Newbie Aleph-X Building

lscangus · 26th January 2006, 07:27 PM

My proposed setting

i use 225va transformer per channel

DC Voltage Input: 26V
Rail Voltage: 20V
BIAS Current 8A
number of mos: 8 per channel

And i have enquiry on the PSU as well

does it connect like this

PSU - AC-DC Bridge - 10000uf X 2 - main board

Thank you everybody!

Angus

metalman · 26th January 2006, 08:05 PM

lscangus, welcome to the club!

For the DC Voltage Rails, do you mean a +20V positive rail and a -20V negative rail, or do you mean 26V from positive to negative (i.e. +10V and -10V). That will help us to give you proper advise.

In the meantime, for the settings you are quoting, a 225VA transformer will definitely be too small, and 8 output Fets per channel will also be too few.

In my Aleph-X I run the Fet's harder than most people are comfortable, and I also made the mistake of undersing my transformer. The settings for my Aleph-X are:

Transformer Rating: 225VA (one per channel)
Transformer Secondaries: 2 x 12V
Supply Rails: +15V / -15V (after CLC filter)
Bias Current: 5A
Number of Fets / channel: 4

My transformer produces a mechanical hum that is audible if there is no music playing. I have been considering relpacing the trafo's with a 300VA to eliminate this.

For your settings, I'd suggest a 600VA transformer as a minimum (assuming that you mean +20 and -20V rails), and I'd also recommend increasing the number of Fets to 12 unless you are planning on using forced air cooling (i.e. a fan).

Hope this helps give you some perspective.

Cheer, Terry

steenoe · 26th January 2006, 08:14 PM

Quote:

I have been considering replacing the trafo's with a 300VA to eliminate this.

Terry, if you consider replacement for those trafos, I think you should use at least 500VA's. I dont think that the extra 75VA will make a lot of difference

Maybe its just me, being overkill all the time??

Steen

lscangus · 27th January 2006, 08:16 AM

Thanks for all you advice

You know there is a voltage suppliy to the main board. If i use a 500va, the minium output voltage of the transformer is 25 volt, which mean after the AC-DC and the capacitor, the votage will be about 36V. +36-0- -36.

I wonder if this voltage will be too high? and also, does the rail need +20-0- -20, becasue i think the rial is the output fets voltage.

Sorry for so many question...

And last, can i parallel tow tranformer to increase the overall output?

Angus

steenoe · 27th January 2006, 08:32 AM

Quote:

I wonder if this voltage will be too high?

Hi Angus. Yes, the 36 volt rails you mention is too high. The standard Aleph-X uses +/-15V rails with 2x12V trafo's, just like Terry's. A highpower version (say 100 watts) uses +/-22V rails from 2x18V trafo's.

Steen

steenoe · 27th January 2006, 08:36 AM

You can pretty much calculate the A-X needs in this nice spreadsheet made by wuffwaff

Steen

NEWER Aleph-X calculationsheet AXE-1.2

lscangus · 27th January 2006, 08:40 AM

Quote:

Originally posted by steenoe
You can pretty much calculate the A-X needs in this nice spreadsheet made by wuffwaff

Steen

NEWER Aleph-X calculationsheet AXE-1.2

because there are two voltage. one is the supplied voltage to the board, one is supplyied voltage to the fets. What value would you recommand?

and can i parallel tranformer?

but 15V / 0.69 is 21V, will 21V be alright?

steenoe · 27th January 2006, 10:30 AM

Quote:

because there are two voltage. one is the supplied voltage to the board, one is supplyied voltage to the fets

There is only one voltage, namely the one supplied to the mainboard. The Fets are "powered" directly from the mainboard. Assuming you are building a standard Aleph-X you need to feed the mainboard with +/-15V and nothing else

I hope I understood your question correctly.

Steen

Netlist · 27th January 2006, 10:53 AM

Here's an example of how i did it. There is only one voltage for the AlephX as Steen explained.
I think you are confused by cell B11 and B12 in the spreadsheet.
B11 is equal to B12 if you don't use CRC or CLC. (Capacitor - resistor - capacitor or capacitor - coil - capacitor).
The final voltage at the fets is important and every R or L in the supply line will lower that voltage. Plan accordingly.

/Hugo

lscangus · 27th January 2006, 01:21 PM

My Aleph-X compact PCB

i am planning to buy this...

what i want is a amp which does abotu 80W output per channel. SO i think 21 V input will be fine..

but ghow abvout the bias current?

26th January 2006, 07:27 PM	#1
lscangus diyAudio Member Join Date: Oct 2005	Newbie Aleph-X Building My proposed setting i use 225va transformer per channel DC Voltage Input: 26V Rail Voltage: 20V BIAS Current 8A number of mos: 8 per channel And i have enquiry on the PSU as well does it connect like this PSU - AC-DC Bridge - 10000uf X 2 - main board Thank you everybody! Angus

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Newbie Building a Lyra	Kofi Annan	Multi-Way	66	20th January 2011 06:32 AM
Newbie building d3A DRD 300B	stefanolo	Tubes / Valves	8	3rd February 2007 03:51 PM
Newbie at this speaker building! Please help!	JiggaD369	Multi-Way	11	23rd June 2005 01:38 AM
Interested in building an Aleph, tons o' newbie questions	JCoffey	Pass Labs	25	10th October 2003 06:46 AM
Newbie building speaker box. Help.	intelceleronman	Multi-Way	14	29th October 2002 09:08 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

26th January 2006, 08:05 PM	#2
metalman diyAudio Member Join Date: Jun 2003 Location: Calgary, Alberta	lscangus, welcome to the club! For the DC Voltage Rails, do you mean a +20V positive rail and a -20V negative rail, or do you mean 26V from positive to negative (i.e. +10V and -10V). That will help us to give you proper advise. In the meantime, for the settings you are quoting, a 225VA transformer will definitely be too small, and 8 output Fets per channel will also be too few. In my Aleph-X I run the Fet's harder than most people are comfortable, and I also made the mistake of undersing my transformer. The settings for my Aleph-X are: Transformer Rating: 225VA (one per channel) Transformer Secondaries: 2 x 12V Supply Rails: +15V / -15V (after CLC filter) Bias Current: 5A Number of Fets / channel: 4 My transformer produces a mechanical hum that is audible if there is no music playing. I have been considering relpacing the trafo's with a 300VA to eliminate this. For your settings, I'd suggest a 600VA transformer as a minimum (assuming that you mean +20 and -20V rails), and I'd also recommend increasing the number of Fets to 12 unless you are planning on using forced air cooling (i.e. a fan). Hope this helps give you some perspective. Cheer, Terry

27th January 2006, 08:16 AM	#4
lscangus diyAudio Member Join Date: Oct 2005	Thanks for all you advice You know there is a voltage suppliy to the main board. If i use a 500va, the minium output voltage of the transformer is 25 volt, which mean after the AC-DC and the capacitor, the votage will be about 36V. +36-0- -36. I wonder if this voltage will be too high? and also, does the rail need +20-0- -20, becasue i think the rial is the output fets voltage. Sorry for so many question... And last, can i parallel tow tranformer to increase the overall output? Angus

27th January 2006, 08:36 AM	#6
steenoe diyAudio Member Join Date: Mar 2004	You can pretty much calculate the A-X needs in this nice spreadsheet made by wuffwaff Steen NEWER Aleph-X calculationsheet AXE-1.2

27th January 2006, 10:53 AM	#9
Netlist diyAudio Moderator Join Date: Jan 2003	Here's an example of how i did it. There is only one voltage for the AlephX as Steen explained. I think you are confused by cell B11 and B12 in the spreadsheet. B11 is equal to B12 if you don't use CRC or CLC. (Capacitor - resistor - capacitor or capacitor - coil - capacitor). The final voltage at the fets is important and every R or L in the supply line will lower that voltage. Plan accordingly. /Hugo

27th January 2006, 01:21 PM	#10
lscangus diyAudio Member Join Date: Oct 2005	My Aleph-X compact PCB i am planning to buy this... what i want is a amp which does abotu 80W output per channel. SO i think 21 V input will be fine.. but ghow abvout the bias current?

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)