F5 Listening Impressions & Discussion

[AndrewT]

I have no idea of Proop's sink and ambient data.

But we can start with some assumptions to show what we might expect to see.
Ta=21degC
Rth s-a = 0.5C/W
Rth c-s = 0.4C/W
Power dissipated @ 0.6Vbias = 30W

Delta T s-a = 30 * 0.5 * de-rating Factor (try 1.3 for dT=15C) = 19.5Cdegrees.
Delta T c-s = 30 * 0.4 = 12Cdegrees.

For 0.71Vbias the dissipated power rises to 35.5W

Delta T s-a = 35.5 * 0.5 * DF (try 1.28 for dT= 17.75C) = 22.7Cdegrees.
Delta T c-s = 35.5 * 0.4 = 14.2Cdegrees.

The data for these sets of Vbias assumed conditions would be
Vbias=0.6 Ts= 40.5degC, Tc= 52.5degC
Vbias=0.71 Ts'=43.7degC, Tc'= 57.9degC

One can insert the data for one's own hardware/ambient and predict (model) the temperatures to be expected before one even buys the hardware.
In this case increases the bias current by 18.3% should increase the FET temperature by ~5.4Cdegrees. From there one can estimate the reduction on SOAR for the higher bias.

[Renron]

Thanks Andrew.

[prooptiki]

Originally Posted by AndrewT

I have no idea of Proop's sink and ambient data.

But we can start with some assumptions to show what we might expect to see.
Ta=21degC
Rth s-a = 0.5C/W
Rth c-s = 0.4C/W
Power dissipated @ 0.6Vbias = 30W

Delta T s-a = 30 * 0.5 * de-rating Factor (try 1.3 for dT=15C) = 19.5Cdegrees.
Delta T c-s = 30 * 0.4 = 12Cdegrees.

For 0.71Vbias the dissipated power rises to 35.5W



Delta T s-a = 35.5 * 0.5 * DF (try 1.28 for dT= 17.75C) = 22.7Cdegrees.
Delta T c-s = 35.5 * 0.4 = 14.2Cdegrees.

The data for these sets of Vbias assumed conditions would be
Vbias=0.6 Ts= 40.5degC, Tc= 52.5degC
Vbias=0.71 Ts'=43.7degC, Tc'= 57.9degC

One can insert the data for one's own hardware/ambient and predict (model) the temperatures to be expected before one even buys the hardware.
In this case increases the bias current by 18.3% should increase the FET temperature by ~5.4Cdegrees. From there one can estimate the reduction on SOAR for the higher bias.

F5 power amplifier

post #7367 last measurements

post #7305 The amplifier heatsink 280x280x70-40

ambient 20.5 oC

this type of fins

[vitalica]

Originally Posted by bear

vitalica,

I was wondering a few things...

what do you hear as the difference in the sound between the balanced and regular?
My friend who is a pianist says the sound is very neutral, especially the voices feel the difference.

what did you use for the resistors in series with the Mosfets?
Output MOSFETS are 2SK1530/2SJ201.
Source resistor 0R22 & 0R18 respectively.

whose balance schematic did you use?
The scheme is of Patrick (EUVL) - XF5.
I thank you very much for the help of the PCB and comp

what are those three pin devices that are in the front on the bottom??
Can you tell me exactly what you mean?

and finally, after how long did you measure the temperature of the heatsinks??
I too thought they might not be large enough and/or perhaps in that orientation they would not work so well...
Did I answer yesterday because I wanted to measure once again
I left the amplifier to function without signal 3 o'clock.
Over a time temperature was 45 degrees
50 degrees in two hours
more than 3 hours 54 degrees.
Do you think we should see what happens more than 5-6 hours?

Oh, you said "2A" bias - measured how?
I measured the voltage drop 0,22R (0,44V)
_-_-bear
Forgot to mention - very nice looking job!

Thanks

[alazira]

Originally Posted by bear

what are those three pin devices that are in the front on the bottom??

I think those are diodes, part of a bridge rectifier.

[vitalica]

Originally Posted by alazira

I think those are diodes, part of a bridge rectifier.

Yes, I MUR 3060

[a.wayne]

.. revival .......................................

[jackies]

Originally Posted by a.wayne

.. revival .......................................

You mean necroposting?

[tinitus]

noone are interrupting anything

[bear]

without revealing too many "secret details" over this way a number of experiments have been run regarding the power supply rails to the front end of the F5. It is daunting. Changes in that path appear at this point to radically effect the sound presentation!

FYI, and FWIW...

Anyone who wants to post pix of their competed F5s and comment on their sound may feel free to do so...

_-_-bear