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Aleph J  versus  Aleph 3
Aleph J  versus  Aleph 3
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Old 10th September 2019, 08:09 AM   #31
ontool is offline ontool
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Please help me find a malfunction.
One amplifier channel started working immediately; in the second, problems started. The sound is poorly audible with noise. The quiescent current of the output transistors is adjustable and set to 0.4v Thank you very much.
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Old 10th September 2019, 08:52 AM   #32
mbrennwa is offline mbrennwa  Switzerland
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Aleph J  versus  Aleph 3
Quote:
Originally Posted by Zen Mod View Post
it is there , on very end of first post , under condition that link isn't ooked in meantime
There is a "link to final schematic and parts placement", but that link just takes me to page 4 of the "About possible Babelfish J interest" thread. I don't see the documentation there. Can you provide a link to the documentation?

Quote:
Originally Posted by TungstenAudio View Post
It also helps to increase the Vds across the output stage transistors, either with original IRFP240s, or better yet, Mosfets with higher transconductance. IRFP140, IRF150, etc. The improved transonductace is only realized significantly with increased Vds.
Ok, thanks, that's useful!

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Originally Posted by 6L6 View Post
Aleph 3 has 3rd parallel transistor per stage...
Are you sure? The Aleph 3 Service Manual shows only two transistor pairs.

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Originally Posted by chede View Post
There was an Aleph power calculator once...
Quote:
Originally Posted by mpmarino View Post
...This one?
Ok, that makes a lot of sense. Output voltage is limited by the +/- rail voltage (minus some residual voltage drop across the MosFETs), and output current is limited by bias. Normal Class A stuff as we know it, easy.

Now I am just trying to understand what I found about the Aleph 3 and FirstWatt Aleph J so far:

Looking at the Aleph 3 Service Manual it looks like each transistor pair is biased at approximately 1 A (0.5 V across the 0.47 Ohm resistors), giving a total of 2 A for both transistor pairs. With +/- 25 Vdc rails, thats 100 W heat dissipation at idle.

What's the bias current the rail voltage of the Aleph J as it is/was sold by FirstWatt? I guess the current was quite a bit less than with the Aleph 3. The lowish 4 Ohm power rating suggests the bias current was quite a bit less. Why is that? Maybe the FirstWatt chassis gets too hot at a higher bias current?

What is the recommended max. bias current per transistor pair with the Aleph J, assuming the heatsinks are not the limiting factor?
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Old 10th September 2019, 09:23 AM   #33
Zen Mod is online now Zen Mod  Serbia
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Aleph J  versus  Aleph 3
Quote:
Originally Posted by mbrennwa View Post
There is a "link to final schematic and parts placement", but that link just takes me to page 4 of the "About possible Babelfish J interest" thread. I don't see the documentation there. Can you provide a link to the documentation?
#138

if you read first 200 or so posts in linked thread , you'll have most of your questions answered

besides , when Aleph circuit is in case , always take in account so called Aleph AC Gain , which represents amount of Aleph CCS current contribution in output current

so , Aleph is an Aleph is an Aleph , only some are more Alephy than others

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