Aleph X transformer thread

[BrianGT]

Originally posted by Peter Daniel
One other thing to consider is a transformer. At least choosing a proper size and voltage. Canadian orders will use Plitron most likely, USA customers might go for VM. As always shipping is the major issue. And Plitron is in Toronto.

I talked to John at Victoria Magnetics about transformers, and I got mine from him. It is possible to organize a group order of the transformers, and get a lower price, and then John deal with everyone seperately for ordering and shipping. He is quite willing to work on us for the custom transformers. His prices aren't too bad, considering the high quality and the custom nature of the transformers.

If you are interested, note how many transformers you would be needing, and what specs, and I can get a price quote from John at VM.

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Brian

[harvardian]

Hi Brian,

Count me in.

Something like 500VA, 2X12VAC

I'd like 4.

Best Regards,

Dale

[haldor]

Hi Brian,

What kind of pricing did you get from VM?

Plitron doesn't have a standard dual 12 V, 500 VA rated transformer. I have ordered specials from Plitron in the past and the upcharge was minor. I expect that if we get the quantity high enough any custom charge will be very low. Plitrons standard, 500 VA transformer sells for around $52 US in volume.

If going the custom route I strongly recommend including a thermal cutout switch. This adds a dollar or so of cost and adds piece of mind to the project.

I would be interested in 2, 500 VA dual 12V transformers.

Since over 500 Aleph X PCB's were bought I expect we could hit at least 100 quantity of transformers. We will need to work out a way to do direct shipment though, double shipping would hurt cost wise (plus what a lot of work).

Phil

[BrianGT]

I will give him a call today, and see what kind of pricing he can work out for us. So, 500VA dual 12v with shield on outside is a good spec to work from?

Regarding shipping and billing, he said that he could bill and ship them out all seperately.

I made a wiki page similar to the heatsinks page for people to express interest.
http://www.diyaudio.com/wiki/index.p...rs+for+Aleph-X

One more thing, shipping in the US should be less from VM than from Plitron in canada. His leadtimes aren't too bad, depending on how much other orders he has ahead of this. I can find this out also.

--
Brian

[BrianGT]

I went down there today and talked to John. For 10 or more transformers, the cost for a 500VA dual 12v secondaries will run $62. This includes a shield on the outside of the transformer. For $65, he can make it 600VA instead, making the wiring a larger gauge on the same core.

For shipping, go to theUPS website and enter shipping from zip code 30071. The weight of 2 transformers is 15lbs.

Here is a picture of what it would look like, except a little smaller (this is a 1kva) and will have dual secondaries, instead of centertapped.

--
Brian

[BrianGT]

I picked up some transformers for my stereo Aleph5 and stereo Aleph-X. The Aleph5 is 25vac secondaries, and the Aleph-X is 12.5vac secondaries. They are both 1kVA, and have 4 pairs of secondaries for 2 channels. They also both have a faraday shield between the primary and secondary windings. I am going to use these to build both a stereo aleph5 and a stereo aleph-x.

I will also pick up a pair of 600va dual 12vac transformers for a pair of aleph-x monoblocks.

--
Brian

[fcel]

Brian,

I was thinking of going over the 100 pages of the Aleph-X thread over the holidays but since you guys are going full speed ahead with this project and since these are electrical components that we are ordering, I thought I might check with you guys first before I commit to any transformer order. Here are some questions I have in regards to the electrical items in addition to the transformers that we are discussing here.

1. Has anybody posted a complete parts list that we are all following? If yes, could you direct me to it? So far, I have only seen Chad/Grataku parts list (without part numbers) and I have to studied some more to figure out what some of those options means. I wonder if Peter has posted his parts list (no need for exotic parts for me for now) since he's the only one that I know of that has build the Aleph-X?

2. It seems that so far everybody is ordering 500VA transformer with dual 12.5v sec. Is that the standard that we are going to go by? Doesn't higher power output requires bigger transformer? Or does it depend on quantity of output mosfet? What I have read (bits and pieces) so far is that Peter's amp has 15v rail and has 16 mosfets per channel and he's getting about 80 watts/ch.

3. I'm aiming for 60 to 80 watts per channel for my Aleph-X. How many mosfets do I need per channel? I have a set of mosfets that I got from "harvadian" that was originally intended for another Aleph 2 but now I think I want to build Aleph-X. Would that set of mosfets be sufficient to get 60 to 80 watts per channel? I assumed Aleph-X does requires matched transistors too?

4. For more quantity of output mosfets, do I just connect them in parallel with a source resistor for each mosfet with the exception that only one of these output mosfets requires a sense resistor .. just like Aleph 2?

5. I might as well ask about the capacitors too. What is the required minimum total capacitance value per channel for this amp and the min voltage rating of each cap?

6. I understand that you're making your own boards. Are they any different from Grataku/Chad's board other than the look of it? And are you using exactly the same circuit diagram that was posted by Grataku/Chad?

Thanks.

[BrianGT]

Originally posted by fcel
Brian,
1. Has anybody posted a complete parts list that we are all following?

I don't know of one, but I am just going from the schematic posted by Grey. I am using Vishay Dale RN60D resistors for the 1/4 watt ones, and panasonic 3w ones for the larger resistors.

Originally posted by fcel
2. It seems that so far everybody is ordering 500VA transformer with dual 12.5v sec. Is that the standard that we are going to go by?

Actually, it seems that dual 11v secondaries are pretty common for the first people ordering transformers. I ordered 12.5v for my first one, because I wanted arount 17v, aiming for a little more. 11v secondaries should give around 15v rectified. I figured that 12v is good for monoblocks, because some will be lost for from the CRCRC filtering, and the voltage might drop for the high current. I am going to set the current as high as I can get it for the heatsinks that are in the group order.

Originally posted by fcel
3. I'm aiming for 60 to 80 watts per channel for my Aleph-X. How many mosfets do I need per channel? I have a set of mosfets that I got from "harvadian" that was originally intended for another Aleph 2 but now I think I want to build Aleph-X. Would that set of mosfets be sufficient to get 60 to 80 watts per channel? I assumed Aleph-X does requires matched transistors too?

You do want matched transistors, and if you have a matched set, 24, I assume for 2 channels, I would use 12 per channel, which would mean 3 per bank. If you are using chad's boards, then you can use the output pads and run the resistors off board into the devices as done with the Aleph board that I made earlier. Peter used 4 devices per bank for his. I am going for 2 per bank on my first Aleph-X.

Originally posted by fcel
4. For more quantity of output mosfets, do I just connect them in parallel with a source resistor for each mosfet with the exception that only one of these output mosfets requires a sense resistor .. just like Aleph 2?

There is one sense resistor needed. It is the same as the Aleph2.

Originally posted by fcel
5. I might as well ask about the capacitors too. What is the required minimum total capacitance value per channel for this amp and the min voltage rating of each cap?

I would go for 25v rating on caps as the min voltage rating. I am going for 63v caps, since I have some. I am going to use 100,000uF per rail, giving 200,000uF per channel. I am hoping that this is enough. Maybe Peter can provide some insight into this.

Originally posted by fcel
6. I understand that you're making your own boards. Are they any different from Grataku/Chad's board other than the look of it? And are you using exactly the same circuit diagram that was posted by Grataku/Chad?

I made my own boards based on Grey's schematic, which I already populated for my first stereo Aleph-X using one of the Aleph2 monoblock chassis. This chassis should be rated at 300w total dissipation, or maybe a bit more, depending on how hot I want it. I am going to play with this until I get some of chad's boards (ordered 10) I am going to use these to build a pair of monoblocks. My first revision of boards have 2 devices per bank. I revised this to 3 devices per bank, and am getting some prototype ones made now. Pictures of all of this on my website.

--
Brian

[fcel]

Brian ... thanks for the response. Could you respond to the following to see if I understand you correctly .... in regards to question #3.

Assuming that I'm using 12 mosfets per channel and as you said that would be 3 per bank, does that mean that:

1. I have to break the trace on the output boards (the output boards that I got from "harvadian" has space for 6 mosfets) to give 3 mosfets per bank and I'll have 2 banks per output board?

2. And that it would need 1 sense resistors for every 3 mosfets?

For Aleph 2, for each channel, it has current source (6 transistors) and gain source (another 6 transistors). Is Aleph-X operating in the same principle?

[Peter Daniel]

I never had a parts list. This design is so flexible, that it will work with any parts you might have on hand. I was working mostly with rtirion schematic, which on my screen is on page 23. The only main part value that you have to adjust are the source resistor, and it depends on how many devices you are using. I used 16 per channel , only because I had 24 originally from A75. But I'd say that 12 per channel in my setup would be fine as well. 15V is actually about the right voltage recommended for the heatsinks I was using. With 6A total current you can drive most loads. 80-90W is into 4 ohms, it is half of it into 8 ohms. My speakers are around 94 dB efficient and less than 6 ohm impedance, it works out fine so far.