Sorry, another heatsink thread

[EsE]

Ok, I want to build an Aleph 30, but I'll have to do this in vacations and such over a year, I guess.
I've ordered prints, the next thing I need is heatsinks.
I've got some on my hand that is 5 3/8" wide, got 1" fin height, and is 12" long. I'm going for monoblocks so I can use two of these on each channel. I want to go the entire way with full bias, If I don't I'll spend years wondering how that would sound.

So is four of these enough?

Regards

[hifimaker]

A pair of them should work for a mono block. If they start to run too hot you could always reduce the output appropriately.

You should be fine.

-David

[jupiterjune]

They sound similar to what I have on my A-75 -- and they are a bit small. The fin height has a lot to do with it, and 1 inch is a bit on the short side. (look for pictures of Pass Labs amps...)
How thick is the backplate? This can make a lot of difference to help spread the heat.

Even if they are undersized, I don't think it will be too bad, but you will want to maximize their effectiveness by making the fins run up and down rather than front to back.

JJ

[EsE]

The fins run up and down.
They have a rather big backplate. As I said, I want full bias.
How big difference would some fans make? I know they would be bad for the sound, but if I suspend them with rubber bands and give them a low voltage from another power source than the amp psu, there is no way they can ruin my sound?

[jupiterjune]

How big difference would some fans make? I know they would be bad for the sound, but if I suspend them with rubber bands and give them a low voltage from another power source than the amp psu, there is no way they can ruin my sound?

How much difference the fans will make depends totally on how fast you run them. If your heatsinks are only slightly undersized, you could run them very slow and reduce the noise they make considerably.

In my experience, the fans ruin the sound by the noise of air wooshing over the blades. I've never had electrical noise bleed into the system, and I've never had much vibrational noise on the chasis.

I haven't tried this yet, but in contemplating how to make a higher power amp in a smaller chasis, I would put the fan at the back with a serpentine baffled inlet, lined with something like sorbothane. (I can draw and post a picture if you don't know what I mean).
As far as directing the airflow over the heatsinks, there was a post here not long ago from a guy in Pennsylvania with a very clever heatsink arrangement for the A-75 he is building. (I will try to find the thread.)
If your fan blows into the main compartment, and the main compartment is used as a plenum, it should give a very quiet even airflow over the heatsinks. Max heat transfer, minimum noise.


JJ

[jupiterjune]

check out the " Yet another A-75" thread started by jgeissen.

he has a link to his website where the pictures of the heatsink arrangement are posted.

JJ

[EsE]

Ok, a pic would be nice. I think I'm going for some other heatsinks, though. Is there any sinks some of you already use with an Aleph 30 with full bias?

[GRollins]

One option that always seems to get overlooked is a quick trip to the Aavid Thermalloy site. They have a million heatsink profiles and you can usually find something similar if not identical to what you have on hand. Once you've found your profile, enter the length into their calculator and it will tell you how your heatsink will perform.

Grey

[hifimaker]

I'd consider building a prototype at full power and test it. Perhaps place the PSU and frontend board on a pice of plywood and arrange the heatsinks on the playwood with standoffs to allow for convection around the heatsinks. Run it for 3-4 hours checking the temperature every 30 mins using the 5 second "can I hold my hand on teh heatsink" rule?

Then build a proper chassis if it works, or drop the power output to full bias for 20 watts instead.

Just an idea.

The other possibility is just to buy a pair of Conrad MF350-151.5 heatsinks for a stereo chassis. The Conrad heatsinks are not very expensive and are PERFECT for an Aleph30.

Here's a link to my own Aleph30 that I've been listening to for over a year. I've run the amp for as long as 12 hours and the heat is still within the 5 second touch range.

Aleph30 with Conrad heatsinks: My 1st Aleph Amp

-David

[Blues]

Originally posted by dw8083
I've run the amp for as long as 12 hours and the heat is still within the 5 second touch range.
-David

Is that with the fan running, David?