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Old 4th April 2009, 06:30 PM   #731
m2003br is offline m2003br  Brazil
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Hi Barry,

Have you already tested the negative rail with 1 KOhm too? it is OK?
Have you conected 0 Volt line to the frontend?
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Old 4th April 2009, 06:46 PM   #732
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Hi m2003br
Quote:
Have you already tested the negative rail with 1 KOhm too? it is OK?
Yes

Quote:
Have you conected 0 Volt line to the frontend?
Yes

I have found that the positive and negative rails are both OK when they are individually connected to the amplifier with the 0 volts but not when both the rails are connected at the same time.

I have just been looking at the voltages on the amplifier board and the LEDs that do not light up......
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Old 4th April 2009, 06:50 PM   #733
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I forgot to say that I typed the voltages the wrong way earlier....

The positive rail is 11 volts and slowly rises and the negative is 19 volts.
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Old 5th April 2009, 03:35 AM   #734
Coulomb is offline Coulomb  England
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I can not seem to find it spelled out in the thread, but is the maximum Wattage disspated per device going to be 20 Watts in Class A operation?

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Anthony
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Old 5th April 2009, 05:14 AM   #735
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by Coulomb
I can not seem to find it spelled out in the thread, but is the maximum Wattage disspated per device going to be 20 Watts in Class A operation?

Regards

Anthony
With the standard 34V supply, 0.1R emitter resistors, and bias at the maximum 20mA (0.2A), dissipation will be 6.8W per device (or 5.1W at 15mA).

Sheldon
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Old 5th April 2009, 05:52 AM   #736
Coulomb is offline Coulomb  England
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Quote:
Originally posted by Sheldon


With the standard 34V supply, 0.1R emitter resistors, and bias at the maximum 20mA (0.2A), dissipation will be 6.8W per device (or 5.1W at 15mA).

Sheldon

Thanks Sheldon, that sounds more like it.

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Anthony
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Old 5th April 2009, 09:47 AM   #737
pooge is offline pooge  United States
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Quote:
Originally posted by Sheldon


With the standard 34V supply, 0.1R emitter resistors, and bias at the maximum 20mA (0.2A), dissipation will be 6.8W per device (or 5.1W at 15mA).

Sheldon

Add some for the drivers, and I believe total dissipation is around 42W for the original 25vac transformer. If 30vac is used for power supply, total dissipation is up to around 71W. Roender recommended .35C/W for a 25vac supply. If using 30vac supply, something in the order of .30C/W or better may be needed
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Old 5th April 2009, 03:15 PM   #738
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by pooge



Add some for the drivers, and I believe total dissipation is around 42W for the original 25vac transformer. If 30vac is used for power supply, total dissipation is up to around 71W. Roender recommended .35C/W for a 25vac supply. If using 30vac supply, something in the order of .30C/W or better may be needed

The original transformer was 34vac http://www.diyaudio.com/forums/showt...9#post1349109. At 6.8W per device, total dissipation for the output devices is 41W. With the latest set-up http://www.diyaudio.com/forums/showt...63#post1705663 (100mA through the drivers), the drivers add about 7W, for a total of 48W.

Output dissipation will scale with bias, emitter resistor value, and supply voltage (20mA, 0,1R, 34vac, for this example). Driver dissipation scales with supply voltage and R5 (12R for 100mA).



Sheldon
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Old 5th April 2009, 04:04 PM   #739
pooge is offline pooge  United States
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Quote:
Originally posted by Sheldon



The original transformer was 34vac http://www.diyaudio.com/forums/showt...9#post1349109. At 6.8W per device, total dissipation for the output devices is 41W. With the latest set-up http://www.diyaudio.com/forums/showt...63#post1705663 (100mA through the drivers), the drivers add about 7W, for a total of 48W.

Output dissipation will scale with bias, emitter resistor value, and supply voltage (20mA, 0,1R, 34vac, for this example). Driver dissipation scales with supply voltage and R5 (12R for 100mA).

Sheldon
It was 34v on the FRONT end, 25V on the output side.
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Old 5th April 2009, 04:11 PM   #740
Sheldon is offline Sheldon  United States
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Quote:
Originally posted by pooge


It was 34v on the FRONT end, 25V on the output side.
I'm not sure how to add the link so that only the relevant post is shown, but I copied the post link for post 8. The schematic in post 8 is a clear as it can be, 39v frontend, 34v output. Either way, the calculation is straightforward.

I did not include the front end power dissipation in the above calculation, but it will be a little over 1W.

Sheldon
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