hello,
I am building a Aleph 4, with a 40-0-40 power supply. However I it seems now it looks I have a overkill in heatsinks (I know sounds stupid). I am using two times the Fischer Elektronik SK160 which is a ribbed (for your pleasure) 500mm x 250mm x 80mm heatsink with a 0.1 C/W value a piece.
My question: I am thinking of changing it in a Aleph 2 when it indeed seems I have a overkill of heaksinks. I need to change the 1.5 ohm into 1.0 ohm and some other small changes. But I still will have the 40-0-40 power supply which will give something in the range fo 48.8V of power.
Is it a problem of running a Aleph 2 circuit on 48.8 instead on 45V?
Is it a problem to use the ZTX450 instead of the MPSA18 ?
I hope it does not, so I can change to it. The reason is, I already bought the 1.5 ohm resistors and the power supply, but I found the huge powersinks. They are available for 'only' 200 euro a piece (a real steal ;-)) but hey, I will have a big amp!
Edwin
I am building a Aleph 4, with a 40-0-40 power supply. However I it seems now it looks I have a overkill in heatsinks (I know sounds stupid). I am using two times the Fischer Elektronik SK160 which is a ribbed (for your pleasure) 500mm x 250mm x 80mm heatsink with a 0.1 C/W value a piece.
My question: I am thinking of changing it in a Aleph 2 when it indeed seems I have a overkill of heaksinks. I need to change the 1.5 ohm into 1.0 ohm and some other small changes. But I still will have the 40-0-40 power supply which will give something in the range fo 48.8V of power.
Is it a problem of running a Aleph 2 circuit on 48.8 instead on 45V?
Is it a problem to use the ZTX450 instead of the MPSA18 ?
I hope it does not, so I can change to it. The reason is, I already bought the 1.5 ohm resistors and the power supply, but I found the huge powersinks. They are available for 'only' 200 euro a piece (a real steal ;-)) but hey, I will have a big amp!
Edwin
I believe that the ZTX450 and the MPSA18 are basically the same thing.
As for the increased power supply, you could always put a couple of big inductors / choke on your power supply, which would take a way a couple of volts.
As for the size of the heatsinks, if my conversions are right, they are about 20" x 10" x 3.15". That is a large pair of heatsinks, but I would recommend trying your stock Aleph 4 setup, and if it is running too cool, then swapping out the resistors and measuring the temperature again. I will be using 4 heatsinks the that are 8" x 9" x 2.6" for each channel of my aleph 2, which probably is overkill. I have a suspicion that your heatsinks might work great for a stock Aleph 4.
My heatsinks
Do you have any pictures of the heatsinks? I am curious to see what a ribbed heatsink looks like. Does it provide for a more pleasurable sounding amplifier?
--
Brian
gte619j@prism.gatech.edu
As for the increased power supply, you could always put a couple of big inductors / choke on your power supply, which would take a way a couple of volts.
As for the size of the heatsinks, if my conversions are right, they are about 20" x 10" x 3.15". That is a large pair of heatsinks, but I would recommend trying your stock Aleph 4 setup, and if it is running too cool, then swapping out the resistors and measuring the temperature again. I will be using 4 heatsinks the that are 8" x 9" x 2.6" for each channel of my aleph 2, which probably is overkill. I have a suspicion that your heatsinks might work great for a stock Aleph 4.
My heatsinks
Do you have any pictures of the heatsinks? I am curious to see what a ribbed heatsink looks like. Does it provide for a more pleasurable sounding amplifier?
--
Brian
gte619j@prism.gatech.edu
I believe he is using Nelson's figure of multiplying by 1.2, which seems to be accurate under load in an amplifier. It is pretty close to accurate in the leach amplifier that I made a couple of months ago.
As for multiplying by 1.41, that is assuming ideal conditions, such as no resistance.
--
Brian
gte619j@prism.gatech.edu
As for multiplying by 1.41, that is assuming ideal conditions, such as no resistance.
--
Brian
gte619j@prism.gatech.edu
Brian,
I think it depends upon how the transformer is specified. Normally this should be under full load with a 1-3% increase at idle (for large transformers.
With the amps I build 1.4 wasn´t too far off (30V-0-30V ac gave +43-0--43 with a bit over 1A bias).
A faktor of 1.2 would give 36 volts wich even at 2.5 amps would mean over 2R of resistance.
I´ll tell you what happens to the Aleph5 I´m building.
william
I think it depends upon how the transformer is specified. Normally this should be under full load with a 1-3% increase at idle (for large transformers.
With the amps I build 1.4 wasn´t too far off (30V-0-30V ac gave +43-0--43 with a bit over 1A bias).
A faktor of 1.2 would give 36 volts wich even at 2.5 amps would mean over 2R of resistance.
I´ll tell you what happens to the Aleph5 I´m building.
william
Brian,
this is the heatsink:
http://www.fischerelektronik.de/fischer/DB_Ansicht.asp?uebersicht=1&sub.x=165&sub.y=14
this is the heatsink:
http://www.fischerelektronik.de/fischer/DB_Ansicht.asp?uebersicht=1&sub.x=165&sub.y=14
Hello,
not only the Nelson factor but a factor from a big transformer company: amplimo here in the Netherlands. They advice the following formula (badly translated from dutch).
Unloaded the voltages are x % higher: 15VA 19%, 30VA 17%, 50VA 12%, 80VA 10%, 120VA 8%, 160VA 7%, 225VA 7%, 300VA 5%, 500VA 4½%, 625VA 4%, 800VA 4%, 1000VA 3½%.
By converting AC to DC the DC part is about factor X times AC when you load the transformer about 63%. This faktor is ca. 1,1 for AC of about 12V secundair, and for 30V it is ca. 1,2, and for 100V ca. 1,25 and for 230V ca. 1,3.
Unloaded it is about 1.4x + the unloaded percentage!
This verififies more or less Nelsons quote of about DC=AC * 1.2 !
BUT: How about my question: Is it a problem of running a Aleph 2 circuit on 48.8 instead on 45V?
Thanx,
Edwin
not only the Nelson factor but a factor from a big transformer company: amplimo here in the Netherlands. They advice the following formula (badly translated from dutch).
Unloaded the voltages are x % higher: 15VA 19%, 30VA 17%, 50VA 12%, 80VA 10%, 120VA 8%, 160VA 7%, 225VA 7%, 300VA 5%, 500VA 4½%, 625VA 4%, 800VA 4%, 1000VA 3½%.
By converting AC to DC the DC part is about factor X times AC when you load the transformer about 63%. This faktor is ca. 1,1 for AC of about 12V secundair, and for 30V it is ca. 1,2, and for 100V ca. 1,25 and for 230V ca. 1,3.
Unloaded it is about 1.4x + the unloaded percentage!
This verififies more or less Nelsons quote of about DC=AC * 1.2 !
BUT: How about my question: Is it a problem of running a Aleph 2 circuit on 48.8 instead on 45V?
Thanx,
Edwin
BrianGT said:
The end rail voltage will depend on a number of factors. The Plitron transformers are beefy and tend to run just about where you'd calculate simply from subtracting the diode losses in the bridge, i.e. a 30-0-30VAC transformer yields about a 42VDC rail. (Incidentally, the no-load VAC coming off of the transformer is about a volt high. Just ignore that and calculate from the rated voltage.)
On the other hand, some surplus 1kVA transformers I got drop an extra volt or two. The final multiplier there (and this includes the diode drop through the bridge), was on the order of 1.3 or so.
Moral of the story--buy a good, hefty transformer.
Grey
On the other hand, some surplus 1kVA transformers I got drop an extra volt or two. The final multiplier there (and this includes the diode drop through the bridge), was on the order of 1.3 or so.
Moral of the story--buy a good, hefty transformer.
Grey
I take it from this later comment you are looking at monoblocks, each with 2x these heatsinks?
If so, then you are in Aleph 1.2 territory - and with this hardware, why not?
No to the first, and no to the second.
I actually e-mailed Nelson about the MPSA18/ZTX450 point recently and his reply read:
Hope this helps,
cheers, mark
Thanks!
I am not building mono's. I do not like the hassle with two separate cabinets etc. I want to build a stereo Aleph 2 ! So I only have two of these monster heatsinks and not 4.
Thanks for you answers about the transisitors and power supply!
Edwin
--------------------------------------------------------------------------------
I am using two times the Fischer Elektronik SK160 which is a ribbed (for your pleasure) 500mm x 250mm x 80mm heatsink with a 0.1 C/W value a piece. My question: I am thinking of changing it in a Aleph 2 when it indeed seems I have a overkill of heaksinks.
--------------------------------------------------------------------------------
I take it from this later comment you are looking at monoblocks, each with 2x these heatsinks?
If so, then you are in Aleph 1.2 territory - and with this hardware, why not?
quote:
--------------------------------------------------------------------------------
Is it a problem of running a Aleph 2 circuit on 48.8 instead on 45V?
Is it a problem to use the ZTX450 instead of the MPSA18 ?
--------------------------------------------------------------------------------
No to the first, and no to the second.
I actually e-mailed Nelson about the MPSA18/ZTX450 point recently and his reply read:
quote:
--------------------------------------------------------------------------------
The bipolars in this circuit are completely generic, and the ZTX450's were chosen for price and availability.
np
--------------------------------------------------------------------------------
Hope this helps,
cheers, mark
I am not building mono's. I do not like the hassle with two separate cabinets etc. I want to build a stereo Aleph 2 ! So I only have two of these monster heatsinks and not 4.
Thanks for you answers about the transisitors and power supply!
Edwin
--------------------------------------------------------------------------------
I am using two times the Fischer Elektronik SK160 which is a ribbed (for your pleasure) 500mm x 250mm x 80mm heatsink with a 0.1 C/W value a piece. My question: I am thinking of changing it in a Aleph 2 when it indeed seems I have a overkill of heaksinks.
--------------------------------------------------------------------------------
I take it from this later comment you are looking at monoblocks, each with 2x these heatsinks?
If so, then you are in Aleph 1.2 territory - and with this hardware, why not?
quote:
--------------------------------------------------------------------------------
Is it a problem of running a Aleph 2 circuit on 48.8 instead on 45V?
Is it a problem to use the ZTX450 instead of the MPSA18 ?
--------------------------------------------------------------------------------
No to the first, and no to the second.
I actually e-mailed Nelson about the MPSA18/ZTX450 point recently and his reply read:
quote:
--------------------------------------------------------------------------------
The bipolars in this circuit are completely generic, and the ZTX450's were chosen for price and availability.
np
--------------------------------------------------------------------------------
Hope this helps,
cheers, mark
BrianGT said:
Thanks,
one small question, there is a small difference in the setup of the 1nf and 220uf capacitor around the MPSA18 incomparision to the Aleph 4. Also there is a swap of the 220uf and 619R between the diagrams.
Can I same layout of the Aleph 4 for the Aleph 2 (without switching routes of parts) and only change the resistors and the 680pf into a 1nf ?
Many thanks,
Edwin
For the difference in the arrangement of the npn compensation cap (C7 on the Aleph 2), it does not matter if it goes across the collector emitter, or the collector base, as long as the correct value is used (0.001uF for collector base, and 0.01uF (labeled 103) for collector emitter). The existing setup of the Aleph 4 should be fine here.
For the connection of the 220uF (C9 in the Aleph 2), it does not really make any difference in the operation of the circuit. The majority of the Aleph schematics and the patent schematic are done the say way that the aleph 4 circuit is done. For the pcbs I made for the aleph, I kept to the way that the aleph 4 is wired. You should not need changes here.
The only real change that I forsee in the transformation from Aleph 4 to 2 would be to change the resistors near the ZTX450, which if I can remember, set up the biasing current for the current source. I am not sure what values you would want to use here.
The board layout for the Aleph 4 should work fine for the Aleph 2, with minor component changes.
--
Brian
gte619j@prism.gatech.edu
For the connection of the 220uF (C9 in the Aleph 2), it does not really make any difference in the operation of the circuit. The majority of the Aleph schematics and the patent schematic are done the say way that the aleph 4 circuit is done. For the pcbs I made for the aleph, I kept to the way that the aleph 4 is wired. You should not need changes here.
The only real change that I forsee in the transformation from Aleph 4 to 2 would be to change the resistors near the ZTX450, which if I can remember, set up the biasing current for the current source. I am not sure what values you would want to use here.
The board layout for the Aleph 4 should work fine for the Aleph 2, with minor component changes.
--
Brian
gte619j@prism.gatech.edu
promitheus said:
I see you live in germany! I can mail you some! I have about 100 of the suckers (minimum order amount :-( )
How many do you need ? (4?)
Give me your home address and I put some of them in a envelop for free!
Do you want to buy matched IRFP240's and/or IRF9610 ? I matched them from 60xirfp240 and 25xirf9610 and they matched damn good, they are all the same lot-code !
Let me know,
Edwin
Substitute for ZTX450
promitheus,
It seems like just about any npn transistor can be used as substitute for ZTX450.
Check out this thread..
http://www.diyaudio.com/forums/showthread.php?threadid=1553&highlight=generic
/Freddie
promitheus,
It seems like just about any npn transistor can be used as substitute for ZTX450.
Check out this thread..
http://www.diyaudio.com/forums/showthread.php?threadid=1553&highlight=generic
/Freddie
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