aleph p: do I have a problem?

[noelectrix]

hello dear forum,

i build up my aleph p 1.7 with veterans great boards. My transformer is still shipping, and so i tried it out at two akkus from my electric screwdriver
I also do not have a power amp (just an integrated one) and so i just fixed headphones at the output.
the akkus have 40Volts what is of course a bit less.
now the problem: The output is about 1/3 to 1/6 voltage of the input signal. could that be normal?
All the fets get warm. Does that mean that they are ok, or could they be nevertheless be smashed? can I test/measure the fets on the board?

ahh, yes- both channels do have the same gain. so if there is a problem it is symmetrical. thats why i do not think that there is a single component broken.

best and thanks
stefan

[spzzzzkt]

check this post:
http://www.diyaudio.com/forums/showt...927#post986927

It's a design feature not a problem. The P1.7 is Class A, and that means the FETS get hot, to the point that some recommend using heatsinks.

The boards are designed to run at 60V so I suspect your voltage measurements @ 40V won't be very meaningful.

Paul

[noelectrix]

thanx paul. nice case. I did not worry about the fets getting warm. In opposite, i just was not shure if this could e a proof if they work correctly. I do not want to solder them out again and was not shure what or how to measure sth.
I just wondered because of the weak gain even with just 40 V. but you are right. I just should wait till I got the transformer

PS. it is my first electronical project in my life! an so the field of questions is a big one

[WALTER BURKHARD]

something for your aleph p?

[spzzzzkt]

noelectrix,

The case has improved slightly, it's all mounted on a slightly too small sheet of 3mm aluminum.

Another good indicator that things are running correctly are the bias voltages across input and output caps. Input should be around 13V, and output caps close 26V ie approximately double input cap bias.

Problem is that these checks, and the voltages shown on Walter's schematic depend on having a 60V supply.


cheers
Paul

[noelectrix]

hey guys, thank you a lot. Thats great information, but it seems that I have to wait till transformer arrives.
I know it is embarrasing, but what means " across" in- and output caps? from caps to ground? I already read that in the groupbuy tread (which I read about 4 times to learn what to buy and so on
)

PS: Its funny that you extreme high and low- level casebuilders do meet here

[spzzzzkt]

noelectrix,

I mean voltage measured between the two terminals of the capacitor. Input caps are C1 and C2, output caps are c7-9 and c11-13. These are DC blocking caps and are in the signal path.

My case is basically a test setup. I'm moving in with my GF in about 4-5weeks and I need to get the P1.7 properly cased before then as her pet bird and exposed wiring won't mix too well. The case will end up being a match for my A30 monoblocks.

cheers
Paul