| MikeZ |
I am working on the power supply for an aleph 2 monoblock and I am trying to learn electronics as I build the amp. The toroid purchase has me a little confused. I want a 1000va toroid, thats my preference per Nelson Pass response to a post prior "You can, of course, always get away with less, and it
also depends on the conservativeness of the manufacturer's
ratings" , but what do I use for the output voltage, 30+30, 33+33 or 35+35 etc. What dictates the value of the output voltage.
that brings me to my next question, when I call a toroid manufacturer what do I tell him I want for example "a shielded 1000va 33+33 toroid."
And finally I read in the post about noise in the amplifier due to the power supply and using inductors to recuce this. As I am learning electronics, does a circuit diagram exist which shows the power supply circuit with said inductors. |
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| kristijan-k |
Hello MikeZ,
Here is the one example of the circuit diagram for the Aleph 2
power supply.
Hopeing that will help you.
Best regards.
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip |
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| MikeZ |
| Kristijan, So if I understand your schematic, It calls for a 1000va, 37+37 toroid? Thanks Mike |
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| Peter Daniel |
| I have two 1000VA toroids from Victoria Magnetics which were custom made specifically for Aleph 2. I plan on Aleph X now, so I want to get rid of those trafos. If you are interested contact me. I'm asking $100 USD ea. plus shipping. |
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| fcel |
| JasonL ... I hope you mean it this time ... just kidding. |
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| JasonL |
| last time some one else got them : O ( sniff sniff. |
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| kristijan-k |
Hello MikeZ,
For the one channel-monoblock of the Aleph 2
power supply, you can use transformers from
at least 600 VA and up.
The 1000 VA transformer is very good choice
for the Aleph 2 amplifier and I would use it
without a seccond tought.
Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip |
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| Mark A. Gulbrandsen |
Mike,
Best of luck building yours....don't hesitate to post here with questions. I've built alot of different amps over the years but the Alsph 2 is something VERY special as you will eventually find out. I used a 769 VA toroid that I was able to buy locally and it works just fine. The Victoria Magnetics toroids are very good, so go for it......I know some of the people down there at the factory and I will be using their toroids on my future projects.
Mark |
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| grataku |
Mike,
Krystian PS is excellent, be sure to understand how it works, what type of coil you need, the wire gauge for this coil, how to arrange everything in the enclosure so that the coils don't disturb the low level input signals etc. It's going to be VERY BULKY, heavy, and expensive. Do you have the heatsinks? |
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| JasonL |
| If i may ask what do the 3,9mh Coials do in the psu section. Do you have to use them.? What happens if i dont have a set up like Kristians. im planning on useing 4 x 70k cap 80v 4 per mono block ( for my aleph 2's ) Is this ok. Im going to buy peter's vc magnetics transformers. and use them i have done lots of research and found that they will work awsome. And they look niceer too. : O ) |
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| MikeZ |
Thanks for all the input. I have heatsinks already. I am in the process of getting some of BrianGT aleph boards. I wont have any trouble stuffing the boards but I am at a disadvantage understanding some of the basics of the power supply, I am planning on victoria magnetics shielded 1000va. I am planning on using the power supply kristijan-k supplied earlier. I want to purchase my toroids now for two monoblocks and I dont know what output voltage to I use? Per kristijan-k schematic I get the impression I must use 37+37.
Is 37+37 correct for the toroid output voltage for the kristijan-k circuit? Or can I use 35+35 or 33+33 or something else? Or do I just call victoria magnetics and say "I want a shielded 1000va toroid"?
Thanks Mike |
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| jh6you |
Instead of the multiplier of 1.414, we normally use the ideally approximated value of 1.20. For example, if V(rms) is 37, V(peak) is estimated as 37x1.2 ~ 44.4 V(peak). Therefore, the secondary of 37+37 is quite ideal for the +/- 45 Vdc we want to have.
35+35 and 33+33 could be used if we are ready to accept somewhat reduced maximum output powers.
The transformer supplier will always ask us about our requirement of power rating, primary voltage and secondary voltage, etc. |
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| fcel |
Mike,
When you are ready to order, just tell the transf manuf the following informations in this manner:
1000va transformer (I assume you're ordering 2)
120v primary
37v-0-37v sec
& shielded |
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| jh6you |
Instead of the 37v-0-37v secondary, I would tell them 2 x 37v secondary. Two 37v secondaries make both possible, i.e. (1) the original Aleph 2 PSU or (2)Kristijan-k PSU.
JH |
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| MikeZ |
Thanks so much for the ordering information, this is all very helpfull! I will now order the toroids.
Now for my next question on the power supply, G1 and G2 on kristijan-k schematic are rectifiers I believe, can anyone tell me what would be the best part number for this from digikey or mouser?
Thanks Mike |
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| harvardian |
Any 30 to 35A 400 to 600V bridge will work
Digikey part numbers
36MB60A-ND
GBPC3504DI-ND |
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| MikeZ |
Thanks harvardian.
For the capacitors what is the minimum voltage rating I should use?
On the Kristijan K schematic what does the MKP by the 4.7uF cap stand for?
Thanks Mike |
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| dshortt9 |
| 50 volts for the capacitors. The MKP is for Polypropylene as far as I know. 4.7 uf. anything from 3 - 10 should do well. |
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| MikeZ |
| how close to the actual values do the 68000 and the 47000 need to be? |
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| dshortt9 |
| They do not have to be very close. The real Aleph 2's have 4 x 25,000 uf caps per monoblock. Most clone builders are using at least this much and adding inductors to make a pi filter. 4 x 33,000 uf and 2 x 2 - 4 mh inductors would work fine. |
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| MikeZ |
dshortt9, That sounds better using fewer components, it would save some space in the amp. Is there any possibility you can sketch or explain the circuit "Most clone builders are using at least this much and adding inductors to make a pi filter. 4 x 33,000 uf and 2 x 2 - 4 mh inductors would work fine"
thanks mike |
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| dshortt9 |
| Look at the previous schematic and substitute one 33000 capacitor wherever two of other values are specified. A pi filter means that ain inductor is used between two capacitors, C-L-C. Two pi filters are needed, one for each polarity, + and - . |
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| MikeZ |
dshortt9, good explanation. Is 14 awg wire adequate for the wiring of the power supply? Any suggestions for some wirre that WOuld work for the power supply?
Thanks Mike |
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| dshortt9 |
| 14 should work fine. Have you looked at the Pass DIY page to get some layout ideas? http://www.passdiy.com/ Look in the Gallery. |
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| MikeZ |
dshortt9, No I have not studied the gallery yet, I wanted to get all the parts together first. Next I will lay them out and compare to what others have done in the gallery and try to create the best setup. I called http://www.brigarelectronics.com/ and ordered 8 of the caps today....thanks for telling me about that place.
What do you think about the inductors for the power supply earlier you said "2 x 2 - 4 mh inductors would work fine", would you use air core or copper foil? I used the copper foil for my speakers but I didnt know if it mattered for the power supply.
Thanks Mike |
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| dshortt9 |
| I also used copper foil in my ProAc 2.5 clones but air core inductors are fine for the Aleph PS |
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| dshortt9 |
| 4 mh ar quite large, 2.5's should do OK. What speakers did you build? |
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| Mark A. Gulbrandsen |
I am using 14 ga. silver plated copper that is teflon covered for my Aeph 2's. As usual I found his silver plated wire at the local Surplus place. Geez, they ahve everything there someplace......even 12 ga silver plated teflon covered wire that has a very unique 3 layer twist to it.......the 12 ga is a bit unweildly to work with though......
Also my toroids have a frame ground wire as well as allthe other primary and secondaries. Connecting this wire really quiets things down a bit so those looking ofr power transformers may want to be sure to get one with the extra ground wire.
Mark |
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| MikeZ |
dshortt9
I built a pair of 2 way speakers, woofer is a seas magnesium cone and tweeter is a seas too. If you are familiar with the Seas Odin, my speaker is exactly the same except I have one less woofer and a smaller enclosure. I really like them. My wife even liked them and could tell a difference. I enjoy building them myself hence the aleph 2 project.
Mike |
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| MikeZ |
Mark A. Gulbrandsen
I live in a relatively small town and havent found any good surplus stores. I end up mail ordering everything.
Mike |
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| Mark A. Gulbrandsen |
Mike, I used to live in Chicago and there was not any really good surplus place there either...just for metal. I am very lucky to have two good places here in SLC...One that has electronics parts in general and another that just has millions of vacuum tubes.
Mark |
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| MikeZ |
any suggestions where to get 4 inductors 2.5 mH 12 or 14 gauge?
Thanks Mike |
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| dshortt9 |
| Try this http://www.mcmelectronics.com/Home/...103&SKUID=34347 They do not specify the gauge of wire so I would call them first but the price is good and 2 mh will work just fine. You may as well order the 4.7 uf caps also as they have AXON Metallized Polypropylene which ar good. |
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| grataku |
Mike, any speaker supplier should stock good quality inductors for relatively cheap. Madisound or parts express come to mind. I would try to stay with a higher reactance and larger possible gauge wire to avoid excessive heating of the coil, it's always better to have the reactance do the filtering work for you. 2mH is good for 120 Hz, 4mH would be better. In Europe with 100Hz ripple 4mH is almost a must. The transformer would be the last thing to get. Before you buy that you should simulate the PS and make sure you don't end up with to much or too little voltage.
The MCM coils are CHEAP! You get what you pay for. They are probably going to heat up quite a bit and the voltage is going to drop quite a bitt too as a result.
I would dunk these in stycast or at least use a few wire wraps to hold them together a little bit better. |
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| dshortt9 |
grataku
I simulated this PS and came up with 20mv of ripple, excellent compared to the commercial Aleph 2 of about .5 v. If the MCM inductors are 16 gague at .5 ohm and 1.5 ohm reactance they are dissipating 18 watts of heat at 3A, not too bad. Tie wraps would be good for mechanical strength. Madisound wants 16.40 each for 14 ga. 2 mh inductors, and they are .31 ohm. They would still dissipate 15 watts of heat but over a larger area. Take your pick. Parts Express has them for a bit cheaper. 14 ga. at 2mh for 15 something each. http://www.partsexpress.com/pe/show...t_ID=6793&DID=7 |
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| MikeZ |
I will probably just use the air core from parts express as I am ordering some other items from them.
I appreciate all the help from everyone on the power supply and next I will be compilling the components for the main boards.
Any advice on what components are worth upgrading that are on the main board?
Thanks Mike |
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| dshortt9 |
| The Parts express inductors will be an excellent choice. Most people upgrade the source and sense resistors to non-inductive ones and upgrade the electrolytic coupling caps to high grade ones. Some say they cannot hear the difference in caps compared to Panasonic FC type and some swear they do. |
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| MikeZ |
dshortt9
I got 8 of the caps today from the place you referred me too, thanks Mike |
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