New Aleph 2 amplifier in the PassDIY gallery

[BrianGT]

There is a new Aleph 2 amplifier in the PassDIY gallery:

Wayne Sankey's Aleph 2

It is a great looking design. I actually like the appearance better then the original Aleph2 amplifiers.

I was planning on doing the exact same arrangement with 4 heatsinks per channel. It seems to work good.

He also posts his PCB layout, which is basically Mark Finney’s boards with a few exceptions. It came out really nice looking. He had the panels brush and anodized.

An externally hosted image should be here but it was not working when we last tested it.

more pictures on the site.

--
Brian
gte619j@prism.gatech.edu

 

[mefinnis]

Very impressive !!

Sort of answers any question about the ability of a committed DIYer to produce "commercial" level boxes, methinks

 

[BrianGT]

I e-mailed wayne to ask about the heatsinks and other stuff, and I got this response for the heatsinks:

> The heatsinks are from:
>
> M & M Metals,
> 908 E. Pioneer Drive
> Irving Texas 75061
> 972-721-7174
>
> Talk to Mike Secor.
>
> What I have is 8 - 9.00" extrusions, profile # MM11645B,
> black anodized.
> You need 4 per amp, they are just under 7" wide.
> You orient the fins vertically.
>
> I paid $14.89 each for 16 (a friend is also making some
> amps and we got the parts from the same place).

That seems like a pretty good deal for heatsinks. They look nice.

The brushing and anodizing for 4 chassis (for him and his friend)was $200.

He also calculated his total cost at: Around $1350.

--
Brian
gte619j@prism.gatech.edu

 

[Gabster]

Seems that my concept is doable !!! Nice post.

http://diyaudio.com/forums/showthread.php?s=&threadid=2642&perpage=15&pagenumber=1

 

[promitheus]

Very very cool.
I am also concidering something similar.
I will post also some pics later.
But these look very very good.

 

[psroczka]

What about a temperature of heatsinks ???
Is that area of heatsinks enough ???

 

[BrianGT]

From PassDIY:

"I did some thermal sims using the Aavid Thernmalloy website calculator on one of their sinks when I was trying to find a suitable sinks. The sinks I ran the sims on were roughly equivalent to the ones I eventually bought. The sims told me that my amps would have junction temps on the order of around 95C to 100C with a 78F ambient, and using the “touch test” I believe that the actual heatsinks I have are running a bit cooler than that. I haven’t measured the thermal profile of the amps yet, although I intend to do that one day. Also, the sims don’t take into account heat that the top, front, and back are pulling from the sides so there are several inaccuracies to the sims. The sims were very helpful though as a tool to size the sinks. For my amps, I ended up with amp sides that are about 14” wide, 9” high, the fins are 2” long, and the base plate thickness is 0.200”. If the fins are about a half inch to an inch apart, that will do well. Any more heatsinking would be a bonus in lowering the junction temps.

In my amps, the temps are good enough that I am not concerned about the junction temps. The hottest exposed part of the heatsinks is quite warm to the touch, but certainly not high enough to cause a burn. A small child would probably perceive it as quite warm though and would want to touch it maybe once and then leave it alone... "

It seems adequate, but I am going for more heatsinking then that for mine. Look at the other post "Heatsinks for Aleph 2" if you want the see the heatsinks that I am using for mine. I am just starting to put the case together now.

My sides will be 8"x18"x2.6" with a thicker baseplate.

--
Brian
gte619j@prism.gatech.edu

 

[WayneS]

update

Hey I'm glad you guys like my amps. It's a pretty simple design actually, anything more sexy than this starts costing real money. The XA-200 front is gorgeous but I haven't the slightest clue how you machine a part like that. Now THAT's a good-looking amp.

The heat is under control. The case definitely gets warm, but the transistors are not too hot. I would strongly advise against having a case any smaller than this for an Aleph 2 though.

An update - I figured out what the hum problem was and have egg all over my face because of it. There were two faults actually which made it hard to track down. First, I had a mounting point that was acting like a 500 ohm resistor to the (-) supply, and second, the chassis was floating. I finally noticed that the chassis was at -45V !!!!! I replaced the rubberized washer that was acting like a resistor, and I have no earthly idea why it is a poor conductor instead of an excellent insulator. The chassis I have grounded by connecting a drain wire directly to the ground pin of the IEC conenector. The chassis was floating because it was touching the ANODIZED back plate - I didn't know anodized coatings are non-conductive. I tested the other amp and it has a connection from the chassis to ground - some metal parts must be touching on that amp.

So, to sum up, I've got conductive rubber and insulating metal that threw me for a loop. Live and learn.

The amps are breaking in nicely and the sound is awesome for something I made in my garage. Very detailed, very clean, lots of bass power.

 

[BrianGT]

I am glad that you got rid of the hum. I had a friend with a similar problem with an anodized case. He had to sand down the part of the back plate of his amplifier that touched his heatsink.

I guess you have no reason to have the strap put around your transformer anymore.

Has the amp sounded any different from the first time you listened to it? How long of a break in period do you think that it took.

--
Brian
gte619j@prism.gatech.edu

 

[WayneS]

On the breakin - funny you should ask. In tracking down the -45V problem, I had a brain fade and as a result blew up the single ended drive transistors of that amp. I'm an idiot. I disconnected the -45V power from the drive transistors and turned on the amp to see if the -45V was still on the case. What this does is exceed the Vgs max on the transistors, and then you get destructive punch-through on the gate oxide, destroying the transistors. I also replaced all the actives on the main board just in case - I had the parts lying around. I also had a nice matched set of the IRFP240s to press into service. So that amp now has about 5 hours on it. The other amp has maybe 50 hours by now.

I thought that they sounded pretty grainy and harsh for the first hour at least. After 10 hours they settle in pretty well, and then I guess a full breakin is on the order of a couple hundred hours. They are very detailed, there is no question about that. I've also found that they get another significant boost in their sonic properties if you use balanced interconnect instead of single ended. Everything sort of "comes alive" when you make this change. Again adequate words are difficult to come by. These amps are clearly far far above average in many sonic categories.

There are no transformer straps, and the hum has gotten far better. They are now pretty quiet compared to most amps.

I just finished insulating the conductive rubber washer on the other amp, and also added a ground wire to the chassis. I finally just put a nylon washer between the rubber washers and the boards as insulators - that way I still get the vibration isolation properties of the rubber washers which is why I put them there in the first place.