Repaired one amplifier which is working and biased according to specs in "class A " which in real life means high bias class AB
The specific application is 4 output transistors per ch supplied with 38+38 volt and each transistor is biased at 410ma which is a bit lower than specified in the manual
HTC is all brand new, plenty and fresh everywhere and the mechano work is done as best is possible everything is very tight considering the assembly
The result is about 57 degrees on the mount area of the transistors while fins of the heatsink will be a few degrees lower ...
Do you think that this is safe enough ?
The specific application is 4 output transistors per ch supplied with 38+38 volt and each transistor is biased at 410ma which is a bit lower than specified in the manual
HTC is all brand new, plenty and fresh everywhere and the mechano work is done as best is possible everything is very tight considering the assembly
The result is about 57 degrees on the mount area of the transistors while fins of the heatsink will be a few degrees lower ...
Do you think that this is safe enough ?
One would need to do a simulation for the temperature de-rated SOAR to compare to the loadings imposed on the output stage.
That is not a quick bit of guesswork.
That is not a quick bit of guesswork.
Member
Joined 2009
Paid Member
I do. Because for most normal listening levels this amp will stay in Class A. It has 400mA x 4 = 1.6A per side. Into 8 Ohm that's 10W already and with Class A the more the music plays the more power goes into the speaker and less for the transistors.
But what about the ambient - you have a nice cool workshop, will customer use it in Greek summer when it is 30C in the house ??
Maybe put a temperature cut-out switch on the heatsink and put it in series with power supply.
Proper vbe multiplier exists in both ch located in proper area and double thermal cutoff separated for both ch exists already in the amplifier .
Thanks Gareth !
Thanks Gareth !
- Status
- Not open for further replies.