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Old 8th November 2008, 08:13 PM   #1
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Join Date: Apr 2005
Location: rochester
Default Hi powered Aleph-X PS

Hi,

I'm in the process of putting together a high powered version of the Aleph X. I'm using CRC power supply filtering to get 22 volt rails with an 18 volt transformer.

My question is this: With recommended power requirements around 800va, would I be able to use two 400 VA transformers instead? Any advantages or disadvantages to this method? I can get 400VA transformers cheaply at Antek.

Thanks
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Old 8th November 2008, 09:36 PM   #2
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Join Date: Apr 2005
Location: rochester
Okay, maybe I should have mentioned this in my first post: I actually have no idea the CRC design for this amp should look like. I've searched high and low and can't find an example. I tried the simulation software, but had no idea how to use it.

I'm trying to build the design from here:

http://www.facstaff.bucknell.edu/esa.../wuffwaff.html'

So it looks like I need 22v rails, but what sort of transformer and what sort of CRC circuit would I need?


Also, to clarify my previous post, the reason I'm looking into 2x400va transformers is because I can't find anything that big in one transformer. I've seen various references to victoria magnetics, but I can' t seem to find a link for a company or a supplier. Any help?
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Old 8th November 2008, 10:13 PM   #3
jpc6204 is offline jpc6204  United States
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Join Date: Sep 2007
Default CRCRC Design

Hi everyone,

I am also working on the high powered Aleph-X design based on the hifi zen rev 1.0 boards that systemerror909 is using. Attached is a figure for a CRCRC design that I have tried to figure out myself. I have based it off of other posts and the basic knowledge I have in circuit design. I am especially concerned about having the correct power and voltage ratings for the resistors and capacitors respectively.

I also tried the demo software and it made me very confused. I am hoping that some good samaritan may take some time to look this over and tell us if it will even work or what needs correction.

We are building the 100W Aleph-X with 3 power transistors in each bank for a total of 12 transistors per channel.

Thanks for any input you may have.


Jeff...
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File Type: jpg crcrc.jpg (32.8 KB, 1014 views)
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Old 9th November 2008, 12:08 AM   #4
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Join Date: Nov 2000
Default Gnd

The GND should be connected to the center tap of the transformer.

2x18V gives 3 wires. AC1- Center Tap- AC2.
Center Tap to GND, AC1 to one ~ and AC2 to the other ~ of the
rectifier bridge.

+ and GND are the upper half of your schematic.
GND and - are the lower half.

Be carefull with the orientation of the electolityc capacitors

Upper half + to + of cap, GND to - of cap
Lower half GND to + of cap, - to - of cap

It is a good idea to make a note in the schematic of this
orientation. (polarity)

regards
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Old 11th November 2008, 07:05 PM   #5
jpc6204 is offline jpc6204  United States
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Thanks for the response. I made the changes to the schematic (see below). I hope it is correct this time. Do you think this is enough capacitance for the 100 W design Aleph-X we plan on building?

Does anyone else see any show stoppers in this design?



Jeff...
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Old 11th November 2008, 08:51 PM   #6
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Join Date: Nov 2000
Schematic did not make it.

I would use a slightly different config:

C - R||R - C - C

instead of

C - R - C - R - C

Few reasons:
The resistors will dissipate a lot of power at 5 amps or more.
Ripple filter action will be comparable.
Reliability will be better in the C - R||R - C - C option.

Just a suggestion.
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Old 11th November 2008, 09:44 PM   #7
jpc6204 is offline jpc6204  United States
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Join Date: Sep 2007
For some reason the attachment function is not working today. I'll try again tomorrow to see if it works.

This C - R||R - C - C configuration is interesting. I am not familiar with it either. Does this translate to a C - R filter in parallel to a R - C - C filter? I tried searching the forum and didnt find any clues. I would like to learn more about this filtering option.

Is this what you are using in your Aleph- x?

Thanks again for all your input. We are learning lots over here!


Jeff...
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File Type: jpg crcrc1.jpg (35.7 KB, 844 views)
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Old 13th November 2008, 09:42 PM   #8
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Schematic is a lot better now.

Do you have some extra info on the anticipated load?
Are you going to feed one or two X-channels with this supply?
Any idea on what ripple to expect? Charge pulses for the caps i.e.
strain on the bridge?
Any provisions for inrush current? Did I forgot to mention safety
and fuses?
(Please do not worry about all the questions. Most of the answers will come in this planning phase)

>Does this translate to a C - R filter in parallel to a R - C - C filter?
Yes.

>Is this what you are using in your Aleph- x?
Almost. I use a C - L - C - C. The L is very chunky and needs
some space. Not only because of the physical size, but keeping
them away (at least far enough) from the amplifier circuit means
quit a large amplifier case. Then there is the weight and cost to
consider.

I will try to provide a schematic example of a C - R||R - C - C
config this weekend.

regards
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Old 15th November 2008, 10:28 AM   #9
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Default A promise

an example
Attached Files
File Type: pdf crc_ps.pdf (40.0 KB, 147 views)
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Old 16th November 2008, 07:49 PM   #10
jpc6204 is offline jpc6204  United States
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Many thanks rtirion. I understand what you say about increased reliability by having the resisters in parallel to share the load. I also saw in the schematic that you sent us there was a dual bridge design. I would imagine this would also have advantages in reliability as well.

>>Are you going to feed one or two X-channels with this supply?
We will be building one PSU per monoblock (channel). So we will be feeding one channel per PSU. My friend and I are each building 2 channels (monoblocks) so thats a total of 4 PSUs.

>>Any idea on what ripple to expect?
I was hoping that the filter would make this insignificant and we wouldn't have to worry about it. Perhaps we need to consider this more?

>>Charge pulses for the caps i.e. strain on the bridge?
Any provisions for inrush current? Did I forgot to mention safety
and fuses?
All very important. I left the thermistor, current inrush limiters, and fuses off of the schematic to simplify it. I'll make sure to add them for completeness on this next one. I suppose a dual bridge design eases the strain on the rectification stage? Is this necessary or just a nice perk that will give us bragging rights over others designs?? (when we are done with the build, we'll have to show everything off right??!?!)

Attached is our latest design incorporating your kind suggestions. Thanks for all your help and let us know what you think of this schematic.

One last question - Our newest design (attached below) has the resistors in the filter in parallel instead of in series. This is half the resistance compared to that of our original design, where they were in series. I know this will effect the voltage drop coming out of the rectifying bridge (24 V out of the bridge then a drop to 22V). So my question is wont the rail voltage be different from our original design with the resistors now in parallel? We still need the 22 V rails.


Jeff...
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File Type: jpg cr_rcc1.jpg (50.7 KB, 682 views)
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