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Old 10th May 2006, 05:12 PM   #1
EsE is offline EsE  Norway
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Default Planning an Aleph

Hi there!
I have for a while tought about building a Aleph 30, and would like some input about how they sound, some building tips etc.
I'll order the pcb's from diyamps.com once I'm sure this is the right project. I don't have the cash to build all the amps I come across, so I want to build a good one.

How do I bias it up, btw? And how big heatsinks do I need for some serious bias? Any recommended suppliers?

Regards,
EsE
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Old 10th May 2006, 06:59 PM   #2
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EsE,

First The Aleph 30 draws 200 watts

the transfo is 600VA or more 2*18 volts giving +-25volts

Well you have to dissipate 100 watts by side {by channel}

and the 2Amps bias is fixed!

** At 25/30 degree C over ambient temp that gives:

coeff for 30 deg = about 1.33 {see chart}

the MF35-151.5 from Conrad is: 350 mm long or 13.7"
151.5 mm height or 5.96"

0.21 C/Watt for 80 C rise

==> 0.21 * 1.33 = 0.28 C/W

so for 30 degrees rise ==> 30 / 0.28 C/W = 107 watts
for each heatsink in a rapid calculus... I would say right on target

take a look at this info:
http://www.conradheatsinks.com/technical-details.html

Good luck with this project.

Alain.
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Old 11th May 2006, 02:56 PM   #3
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I recently built an Aleph30. I found that I needed a a transformer of 21 to 22 volts to get 25VDC rails.

The MF350-151.5 heatsinks are perfect for an Aleph30. The operating temperature is exactly on spec for what Nelson has described when built with the factory rail and bias settings. Alan's calculations are correct for the Conrad heatsink. I'd consider modeling or experimenting with the transformer voltage you actually select.

Think about a largest VA rating for your transformer. I've experimented with different VA ratings. Currently I'm using a 700VA trafo with 22.5vac with a small amout of R in a CRC PSU. The trafo get very hot. There are more standard trafo's available with 45vac secondaries, and could be wired to 220vac for use in 120vac countaries to get close to 22.5vac for the PSU.

Here's a link to my amp for reference:
My 1st Aleph Amp

Good luck,

-David
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Old 12th May 2006, 10:13 AM   #4
EsE is offline EsE  Norway
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Ok, thanks!
I live in Norway, so 230V is my mains current, actually..
Most people agree that Alpeph's sound great, but what would you compare it to?

The heatsinks look allright, but can I make the rest of the chassis in wood when it's running at 70 degrees? I'm not to good with metal, and I don't have the tools if I'm willing to try.

And at last, what kind of power supply will make the best sound?
I'd love some schemes..

EsE
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Old 12th May 2006, 07:21 PM   #5
folkeb is offline folkeb  Norway
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I'm currently building the aleph 1.2 monoblocks and for me main issues with this amp is getting the heatsinks and the metalwork done. For the Aleph 30, these issues are not that difficult. It all depends on how much money you want to spend. However, I may have input.

Heatsinks: I bought mine from fisher. They have a sales contact office in Norway, and they can help you find what you need. I had to spend 8500 kr for 4 heatsinks - but they dissipate 1000 w (all 4 together).

A good starting point would be fisher SK56 (200x400x40mm)

If not you could try clofis - a dutch vendor who sells good quality heatsinks (seifert), and they aren't expensive. This is probably the way to go.

Or...you could go the easy way and buy a casing from one of several vendors.

I have bought my parts from www.RT-audio.nl. He can also help with casing and/or heatsinks. Send him an email.

If you need any more information, send me a PM and I'll be glad to help you. I am however a newbee to DIY myself so I don't think I will be of much assistance with regard to tech stuff.

But when it comes to vendors of this and that...just ask!
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Old 13th May 2006, 04:07 PM   #6
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Quote:
Originally posted by EsE
Ok, thanks!
I live in Norway, so 230V is my mains current, actually..
Most people agree that Alpeph's sound great, but what would you compare it to?

The heatsinks look allright, but can I make the rest of the chassis in wood when it's running at 70 degrees? I'm not to good with metal, and I don't have the tools if I'm willing to try.

And at last, what kind of power supply will make the best sound?
I'd love some schemes..

EsE

I believe wood would deteriorate over time coming in contact with that much heat. A fire hazzard might be a consideration, depending on your design. You still have some machining to do even with a wood chassis. The heatsinks need to be drilled and tapped for mounting the mosfets and angle brackets to a wood base.

Lots of folks have had aluminum panels cut by a shop and attached together by using aluminum angle or rectangular bar stock. You could have www.frontpanelexpress.com machine a back panel for you with the connector holes cut and labeled.

Surprising how more the chassis costs than the amp internals.

Good luck on your build,

-David
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Old 14th May 2006, 11:22 AM   #7
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Quote:
I'm not to good with metal, and I don't have the tools if I'm willing to try.
Dear David DW 8083,

Well, I have nearly no experience with metal. But the tools are simple and cheap, and the box is simple to build. My plan is as follows:

You could start with two of those Conrad heatsinks. Their baseplates are 8mm thick and can easily be drilled for either 3 or 4 mm metric bolts. Purchase the correctly sized drills (Aus$ 2.20)and taps (AUS$8.00)from your local engineering shop. A nice T-handle for the taps would cost about AUS$12 ... more or less. A nice counter-sink AUS$ 8.00.

Use the heatsinks as the sides of the box. Then get some second hand plate aluminium for the top, bottom (perhaps thicker for which ever piece you are using to mount the transformers on)and the back of the box ... maybe 3 mm thick and perhaps a nice thicker piece for the front plate.

A satisfactory bench drill press costs only about AUS$60. A few pieces of angle aluminium for the edges. Build it, screw it together, put on the top and you have a wonderful rectangular prism!!!

Polish up the aluminium, perhaps a clear spray on finish or better some anodizing, put it out of the way, because your wife really doesn't really want to see it ... she wants to see the pre-amp with nice knobs and a few LED's ...

Some nice rubber feet, perhaps with a touch of gold.

Search this website for Mark Finnis ... he has some simple techniques to build a box for an Aleph 4 and 5.

Problem solved ... or at least that is the plan.

Good Luck and have lots of fun.

Regards,
George.
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Old 14th May 2006, 03:36 PM   #8
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Hi George,

My chassis is similar to Mark's. I had www.frontpanelexpress.com make a 1.5mm sluminum plate based on a CAD drawing from their free CAD tool. Next I had a local sheetmetal shop bend the design into a box on a sheetmetal brake.

I used 1/4-20 inch hexhead cap screws a 1/4 inch long to fasten the Conrad Heatsinks to the chassis. Using round head or hexcap screws eliminated the need for countersinking.

Here's a link the the final chassis and some work in progress pictures.

My 1st Aleph Amp

-David
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Old 14th May 2006, 06:04 PM   #9
jleaman is offline jleaman  Belgium
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Default Re: Planning an Aleph

Quote:
Originally posted by EsE
Hi there!
I have for a while tought about building a Aleph 30, and would like some input about how they sound, some building tips etc.
I'll order the pcb's from diyamps.com once I'm sure this is the right project. I don't have the cash to build all the amps I come across, so I want to build a good one.

How do I bias it up, btw? And how big heatsinks do I need for some serious bias? Any recommended suppliers?

Regards,
EsE

I'd like to note for this project. You will need to buy / find. Heat sinks that are going to disapate all this heat.

Heat sink's and power transformers are the most costly thing's the rest is fairly cheap. If you need any help with the aleph boards please let me know i have built up alot of them.
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Old 15th May 2006, 02:20 AM   #10
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Default EsE and DW8083

Dear EsE

My posting was meant for you, EsE, in an effort to encourage you to get started and not worry too much about "working with metal"!!! Also, you can cut thinner aluminium sheet with your tungsten-carbide tipped "wood" blade on a bench saw. For thicker stuff, I would still pop in a cut-off disc and use that, and lots of eye and ear protection ... and thick leather gardening gloves.

Sorry David, DW8083! I got the addressee wrong. It is clear that you have done a fine job, and your gear will look lovely in comparison with my hodge-podge.

Oh well, I was just trying to encourage people, as does Nelson Pass, to "just build something" rather than analyzing too much.

Regards,
George.
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