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Old 2nd January 2005, 02:18 AM   #1
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Default A30....I still have a ways to go !!!

Hi guys,
This is my first DIY audio project that doesn't have wood and drivers in it. I am constructing a Pass A30 and am starting to see things come together. I am not near power up but a lot of the construction has been completed.

The chassis is (what I think is) unique. The cross section is a "H" with the PSU entirely below and the amp above. The uprights of the "H" are entirely heatsink. The "-" of the "H" is a 1/2" thick aluminum plate with some welding steel and a piece if 2oz double sided fr4 anong with another 3/32 alu plate laminated together. This will serve to shield the 2 compartments from each other. The front plate will also be 75% heat sink for the bridges. The outputs are secures to the "-" with alu bar. The "-" appears to be "hardcoated and will only see heat sink compound with no mica etc.

All aspects are surplus/bargain items. The amp boards are home brew based on a layout by "Asen". The boards you see are for experimentation and the real boards will have higher qual components etc. The Transformers are 250VA 21+21 secondaries. There are 5x15,000uf caps per rail....4 rails as it is dual mono (for 300,000uf total) They are 35v 105C snap in caps. Experimentation tells me I will see approx 26v rails under load. I am integrating a soft start - powering through a resistor - and a relay to short the resistor after all charges.

I have seen a signature by a forum member reading: "All right, who's next to be ridiculed" ...Is it me?

Seriously, constructive criticism is welcome..especially from you guys!

Sorry if some pics are big

Top View:

Click the image to open in full size.

Another top:

Click the image to open in full size.

"H" cross section:

Click the image to open in full size.

Up side down PSU view:

Click the image to open in full size.
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Old 2nd January 2005, 02:55 AM   #2
Gaucho is offline Gaucho  Canada
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Hi mpmarino,

I like the 'split level' chassis design, I was going to try that route with my next amp but yours is the first I've seen in practice. I plan on using sheet steel as a barrier instead of aluminum, I don't think aluminum shields too well.

Regards.



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Old 2nd January 2005, 03:00 AM   #3
jleaman is offline jleaman  Belgium
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I like the Design. Not bad. I really like how you mounted the fet's. I like that idea better than the screw for each fet. Good work. : O )


J"
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Old 2nd January 2005, 12:33 PM   #4
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Goucho,
There is a piece of sheet steel in the lamination. Welding Iron..

Marc
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Old 2nd January 2005, 04:04 PM   #5
Gaucho is offline Gaucho  Canada
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Quote:
Originally posted by mpmarino
Goucho,
There is a piece of sheet steel in the lamination. Welding Iron..

Marc
Perfect!
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Old 5th January 2005, 09:29 PM   #6
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I want to know if there a problem to use a 10W, 1 Ohm resistor for the CRC filter of each channel of an Aleph30 ??
I saw 0.5 Ohm but never see 1 Ohm.

How much volt I can loose with that resistor value ??
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Old 5th January 2005, 10:13 PM   #7
Stabist is offline Stabist  Slovenia
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Interesting idea, kinda like the front heatsink with "chopped" top ...

Btw - only one remark though ... My first version of Zen was a little bit similar - I mean - PSU "in the basement" and circuitry on the top and all ...

What I discovered during mods:
- to change/experiment with anything I had to dissassembled whole amp
- there was hum (OK, you have much better shielding than I did and I had my transistors conected to PCB through some wires)
- so in my mkIV version - I've put PCB directly to heatsinks (verticaly) and I've moved trannie as much away as possible ... Hum disapered and also mods are much much eayier now
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Old 6th January 2005, 03:53 AM   #8
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Stabist,
Yes, I'm sure your right about the potential for hum. I have every intention of possibly mounting the toroids vertically (or whatever) if that is the case.

The bottom panel will be just as easy to remove as the top, so the toughest part of servicing the PSU will be to flip the whole thing over....the sucker's gonna be heavy!

Marc
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Old 6th January 2005, 05:44 AM   #9
Stabist is offline Stabist  Slovenia
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Hi!

Yes stupid me - it's quite obvious it was around 2am here in SLO when I saw my upper reply ... It's very clearly seen how the PSU is mounted ...

Way beter than mine version ...

Btw - considering you have transistor mounted directly to PCB and that the shield between PSU and PCB is quite massive - I think that won't cause hum. BUT! be very carefull how to route input and output wires ...
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Old 6th January 2005, 11:30 AM   #10
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Thanks for your posts Stabist,

Not only is getting the thing to work at all a concern for me,...but unnecessary noise is as well. Your advice is appreciated.

Marc

Quote:
Yes stupid me
No..not at all, all you say is valid in my opinion
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