hitachi symmetry topology. If you like this topo, try ''The Techno'' and ''Sigma'' from Dr. Bora. It's simple and higher quality.
50VDC rail would send you 100W/8 Ohms. Higher supply voltage will get higher power output, but, not use Toshiba's devices. Sanken/ON Semi better!
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