My DIY Aleph 5 is Alive!!

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So here she is...I spent quite a bit on the chassis (thanks Cowrang), but I knew this amp would be a keeper. So far not disappointed....

Need a little more critical listening, but so far, I am happy...no hum, hiss or anything. DC Offset at 20mv and 17mv. .7v across R91 source resistors, 34.5V rails, 600VA Piltron tranny. Power Supply Filter is a 56kuf/.215 ohm/56kuf per channel. And she looks quite nice too. Still have to put in the 75C thermal cutoff and cool VU meter in the center hole...work I hope to hit this weekend...

Driving it is my Audionote M7 clone with LED Bias and other fun stuff...and a crappy Sony 400CD player as transport with a DIY Cirrus Logic CS4397 DAC that I am still modding...

And my Magnepan Tympani IVa's love it so far...

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


An externally hosted image should be here but it was not working when we last tested it.
 
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I garbage picked that LCD. Not too proud to pick, I say...

A new 12VDC SMPS and it sparked right up. Even my wife was impressed, which doesn't happen very often....

Besides, I have a projector based Home Theater in the other room....this TV needs to be just big enough to follow CNBC.
 
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Yes, that chassis really made the amp worth while. I sand blasted the inner panel that the output devices and heat sink bolt to in order to get the best heat transfer, and was considering sandblasting the heatsinks. I found a local shop that will Anodize the sinks after the sandblast, but decided to hold off until I see how the powerder coated sinks work out.

I ran it for a couple hours last night and had a thermocouple jammed into one of the top screw holes on the inner panel. It got no hotter than 110F on both sides. I also used Kapton insulators on the output devices for their superior heat transfer to the panel and sinks.

So far, quite happy. Now to finish the meter and thermal switch...
 
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OK, so the DAC info can be found here

I do not know if the are still selling them. The only mod I did was a better power supply and swapped the LT1364 opamp for a a LM4562.

Tried the LM6172 and OPA627, but liked the 4562 best. After swapping the opamp, I sold my Benchmark DAC1.

Working on its replacement (?) CS4398 with LM4562 opamp coupled to an 6SN7/6SN7 Aikido preamp.
 
john65b said:
I sand blasted the inner panel that the output devices and heat sink bolt to in order to get the best heat transfer, and was considering sandblasting the heatsinks. I found a local shop that will Anodize the sinks after the sandblast, but decided to hold off until I see how the powerder coated sinks work out.
Could you expand on these two points:
A. Wouldn't a polished (smooth) surface be a better interface for mounting the devices to the heatsinks? (The transistors themselves are lapped mirror smooth.)

B. Doesn't powder coating or almost any paint in effect insulate the heatsinks?
 
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A. Wouldn't a polished (smooth) surface be a better interface for mounting the devices to the heatsinks? (The transistors themselves are lapped mirror smooth.)

Yes, a polished surface is always best. But I would take a fine sandblasted finished bare Aluminum plate over the same Aluminum plate that has a smooth, Powder Coated paint finish. I was just a bit to lazy to further polish the plate any further than the fine sandblast finish. I am using these Kapton Insulators that are like sponges, and seem to be able to adhere to the plates well as they are now finished.


B. Doesn't powder coating or almost any paint in effect insulate the heatsinks?

I struggled a little with this, and what has the most effect on heat transfer on these sinks -

The black powder coated finish reduces Convective heat transfer as the heat transfer must go through Aluminum and powder coat finish (the conductivities of aluminum and powdercoat are additive like resistors in series) , but the black color has a higher emissivity for better radiative heat transfer.

The bare aluminum has better Convective heat transfer (since no powder coat to conduct through), but silver color does not have very high emissivity, so radiative heat transfer is reduced.

If I remember my Heat Transfer right (only been 24 years since graduating from College), Radiative heat transfer effects really only govern at very high temperatures (higher temps than we deal with on these sinks) - If you can feel your skin get hot a foot away from a heat sink, you know those sinks are at very high temperatures...

So my logic points that I should remove the powder coating finish, as I would be better off with bare Aluminum sinks, but in the end, I am able to dissipate the 150 watts per channel easy enough with what I now have.

The ideal would be bare aluminum and the Anodize Black
 
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