Very sorry for your work, useful information for lovers of radio electronics lost ((
I hope you manage to restore the work completely. Success to you.
My friend Bruce is not an EE but he does have an uncanny, almost superhuman ability to notice weirdness in EE designs. Often these turn out to be design errors (!). Bruce modestly refers to his skills as "simple pattern matching".
Just now I did some simple pattern matching between the schematic of post #3486 and the schematic of post #1. One thing that positively JUMPS OUT at me is: Capacitor "C4" (220uF) in #3486, is not present in #1.
I will leave it to the EEs of diyAudio to decide whether this is a fatal error in the circuit design of post #1, a fatal error in the circuit design of #3486, an insignificant difference that has no impact whatsoever, or perhaps some other conclusion.
Just now I did some simple pattern matching between the schematic of post #3486 and the schematic of post #1. One thing that positively JUMPS OUT at me is: Capacitor "C4" (220uF) in #3486, is not present in #1.
I will leave it to the EEs of diyAudio to decide whether this is a fatal error in the circuit design of post #1, a fatal error in the circuit design of #3486, an insignificant difference that has no impact whatsoever, or perhaps some other conclusion.
My Aleph J does this also - that bias current slightly goes down when the MOSFETs and heatsinks heat up. (and therefore voltage over the source resistor gets lower as well)
I think this is perfectly normal.
Also, bias, resp. voltage over-source-resistor varying by 10 mV does not seem to be something to worry about.
As Zen Mod and 6L6 said, small temperature changes caused by light air drafts (or blowing on the board / the Front-End JFETs) can cause changes in bias.
Therefore, put the multimeter leads on the resistor in a way that you can put the lid on, let the amp sit for a while with the lid closed, and look at the bias without removing the lid or having too much air drafts in the room (I try to sit still as well
)
Also, there is another factor affecting bias that you can't alleviate by this: (even slight) fluctuations in mains voltage will cause changes in bias as well ...
So, after measuring with the lid on and confirming that the fluctuations stay small (or monitoring mains voltage simultaneously), I think there is nothing to worry about.
Best regards,
Claas
I think this is perfectly normal.
Also, bias, resp. voltage over-source-resistor varying by 10 mV does not seem to be something to worry about.
As Zen Mod and 6L6 said, small temperature changes caused by light air drafts (or blowing on the board / the Front-End JFETs) can cause changes in bias.
Therefore, put the multimeter leads on the resistor in a way that you can put the lid on, let the amp sit for a while with the lid closed, and look at the bias without removing the lid or having too much air drafts in the room (I try to sit still as well
)Also, there is another factor affecting bias that you can't alleviate by this: (even slight) fluctuations in mains voltage will cause changes in bias as well ...
So, after measuring with the lid on and confirming that the fluctuations stay small (or monitoring mains voltage simultaneously), I think there is nothing to worry about.
Best regards,
Claas
Did somebody tried a regulated PSU with the Aleph J?
Do you think four kits like these (one per rail and per channel) could do the job?
AUDIOPHONICS PSU S3-LP Linear Power supply Module DC LT1083 - Audiophonics
Do you think four kits like these (one per rail and per channel) could do the job?
AUDIOPHONICS PSU S3-LP Linear Power supply Module DC LT1083 - Audiophonics
Based on my experience with the ACA amps that I have been building recently, it would be better to use a simple CRC power supply filter. If you wish to enhance your power supply, you could use transformer(s) with 20 Volt secondaries and a diyAudio style PSU board with 18000 uF, 50V capacitors for a total of 72000 uF per rail. Or go full dual mono with a separate transformer and PSU board for each channel. You will also want to invest in a good chassis such as the Modushop 4U, 400mm deep one. Take a look at the pictures posted above by nikko03 for an excellent example of an Aleph J build using this chassis.
The Aleph J uses the NP patented Aleph current source, which is interactive with the signal being played through the amplifier. In order for the output stage to maintain correct class A operation, this current source requires a power supply with very low, broadband impedance. It is very difficult to build a power supply based on an integrated circuit (IC) regulator that will perform as well as a proper CRC filtered supply. The regulator board in question does not look like it will do very well for a high current amp such as the Aleph J.
The Aleph J uses the NP patented Aleph current source, which is interactive with the signal being played through the amplifier. In order for the output stage to maintain correct class A operation, this current source requires a power supply with very low, broadband impedance. It is very difficult to build a power supply based on an integrated circuit (IC) regulator that will perform as well as a proper CRC filtered supply. The regulator board in question does not look like it will do very well for a high current amp such as the Aleph J.
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