Aleph-X: High-Power Version

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Edwin Dorre

Member
Joined 2002
Aleph 4

0.47 / 6 * 1000
-------------------- = 0.508
1.5 / 6 * 619

0.47 / 6 = R52, 46, 43, 45, 44, 42

1.5 / 6 = 6 times the 1.5 ohm R at IRF244

1000 = R28

619 = R29

Accoording to the patent

R4 * R3
---------
R1 * R5

where I put in the values!

I like to know why GRollins choose the the second resistor 1K2 instead of 1K because with 1K he would have the perfect 50% !

Edwin
 
K

Kelly McDonald

Member
Joined 2001
BrianGT said:
Here is my first prototype with 8 devices, in its current state. If desired, we could work out a higher power pcb version, and get a group order together for those desiring more power.

--
Brian
Click to expand...


What about the possibility doing a group buy on some output boards that could be added to the existing 1.0 boards. Each could hold 3-4 devices, use 4 per amp.
 
nar

nar

Member
Joined 2002
Edwin,

Please find attachement for a 100W version by Blitz I found in the thread.

If you have a look at schematic,

AC gain = (0,47 / 6 X 1000 ) = 0,5
-----------------------
(0,47 / 6 X 2000 )


So R must be adjusted to 2 k ohms

Or set another value for the R series output....

Regards

Anael
 
E

Edwin Dorre

Member
Joined 2002
nar said:
Edwin,

Please find attachement for a 100W version by Blitz I found in the thread.

If you have a look at schematic,

AC gain = (0,47 / 6 X 1000 ) = 0,5
-----------------------
(0,47 / 6 X 2000 )


So R must be adjusted to 2 k ohms

Or set another value for the R series output....
Click to expand...

So far I understand the old Aleph circuit, and the X are as far as I know two of these together;

AC gain = (0,47 / 6 X 1000 ) = 0,5
-----------------------
(0,47 / 3 X 1000 )


So R must be adjusted to 1 k ohms because there are only 3 resistors parallel in the current source not 6. There are 6 resistors parallel in the sense-circuit. But I can be wrong. Grollings writes he used 1K2 because of thermal drifting. But 2K to 1K2 is a big drift...

I do not know why Nelson used two different values in the Aleph 2 (1 ohm and 0.47 ohm) and choose to change the other resistor to get 0.50 !

Edwin
 
E

Edwin Dorre

Member
Joined 2002
little update;

I think I know why Nelson used 6x 0.47 and 623 ohm instead of 6x 1 ohm and 1k;

6x 0.47 = 0.0783 ohm in serie with the loudspeaker

and

6x 1 = 0.16 ohm in serie with the loudspeaker

I think 0.0783 in serie mis-uses less power from the amp itself and gives a better damping factor!

Can somebody acknowledge this? And isn't 6x 0.22 better? Or will the feedback sense circuit stop working at a certain level?

Edwin
 
nar

nar

Member
Joined 2002
Edwin,

My calcs for the Aleph 2 give

(0,47/6 X 1000) / (1/6 X 681) =0,69

AC current gain is 69 % according to your formula and values in schematic of the Aleph 2.

On the specs of the amp,it is given for 100 W 8 ohms and more on 4 ohms.I guess this is because of the AC gain of the current source that it can deliver more current into lower impedance loads ;)

What do you think ?

I agree for the series impedance with the speaker less ohms gives better results I guess :nod: :nod: :nod:

Regards

Anael
 
E

Edwin Dorre

Member
Joined 2002
Sorry about the slip up between the Aleph 2 and 4 . Yes of course the Aleph 2 has about 69% and the Aleph 4 50% . The more the current source gains the more 'free' power. At a cost accoording to Nelson. He can not make his mind up as well (as I have read before somewhere) between the 523 or 619 resistors. More power, or more 'real' class A .

Ok, so we both agree that the resistor 1K2 of GRollins looks a bit off. Ok, I am glad I am not the only one!

Edwin
 
E

Edwin Dorre

Member
Joined 2002
Nelson Pass said:
The 69% figure is too high. Actual current gain on an Aleph 2
is close to 50%.

Also, I have no difficulty making up my mind at all. Every amplifier is a little different, and once the value is fixed, it stays.
Click to expand...

Ok,

So the only way to know is to calculate and put in a sensible value and a pot and measure the gain ?

About the 'making up your mind' I was referring to Mark Finnis his quote;

"Another point of confusion is the value of R29. This is different on the 2 circuit diagrams in the service manual. On questioning Nelson has stated, "the value of R29 has varied over the production life of the amp, personally I prefer the higher value", so I went for 620ohm"

Edwin
 
E

Edwin Dorre

Member
Joined 2002
Perhaps you guys can use this as well!

I updated the wuffwaff excel sheet to have the K/W value calculated, a nice graph from 0.5 ohm to 12 ohm and all the watt values from 0.5 ohm to 12 ohm... It helped me alot to find the sweet spot between dissipation, watt at which ohm etc.

Edwin
 

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U

ungie

Member
Joined 2002
Since this thread has seemed to die out somewhat, I thought I would pick it up again by asking some questions! :rolleyes:

How many of you are in the process of actually buidling a high powered version of the X?

Has anyone successfully built and used one yet?

If so, can you give us some details on number of output devices, transformer details, power supply, fancy passives, etc?

How about thermal issues?

Finally, is there enough interest here to look into a small group purchase of transformers? :)

Good listening!

Andrew
 
Netlist

Netlist

Moderator
Joined 2003
Paid Member
ungie said:
How many of you are in the process of actually buidling a high powered version of the X?

Andrew
Click to expand...

Parts are slowly coming in;
what I have so far:

4 massive heatsinks 30*30*4cm 0.3°C/W (hope this will be enough)
8 Panasonic GBA 68.000µF/25V 105°C
Enough selected IRFP240's to put 16 of them in a monoblock.
Enough IFR9610's to build the current sources.
TL431CLP for the current sources.
Enough source resistors 0.47ohm(?) silicone wirewound from Meggitt.
2 Bridge rectifiers IR 26MB40A
Still searching for good trafo's.
Struggling with voltages: 2X18V, 2X 20V; don't know.
Thinking of the possibility to work P2P.
So nothing exotic here.

/Hugo - will keep you informed ;)
 
wuffwaff

wuffwaff

Member
Joined 2001
ungie said:
Since this thread has seemed to die out somewhat, I thought I would pick it up again by asking some questions! :rolleyes:

How many of you are in the process of actually buidling a high powered version of the X?

!

Andrew
Click to expand...


Hello Andrew,

I´m also waiting for parts to complete the amp.
What I´ve got is 4x SK157/200 heatsinks (0,2°/K)
Most semiconductors (16 IRFP240 per channel)
All of the caps in 1000 and 3300uF portions for about 0.3F per channel.

Resistors (dale) and Transformers (800VA 18V) are ordered.

Still not shure what chokes to use. I wanted to use torobars (2.2mH / 0.12 Ohm) but I still haven´t got an answer from Intertechnik about the DC-saturation current. I think I´ll use air chokes instead but with lower inductance (about 1mH) cause otherwise they won´t fit and dc-resistance will be too high.

Still not shure if I´ll make a print for the amp or do it point to point.
 
U

ungie

Member
Joined 2002
High-Power Aleph-X Parts and Boards

Well, this thread has died off again!
I hope all of you are busy working on your high-power Aleph-X's which is why no-one is posting pics of their projects yet!

First off, does anyone have any extra Aleph-X PCBs? :bawling:
Please contact me directly if you can help me out.

Secondly, here are the parts for my Aleph-X so far, in case anyone's interested! ;)

I will be building 100W (or thereabouts) monoblocs.
Each channel will have:

2 R-Theta group buy heatsinks (11"x11"x2.3")
12 IRFP044 output fets per channel
Dale or Panasonic 3W power resistors (0.47 or 0.68ohms depending if I build based on Grey's original design or the Ian MacMillan version posted a page or two back)
Dale/Vishay signal resisitors, or Beyschlag from Digikey?

Power Supply will consist of CRC filter using
4 40,000uf/70V Nippon-Chemicon Caps bypassed with Wimas or Roes
Paralleled Keystone CL-60 termistors a-la Peter Dainel
750 VA Plitron or ? toroidals with dual 18 or 20 V windings (maybe higher voltage based on the supply sag that Peter Daniel experienced)
Dual discrete bridges (haven't decided on what diodes yet, suggestions?)

If I am unable to obtain some PC Boards I will have to resort to Vector perf board (anyone in Toronto know where I can find some cheap??)

That's it so far.
Comments/Questions/Suggestions?? :scratch:

Andrew
 
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