Try adding the keyword "convection". I googled "online heatsink calculator convection" and was served this as the top result (not counting the shopping links):
Heat Sink Size Calculator
I tried it with a heat sink I have that is specified to 0.40 K/W (@ T_rise = 70 ºC). To compensate for the temperature difference (I used T_rise = 40 ºC in my calculation), I divided the power dissipated (100 W) by 1.170 (so 100/1.170 = 85.5 W) and punched it and the dimensions into the calculator.
The results are pretty close to reality. In reality the heat sink is 300 mm wide and has 30 fins. The calculator says it should be 331 mm wide and have 33 fins.
Tom
Heat Sink Size Calculator
I tried it with a heat sink I have that is specified to 0.40 K/W (@ T_rise = 70 ºC). To compensate for the temperature difference (I used T_rise = 40 ºC in my calculation), I divided the power dissipated (100 W) by 1.170 (so 100/1.170 = 85.5 W) and punched it and the dimensions into the calculator.
The results are pretty close to reality. In reality the heat sink is 300 mm wide and has 30 fins. The calculator says it should be 331 mm wide and have 33 fins.
Tom
Attachments
Ah. I thought I recommended Toroidy to you. You hid them well. 
I just bought a pair of transformers from Toroidy for a couple of demo builds and have the same positive experience as you.
A 200 VA and a 300 VA, potted "audio grade". EUR 50/each (give/take). Total with shipping EUR 161 for the two. That's pretty darn amazing for a pair of custom wound transformers.
Tom
I just bought a pair of transformers from Toroidy for a couple of demo builds and have the same positive experience as you.A 200 VA and a 300 VA, potted "audio grade". EUR 50/each (give/take). Total with shipping EUR 161 for the two. That's pretty darn amazing for a pair of custom wound transformers.
Tom
I agree with that Tom. You have found a good vendor and hope they see more business from DIY folks.
My units if you remember were 420VA with secondaries for bipolar power supply of two voltages.
I got the 'audio grade' without potting and two transformers shipped were around EUR230. Good value.
My units if you remember were 420VA with secondaries for bipolar power supply of two voltages.
I got the 'audio grade' without potting and two transformers shipped were around EUR230. Good value.
Last edited:
Hi Tom I tried shorting the inputs and there was no hum. As soon as I connect the B1 korg or dac directly I get constant hum regardless of volume. I have used two other amps with the B1 korg and the dac in question and there is no hum. One amp is a Diy First Watt F6 ( the F6 use trafo for voltage gain) and the other is a Diy 30 hypex. The hypex is without a buffer an has a sowter trafo to go from rca to balanced input.
You probably have a grounding issue (ground loop).
The transformer in the Hypex probably is eliminating the grounding issue when it is used.
I have a hard time understanding the actual configuration of your system when it hums. Can you describe it in detail, e.g., source DAC via unbalanced RCA to X, via unbalanced to balanced to Modulus 86, etc.
The transformer in the Hypex probably is eliminating the grounding issue when it is used.
I have a hard time understanding the actual configuration of your system when it hums. Can you describe it in detail, e.g., source DAC via unbalanced RCA to X, via unbalanced to balanced to Modulus 86, etc.
Yes there is hopefully some grounding issue. The setup is pretty simple. System using ca 86db/w speakers hums in these configurations. Dac, rca to Mod86 or Dac, rca to B1Korg pre, rca to Mod86. Other amps mentioned do not hum at all in this system.
In the system that does not hum. 100+ db/w speakers Dac or phono, rca to Cheap chinese passive pre (relay), rca to aikido diy tube pre, rca to Mod86
In the system that does not hum. 100+ db/w speakers Dac or phono, rca to Cheap chinese passive pre (relay), rca to aikido diy tube pre, rca to Mod86