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Old 22nd October 2009, 05:50 AM   #1131
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Default i tdont belive that this will work

Quote:
Originally Posted by sajti View Post
Hi,

I'm working on my new hybrid amplifier. The whole amplifier will be point to point wiring except the protection pcb. The following pictures contains the ss output stage.

Sajti
the wire you use to supply all these transitors is way to thin...that apply for both rails and output

meaning that at full power if your rail voltage intransistor 1 is 10 volts in the last tranistor it will be much less ..... much less is even 0.2 volts that also means that in any stress conditions the transistor with less voltage will fail first and take with all the others

you may get away with it if you supply rails and output in the midle of the connstruction but this will onle share the currents meaning that if you have 0.2 volts drop from side to side you will manage to make 0.1 volts from side to side

still this is not enough to make the amp work safe

i just noticed that i was in a harry and the rail and output lead is missing also that output resistors are allready curved for something biger .... still the above point is something worth looking at ..... often if length is too much you get problems like that

regards sakis
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Last edited by east electronics; 22nd October 2009 at 05:54 AM.
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Old 22nd October 2009, 07:15 AM   #1132
sajti is offline sajti  Hungary
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Originally Posted by sakis View Post
i just noticed that i was in a harry and the rail and output lead is missing also that output resistors are allready curved for something biger .... still the above point is something worth looking at ..... often if length is too much you get problems like that

regards sakis
The rails, and the output will use 2mm thick copper wire. But this wire will be soldered after the mounting of the heatsinks, due I want to curve them using one piece of wire to the capacitors.

Sajti
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Old 22nd October 2009, 07:54 AM   #1133
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depenting on the power and the operating conditions of the amp i belive that 2mm might not be enough ...... consider also the epidermic phenomenon

regards sakis
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Old 22nd October 2009, 08:26 AM   #1134
sajti is offline sajti  Hungary
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The amplifier will be bridged, and use +/-35V. Expected ouput power 200W/8ohms, 350W/4ohms, and 550-600W/2ohms. The peak current from the rails about 50A. This is short time peak, and I will use 20A slow fuses.

Sajti
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Old 22nd October 2009, 08:43 AM   #1135
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then yes 2mm thickness of cable is for sure not enough at this length and especially if supplied at the left or right side of your construction

even if terminolgy of electrical laws is used 1.5 mm is good enough for 10A with max 16 and then again 2.5mm is good enough fro 16a and max 20 ....but all the above is for bulding a house and supply lampsand other resistive loads in 50-60 hz freq not amplifiers ....
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Old 22nd October 2009, 09:38 AM   #1136
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Hi Sajti,
I'm inclined to agree, that 2mm is a little on the low side, for the high current links.
If the collectors are middle fed then 2mm would do, but the links to the smoothing caps could/should be dual 2mm.
The emitter cable should be increased to dual 2mm or single 2.5mm and again the output from the middle would be better. Remember that the NFB tapping must come from the output end of the connecting wire.

If your target is 200W into 8ohms (40Vrms) then you must achieve at least 600W into 2r0 (34.7Vrms) to make an effective 4ohm speaker amplifier. Using Cordell's rule for resistive load driving ability then the 2r0 test must be >=1.8times the 4r0 test power. which for 380W (39Vrms) into 4r0 becomes 680W (37Vrms) into 2r0.
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Old 22nd October 2009, 09:39 AM   #1137
sajti is offline sajti  Hungary
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Quote:
Originally Posted by sakis View Post
then yes 2mm thickness of cable is for sure not enough at this length and especially if supplied at the left or right side of your construction

even if terminolgy of electrical laws is used 1.5 mm is good enough for 10A with max 16 and then again 2.5mm is good enough fro 16a and max 20 ....but all the above is for bulding a house and supply lampsand other resistive loads in 50-60 hz freq not amplifiers ....
The wire will be not too long. The maximum lenght from the capacitors to the last output device will be 25cm. This should be OK.
Each amplifier modul has independent wires.

Sajti
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Old 22nd October 2009, 09:54 AM   #1138
sajti is offline sajti  Hungary
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Originally Posted by AndrewT View Post
Hi Sajti,
I'm inclined to agree, that 2mm is a little on the low side, for the high current links.
If the collectors are middle fed then 2mm would do, but the links to the smoothing caps could/should be dual 2mm.
The emitter cable should be increased to dual 2mm or single 2.5mm and again the output from the middle would be better. Remember that the NFB tapping must come from the output end of the connecting wire.

If your target is 200W into 8ohms (40Vrms) then you must achieve at least 600W into 2r0 (34.7Vrms) to make an effective 4ohm speaker amplifier. Using Cordell's rule for resistive load driving ability then the 2r0 test must be >=1.8times the 4r0 test power. which for 380W (39Vrms) into 4r0 becomes 680W (37Vrms) into 2r0.
Hi Andrew,

I will try it with 2mm, because I have the wire. If I find any problem, than I will go to double 2mm. I have enough space, and short lenght to change the wire if necessary. I have some 4x2mm flat copper wire as well, so I have chances.

The output will be close to the middle of the emitter wire, to the protection relay, and to the output terminals. The will be no feedback.

The output power is mainly depended by the PSU in my case (16pairs of output devices should be enough for 2ohms load), and the PSU is based on 1500VA toroid, and 198000uF smoothing.

Sajti
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Old 22nd October 2009, 10:10 AM   #1139
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and visa versa....ha ha ha ...meaning that often many of so called professional amplifiers last longer (while producing average sound ) but last under a lot of stress cause the power supply is weak ...meaning that when the load is very high rails will dive sound is distorted but amp is safe

in your case a rowbust supply will perform perfectly sound wise but will provide a hell of a lot of current to the boards and that is why you should be twice carefull regarding wiring and power distribution ....

kind regards sakis
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Old 22nd October 2009, 10:24 AM   #1140
sajti is offline sajti  Hungary
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Quote:
Originally Posted by sakis View Post
and visa versa....ha ha ha ...meaning that often many of so called professional amplifiers last longer (while producing average sound ) but last under a lot of stress cause the power supply is weak ...meaning that when the load is very high rails will dive sound is distorted but amp is safe

in your case a rowbust supply will perform perfectly sound wise but will provide a hell of a lot of current to the boards and that is why you should be twice carefull regarding wiring and power distribution ....

kind regards sakis
The professional amplifiers designed for other purposes. The live music has high peak ratio, so smaller PSU is enough, due the capacitors keep the rails for short time.
Another issues are the price, size, and weight, which are not so important for DIY amplifier.
My amplifier has 1.6m heatsink for one stereo amplifier, which has the weight of 10kg...

Sajti
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