The Aleph-X

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#1,441
gnomus said:
It seems every one wants more power. Not me. 30 to 50 watts is plenty.

Can the board work for lower power?

How many mosfets would be needed?

And I guess all the same adjustments for adding power would be needed for less power output?. How would these be calculated?

Thanks in advance.
Click to expand...

It is not just power that is desired. Higher bias currents are required for low impedence loads, and using a single device for each bank exceeds the SOA for the output devices with the increased current. Multiple devices per bank solve this, and increase the reliability of the amplifier.

--
Brian
 
#1,442
hifiZen said:
Actually, Brian:

A tip for you: Move as many traces as possible to the bottom layer so that the top layer ground plane has the fewest breaks possible. In some cases where you have a single trace on the top layer going from pad to pad, you can improve this by running as much of the trace as possible on the bottom layer, and using vias to jump to the top layer where you need to cross over another trace. The goal is to provide the greatest uninterrupted ground plane area possible on the top side. Ideally, the ground plane has no holes, slots or anything... it would be one continuous solid sheet.

You can also insert plenty of vias between the top and bottom ground planes to connect the two sides, especially around areas where there is a discontinuity on one side. The best location for vias is along edges of the plane polygons, and possibly a sprinkling through large unbroken areas. Try to make one side of mostly traces, and the other side primarily unbroken ground plane.
Click to expand...

Somehow I'm not used to the idea of using vias in analog circuit boards. From looking at many other famous designs and their PCBs, I didn't noticed that they used vias in the layout. Yet the rev. beta of Aleph X PCB doesn't spare any chance to use vias. Can you comment on this? Is it really a common practice in amps/preamps layout design and are there any drawbacks?
 
#1,444
Well, from a consistency point of view (and a manufacturing cost perspective), it is preferable to minimize the number of vias, and have all of the signal traces on a single side of the PCB, but in reality it's just not possible. Some people are a little too afraid of using vias, I think this is just phsycological. There's really no difference between a via and a trace... they're both just copper deposited onto a fibreglass substrate. OK, so that's a simplification... there are subtle differences with vias, but electrically, there's very little to justify fanatical avoidance of their use. The application of vias depends very much on your priorities and layout strategy.

When using vias, there are just a few simple things to consider. One of the main tricks with vias that carry analogue signals or power is to ensure adequate copper cross-sectional area through the via. Usually this is accomplished by adjusting the hole size so that it's circumference is large enough in combination with the plating thickness. Note that vias and plated pads typically have thinner plating than traces, since they do not start with any copper in them at all (a few microns are chemically deposited to "activate" the surface for electroplating). For typical 1oz plated boards, the outer layers usually start with 0.5oz copper laminate, and are plated up to 1oz. That means the vias receive only 0.5oz plating. Note that component pads are often used as vias too, even though they don't immediately appear to be the same thing, and they aren't obvious when looking at a PCB. Using a component pad as a via is usually a good idea if a proper soldering job is done, since the component lead increases the conductor area through the via. In addition, there are fewer holes to drill, thus reducing fab costs.

For the Beta and rev1.0 boards, we've judiciously applied vias in a number of areas where they should improve the design overall... side-to-side connections for the identical high-current traces, and at points where signal traces join these double-sided high current areas of copper. In some cases, there are signal traces run on both sides, and component pads are used to join them along their length. Note that these are all parallel connections. Since we went with such a heavy plating, I was more comfortable than usual in applying vias. In our case, the vias are plated with a hefty 1.5oz, and outer layers are all 2oz. Even so, you'll notice that there are few vias used as series connections along traces. My only dissapointment with the beta boards is that the manufacturer stepped up most of my specified drill sizes too much, so there are a few vias where the annular ring is pretty skimpy. Thanks to the heavy plating, this should have no electrical effect, but I like to see some larger annular rings on vias and pads. This will be corrected on the rev1.0 boards. Speaking of which, do you find the Beta hole sizes too large in general? Would you prefer smaller holes?

When designing a ground-plane layout, the priority usually goes to the plane first, so that vias are used more often than usual, to ensure that holes and slots in the plane are minimized.
 
#1,445
To judge from other threads recently I think some think the main reason to not use vias is that any via would, AFAIK, mean at least 2 solder joints extra compared to no via. The number of solder joints should perhaps be minmized it seems as some claim that the fewer solder joints in the signal path the better sound.

/UrSv
 
#1,446
Umm... there are no solder joints in a via. It is one continuous piece of copper with the traces on both sides - it's electroplated in place to coat the inside of the hole simultaneously as the top and bottom layers are coated with the same copper. If there is no solder mask over the via, then there may be solder plating applied when the component pads are also solder coated. But, in the case of my Aleph-X boards, all vias are completely solder-masked, so there is only copper through the via.
 
#1,449
gnomus

gnomus said:
It seems every one wants more power. Not me. 30 to 50 watts is plenty.

Can the board work for lower power?

How many mosfets would be needed?

And I guess all the same adjustments for adding power would be needed for less power output?. How would these be calculated?

Thanks in advance.
Click to expand...

HI gnomus,

i`m owner of an absolute superb sounding x Soz and Xbosoz.
But since i plan to build new speakers with less than 85db efficienciy i must build an amp with more power, say about 100 Watts. And i hope i can realize that with aleph x.

I`m not one of the persons, who always want to have lots of watts. in earlier times i had very efficient speakers which drove with 3 watts tube amps. but with less than 85db 30 -50 watts are too less..


regards,

Ralf
 
#1,452
diyman
you could still use the original to220 mosfet WITH the lm329 voltage reference, by original I mean whatever grey put it the original schematic which, not incidentally, is what Nelson is using as well in the XA. I believe that Fred decided to go to the ZVP to get a more ideal CS with higher impedance.
 
#1,453
hifiZen said:
Speaking of which, do you find the Beta hole sizes too large in general? Would you prefer smaller holes?

When designing a ground-plane layout, the priority usually goes to the plane first, so that vias are used more often than usual, to ensure that holes and slots in the plane are minimized.
Click to expand...

As long as the plating in vias is thick, it shouldn't make much difference indeed. As to the hole size I found them just about perfect. While it's true that they might be too large for Beyschlag resistors from Digi-Key, yet the can't be any smaller for 1/2W Holcos or Vishays. Also the holes for semis are right on the mark. The pads could probably be a bit bigger, but again, with that amount of in hole plating it's still OK.😉
 

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#1,454
#1,458
about the XA manual:

the comparison between the 650W consumption to that of a small hair drier is very cute. I wonder who came up with that first. I use it with my wife all the time when explaining the electricity bill while acting perplexed.
The parallel relates to something she has no problem understanding. However, when I turn around and buy $300 worth of heatsinks she becomes confused, upset, and hurt. :bawling:
 
#1,459
Taken from XA manual:

"In addition to a main power switch the amplifier has
a standby mode, which shuts down the bias to the
circuit while keeping the supply active, significantly
extending the life of the filter capacitors."

Mr. Pass would mind explaining how this feature is implemented. My wife started to complain about electrical bill as well and I usually have my amps on all day.😉

Is it done around Q104 (Aleph 3) or some other way?
 
#1,460
The parallel relates to something she has no problem understanding. However, when I turn around and buy $300 worth of heatsinks she becomes confused, upset, and hurt.
Click to expand...
Why telling her about $300 purchase at all? Why don`t make her (and You) a favour and tell her You made a fantastic deal and the stuff was only $30 - works always fine for me.😀 😉
Good that women do nothing (in general) understand of DIY-Audio parts prices - with clothes this wouldn`t be so easy working...
 
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