It's a Class AB, it's not supposed to heat up a lot when idling.
Very nice amp, I sold it towards the end of the 90s.
there is some information and diagram on their archive site but no diagram for the forseti APD20, only the 15.
https://www.alchemisthifi.info/ranges/forseti/alchemist_forseti_apd20a_power_amplifier.htm
Very nice amp, I sold it towards the end of the 90s.
there is some information and diagram on their archive site but no diagram for the forseti APD20, only the 15.
https://www.alchemisthifi.info/ranges/forseti/alchemist_forseti_apd20a_power_amplifier.htm
Without the real diagram and without the supply voltages, it is almost impossible.
As long as the amp is thermally stable, has no audible distortion and its output signal before clipping is not too messy on the oscilloscope, leave it like that.
As long as the amp is thermally stable, has no audible distortion and its output signal before clipping is not too messy on the oscilloscope, leave it like that.
Thanks but when I put my hand on top it's almost cold after some warm up period and that doesn't seem right.
I also have the Nemesis and it gets a lot warmer.
So I am suspecting the technician to have set the bias too low. Also I think it doesn't sound the way it should.
But I need an argument to make the technician have look at it again. That's why I asked for the bias.
The technician said it was dialed in at 10 mV??
I also have the Nemesis and it gets a lot warmer.
So I am suspecting the technician to have set the bias too low. Also I think it doesn't sound the way it should.
But I need an argument to make the technician have look at it again. That's why I asked for the bias.
The technician said it was dialed in at 10 mV??
Alchemist tended to overbias their Class AB, many did not appreciate this treatment in the long term.
10mV without supply voltage, nor where and on what it was measured means nothing.
With a supply voltage and measuring the consumption at idle on each channel (for example by removing the fuses from the positive power rail of each channel and bypassing them with an ammeter) could give an idea based on on the dissipation in W at idle for a Class AB, but once again, these would only be estimates.
10mV without supply voltage, nor where and on what it was measured means nothing.
With a supply voltage and measuring the consumption at idle on each channel (for example by removing the fuses from the positive power rail of each channel and bypassing them with an ammeter) could give an idea based on on the dissipation in W at idle for a Class AB, but once again, these would only be estimates.
Another solution would be to find another technician capable of using an oscilloscope and setting this amp as it should be.
Thanks but to me a non technician I doubt it was done correctly since it hardly gets warm at idle. Something must be wrong.
But thanks anyway.
But thanks anyway.
Go back to your technician, explain it to him and ask him to review his copy.
If you have used this amp regularly before and are familiar with its behavior, your technician should take your comments into account.
Take care, they (the nemesis and the forseti) are great amps.