Salas hotrodded blue DCB1 build - Page 218 - diyAudio
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Old 25th August 2012, 02:42 AM   #2171
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Let us know, I hope the sinking is enough for 1A yes? 1A means 20W dissipation per rail constantly for DCB1 usual voltages across the power semis.
Ended up replacing all fets with new and spares - 240s and 9140s. This time with lots of arctic silver on fets/pads/chassis contact. Now I have a tight -10.2 and 10v. With 1.5R instead of 1R I am pulling 866mA and 1A . But I have a PC fan on the enclosure (Antek 12in*12*2) so we'll see how it goes. An infrared thermometer is on the way so I can properly gauge temps. Not sure what happened before, must have shorted something?

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Old 25th August 2012, 03:13 AM   #2172
Salas is offline Salas  Greece
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Probably no good thermal transfer because you caught a couple of loose screws, when you pushed the amperage, boom. Can you feel a difference in your system from 600mA to circa 1A?
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Old 25th August 2012, 09:34 AM   #2173
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1A is more refined with increased three dimensional qualities. Not huge but noticeable. I also swapped out Muse KW 100ufs for Silmic IIs and the 470r metals for carbon comp. Not sure which is responsible but delivery is smoother - there was a slight etchiness before, not bad per se but board sounds different now.

Heat dissipation is MUCH better; the chassis is barely warm by the fets at shutdown.
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Old 25th August 2012, 10:01 AM   #2174
Salas is offline Salas  Greece
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Some tightening and a good thermal compound can do wonders.
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Old 1st September 2012, 08:09 AM   #2175
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Out of curiosity: what is the lowest value that can be used for output impedance resistors?
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Old 1st September 2012, 09:37 AM   #2176
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Takes to know it does not oscillate in a certain setup by scoping the output down to a minimal value. Maybe 100 Ohm or less depending on interconnects used.
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Old 1st September 2012, 09:50 AM   #2177
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Ok, I've been using 100R with dcb1 more or less directly to the amp with only a few inches of wire. I am curious because with this current build and the previous I have found the lower I go the more dynamic, open, and transparent the sound (previous amp had 7kinput imp, current amp 16k)...
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Old 1st September 2012, 11:49 AM   #2178
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A lower value of gate stopper allows the FET to operate faster. The filter created by the gate stopper and the internal capacitance of the FET moves to a higher frequency.

You can go as low as you like with the gate stopper value. The limit will be when instability sets in.
You will need to test the circuit thoroughly with all manner of interference and fast changing demands to ensure that stability is good. The lower the gate stopper value the more thorough your testing regime must be.

Or just play safe and use the recommended value or half the recommended value if you like to take chances.

But listening and hearing extra detail may be the sign/symptom that the PSU has already reached the instability operating area and the non smooth output is affecting the amplifier and giving the "sound effect" of extra detail.
you really need to test the PSU properly if you reduce the gate stopper value.
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Old 1st September 2012, 11:31 PM   #2179
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Ok, thanks Andrew. I'll play it safe and keep things as they are.
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Old 2nd September 2012, 02:27 AM   #2180
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you really need to test the PSU properly if you reduce the gate stopper value.
Can you share some details of how to do this? (The PSU testing part, I know how to change the gate stopper )
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