New Aleph Mini PCB GB

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#542
Transformer options

All,
I don't want to steer this thread off course, but I would appreciate to hear your opinions on the following.

Which makes the most sense for an Aleph 5 implementation

1. Dual 2 x 25 400VA
2. Single 2 x 25 1000VA

Neither may be optimum but I have them in hand.

Thanks for your thoughts.

Ryan
 
#545
hi People
stuffing my pcb today. Im going for aleph 5 , it seems I will have to swap c2 for r12..... but looks quite straight forward... not much else different. I am trying to take notes of the parts difference so I should be able to post the alternative parts list and stuffing diferences afterwards.
regards
dave
 
#551
transformer spec / using one power supply board

I also have a question regarding sizing of transfomer for a STEREO Aleph 30 using ONE of Brian's Power Supply board.

Is this correct for minimum requirement?

Dual sec coil, 18-0-18, 650VA (1 piece) or
Single sec coil, 18-0-18, 320VA (2 piece)
 
#553
dhole said:
Brian

I think I may have found an error on the boards. C1 (or c11 on aleph 30 or c5 on aleph 5) has the polarity marked on the board wrongly. the + leg should connect to R9.

Can you confirm this .
regards
dave
Click to expand...

You are correct. Thank you for pointing out this error. I will put an update on the website. Here is a comparison of the schematic and the manual. I am sorry for the mistake. I will send out a mass e-mail about this soon.

The prototype amp (same amp board layout) has C1 with the polarity backwards and worked without problems:
http://www.briangt.com/gallery/miniALEPH-prototype/Brian_GT_Mini_Aleph_044_copy
I will talk to Mark and see if he noticed any problems. Sorry about this issue.

One more issue that I found last night, if you are using the 4 pin caps on the power supply board, you will want to remove the 2 unused pins, as the connected to the + capacitor lead, and this might cause problems. I will include this in a mass mail, and I will put an update on the webpage.

--
Brian
 

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#555
dhole said:
Hey Brian whats the led resistor value on the psu board ? I can work it out but it dosent seem to be on the parts list, so might be worth updating for others.
regards
dave
Click to expand...

Dave,

I have updated the parts list on the webpage:
http://www.diyamps.com/aleph/ps.shtml

The correct designation for the resistor for the LED is R20, which is a little hard to read on the pcb. It is the rectangular component closest to the LED, and the right resistor choice would be a 4.75k 0.5w resistor. I choose the compact metal film ones available from Digikey:
PPC4.75KXCT-ND
I am sorry for the confusion. I had forgotten to update the parts list to match the finalized power supply board layout.

Let me know if there is still some confusion.

--
Brian
 
#557
Brian,

I've looked at the schematics. For minimum requirement, is this the right spec for the transformer for a stereo Aleph 30?

330VA, 18v-0-18v secondary, 120v primary (Full load amp on secondary side = __)

If I'm utilizing the resistors on the PS board for a CRC configuration, would there be some sort of voltage drop across the resistors? And thus should I order the transformer with a little higher voltage on the secondary side? Say 20v-0-20v?
 
#558
dhole said:
Cheers Brian

I had kinda guessed it was r5 , thanks. Still other people will benefit from the updated parts list. Thanks alot for the boards again .Oh do you have a spare psu board ? only bought 3.....
dave
Click to expand...

I have about 10 power supply boards left, and 20 amp boards left (not including some boards I set aside for people who haven't paid yet). I will leave them available on the order page until I am completely sold out.
http://www.diyamps.com/aleph/orders.shtml

Best of luck with your project. I am hoping to get mine done soon, but other things keep on popping up, keeping me busy. I am going to try to put more time into this project this weekend.

--
Brian
 
#559
Another question .... what are the values of those resistors located between the capacitors? Your Power Supply Parts List shows it as a short circuit jumper for R3 to R12. Is that something we should calculate on our own? Thanks.
 
#560
fcel said:
Brian,

I've looked at the schematics. For minimum requirement, is this the right spec for the transformer for a stereo Aleph 30?

330VA, 18v-0-18v secondary, 120v primary (Full load amp on secondary side = __)

If I'm utilizing the resistors on the PS board for a CRC configuration, would there be some sort of voltage drop across the resistors? And thus should I order the transformer with a little higher voltage on the secondary side? Say 20v-0-20v?
Click to expand...

Without the CRC, 18-0-18 would be the minimum for the Aleph30. My initial plan was to try one of these per channel:
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=122-620
due to their quick availability.

If you are going to experiment with the CRC, 20-0-20, 500va might be a good choice to try out for a stereo amp. Victoria Magnetics should be able to wind a custom transformer for this if you are unable to find another source.

--
Brian
 
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