refer #3216, bias will increase if 75k ohm is used instead of 15K, to further increase the bais, change the two reisistors of 1.5K connect BC550 to 511 and 1k.
I have finished the build of the Aleph X Original version 15V; 4.5A bias. If the sound is better I can increase the bias for esample at 5.04 A (0.555V/0.22Ohom= 2,52Ax2=5.04V) or differents value?
Virginio
Virginio
Depend on speaker you have (resistance..) but normal allmost of them is 8ohm.--> bias is enought at 4,5A.
I designed and built a balanced balanced, Class A mosfet amp about 10 years ago - I recently posted the schematic and a description on this forum.
http://www.diyaudio.com/forums/solid-state/212424-balanced-class-fet-amplifier.html
Now I've read a bit more about the Aleph X principle - sounds good to me. It seems that I could easily convert my amplifier to this configuration by returning the feedback to the input of the opposite phased input (currently it goes to the source of the input fet, same phase).
Before I commit to wholesale surgery on my amp, what do you think would be pro.s and con.s of making such a switch? Schematic of current amp is attached. I am very happy with it, and one of my friends has built 4 of them to power his bi-amped speaker system.
http://www.diyaudio.com/forums/solid-state/212424-balanced-class-fet-amplifier.html
Now I've read a bit more about the Aleph X principle - sounds good to me. It seems that I could easily convert my amplifier to this configuration by returning the feedback to the input of the opposite phased input (currently it goes to the source of the input fet, same phase).
Before I commit to wholesale surgery on my amp, what do you think would be pro.s and con.s of making such a switch? Schematic of current amp is attached. I am very happy with it, and one of my friends has built 4 of them to power his bi-amped speaker system.
Attachments
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Case and Heat Sinks for Aleph-X
What do you guys think regarding the Aleph-X Mini in a 4U case from the store? Looking to use +/-15v and 2 amps total per channel. Spreadsheet says peak of 120w for those specs. Nominal is 90w.
Max usable output is 20w into 8 ohms.
Is using the 4U chassis cutting it too close?
Thanks,
Vince
What do you guys think regarding the Aleph-X Mini in a 4U case from the store? Looking to use +/-15v and 2 amps total per channel. Spreadsheet says peak of 120w for those specs. Nominal is 90w.
Max usable output is 20w into 8 ohms.
Is using the 4U chassis cutting it too close?
Thanks,
Vince
Pass DIY Addict
Joined 2000
Paid Member
The 4U 12" deep chassis has sinks that are approx 0.31c/w. This is a bit small. The original sinks that Peter Daniel secured in a group buy at the time were 11"x11"x2" and measured 0.27c/w. This is right on the edge of being too small for 100w dissipation. It will work, but it will also run hot, probably north of 55-60c total temp.
I've been playing around with this over the past little while and have settled on a not-quite-so-precise rule of thumb: You want somewhere in the ballpark of 8-10 sq in of "good" heat sink for every 1 watt of power that you will dissipate. Now, what makes a "good" sink? Clearly, one that is wider than it is tall is a good start. You also want one with relatively deep fins. The ones from the DIYAudio store are about 1" deep - they work well, but 2" would be nicer. You also want black anodize for better emissivity, blah, blah, blah...
The 4U sinks each have about 565 sq in of radiating surface. Using my formula, you want closer to 800-1000 sq in per channel order to dissipate 90-100w of power. 4U will run hot. I'd look for something larger... 5U is still a bit small, but will run cooler than 4U.
I've been playing around with this over the past little while and have settled on a not-quite-so-precise rule of thumb: You want somewhere in the ballpark of 8-10 sq in of "good" heat sink for every 1 watt of power that you will dissipate. Now, what makes a "good" sink? Clearly, one that is wider than it is tall is a good start. You also want one with relatively deep fins. The ones from the DIYAudio store are about 1" deep - they work well, but 2" would be nicer. You also want black anodize for better emissivity, blah, blah, blah...
The 4U sinks each have about 565 sq in of radiating surface. Using my formula, you want closer to 800-1000 sq in per channel order to dissipate 90-100w of power. 4U will run hot. I'd look for something larger... 5U is still a bit small, but will run cooler than 4U.
Thanks Eric. I'm glad I checked.
I bought a set of 3x8x15 heat sinks for the MoFo amp. Probably need 4 of these for an Aleph-X.
Thanks
Vince
I bought a set of 3x8x15 heat sinks for the MoFo amp. Probably need 4 of these for an Aleph-X.
Thanks
Vince
Pass DIY Addict
Joined 2000
Paid Member
Vince, I'm thinking the issue with finding adequate sinks is part of what is behind the drop-off in interest in the Aleph-X amps. The awesome benefit of the design is that it is scalable, but the drawback is finding a good set of sinks for even the smallest iteration of it is a challenge. Using the 4U sinks for the Aleph-X would work best with 4 of them. But then you have a 22-24" deep chassis. An alternative is to copy Nelson's original Aleph design with sinks all around.
For your 3x8x15 sinks, add up the total surface area (don't include the flat back of the sink as it will be trapped inside the chassis) and see where it comes out...
For your 3x8x15 sinks, add up the total surface area (don't include the flat back of the sink as it will be trapped inside the chassis) and see where it comes out...
I also have a 60" XA.8 looking heat sink sitting in the garage. Might have it cut down to equal parts.
If that doesn't do it, then I dont know what will. 🙂
If that doesn't do it, then I dont know what will. 🙂
Pass DIY Addict
Joined 2000
Paid Member
Eric,
each Hi-Fi 2000 4U sink Is 0.31 Is that right
would you please advise what Is nominal to max power dissipation you can get with 2 x 4U / 2 x 5U sinks used per channel
each Hi-Fi 2000 4U sink Is 0.31 Is that right
would you please advise what Is nominal to max power dissipation you can get with 2 x 4U / 2 x 5U sinks used per channel
Pass DIY Addict
Joined 2000
Paid Member
Samoloko, Yep, check the heat sink page in the store. This is where I got my data from.
2x4U sinks per channel, arranged side by side combine to provide ~0.15c/w. In an ideal world, you multiply this figure by the power you wish to dissipate in watts to obtain your thermal rise above ambient. You want to limit thermal rise to about 25c. But nothing in this world is ideal, so you need to apply a "fudge factor" to get a more realistic figure.
Here is my generic protocol:
1) Divide 25c (max thermal rise that you want) by the quiescent power consumption of your amp (per channel for building monoblocks or for 2 channels together if building a stereo chassis, keep in mind this is the wattage dissipation, NOT output wattage - they are very different specifications).
2) Take this number and de-rate it by 25%. This de-rating takes into account all of the inefficiencies of mounting your output transistors to the heat sink and the less than favorable conditions that you are likely to create in building your amp even if you follow the advice above (trust me, no matter what you do, it won't be ideal).
3) Take this number and round it down to the nearest 100th decimal place.
4) This is the size of a heat sink that you really need. Then think of a way to get more...
An example: the Pass Labs Aleph2 monoblock delivers 100wpc into an 8 ohm load and dissipates 300 watts of heat all of the time. Nelson Pass states that the Aleph2 requires heatsinking of 0.06c/w per monoblock. Using the theoretical calculation dissipating 300 watts of power while limiting thermal rise to 25c above ambient (25c/300w) should require 0.083 c/w worth of heatsinking. Derating the theoretical result of 0.083c/w by 25% (0.083/1.25) provides us with a more realistic figure of 0.0656c/w and rounding down to the nearest 100th yields exactly the target value of 0.06c/w indicated by Nelson.
An easier to apply ballpark-approximation-rule-of-thumb is that you want 10sq in for each watt of power you need to dissipate. A single 4U 12" wide sink is about 565 sq in. Thus, each 4U 12" wide sink can dissipate 50-60w of power and stay near 25c temp rise.
A single 5U 12" wide sink is about 717sq in, so it can dissipate about 70w with a 25c rise.
2x4U sinks per channel, arranged side by side combine to provide ~0.15c/w. In an ideal world, you multiply this figure by the power you wish to dissipate in watts to obtain your thermal rise above ambient. You want to limit thermal rise to about 25c. But nothing in this world is ideal, so you need to apply a "fudge factor" to get a more realistic figure.
Here is my generic protocol:
1) Divide 25c (max thermal rise that you want) by the quiescent power consumption of your amp (per channel for building monoblocks or for 2 channels together if building a stereo chassis, keep in mind this is the wattage dissipation, NOT output wattage - they are very different specifications).
2) Take this number and de-rate it by 25%. This de-rating takes into account all of the inefficiencies of mounting your output transistors to the heat sink and the less than favorable conditions that you are likely to create in building your amp even if you follow the advice above (trust me, no matter what you do, it won't be ideal).
3) Take this number and round it down to the nearest 100th decimal place.
4) This is the size of a heat sink that you really need. Then think of a way to get more...
An example: the Pass Labs Aleph2 monoblock delivers 100wpc into an 8 ohm load and dissipates 300 watts of heat all of the time. Nelson Pass states that the Aleph2 requires heatsinking of 0.06c/w per monoblock. Using the theoretical calculation dissipating 300 watts of power while limiting thermal rise to 25c above ambient (25c/300w) should require 0.083 c/w worth of heatsinking. Derating the theoretical result of 0.083c/w by 25% (0.083/1.25) provides us with a more realistic figure of 0.0656c/w and rounding down to the nearest 100th yields exactly the target value of 0.06c/w indicated by Nelson.
An easier to apply ballpark-approximation-rule-of-thumb is that you want 10sq in for each watt of power you need to dissipate. A single 4U 12" wide sink is about 565 sq in. Thus, each 4U 12" wide sink can dissipate 50-60w of power and stay near 25c temp rise.
A single 5U 12" wide sink is about 717sq in, so it can dissipate about 70w with a 25c rise.
Don't worry too much about running it hot. Just use the biggest heatsink that is readily available to you and at your budget. Giant 4U sinks are not minimum requirement. Fear not and get it done.
pcb
hi, I would like to make Aleph X monoblock 100w, can you recommend schemes x pcb or gerber x file to achieve? thank you
hi, I would like to make Aleph X monoblock 100w, can you recommend schemes x pcb or gerber x file to achieve? thank you
You have schemes , pcbs just maybe
Babelfish XJ , or JX …….. or whatever | Zen Mod Blog
Babelfish XJ , or JX …….. or whatever (Aleph X servo for Greedy Boyz)
are you really ready to have beasts with 350W of heat per channel ?
Babelfish XJ , or JX …….. or whatever | Zen Mod Blog
Babelfish XJ , or JX …….. or whatever (Aleph X servo for Greedy Boyz)
are you really ready to have beasts with 350W of heat per channel ?
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Zen, congratulations .. great job .. super X !!! I do not know if I have the skills to achieve but, if I wanted to try to realize for myself; can you lure me to the pcb? I had made a toroidal 1000w 2x18 and I have 16 capacitors 47000uf 63v coming from an Aleph 2 .. I could reuse here? thank you