Aleph-X builder's thread.

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Joined 2002
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parallel jfet front end...

Hello,

I'm trying to resurrect my long-dormant Aleph-x build. It was to be
a standard build with +/-15V rails and 4 IRFP044 mosfets.

Since I have a bunch of 2sj108V parts and I want to try a jfet front
end, I wonder if it might be a good idea to replace the differential
pair of IRF9610 with 4 matched 2sj108V? That way I can comfortably
keep the original 22mA or so current of the original front for driving
the big mosfets.

Does this make any sense?

Thanks,
Dennis
 
sorry to all but i want to know what to do if your voltage is 30 volt installed of 18 or 24 any thing need to change? i am building my new aleph-x please help

That will be a giant furnace a lot of extra power very likely you do not need..
I think you need some extra pair power mosfet and some extra money to pay hydro:D
Very likely you need to adjust the bias accordingly because the higher rail voltage
 
I agree with the Furnace comment- 30v rails is rather high and you'll be burning off a TON of electricity. 30v rails and 24 mosfets per channel seems like overkill. What are your power requirements? Start there and work backwards. I run my Aleph-Xs on ~22v rails with 8-9A of bias for 12 mosfets per channel and they kick off a great deal of heat. I get about 100w of power into both 8-ohm and 4-ohm loads. If you are looking for more than 100w of power, perhaps more efficient speakers is a more sane approach.

Check out my web page (signature link) for a parts list for both low-power and high-power version of the Aleph-X.
 
Variable needs

I agree with the Furnace comment- 30v rails is rather high and you'll be burning off a TON of electricity. 30v rails and 24 mosfets per channel seems like overkill. What are your power requirements?

Hi Eric,

I am thinking of building a Aleph-X amplifier version and have spend like 20-30h of reading and researching on the topic.
I have read your very good written webpage on the topic very thoroughly (thank you very much for it) and am in the decision making part of „how big or small shall I go“?

In general I am wanting to build something between 30 to 60 watt class A into 8 ohm (dual mono).
As far as I understand the Aleph-X it is more a „scalable concept“ of an amplifier than „a amplifier“ - dependent on the amount of rail voltage and heatsink size.

Your description of using a variac to power the amp up in the beginning and me not finally knowing what wattage (rail voltage) to finally settle on, brought me to the idea of having a variable rail voltage.
The idea is to use a transformer that can provide switchable rail voltages. A transformer that can provide something like 12v, 18v, 24v, 28v at 1000 to 1500va. The capacitors of the power supply would have to be rated for the highest rail voltage and the heatsink (and enclosure) would have to be made for the highest rail voltage.

What bugs me a bit with class A is the power consumption when not needing the big power. This way the amplifier could be set up for 20 watt class A for less power needs or at 60 watts class A for high power.
Adding the possibility of more or less AC Current Gain gives even more possibilities. A sort of having your cake and eat it too class A (in certain boundaries).

My question is: is it possible? Reasonable? Has it been done? Or am I completely of the (voltage) rails with this idea? :confused:

Another question is concerning the number of output transistors: Why is it that a Aleph-X has less output transistors than a original XA.5
There are for example 20 output transistors per mono side in a XA 30.5 ( as I count on pictures). Why? Reliability? Manufacturing cost (one size fits all)? Audiofoolary for those who need transistor count?

Love to hear some from ya all.
 
amplifier is not a bulb

Hi Zen,

That is not what I meant :) I don't want to "dim" an amp.

What I am thinking of is sort of 3-4 settings of wattages (rail voltages)

Lets say something like "eco", "normal" and "full power mode".
Avoiding the always full wattage draw when not wanting to listen to all flagged out best class A and being able to have it when wanted.

The case, heatsinks, transformer va would be the largest for the highest wattage, but not the "running costs". A sort of green Aleph-X.

I know now you want to point me to the class D section of the forum :D

Nope just looking for class A variability...

So what's up with these 40 output transistors in a XA 30 compared to Aleph-X?