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Old 26th August 2003, 10:59 AM   #11
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So if I change BC549, to BD139 and Increase the output resistors to 0.1 The Amp shuold be fine?
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Old 26th August 2003, 11:52 AM   #12
sajti is offline sajti  Hungary
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Let's discuss about thermal compensation:

1, The thermal resistance of "juction to case", and "case to sink" is no problem in this case. Remember this is problem if Your trannies dissipate power. The bias sensor device doesn't dissipate high power. So the junction will be almost same temperature as the heatsink.

2, With CFB, the thermal runaway caused by the driver but not the output device. This is true, because the feedback loop avoid the change of output device's temperature change.

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Old 26th August 2003, 11:54 AM   #13
sajti is offline sajti  Hungary
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Quote:
Originally posted by Marvellous
So if I change BC549, to BD139 and Increase the output resistors to 0.1 The Amp shuold be fine?

The emitter resistors (R10, R11) is OK with 0R33.

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Old 26th August 2003, 12:04 PM   #14
Freddie is offline Freddie  Sweden
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Default CFP bias

Quote:
The CFP in the output stage is extremely difficult to handle. Probably you get in trouble with your DC bias
I have an amp with CFP output stage. There's absolutley no problem to get stable bias. No problems at all. I mounted the the Vbe multiplier transistor on top of the driver transistor. Reffering to the schematic above: Q8 mounted on top of Q4. I also used the same sort of transistor for Q8 and Q4.
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Old 26th August 2003, 12:32 PM   #15
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Default Follow Up

So Changes that I must Make are

1. Leave the Emitter resistors (R10, R11) as 0R33.
2. Change BC549, to BD139
3. mount Q8 on top of Q4


What is the maximum Voltage that this Amp can Handle?
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Old 26th August 2003, 01:01 PM   #16
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Default updated Schemetic

Here is the updated Schemetic!

I have started to build my amp will keep you updated
and will post some pics!
Attached Images
File Type: jpg sound-boy-new4.jpg (36.7 KB, 167 views)
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Old 26th August 2003, 01:04 PM   #17
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Please All Coments & suggetions Welcomed!!!
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Old 26th August 2003, 01:09 PM   #18
sajti is offline sajti  Hungary
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The maximum voltage depended by the transistors You use.
With this devices the maximum voltage about +/-40V, but as I know T3 is the limit for the voltage. Maybe it can be change to MJE340.
But there is another limitation:
Higher voltage means higher output current. And the output device has some limitation to handle the higher current. So over 35V I recommend to use more output devices parallel.

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Old 26th August 2003, 01:42 PM   #19
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that makes sense to me!

but now
if I Parallel my outputs then can the output stage handle more voltage or will it be able to handle more current
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Old 26th August 2003, 01:52 PM   #20
sajti is offline sajti  Hungary
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More current. With TIP31C/32C drivers, and TIP35C/36C output, the output stage can handle +/-50V, and will gives about 200W/4ohms. But with 1pair of output trannies it's not possible.


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