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Nelson Pass A40 Help
Nelson Pass A40 Help
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Old 8th February 2019, 09:20 PM   #11
Robbie010 is online now Robbie010
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Originally Posted by Nelson Pass View Post
I don't recall complaints about the original....

😃

Is this THE Nelson Pass!!??

No complaints here, I bought this amp as a used, faulty item from Germany.

It took me a while to work out it was an A40, Im new to DIY electronics.

Really enjoying working on the amp and learning lots along the way but whoever made this amp didnt follow the instructions word for word which makes it difficult for a newbie like me to properly compare it to the original schematics.
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Old 8th February 2019, 10:50 PM   #12
mpmarino is offline mpmarino  United States
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Originally Posted by Robbie010 View Post
😃

Is this THE Nelson Pass!!??
Yup - pretty cool, huh?
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Old 10th February 2019, 02:18 PM   #13
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Default Nelson Pass A40 anomolies

Hello all,

The project amplifier that I picked up turned out to be a Pass DIY A40, which is great as there is lots of info for me to use when trouble shooting. However, I have noticed a few anomolies as the amp is not 100% true to the published information. Please see the main schematic in the link below.

I have noticed that R4 seems to be in the wrong place as it is between R2/R3 and the positive side of C2, rather than between the negative side of C2 to C4. Please see the small schematic and image below.

Would anyone be willing to take a look at the schematic I have drawn-up via the link below and tell me whether this is a mistake by the person that built the amp or if it is an intentional change to the circuit design?

Dropbox - Schematic - Simplify your life

Thanks.
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Old 10th February 2019, 06:44 PM   #14
Nelson Pass is offline Nelson Pass  United States
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Nelson Pass A40 Help
It's of no consequence, being that the cap and resistor are
just in series in both cases.
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Old 10th February 2019, 07:59 PM   #15
Robbie010 is online now Robbie010
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Quote:
Originally Posted by Nelson Pass View Post
It's of no consequence, being that the cap and resistor are
just in series in both cases.
Thanks Nelson!

I must say, I think it is great that you take the time to read the forum and answer these questions. After 40 years Im sure youre fed up of some of these questions and queries.
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Old 10th February 2019, 08:24 PM   #16
Nelson Pass is offline Nelson Pass  United States
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Nelson Pass A40 Help
No, not really. I like the easy ones...

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Old 10th February 2019, 10:58 PM   #17
Robbie010 is online now Robbie010
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Originally Posted by Nelson Pass View Post
No, not really. I like the easy ones...

Yes, after reading through the numerous threads I can see there have been many queries over the years..... most far beyond my comprehension

As mentioned, with my amplifier there a couple of deviations from the published design, if I message you with a copy of my schematic would you mind having a quick look over it and checking for any potential design flaws?
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Old 11th February 2019, 12:04 AM   #18
Zen Mod is offline Zen Mod  Serbia
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Nelson Pass A40 Help
why bothering him , post schm here , somebody will chime in
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Old 11th February 2019, 10:15 AM   #19
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Default Pass A40 Schematic Review

I have managed to draw up a schematic of my project amplifier and while it is most definately a Pass A40, it is not 100 true to the published information.

The amplifier uses two centre tapped transformers, one for each channel, it has a triac transistor in the power stage and a thermostatic switch, so I was hoping someone with the skill and knowledge would be willing to review the schematic and provide some feedback, maybe point out any potential design issues?

Thanks.
Attached Files
File Type: pdf a40 schematic.pdf (76.5 KB, 52 views)
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Old 11th February 2019, 11:32 AM   #20
jazbo8 is offline jazbo8
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Nelson Pass A40 Help
Please don't start multiple threads for the same topic.
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