Aleph-X builder's thread.

[MikeW]

The heatsinks will get hot only 50-60 deg. C. If it gets to 70 it is a good idea to shut it down. It will also depend where you put the switch.

[Mark A. Gulbrandsen]

Thanks Grey for the biasing tips. My resistirs are 1% tolerance but I think I'll still take a few minuites and read em all and see exactly what I've got here. I'll probably start off using the .25 ohm jobs. I suppose I can always adjust the operating current slightly from there anyway.

Larry,
I reccomend building a regular Aleph first so you can get used to matching fets adjusting bias and such. They are still just about the best thing going out there. From what I've read the AX sounds a bit brighter and packs a bit more slam than a same size Aleph. I'm about to find out....hopefully this weekend.......

Mark

[Zapped]

Hi Mark: I may take your advice, just to get another success under my belt after the ZenV4. My previous effort, an A-75, is sitting on the shelf awaiting my return to fix it after screwing up the power leads to the output stages at the very last minute (what a dummy thing to do). I actually did quite a lot of Vgs matching of devices for that and got some very tight groupings of all three Q types, especially the IRF230 and IRF9230 output devices. Still have quite a few of those matched devices and have mulled over the idea of using them, like Peter D., in an X. As Nelson recently suggested, I gave them about 5 seconds of test time, but made sure they were all about room temperature first.

As elsewhere posted in this forum, the pot adjustments on the A 75 were a little twitchy too. When I go back to the project, I am going to use multiturn pots to make it easier. I think if I do the X I will go that route with it too. Those blue and white Bourns (or whatever) single turn jobs are for the birds. Seems like the X (like the A 75) is hard enough to set without dealing with a balky pot too.

thanks for your comments. I may take the easy way out on this next project. Don't know yet.

Larry Wright
Seattle area

[Mark A. Gulbrandsen]

Larry,

I agree with you on the single turn Bourns stuff. I deal with so many things in the field that have single turn that should be 10 turn....it gets frustrating sometimes. I am using Bourns 10 turn on my X's

Mark

[kilowattski]

Howdy Gents,

I am getting parts together to start my Aleph-X in parallel with finishing my Zen IV. I would like to start by designing the power supply. I will design a board for the rectifiers and capacitors. I would like to use a good quality snap-in capacitor. The rails will be +15V and -15V and I would like to do a CLC filter with 47,000uF cap, 3 mH inductor and 47,000uF. Could anyone recommend a capacitor manufacturer? I would like to use better components. Would you recommend 105 degree caps? Thank you in advance.

[Mark A. Gulbrandsen]

Well, I definately know that Igor would have his power supply located VERY close to the incomming power meter thats for sure.... Perhaps you could do the first X with a 3 phase primary on the power transformer

Mark

[Thunau]

Today I ordered a couple of dual secondary 16V transformers rated at 17.5A each secondary (they were only $45.00 each). Was it a sound purchase? I would like to use four devices per board. The AX spreadsheet tells me I can only get about 29W in 8Ohm with these and 15W in 4 Ohm. I would like to bias a bit higher but with lower supply voltage. Can I do something to the power supply to drop the voltage a bit? The spreadsheet suggests that the actual voltage at the Fets is a bit higher than the secondary. Maybe I should go with eight devices per channel. What's the concensus?
Sorry if the questions are a bit basic. This is my first amp. I did a few DIY speakers before but this is a new territory.

[grataku]

The spreadsheet is off actually, on my amp (built, tested and presently being used) it's more like 50 W/8ohms with an adjusted 50% ac current gain.

In other words, if that's what u want to built you got a pretty good deal.

[CheffDeGaar]

Originally posted by Mark A. Gulbrandsen
Thanks Grey for the biasing tips. My resistirs are 1% tolerance but I think I'll still take a few minuites and read em all and see exactly what I've got here. I'll probably start off using the .25 ohm jobs. I suppose I can always adjust the operating current slightly from there anyway.
Mark

Hi Mark,
As Grey said, with 1% tolerance, you'll be fine, even without measuring them. To be overkill, I'd chose resistors of twice the original value in 1% tolerance, and paralell 2 of them (or 3 with three times the value, etc... - I used 4 //ed ). Two advantages here IMHO : a larger saftey margin re. dissipation and stability, and the couple of resistors will average the total resistance value in all the places they will be used, leading to a better match between resistances values all over the amp. I felt better this way, with all the time I spent closely matching the mosfets

Originally posted by kilowattski
Could anyone recommend a capacitor manufacturer? I would like to use better components. Would you recommend 105 degree caps? Thank you in advance.

Hi Guy,
I "usually" use Panasonic TSHA snapin caps. 105°C rated (mandatory in this use IMHO, longer life), can be easily sourced (Digikey), and very robust. Try to bypass each cap with a small film cap (100nF/MKF), and you're in

Hope this helps

[Brian Donaldson]

Hey Mark, I like you three phase idea. In my new house, my listening room backs up to the attic, and I was considering an auto parts AX. I could use the radiator and electric fan from a front wheel drive car and I even thought about using a electric motor to spin a car altinator instead of huge transformers. You can vary the output voltage by the feild voltage and the output is three phase if you connect straight to the stator and make your own bridge. It may take some surgery to convert from delta to wye. Even without capacitors, rectified three phase from a car alt only has like 15% ripple and would be much higer frequency (like 2000 hz) meaning much less needed capacitance.
Hummmm. This idea needs more developement. I could build an ugly as $hit frankenamp and have it out of sight on the other side of the wall in the atic (I have a 2' x 6'8" door right next to the amps home) and it wouldn't offend the wifes sence of decor.