Building Aleph 2

[Coulomb]

Hello Saad, did you clean the board of flux and solder debris? It sounds like a short circuit in the immediate area around the FET, as no other of the parallel devices are experiencing any trouble.

I wonder if you leave it out of the circuit and test the other FETS to isolate the problem what you may discover?

Regards

Anthony

 

[Rarkov]

Hi,
Sorry to hijack but I have a couple of questions regarding the Aleph power supply.

I have modelled it on Duncan's PSU Designer II, and in a CRC setup (68,000uF -> 10Ohms -> 263,000uF) and a 5kOhm load, the simulator predicts a whopping 29 seconds to get upto full 24.6V!

Also, another discrepancy is that the 'R' section of the PSU does not seem to lower the voltage. I wanted a great big resistor that was going to drop the voltage to around 20V.

Any comments asto whether this is normal would be greatly appreciated!

Thanks,
Gaz

 

[Brian Donaldson]

Rarkov
Use a constant current load of 4 amps or so (set to the bais of your amp) The resistor in CRC will likely need to be somewhat lower.

SI,
Is the smoker a output fet?
If so, leave it disconnected and try again. The rest will take up the load. You may have shorted it by static discharge during construction. I did the same. That means rematching likely replacing the set. Or you could *** a non matched one in and adjust the source resistor so that it carries the same current as the rest of the team.

 

[Rarkov]

Thanks for the reply Brian. I tried it again and got the following...

Why is that happening?!

Gaz

 

[wuffwaff]

2 Ohms is a bit much for a cap, try something like 10 or 20 milliOhms. Show us the other voltages too!

William

 

[roddyama]

Gaz,

Also, you want to look at "Vc2". That will be the output voltage of the supply. To see that on the graph, you need to check just the little square box next to Vc2.

 

[tomchaoda]

Btw, what type of caps are recommend for C6,C7,C8.

I found the Nichicon's Bi-Polar MUSE series 220uF/50V is very good. They are Audio grade and cost about $1.10 per piece. The sound is great in my Aleph 5 and is what I plan to use again in my upcoming Aleph 2. The other good one is the Nichicon Premium KZ MUSE (Non-bipolar) series and it cost $1.25 per pcs.

both are good, but I prefer the BP one.

FYI

Thomas

 

[Rarkov]

Fantastic! Thanks guys. It seems to be the Cap ESR that was causing it. Here is a new screen dump looking much better. What is a typical resistor value for CRC? I am assuming that if it was 1Ohm then it'd need to be a 4W resistor (minimum)?

I really needed a way to drop the voltage <= 20V. the 263mF is two caps in Parallel (230mF and 33mF) both rated at 25V. I need to keep and eye on the voltage to make sure it stays below 23V or so, even unloaded!

Thanks,
Gaz

 

[SI]

IT'S DONE!

Hi, Little up date: The Aleph 2's are done. Yessssss!

The first channel I let it sit on the work bench for about 30 min. and just had to plug it in right away to my pre see if any sound coming out of it. The wife was sitting on the couch and when the sound came out of the speaker I was speech less and all I could do was point at her then me then the amp and speakers, and all she could do give me was a very supportive eye roll .

Both channel are up and running. After leaving them on for about 10 Hrs straight the sink temp was about 60C. I don't know if I trust the number, Only because walmart said they can't supply the calibration papers for the "Candy" thermometer .

The problem I'm having is I keep blowing fuses and when I hook them up with my pre it hums. It's a Nakamichi CA-5 and only has RCA out. When It's not hooked up to the pre it is dead quiet. The funny thing is if I unhook one channel, either channel the hum stops in the hooked channel.The ground is connected as per Mr. Pass's schematic. In the PS, I'm using only .5f of C, No R or L.

Oh, The sound........Let me put it this way I have been listening to same B.B. King's album for a while and when I played it with the Amps, on the right channel in this particular song which I'v heard a 100's of times, There was this unfamiliar noise and I thought I blew some thing in the speaker, But when I listen to the same part over I finally figured it out it's back ground horn I never heard before and the speakers are ok.

This is the Grammy moment: Thanks goes to Mr. Pass, Mr. Rollins, Coulomb, Brian, MikeW, Rodd for those nice cardas parts and every body who at least tried to trun me in right direction. I think my 3 sec is up .
Thank you all.
Best regards.
SAAD//

 

[roddyama]

Congratulations Saad.

How about some pics.

 

[SI]

Thanks Rodd. Here's some pictures. The heatsinks are from some old frequency drives that got updated. So they have many holes in them, It kinda works out as vents.

 

[SI]

Here's the in side:

 

[SI]

Here's another:

 

[Coulomb]

You know Saad you can split those output boards in half and center them on those Heat sinks for better thermal performance.

You just reconnect the three traces with wire jumpers and run a second sense line back the the same origin as the first.

Regards

Anthony

 

[Coulomb]

Nice job BTW,

Next you got to replace those BR's with a high performace FRED rectifier.

Anthony

 

[jleaman]

Ive got a friend here in a machine shop that is going to help me build my chassis then i have to order a few small parts then my amps will be done also. : O ) Cant wait.. then on to the speaker project's : O)

YUMMM FOCAL!!!

 

[Brian Donaldson]

Nicely done. They'll run a little cooler if you raise them off the carpet 6" or so. The hum is ground loop. Is the RCA insulated from the chasis? Use a cheater to disconnect the ground. If that fixes it, Connect the grount to the chassis via a bridge. Hook ground to ac in and chassis to other ac in and It'll let the chassis potential float around +- 1.2v off ground and isolate the buzz. I think 60deg is ok for diy, just be shure that buth sinks have lots of clear air space. And you may need to add some holes on the top and bottom plates. If not, the inside temp my soar above 80 deg c, and that's not good for caps.

 

[highbias]

Oh no... Now your stuck looking at them for a year or better in the raw state!! They'll sound soooo good to you that you couldn't live with the thought of being without them for the better part of 2 weeks. I did the same thing and mine have gone unanodized for almost a year and a half now but they are soon to be two tone, black heat sinks / chassis with a Pewter gray front panel. The gorl friend says either get em done or tot he absement they go .

Mark

 

[Brian Donaldson]

Hey Mark
If she'll say that as a girlfriend, consider the problems you'll have if you're married.


There's is nothing even remotely unatracitve about an unfinished Aleph if it can hold it's magic smoke and only release it out the speaker cables.