[jtostenr]

Hi all,

So I have what I need to populate 4 B22 boards and have the Par-Metal cases on the way. Now the hard part (at least as far as sourcing things goes) seems to be finding heatsinks.

I had originally planned to do a Beta 22 as a preamp only, but now have decided that I would like to power speakers as well. So, without having to use a monstrous case (I'm already having to get a 12"x16"x3" case), I need to find some appropriate heatsinks.

After a great deal of searching, the best thing I can come up with is this:

http://www.mmmetals.com/extrusions/drawings/MM13905.JPG

I have been quoted $200 for 8 of these (enough for 4 B22 and 4 S22 boards). The minimum order is $200, so there is probably a significant price break for a larger quantity, however they would not give me specific numbers.

So, I am trying to figure out if there is a better option out there. Maybe I am missing something. I've already looked at the Conrad heatsinks and many others. The biggest problem is that I need a maximum fin height of 1" in order to fit within the 12x16 case.

Thanks,
Jeff

 

[MisterX]

# HSITQD-95 from this page---> Heatsinks - Medium, One Surface

look like they would work but the fins go in the other direction so maybe one of the three on the top of the page instead?
("half" length heat sinks mean more work but it's hard to argue with their prices)

 

[FallenAngel]

4 Beta22 boards and 4 Sigma22!? It would actually be a better idea to use the Beta22 as preamp and build a Beta24

Also, if you are using a single-chassis solution, STRONGLY consider not to, balanced + single-chassis with transformers/PSU in same case = NOISE.

 

[jtostenr]

Thanks MisterX. I did see that webpage, but I think I will take a closer look. Even though it wouldn't be the perfect heatsink, it would be a huge cost savings. Sometimes the dimensions they list don't really match up with the picture....probably just using a generic pic I guess.

Just for some additional background info... this is going to be a 2-box fully balanced Beta 22 with 4 S22s. For the next couple of years I plan on using it to power speakers, but eventually I would like to build a power amp and use the Beta 22 as a preamp.

One of my issues is that I don't have a bunch of space, so the largest possible case I could use is a 12"x16"x3" (x 2) Par Metal 20-series. Otherwise, I probably would have just bought some Conrad heatsinks and larger cases.

Anyway, I'm taking my time on this project and looking forward to hearing everyone's thoughts.

Jeff

 

[TimmyMac]

With offboard heatsinks, 2 s22's is plenty for 4 boards in my experience, unless you're planning on max gain and 4-ohm speakers. You should also be able to use much smaller cases.

I used these:
Aluminum Extruded Heatsink
and used wood panels for the front/back and steel plate for the top and bottom.

 

[jtostenr]

I'm using 8 ohm speakers with 88dB sensitivity at the moment. Part of the reason why I want to use 4 S22 boards is to not limit my options in the future. Be able to use whatever speakers I choose at whatever volume, without having to worry about the power supply.

When looking at the total cost of building a balanced Beta 22, going from 2 to 4 S22 boards is really not a big expense. I'd rather do it now than deal with it later.

Jeff

 

[cotdt]

I used custom CNC'ed heatsinks especially designed for the Beta22 boards and the specific casing. It seems to be the only way to do it. I did 8 heatsinks for $50 in raw material.

Pics:

http://www.head-fi.org/forums/f6/got...7/#post5808989

Don't forget that the amp modules themselves need other modifications to handle the extra power.

 

[luvdunhill]

The sigma22 is effectively current limited by the amount of heat sinking you have. If you want to pull around 4A, then your solution of four boards is fine, assuming you're using the recommend on-board heat sinks. Don't forget that you will need 8 secondaries. I'd be curious to know how you'll address this.

If you use external heat sinking, I think 2 boards will suffice, given you run the numbers.

 

[sachu]

He could run it off a pair of secondaries off of a huge transformer..Use a terminal block to draw wires for all 4 boards from the one pair.

 

[jtostenr]

I'm working on running through the calcs on AMB's site but I'm not sure what to use for some of the values.

I'm planning on using 4 toroids each with dual secondaries.

Jeff