~ 50 WPC Class A Kit for existing Trafos?

[briansz]

Have a bunch of toroids and heatsinks here and would like to build a pair of Class A monoblocks or a stereo amp in the 50 watt per channel range.

Trying to use my existing parts and having problems finding kits based on a proven design to work with my voltage ranges.

I have:

225VA Toroids 38-0-38 @ 3A and 12-0-12 @0.5A

500VA Toroids 51-0-51 @5A and 15-0-15 @0.5A

350VA Toroids 38-0-38 @4.5A and 15-0-15 @0.5A

and one

600VA 28-0-28 @11A and 60-0-60 @.6A

So theoretically there are 225VA @ 53.6V, 500VA @ 71.8V, 350VA @53.6V, and one 600VA @39.4V power supplies available. I've got more than one of everything but the 600VA donut. Looking for something fairly high end with low to moderate complexity and available PCBs or full kit. I've got a Weller WTCPT iron, DMM, 20MHz scope, and have repaired a couple car amps, but am far from an expert, will be learning as I go.

Rest of system so far is Sony CDP-707ESD transport, Adcom GFP-555II preamp, Velodyne ULD-15 servo sub, slightly tweaked JBL L20T minimonitors. This is my $400 2-channel system <lol>. Speaker project probably next year but I'd like to build the amp over the winter months.

Budget, hmmm, less than or equal to $500 not including chassis or power supply........

What would you build?

[siliconray]

How about this one?
60W+60W.

[diyroger]

225VA don't have enough power for 50W+50W Class A. I think 350VA or higher would be better.

I will make one or two Class-D for at least 200W if I have your donuts.

[briansz]

Looks interesting, more details, please. Amp topology, kit cost, etc.

I did find an article detailing an update of the Hiraga Class A design that may work with my 600VA toroid. The builder of that ended up using 500VA +-35V and I would have 600VA @ ~ +- 39.4V on Toshiba 2SA1943 and 2SC5200 devices.

It'll cost about $400 for the capacitor bank alone, however. That's not a deal breaker, but it is a lot of capacitors (1.2 farads @ 50V, 12x 100000uf or 6x 220000uf).

I should mention that I built and am currently running 2 channels of a 4x100 Sure Electronics module with a large SMPS. It's quite good, but I'm looking for the next level in design and performance.

[briansz]

I've got eight or ten of the 38-0-38V 350VA toroids. Not a problem to use even one of those for each channel if I can find a circuit that will run reliably @ 54V. Most kits I've found use lower voltages.

Don't really want to exceed 50 watts Class A per channel due to the power bill <lol>.

[digits]

At 54V rails you will spend more on heatsinks than transformers, I think.

[briansz]

I think I may have to use the single 600VA trafo, it should yield 40 volt rails and should adapt pretty well to the Hiraga Super Class A design shown over at diyaudioprojects.com.

The other toroids may end up being more useful for Class AB, B, D, or T designs, I'm just looking to try and build something that's not a chip amp for my next project. All the toroids are already paid for, as are eight or more finned heatsinks measuring 11.375 x 5.25 x 1.6875 each. I'm just trying to use some of these parts I already have as opposed to buying everything from scratch.

So far, the Hiraga design is the only thing I've found that seems like it may work at all. I'm sure there have to be more Class A circuits than that for use with 40 volt rails.

[afgabriel]

Originally Posted by briansz

I think I may have to use the single 600VA trafo, it should yield 40 volt rails and should adapt pretty well to the Hiraga Super Class A design shown over at diyaudioprojects.com.

The other toroids may end up being more useful for Class AB, B, D, or T designs, I'm just looking to try and build something that's not a chip amp for my next project. All the toroids are already paid for, as are eight or more finned heatsinks measuring 11.375 x 5.25 x 1.6875 each. I'm just trying to use some of these parts I already have as opposed to buying everything from scratch.

So far, the Hiraga design is the only thing I've found that seems like it may work at all. I'm sure there have to be more Class A circuits than that for use with 40 volt rails.

Hi Brian,

I also like Hiraga Super Class A.
For bigger watts, you could try 'Curtis 60 watts' and the one 'ExtremeA' - sorry i forgot the web link but if you need that you could send me your email address so i could provide you.

[ingenieus]

The 600VA 28V-0-28V sounds about right - you don't a lot of voltage swing for 50W but for class A you do need lots of current. It should be sufficient for a stereo amp, with a bit left in reserve.

[siliconray]

Remember that the heatsink always suck more power than speakers for class A amp.