I guess you could keep biasing up till the Class-A output matches what the rail's limits are, at the point, class A ouput should = AB... theoretically speaking ...
tell us what voltage you want across your 1r0 or 1ohm (reactive) load and we will show you why you should not try to achieve ClassA into a 1ohm load.
Since this is the ksa100 Klone thread let's use that as an example.
Increase the output stage to 12pairs of MJ15003/4.
Increase the bias current to 6A (500mA through each).
The total dissipation is now ~51V * 6A * 2 ~600W
The maximum ClassA output current is ~12Apk
The maximum output voltage is ~45Vpk.
The peak transient current into a an 8r0 resistor ~45/8 ~5.6Apk. This is well inside the ClassA limit.
The peak transient current into an 8ohm speaker is ~45/8*3 ~16A. This is outside the ClassA limit.
If we biassed a 100Klone to about 16A, total dissipation ~1.6kW, it should just about never leave ClassA driving a real 4ohm speaker load.
Biassing a KSA100Klone to 6A can never guarantee that it does not enter ClassAB with a real 8ohm speaker.
Similarly, we hit a current limit long before we hit a voltage limit with low impedance loads, eg. 4ohm and 2ohm.
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hi.I have 600 VA torodidal transformer and it has 4x18 volts output.I will connect in series and have 2x36volts ac.I am planning to build a low bias Class AB krell ksa100 or ksa50 version amp with this transformer..How many output transistor should i use? I have MJL1302/3281 and NJW132/3281 transistors.and which of them are more suitable?thank you
Yes, i have done the calculations and 1 ohm class A operation is not feasible . I would assume a sliding bias would be the best route , class A for the first 100 watt @ 8 ohm which would net 12.5 watt@ 1 ohm or 25 @ 2 ohm on the revised speaker imp of 1.8 Ohm ...
Now to select the topology to use , any suggestions there ?
KSA 50 value of C105 and C106
I am in the process of building a KSA50 Clone. On the boards I obtained and the circuit diagram the value for C105 and C106 is 22pf, yet on other diagrams I have seen the value is 390pf.
What is the correct value?
I am in the process of building a KSA50 Clone. On the boards I obtained and the circuit diagram the value for C105 and C106 is 22pf, yet on other diagrams I have seen the value is 390pf.
What is the correct value?
Testing....
Tested for about 1h... will let it be on for another hour tonight...
VCC: 50v - 2.54amp
Emitter: 625mv
Heatsink: ca: 36C with fan at full speed
In/Out signal 1Khz
In: 0.1v / square
Ut: 0.5v / square
Pictures are taken before I went up to 625mv
Question: is the emitter voltage supposed to drop 0.1-0.3v when getting hot ?
If I turn pot up again to 625mv then it after 5min drop 0.1-0.2v..
Guess something isn't stable in my powercube or signalgenerator.
** Just touched my powercube, it's super hot ... hahaha...
Hope it won't burn up...
Question 2:
Is it normal that the emitter voltage is NOT the same on all transistors ?
625mv
618mv
630mv
622mv
.....
thank you Andrew
great to hear It from expert
resistor values to change are 1 Ohm emitter resistors In output, right
what Is min voltage of rails needed In order not to change the zeners
would you please tell what are your amp specs
I still don't know what toroid to buy - I don't need 100 W at 8 Ohm and so much heat but want to be close to original amp
last question how this amp compares to Nelson Pass amps
I have build F5
great to hear It from expert
resistor values to change are 1 Ohm emitter resistors In output, right
what Is min voltage of rails needed In order not to change the zeners
would you please tell what are your amp specs
I still don't know what toroid to buy - I don't need 100 W at 8 Ohm and so much heat but want to be close to original amp
last question how this amp compares to Nelson Pass amps
I have build F5
I am no expert.
I think I am good at sorting the wheat from the chaff, but I get that wrong as well.
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