I don't think you can get a reliable 800 watts from this design.
Even a 250 watt BJT has a high linear derating on the case temp. So if the case temp is say 60 or so degrees, you could only expect about 90 to 100 watts maximum case dissapation per device.
This design has only 8 o/p devices.
400 watts RMS continous operation into 4 Ohms is all I would drive this o/p stage and as for say running it at 110 volts +- forget it....
Regards
Anthony Holton🙂
Even a 250 watt BJT has a high linear derating on the case temp. So if the case temp is say 60 or so degrees, you could only expect about 90 to 100 watts maximum case dissapation per device.
This design has only 8 o/p devices.
400 watts RMS continous operation into 4 Ohms is all I would drive this o/p stage and as for say running it at 110 volts +- forget it....
Regards
Anthony Holton🙂
I dont know then what author of that was thinking🙂 I have stuff at home, I will run it with more transistors.. Pobably i will buy Anthony Holtons pcbs and used them with that chasis and toroid which specs are similar for both amps, so i wont have to buy another 1..
Anthony: Is 2kW/2x70V toroid ok for your av800?
I dont know where ill get the 2s_xxxx transistors - they arent selling these in Slovenia, does somebody knows the substitutes for these:
2SC2240 TO-220
2SC2240 TO-92A
2SA1306 TO-220
2SC3298 TO-220
Anthony: Is 2kW/2x70V toroid ok for your av800?
I dont know where ill get the 2s_xxxx transistors - they arent selling these in Slovenia, does somebody knows the substitutes for these:
2SC2240 TO-220
2SC2240 TO-92A
2SA1306 TO-220
2SC3298 TO-220
Hi skaara. Check company in Ljubljana named Terna. They sell transistors from Bürklin catalog and I am sure you will find something usefull.
Supernet
Supernet
Hi skaara
The transformer you have will work more than well with the AV800 amp module. However I would suggest that you just add a few more o/p devices to this design and also increase the emitter resistors from 0.22 too 0.47. If you have already invested in the PCBs for this design, then let's see what we can do to get these existing modules up to spec.
Regards
Anthony Holton
🙂
The transformer you have will work more than well with the AV800 amp module. However I would suggest that you just add a few more o/p devices to this design and also increase the emitter resistors from 0.22 too 0.47. If you have already invested in the PCBs for this design, then let's see what we can do to get these existing modules up to spec.
Regards
Anthony Holton
🙂
The whole article about this amp is scanned here (cutted in 3 zips), u wont understand whats written, but pics are watchable🙂 I didnt scanned this article, if I would have a scanner I would post pics of bottom of pcb too (there is no pcb side in the article, because hes selling them, I payed a $40 for 2 channels and thats a lot because its a bad amp!!
http://www.elektro-n.com/forum2/uploads/1.del.zip
http://www.elektro-n.com/forum2/uploads/2.del.zip
http://www.elektro-n.com/forum2/uploads/3.del.zip
I have all PCBs populated, just need appropriate heatsink (im waiting my neighbour, who has a company which works with aluminium, to come from the vacations and he will made me something..)
http://www.elektro-n.com/forum2/uploads/1.del.zip
http://www.elektro-n.com/forum2/uploads/2.del.zip
http://www.elektro-n.com/forum2/uploads/3.del.zip
I have all PCBs populated, just need appropriate heatsink (im waiting my neighbour, who has a company which works with aluminium, to come from the vacations and he will made me something..)
skaara said:
Than i have too go into the books 🙂
The exact meaning of the word ring emitter is something in the build up.
I don,t know the real thing at this moment because all my stuf is in boxes i,m in the middle of leaving my house for an athor one 🙂
In theorie it means that a normal transistor take the most famous one the 2n3055 will have a cutt off in an open loop configuration by 800 hz which mean you need a lot off correction in example the feedback.
BUT EVEN with a high overal feedback(or local) it will give you the full frquentie response but not that easy EVEN with boostup frequentie works local it will never give a full range amplifier without hills end valley,s in tyhe freq spectrum.
AT highest the 3055 will go to example 40 KHZ with a enormus cutt off in frequentie.
The RE however is a much faster transistor maybe even faster tha a fett.
Easily it will have a range off example 20mhz so you can imagine the pro,s of this types.
In a open loop they will even give a satisfactionery spectrum but with a little feedback (only to reduce the thd and tim and too heva it stable in case off oscilation) it,s a dan good amplifier very sensitive and with ALL the pro,s off not using that much feedback.
So in practice it means you can use a more specific shematic diagram with LESS electronic which will sound much better .
ONLY the dempingsfactor i don,t know the englisch word for it will gar back in number but who cares? 50 of that is more than enough .
Don,t stare blind on the numbers the only thing which counts are your ears end for my ears a transistor amp with RE transistors is best
Good luck DDD
For more info you can for examle have a look at the data sheet of one off them example the 2sa1492 compl 2sc ......
Take www.google.com and you will find out
Hmm, I connected these two toroids, and the voltage on secondary of each transformer is 2x 80V... Is that ok for your amp too (if this one fails ill order yours.. still waiting the heatsinks🙂 Anthony?
Hi Skaara
When you say you get 2x80 volts do you mean AC volts or DC volts.
If you mean DC then that's just fine... But AC would mean once you rectify and filter the supply you would get about 113 volts DC+-. Much too high.
Its OK for my 1kw design, But a little high for the AV800...
Regards
Anthony
When you say you get 2x80 volts do you mean AC volts or DC volts.
If you mean DC then that's just fine... But AC would mean once you rectify and filter the supply you would get about 113 volts DC+-. Much too high.
Its OK for my 1kw design, But a little high for the AV800...
Regards
Anthony
Its 2x80VAC.. I thought like this: 2.4v falls on bridge rectifier so 77.6V x 1.2 = 93V on full wattage and 77.6 x 1.41 = 109.5V with no load... If this isnt ok, would I have to add 6 more mosfets (20 total) and this voltage would be ok?
skaara said:
It doesn,t matter how much mosfets or bipolair semi conductor you will place.
Even a hundred will fail when the battery voltage is too high .
I think best you can do is taking the 1/2 or at highest 3/4 of the spec voltage of te power output stage.( i mean the spec,s off the semi conductor)
For te voltage amp you can much better use a seperate supply soo not the same which feed the output stage the current output stage.
With voltages like you name you sure will get into trouble finding the right caps for the current output supply.
Grtz DDD
If you want to build this amplifier with four pair of MJ15024/25 as shown then use a transformer of no more than 55-0-55 at 1.6KVA
Skaara and others .
The spec,s of the mje power transistor,s are not that good.
Look the differents between a power SANKEN ringemitter and the motorola and you see a lot off different,s and the most importants is the speed off the transistor as we call it the frequency.
I think it,s high for a MJ transistor a 4 mhz but instead of the minimum of 20 mhz by a ring emitter transistor it,s not that good which mean a lot more feedback to get in stable.
Believe me the SANKEN ring emitters are the best too get ! and most off all in a good configuration very very stable.
Maybe you can,t get this power out off a ringemitter which wil noet aloud the higher voltage but that,s very simple too border because you can easily used a bridged version with the pro,s off it.
It,s only a suggestion and i believe teh MJ .s wil give in the above schematic a good sound but there is a way too get is easier and better.
Don,t focus on one, overvieuw a lott off others and nevertheless forget the high output,s more than 1 KW you can better have an amp which is stable by example 1 ohm which happens by difficulty speakers and that,s important than you need a loot off current and not an amp which blow away because when your talking about an amp which delivers 1,2 kw at example 4 R than you need a lost off reserve too get a power 4 times higher by 1R
So look at your supply it needs to be very big very big at least you need a 3 kw power transformer and a lot off booster elco,s which i gues by 1,2 kw a 200.000 uf is the minimum !
For the voltage amp you need a less trasnformer but also high capacity off elco,s(a lot off small ones instead off a big one too get it faster)
Which bring me too the point that by this kind off power you can,t do it easily it,s a hell off a job and it cost you a lot and for that money i think it,s better too buy a factory amp like Krell
The spec,s of the mje power transistor,s are not that good.
Look the differents between a power SANKEN ringemitter and the motorola and you see a lot off different,s and the most importants is the speed off the transistor as we call it the frequency.
I think it,s high for a MJ transistor a 4 mhz but instead of the minimum of 20 mhz by a ring emitter transistor it,s not that good which mean a lot more feedback to get in stable.
Believe me the SANKEN ring emitters are the best too get ! and most off all in a good configuration very very stable.
Maybe you can,t get this power out off a ringemitter which wil noet aloud the higher voltage but that,s very simple too border because you can easily used a bridged version with the pro,s off it.
It,s only a suggestion and i believe teh MJ .s wil give in the above schematic a good sound but there is a way too get is easier and better.
Don,t focus on one, overvieuw a lott off others and nevertheless forget the high output,s more than 1 KW you can better have an amp which is stable by example 1 ohm which happens by difficulty speakers and that,s important than you need a loot off current and not an amp which blow away because when your talking about an amp which delivers 1,2 kw at example 4 R than you need a lost off reserve too get a power 4 times higher by 1R
So look at your supply it needs to be very big very big at least you need a 3 kw power transformer and a lot off booster elco,s which i gues by 1,2 kw a 200.000 uf is the minimum !
For the voltage amp you need a less trasnformer but also high capacity off elco,s(a lot off small ones instead off a big one too get it faster)
Which bring me too the point that by this kind off power you can,t do it easily it,s a hell off a job and it cost you a lot and for that money i think it,s better too buy a factory amp like Krell
For the price of a Krell you can build an army of very
fine amplifiers. (Of course one Krell might be considered
an army by itself) 😉
Personally, even if it it costs as much as a Krell, I'd still
rather build them myself. That is why this is DIYAUDIO.
fine amplifiers. (Of course one Krell might be considered
an army by itself) 😉
Personally, even if it it costs as much as a Krell, I'd still
rather build them myself. That is why this is DIYAUDIO.
Nelson got the point, I would still rather built them myself too🙂
And anyway, I will get the chasis for free, I already have the toroids so I just put the amp in.
I dont know how much heat that amp dissipates,
I will use 10" (H) x 3.2" (W) x 20" (D) heatsink for each channel.. is this big enough?
And anyway, I will get the chasis for free, I already have the toroids so I just put the amp in.
I dont know how much heat that amp dissipates,
I will use 10" (H) x 3.2" (W) x 20" (D) heatsink for each channel.. is this big enough?
Off Course your right but is this building yourself?
No it,s getting stuff together i guess!
You know i like to build things myself beginning by the begin and then with a basicly schematic in my head devoleping.
Off cours i build them too from elektor etc but i also build amp myself with the old ones 2n30 55 and even in the early days with the ad161/62 .
So that,s what i mean THAT,s building yourself and THAT,s why i told you to considder the use off the SANKEN RE transistors because believe me they are soo much better dan tha MJ.
Finding a KRELL second hand isn,t that difficult and they are build like a tank so what,s the problem and that,s why i said if you realy goes for the high output don,t even think about your schematic and buy a ksa300 (second hand off course)which delivers more than enough and stable like a rock(accept the transformer)
If you want to build it yourself begin by the begin keep it simple and buy some books about it and on a moment your on the point too get the bias into the right place and build that one stable believe me and when you realy have it stable you can get the damn relais throwing away.
Sorry too tel it this way but,s that,s how i think about buid one yourself or use other ones schematic which isn,t building yourself but getting stuff together or buy a complete one which in my eyes is the best too do for the economic reason because don,t forget the price off the buffer!
Although i whish you off course all the luck with your schematic and building it and off course you can ask me everyhing .
I think you need an ossciloscope to measure from the beginning the waves of the output off an frequenty generator too see everythings going the right way and to see if the frequenty will get straight without hills and valleys .
GRTZ DDD
No it,s getting stuff together i guess!
You know i like to build things myself beginning by the begin and then with a basicly schematic in my head devoleping.
Off cours i build them too from elektor etc but i also build amp myself with the old ones 2n30 55 and even in the early days with the ad161/62 .
So that,s what i mean THAT,s building yourself and THAT,s why i told you to considder the use off the SANKEN RE transistors because believe me they are soo much better dan tha MJ.
Finding a KRELL second hand isn,t that difficult and they are build like a tank so what,s the problem and that,s why i said if you realy goes for the high output don,t even think about your schematic and buy a ksa300 (second hand off course)which delivers more than enough and stable like a rock(accept the transformer)
If you want to build it yourself begin by the begin keep it simple and buy some books about it and on a moment your on the point too get the bias into the right place and build that one stable believe me and when you realy have it stable you can get the damn relais throwing away.
Sorry too tel it this way but,s that,s how i think about buid one yourself or use other ones schematic which isn,t building yourself but getting stuff together or buy a complete one which in my eyes is the best too do for the economic reason because don,t forget the price off the buffer!
Although i whish you off course all the luck with your schematic and building it and off course you can ask me everyhing .
I think you need an ossciloscope to measure from the beginning the waves of the output off an frequenty generator too see everythings going the right way and to see if the frequenty will get straight without hills and valleys .
GRTZ DDD
Ill use variac to put rail voltage to +-16V (at this voltage this amp goes to "normal mode") and ill put in two 10ohm resistors instead of fuses, then ill apply signal genereator and ill look with osciloscope - then ill see if there are any spikes or grass on o/p of the amp and, if it will be ok, ill raise the voltage to +-26V and so on until i will get it work..
skaara said:
Right that,s the way to do it.
I used the same method by repairing but don,t forget when it,s going wrong too discharge de caps !
Normaly i used a resistor but with a normal lamp is will do the job too.
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