Yes, I used those for all the measurements I have posted about this project. They have plenty of AC voltage under the low current demand that this circuit represents. I think I measured the rectified and smoothed DC before the regulator at about 20-22V (My mains voltage is about 122Vac). Even two boards (like you wanted to do) would not be a problem. I like those little MCM trafos. They sent me a free shipping offer, so I bought 16 of them! You have to solder some wires on to the tabs where the transformer windings are brought out, but this is no big deal.
My preference would be Antek. Unfortunately they are pretty much sold out of all of the low VA 15+15Vac transformers that would be suitable for use with this board. They were supposed to order more and get them in NOV but they are still showing as out of stock. In the meantime, the MCM transformers are fine and are actually less expensive even though you have to use two of them.
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One way that I could help get the pricing lower is to organize a group buy for the parts needed for the gain stage boards. I already have a bunch of the PS smoothing caps, rectifiers, and some other parts. If there is enough interest I will start a group buy thread and can figure out how to go from there. I will be building several of these for myself as well, so I will also need parts. There is no sense in everyone ordering ones and twos of components and paying the max price from Mouser. If we can get even 10-20 people together we have a significantly more buying power.
Please post in this thread if you are considering building the gain stage and would be interested in participating in a component group buy. If it actually seems like it will be a go I will create a dedicated group buy thread.
Spread the word!
I think we might need a fresh thread in vendor or group buy or wherever this stuff usually happens, the first few pages of this thread are a little ..how do I say this..."stop needing things I don't need." grumbly.
I think there's a couple of people if you go back a few pages that seemed interested, perhaps they should be PM'd if you decide to start a thread in a commercial area. I might put the link in my signature as well, if that's not a problem.
Edit: What are the dimensions of the boards? I'm starting to window shop for chassis
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I think we might need a fresh thread in vendor or group buy or wherever this stuff usually happens, the first few pages of this thread are a little ..how do I say this..."stop needing things I don't need." grumbly.
I think there's a couple of people if you go back a few pages that seemed interested, perhaps they should be PM'd if you decide to start a thread in a commercial area. I might put the link in my signature as well, if that's not a problem.
Edit: What are the dimensions of the boards? I'm starting to window shop for chassis
I will start a "for sale" thread in the vendor forum after I am back from my vacation - this may just link to my web site where I will list my boards and projects. The BOM will be made available so that people can get the parts they need, or figure out if they already have some parts lying around, etc. It looks like a group buy is not going to come together. I'm not planning on pushing the boards on anyone by contacting them as that is not really appropriate.
RE dimensions: the board is 4"x4". The caps and rectifiers make it around 1.75" tall I think - just guessing on that because I don't have a board with me at the moment and it depends on the caps used.
I have decided to offer the PCB for free. I started a thread about it in the Vendor's Bazaar:
http://www.diyaudio.com/forums/vend...n-stage-onboard-power-supply.html#post4164189
http://www.diyaudio.com/forums/vend...n-stage-onboard-power-supply.html#post4164189
I'm thinking of using something like this:
VPT30-830 Triad Magnetics | Mouser
It's a bit more expensive than the other ones, but I'm planning to do this up nice, as it's going to end up being my first real adventure of "order BOM to build audio gear" type thing. I'm pretty excited.
I've found a case as well: New 1U Rackmount Enclosure 37-1U - Electronic Enclosures | Circuit Specialists
It seems large, but it'll have plenty of breathing room for 2 2x4 MiniDSPs, the two gain boards and the trafo, and fit nicely underneath my 6 channel amp.
Edit: Would 17-0-17 work? I've got one of those white van scam receivers sitting here one of my friends gave me, which for all it's junkiness, has a 10-0-17 trafo in it I can scavenge.
VPT30-830 Triad Magnetics | Mouser
It's a bit more expensive than the other ones, but I'm planning to do this up nice, as it's going to end up being my first real adventure of "order BOM to build audio gear" type thing. I'm pretty excited.
I've found a case as well: New 1U Rackmount Enclosure 37-1U - Electronic Enclosures | Circuit Specialists
It seems large, but it'll have plenty of breathing room for 2 2x4 MiniDSPs, the two gain boards and the trafo, and fit nicely underneath my 6 channel amp.
Edit: Would 17-0-17 work? I've got one of those white van scam receivers sitting here one of my friends gave me, which for all it's junkiness, has a 10-0-17 trafo in it I can scavenge.
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It won't work -. you can't use a center tapped transformer with the gain stage board. You need either a transformer with dual (indpendent) secondaries or two identical transformers such as those inexpensive MCM transformers I mentioned earlier in the thread. Here is the link once again:
Power Transformer | 28-0010 (280010) | Distributed By MCM
If you sign up for their "deals" via EMail they may send you a free shipping voucher, in which case I would pick up several of these little guys.
Aha, ok. Figured I'd check the spare gear for parts, just in case
Edit: Just for educational and window shopping purposes, I'm still looking around online to see if I can find a single transformer with independent secondary windings.
Edit2: Just so I'm sure that I've learned the right lesson from this, this diagram (image) is what I'm looking for, yeah?
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Good dual secondary transformers are fairly easy to find online. Here's an example from Tamura that can be obtained from Digikey:
http://www.tamuracorp.com/clientuploads/pdfs/engineeringdocs/3FD-4XX.pdf
Multiple output voltage, VA ratings, and mounting schemes are available.
In this particular application a split-bobbin transformer is probably preferable to a toroid style because of the very high primary/secondary isolation.
Dave.
http://www.tamuracorp.com/clientuploads/pdfs/engineeringdocs/3FD-4XX.pdf
Multiple output voltage, VA ratings, and mounting schemes are available.
In this particular application a split-bobbin transformer is probably preferable to a toroid style because of the very high primary/secondary isolation.
Dave.
Something along those lines will probably work. The only problem I have is that the specs are not clear in the datasheet. Let's say that we have the Tamura 3FD-424 (12V dual secondary) model. What is the no load voltage and what is the voltage under the specified load? The regulation is approximately 18% in the datasheet. So does that mean that the voltage will be 1.18*12V = 14.16V under no load conditions and 12V when loaded with the rated current of 0.25A on each secondary? I'm never sure about the MFG specs, even with a pretty complete datasheet like the Tamara example.
Those MCM transformers are a known known, meaning that I own some of them and I have measured them. I have also measured the performance of the circuit connected to them. They are also very, very inexpensive.
My reliable source, Antek, is out of stock of the appropriate type. Otherwise that would only be $11 for 25VA or $17 for 50VA.
Aha, ok. Figured I'd check the spare gear for parts, just in case
Edit: Just for educational and window shopping purposes, I'm still looking around online to see if I can find a single transformer with independent secondary windings.
Edit2: Just so I'm sure that I've learned the right lesson from this, this diagram (image) is what I'm looking for, yeah?
Yes, that is the representation of a dual primary, dual secondary transformer.
If you have any questions about how to choose an appropriate transformer in terms of the VA (power) and secondary voltage ratings, just ask.
-Charlie
Cool. Yeah, I haven't really made up my mind which supply I'm going to get. Part of me wants to just order the mcm ones and be done with it, but I would really like this to all be in a nice chassis at some point, and I want to do the innerds all slick and tidy, so maybe something like a Nuvotem 72473 is in order.
Meh, I've got a little while to think about it.
Would an R core be a bad idea?
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