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Old 20th October 2017, 12:48 AM   #1281
alazira is offline alazira  United States
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Hi Salas,
What would be the effect of a small cap in this position?
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Old 20th October 2017, 10:33 PM   #1282
Salas is offline Salas  Greece
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Some noise curve shaping at the few MHz territory I suppose since it forms an RC with the base stopper resistor.
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Old 22nd October 2017, 05:49 AM   #1283
nautibuoy is offline nautibuoy  United Kingdom
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I am using a Reflektor-D, built from a Tea-Bag supplied kit, to power my Twisted Pear Buffalo 3SE board.

I plan to upgrade the DAC to TP's new ESS9028 based Buffalo board but it demands more current from its power supply, specified as 750mA. In my build I will only need about 720mA (because I don't use the Buffalo's onboard oscillator) but this is still well beyond the Reflektor-D's capability. Is it possible to modify the Reflektor D to deliver this level of current?

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Old 22nd October 2017, 06:28 AM   #1284
Salas is offline Salas  Greece
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The Ref-D's current ability is a matter of sinking mostly. The spec limit is for the certain on board sinks. Its a conservative current spec not a break down spec though. If you have the bare minimum Mini version for example, which is externally sinkable only, you can readily bolt it to larger sinking. If you got the full version with the onboard rectification and sinks you can either affix a mini fan on them as they sit close together forming a hollow square top, or remove them and extend the Mosfets pins to sink them externally.

A quality mini fan can be used with under-voltage to 2000-2800 rpm where it should be quiet. If you will need set for more than 850mA, especially when without forced cooling, better replace the the IRF9610 with a Fairchild FQP3P20-ND. Tad slower by gate input pF number but significantly cooler in its core per dissipated Watt. Then you can go over 1A even. As a rule of thumb don't allow much more than 55C on sinks for good long term reliability. If they don't suffice for that make them bigger or cool them.
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Old 22nd October 2017, 11:00 AM   #1285
nautibuoy is offline nautibuoy  United Kingdom
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Quote:
Originally Posted by Salas View Post
...replace the the IRF9610 with a Fairchild FQP3P20-ND...
Thanks Salas, I have the full sized Reflektor-Ds with onboard heatsinks.

So, if I keep the board as is except for swapping in the cooler-running Fairchild device and changing the current setting resistor (R1 = 0R8 will give about 760mA total current) it looks like I might be able to get 720mA the DAC would need - I don't have space for a fan or off-board mounted devices.

The Buffalo 3SE DAC board obviously has its own local Trident regulators following the Reflektor-D

Last edited by nautibuoy; 22nd October 2017 at 11:09 AM. Reason: more detail added
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Old 22nd October 2017, 11:28 AM   #1286
Salas is offline Salas  Greece
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The dissipation of that Fairchild will be the same of that IRF. Because the voltage drop and the current in the circuit dictate that. Its just that the Fairchild will be safer on a pushed current and small sink situation because it has better θjc i.e. transfers heat from its core to its case mounted at the sink more efficiently than the IRF. Safer, but up to a point of course. For more on thermal design basics this is a good read: http://www.analog.com/media/en/train...als/MT-093.pdf
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Old 22nd October 2017, 11:46 AM   #1287
nautibuoy is offline nautibuoy  United Kingdom
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Quote:
Originally Posted by Salas View Post
The dissipation of that Fairchild will be the same of that IRF. Because the voltage drop and the current in the circuit dictate that.
Yes. of course!
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Old 22nd October 2017, 11:48 AM   #1288
Dimdim is online now Dimdim  Greece
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IMHO 760mA of CCS current is cutting it a bit too close if the Buffalo's actual current consumption is indeed 720mA.
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Old 11th November 2017, 01:25 AM   #1289
AnthonyA is offline AnthonyA
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Hi Salas,
Will solid core wire perform better?
What do you suggest I do to make bass perform better? It's slightly soft.
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Old 11th November 2017, 08:55 AM   #1290
Salas is offline Salas  Greece
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Try the JFET mod first
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