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Old 26th May 2012, 01:54 PM   #21
lhquam is offline lhquam  United States
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Quote:
Originally Posted by qusp View Post
coolness! i'll keep watching the thread, i'll volunteer to test out the balanced headphone amp version, should be able to get away with passive heatsinking for that with a reasonably small heatsink
The same card is used for all different configurations. The difference is what components, rail voltages, bias currents, and packaging options are used.

For example, an F5-Turbo-V1 is created by only populating the MOSFET and its gate and source resistors on one of the amplifiers of the board, and (externally) connecting the 2 output standoffs together. Two wire jumpers are needed to connect the gate resistors to the JFET drain node of the other amplifier.

Similarly, the F5-Turbo-V2 is created by implementing the V1 configuration and adding the MUR3020WT diodes.
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Old 26th May 2012, 02:03 PM   #22
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yeah I know, but it didnt seem you had built the headphone version and I presume possibly dont have any balanced headphones?, I have several.. so I would build and test; thats what I meant
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Old 26th May 2012, 02:17 PM   #23
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INteresting build. I have seen the effectiveness of fan cooling in my testing. I can run 2 fans across a 12" heatsink of the 10,08 from heatsink USA and even with 6 fets at 2A bias, cant get the thing to get hot. It is really amazing the amount of heat you can pull off with just that simple concept. May have missed it, but do you try to control heatsink temp at a certain level or do you just set fan to a quiet level and let it be? Consider diode addition. You will be using the fets to their full potential, leaving nothing on the table. Allows reduction of output pair sets.
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Last edited by buzzforb; 26th May 2012 at 02:19 PM.
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Old 26th May 2012, 02:17 PM   #24
lhquam is offline lhquam  United States
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yeah I know, but it didnt seem you had built the headphone version and I presume possibly dont have any balanced headphones?, I have several.. so I would build and test; thats what I meant
I am not sure how to size the power supply for headphones. What wattage do you think is necessary for your headphones. What impedance?
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Old 26th May 2012, 02:24 PM   #25
AndrewT is online now AndrewT  Scotland
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I'd suggest you aim for 12Vac absolute max for high impedance phones and for absolute max ClassA current of 100mA for lower impedance phones.
If this is set up as a Optimally biased ClassAB amplifier then it can even drive 8ohms phones to low voltages for very High SPL.

The PSU would be +-15Vdc delivering a quiescent current of ~60mA/channel.
Theoretically 7VA 12+12Vac would be sufficient.
I would go for 30vA 15+15Vac and regulate to +-15Vdc.
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Old 26th May 2012, 02:48 PM   #26
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Use laterals for headphone version. Needed bias will put you closer to sweet spot with them over Fairchild alternatives.
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Old 26th May 2012, 04:17 PM   #27
lhquam is offline lhquam  United States
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Quote:
Originally Posted by buzzforb View Post
INteresting build. I have seen the effectiveness of fan cooling in my testing. I can run 2 fans across a 12" heatsink of the 10,08 from heatsink USA and even with 6 fets at 2A bias, cant get the thing to get hot. It is really amazing the amount of heat you can pull off with just that simple concept. May have missed it, but do you try to control heatsink temp at a certain level or do you just set fan to a quiet level and let it be? Consider diode addition. You will be using the fets to their full potential, leaving nothing on the table. Allows reduction of output pair sets.
I have made temperature measurements at different bias currents and estimate a temperature rise of .1 C/W at 1200RPM fan speed (Noctua NF-S12B-FLX Noctua.at - sound-optimised premium components "Designed in Austria"!). At around 500 RPM, I estimate .16C/W), but I haven't made enough measurements at the lower speed to be confident in this number.

V1.1 of the board will support the Turbo diodes.
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Old 26th May 2012, 04:21 PM   #28
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If you want to try some laterals for the headphone amp version, I'll send a couple pairs your way.
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Old 26th May 2012, 05:14 PM   #29
lhquam is offline lhquam  United States
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Default V1.1 Board Layout

Here is the new V1.1 board layout. It includes the optional Turbo diodes.
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Old 26th May 2012, 07:49 PM   #30
lhquam is offline lhquam  United States
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Originally Posted by buzzforb View Post
... May have missed it, but do you try to control heatsink temp at a certain level or do you just set fan to a quiet level and let it be? ...
Currently I run the fan at a constant voltage. I have considered a temperature control servo, but I haven't spent the time to implement it. It is worth considering further.
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