The Aleph-X

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#2,344
I am still looking for a good speaker protection to implement in my future Aleph-X s .

Nelson stated that if one power mos of the 2 output stages failed , the DC was tracked automatically to the other side , thus staying at a minimum differential output DC .

Well , this is good news indeed , but ...

1) what happens to the differential output DC if a mos on one of the 2 ALEPH CURRENT SOURCE fails ???

2) If same thing happens in a regular Aleph , what about the DC at the output ? Is a mains protection ( i.e. fuse + thermistor + temp sensor ) enough to protect high value speakers in case of failure in the amp ? :bigeyes:

I ran questions again because one certainly wants to keep his speakers OK in case of a failure into an Aleph or an Aleph X ... 🙄

So what to do ? It is a differential sensor we need watch the differences in DC between the 2 outputs !!!

Help !!! Thanks in advance :devily:

Best regards

Anael
 
#2,346
nar said:
1) what happens to the differential output DC if a mos on one of the 2 ALEPH CURRENT SOURCE fails ???

2) If same thing happens in a regular Aleph , what about the DC at the output ? Is a mains protection ( i.e. fuse + thermistor + temp sensor ) enough to protect high value speakers in case of failure in the amp ? :bigeyes:
Click to expand...

People worry too much about amplifiers failing in such a way
as to break their speakers. If your speakers cost a fortune
or are otherwise irreplaceable, I suppose this concern might be
justified, but in my experience the probabliity of an Aleph or
X Aleph taking out a speaker in failing is just about nil.

If you still can't sleep at night, then build one of the many speaker protection projects. There is no lack of them on the
net or in the magazines such as AudioXpress.
 
#2,347
Hi,
I have breifly scanned through this whole thread over the past few days have decided to build a fairly low power Aleph-X. Here is what I'm going for:

+- 17.5V
6A Bias
and 12 Fets per Channel

I don't really know what I'm talking about here so I'm hoping someone can point me in the right direction or to a relevant post / thread.

This setup puts about 60W into an 8R load. My questions are as follows:

1) Is there some artwork (preferablly single sided but not a must) that I can use to run my own boards.

2) Where is the relevant schematic for 1)

3) Will two 0.35degC/W heatsinks be enough. I calculate the dissipation to be 210W so 105W per heatsink. That equates to 36.75degC about room which is 57.75degC. Is that acceptable?

4) These will be monoblocks. Is a 500VA xformer enough?

5) Is there a suitable PSU schematic anywhere?

6) Finally - Is the really a need for so much capacitance? Why so much - can you get away with less?! Are they just part of the PSU?


Thanks so much! Any help is really appreciated!

Thanks again,
Gaz
 
#2,348
1. There are at least two.
2. Yes, They should be on this thread. If you can't find them E-mail me and I can send them.
3. For Mono's maybe
4. 500 is plenty
5. There are many
6. It seems like alot but you need it to get rid of the ripple. Caps at lower voltage are cheaper.
Someone may have extra boards to sell. It would be cheaper than making your own.
 
#2,350
Hi Rarkow
IMO, With this setup you can get about 60W peak. With 17.5V rail the signal swing can achieve about 23V peak max. Than 6 A total bias for one channel will be enough. But I don't understand why do you want 12 Fets for this? I would start with four. More Fets more troubles with work.
:bawling:
 
#2,351
Hi,
I didn't think I'd be able to get away with so few FETs considering the dissapation that goes through them...I'll start with 4...

Thanks for the advice and also the money saving!

BTW - what is a typical percentage for the third item in that spreadsheet. I think it was how much of the bias does the CCS source? What is it?

Thanks,
Gaz
 
#2,352
Rarkov said:
Hi,
6) Finally - Is the really a need for so much capacitance? Why so much - can you get away with less?! Are they just part of the PSU?
Click to expand...

I'd go with 8 fets, 12 is too much and 4 definitely too few (unless you lower the bias or the rails)

This is a good place to find some good caps with not so much $$ (or ££)

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2547460464

But you have to promise to sell me some if you buy them!
😉

Cheers

Andrea

PS I have 4 Aleph-X boards that I plan to use to bi-amp my system, but in case I won't I'll let you know (will take time tough, slowly building the first 2 channels...)
They are from the group buy, 2 sides
 
#2,355
Personally, with 17.5V rail I would stay with 4 Fets, even if decreasing bias would be necessary. With 8 ohm speakers it isn’t a problem. But even with 3 A bias per side it gives about 50 W dissipation per device. IRFP044 can dissipate about 120W at 60 deg C. I think , there wouldn’t be a disaster here.
With 8 Fets I’d go for 20V per rail.
Regards
 
#2,357
Now you're all just confusing me! I will go for 8. That seems to be a nice half way house. I take it that it means I need 16 fets for a stereo pair of Aleph X. I will put some figures into my spread sheet when I get home from work.

I am trying to get hold of some boards...I'm talking to someone at the moment...We'll see how that goes!

Thanks,
Gaz
 
#2,359
Hi,
8 fets is what I would use especially if you plan to run them at 36 deg C above room temp (which realistically probably means 65 deg at the sink). That is pretty HIGH, higher than I would go anyways.
That should give you high bias for sweet sound and a good safety margin. One thing that is of PARAMOUNT importance is the placement of the boards in such a way as to allow access to trimpot adjustment under under the final operating conditions with the complete enclosure.
 
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