KODA clone - slightly new topology (1000 watt amp)

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#21
PB2 said:
Q90 and 91 should be larger devices IMO considering thermal derating, SOA, idle current, and survival (hot) with a short circuited output.
I'd probably use one per output if you must use that device.
Have you tested into 1 or 2 ohm loads, or are you not allowing those. Lower supply V would be suggested for low Z loads.
Click to expand...

Yes , you are right. The 2sc4793/2sa1837 are NOT good at 2R - 70+V. At 4R- 60V , even 2R 60V and main HS mounting ,even DC SOA is not exceeded.
I recommend the bigger MJE15032/33's for even 4R @ 75V. Now this is curious,
Carlos - DX , is trying to run 10 pair OP's from the MJE's and I am "sweating" just
4 pair.

Below you see below the 4793 can just pass 150ma DC/70V and 220+mA @100ms/70V. The plot (@20hZ) ,shows actual driver Ic which exceeds that (280mA) , but only for 20mS. They might just "squeak by" , but the MJE's can do over 500mA @ 100mS/70V.

CAN YOU IMAGINE 10 bloody flippin' output pairs !!!! 😛😛😀:no::no:

OS
 

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#22
Note in that SOA curve where it says must be derated linearly with temp. 25 deg case temp is not even warm. Also, beta droop will depend on your output device models. MJEs are what I was going to suggest ... good choice.

I think it is best to state your case with Carlos and let people do as they please since they will anyway.
 
#23
PB2 said:
Note in that SOA curve where it says must be derated linearly with temp. 25 deg case temp is not even warm. Also, beta droop will depend on your output device models. MJEs are what I was going to suggest ... good choice.

I think it is best to state your case with Carlos and let people do as they please since they will anyway.
Click to expand...

I got moderated doing that.. :no: I was just concerned about fire :hot: and the fact that novices build many DX projects , a bad combination.

Linn Inc. Recall of Power Amplifiers for Sound Systems

It can happen , even to the pro's. I have noticed that my 100Kuf/1kva @77-0-77VDC setup has NO MERCY on parts :hot: :hot: They will not just get hot , THEY WILL BURN ... flames and all.
OS
 
#24
PB2 said:
Note in that SOA curve where it says must be derated linearly with temp. 25 deg case temp is not even warm. Also, beta droop will depend on your output device models. MJEs are what I was going to suggest ... good choice.

I think it is best to state your case with Carlos and let people do as they please since they will anyway.
Click to expand...

Also, remember that the pulsed ratings are for non-repetitive conditions so they do not apply to this situation. Worst case will probably be short circuit with the input overloaded so that it clips - you might want to look at that in order to size the rail fuses.
 
#25
hi ostripper
greetings want to ask you if schematic of KODA amplifier is complete working
schematic and your expert opinion is it possible to diy this amp can 2sc5200 2sa1943 be
used as output transistors as ones shown in schematic are not available here
thanking you
andrew lebon
 
#28
andrewlebon said:
Hello Ostripper
greetings nice to see you back is this koda schematic a tested
design to diy whats your opinion
warm regards
Andrew
Click to expand...

The Koda is closest to the Apex audio AX14 project.

If it is the "voice of" the Baxandall super pair you are after , either the AX14
or my Kypton C/ND are the ticket.
If it is the 1000 watts you seek , a 6 or 7 pair EF3 outputs stage (MT200)
would do. All 3 IPS's (AX14 , kypton C/ND) have been tested on the Slew
output stages with perfect reliability.

OS
 
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