[amb]

I don't recommend paralleling two transformers because the two may not put out exactly the same voltage. Also, why give up the benefit of truly independent power supply for each channel when you have all the ingredients to do it? Don't worry about the current loads as long as each transformer is sized properly for the job. The σ22s themselves will certainly not be a bottleneck.

 

[Covenant]

Would running independant power supplies for each o22 actually be of benefit, beyond the aesthetic appeal of knowing each channel's power supply is completely dedicated?

I'm intending to build a 3-channel beta22 fed by three o22's, and the choice of toroid would likely be between one Plitron 500VA (the same encapsulated one you're using for your prototype B24, AMB), or three avel-lindberg 100VA toroids.

I'm leaning in the direction of three 100VA units, as i expect the benefits of a shielded, encapsulated toroid like the Plitron would be largely pedantic and more for bragging rights than any actual benefit with the PSU in a seperate enclosure.

Thoughts?

 

[amb]

Quote:

Originally Posted by Covenant /img/forum/go_quote.gif Would running independant power supplies for each o22 actually be of benefit, beyond the aesthetic appeal of knowing each channel's power supply is completely dedicated?

If by "power supplies" (bolded in quote) you mean power transformers, then no, there is no real benefit in a β22 serving as a headphone amp in 3-channel active ground configuration. If you plan to also use the β22 as a speaker amp, then it boils down to whether it's easier to fit 3 smaller transformers vs. one big one in your choice of case.

Quote:

I'm intending to build a 3-channel beta22 fed by three o22's, and the choice of toroid would likely be between one Plitron 500VA (the same encapsulated one you're using for your prototype B24, AMB), or three avel-lindberg 100VA toroids.

The Plitron I'm using for my β24 is not really a good choice for your application. First, 500VA is hugely overkill for the β22 in any configuration. Second, that Plitron has four 30V secondaries, which works nicely for a 2-channel or 4-channel amp (two secondaries are wired in series to make a 60V center tapped). For a 3-channel amp, it doesn't divide up as neatly.

Thus, it makes more sense to use either three smaller transformers or one bigger one (each one having two secondaries or a single center-tapped secondary).

Note that if you're planning to use the ε22 backplane board, then it only has provisions for a single σ22 PSU board to supply all three β22 boards.

Quote:

I'm leaning in the direction of three 100VA units, as i expect the benefits of a shielded, encapsulated toroid like the Plitron would be largely pedantic and more for bragging rights than any actual benefit with the PSU in a seperate enclosure.

Shielding of the transformer is not needed if you're going to put it in a separate box from the amp. Encapsulation is a nicety (appearance and mechanical vibration control) but not necessary.

 

[Covenant]

Thanks for the reply AMB

I've noticed that Parts Express stock Avel Y236751 330VA 30V+30V Toroidal Transformers that should neatly fit the bill for a triple-o22 configuration. I was looking at possibly sourcing some high-quality RCA sockets from them anyway, so this makes ordering nice and easy.

 

[rhester]

amb, why is the 6.5" transformer too large? Should fit in with everythig else that I can see. That is how I was leaning rather than the $310 Plitron.

I have everyhitng amlmost finished and waiting to either buy the HiFi2000 case or standalone heatsinks and build the rest of the case.

 

[amb]

Quote:

Originally Posted by rhester /img/forum/go_quote.gif amb, why is the 6.5" transformer too large? Should fit in with everythig else that I can see. That is how I was leaning rather than the $310 Plitron.

A 6.5" transformer is not too large for a β24, but two of them might be, depending on the case and configuration. In case you're referring to my reply to Covenant, he was asking about transformer(s) for a β22.

 

[rhester]

Amb, I was referring to your initial post which states that the transfo is too large.
Off topic but also saw your pics of your progress. Why did you choose to use the upgraded resistors in the positions that you did? And what typr of caps are you using?

 

[amb]

Quote:

Originally Posted by rhester /img/forum/go_quote.gif Amb, I was referring to your initial post which states that the transfo is too large.

My initial plan was to use two transformers, one per channel. Two of the 6.5" units would be too big for the Hifi2000 case I had in mind.

Quote:

Off topic but also saw your pics of your progress. Why did you choose to use the upgraded resistors in the positions that you did? And what typr of caps are you using?

Those pics are not of my build. They are housing's. For my own build I am using everything as specified in the BOM.

 

[zare]

I was looking for beta24 transformer and got quote for RC0300 930 1:
".. 300VA toroid fully encapsulated and shielded in the standard grey toroid box is $ 94.00 + shipping ".
Will need two, but still cheaper then Plitron if you are in Canada.