mail slavcovic:best amp is next amp
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with mj2955/2n3055 (2pair) can i use +-50 volt for 4 ohm load?
see and enjoy:
tnx again from mail slavcovic and all of friends in diyaudio.com
with mj2955/2n3055 (2pair) can i use +-50 volt for 4 ohm load?
Attachments
No! Never!
https://www.onsemi.com/pub/Collateral/2N3055-D.PDF
For MJ15024/15025, OK!
https://www.onsemi.com/pub/Collateral/MJ15022-D.PDF
The BC546 transistors that I had quite a few from genuine sources was able to match them 2 pairs to hfe value of 431 so got a quad matched. Is this hfe value low or good enough for this amp? The reason being that offset hovering >20mV always and does not drift below this number even after heat stabilizing for an hour or so.
Thanks
Never say never!
The maximum voltage I would use with 2N3055/MJ2955 single or parallelled devices is +/-37.5V.
This is on the basis that the Vcer is 70V, and a small voltage limit due to VAS/CCS etc.
In practice the amplifiers I have made have run from 40V rails without trouble, but I checked the breakdown voltage first. All the 3055/2955's tested from ST and ON semi were 80V+.
But you could connect additional devices in series. If you had 4 pairs in series-parallel they should be able to run from +/-50V, but it would need a different output stage arrangement to the usual one.
my ax14 stop working. 
it was working bias was stable. but now bias changing too much go up and down. for the bias changing and get high 5200 getting hot too much. is there any one get this problem and find solition?
i am going to change bias pot maybe that was bad but 2 channel is same i dont think its cause of that.
it was working bias was stable. but now bias changing too much go up and down. for the bias changing and get high 5200 getting hot too much. is there any one get this problem and find solition?
i am going to change bias pot maybe that was bad but 2 channel is same i dont think its cause of that.
whel done.good jobI think im getting ahead of myself with all this building. Today I got all the parts for the APEX A38/40. Got home and printed pcb's. Will cut, etch and drill tomorrow.
Bag O'parts
Has anybody got the pcb layout for the P30ZF preamp please? Would like to start that as well
i am going to burn my brain. why ax14 bias is rising
no input, sgnd connected to the psu gnd, i set 8mV on 0R33 but its going up slowly.
i wait 10 min it look like stop at 9mV and i set again to 8 mV nut its same want to go up 9mV and stay there.
i change 1k R16 to 2.2k (from bd139 collector to the base)i read in forum. it not fix any thing same same .
what can be rising bias slowly? mje340 getting warm withouth input signal i can touch with hand...
it was working perfect why its stop working i dont understand this amp.
no input, sgnd connected to the psu gnd, i set 8mV on 0R33 but its going up slowly.
i wait 10 min it look like stop at 9mV and i set again to 8 mV nut its same want to go up 9mV and stay there.
i change 1k R16 to 2.2k (from bd139 collector to the base)i read in forum. it not fix any thing same same .
what can be rising bias slowly? mje340 getting warm withouth input signal i can touch with hand...
it was working perfect why its stop working i dont understand this amp.
Where did you mount Q10? If it's on the same transistor that R33 goes to, you need to check another resistor, because Q10 might be compensating for over-bias and trying to reduce and limiting current through R33. I recently had that issue and lucky I checked the other emitter resistors, the bias was actually 70-80mV not the 20 I thought.
Hard to follow what you are saying - is the amp working, or not? It was working, but now it's not? Have you tried with a shorted input? open inputs can sometimes give weird results.
Here some pics
Attachments
amp was working good alone outside the chase i test booth channels all was ok and i leave it cause it was late so afternoon i connect and see its too much hot. and then i check bias and it was 120mV i fix it but it was keep changing fast 10mV to 120 some times 150mV and then i change pots now not fast and not that much big raise. it is coming to almost 10mV and then going little down and up again not metter if you fix again and again to 8mV its rising to 9.
thank you soo much by the way you allways trying to help.
thank you soo much by the way you allways trying to help.
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