[amb]

Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif is there any reason NOT to use a balanced Beta22 for speakers as a 50 Watt amp?

A balanced β22 will comfortably give you 50W+ of power into 8Ω (provided that the PSU is sized appropriately), but it wasn't designed to do so in a sustained manner. The TO-220 MOSFETs' thermal resistance is not low enough, even if you use big heatsinks, to run at high output continuously without risk of overheating (and this applies to both the amp and the σ22 PSU). Obviously, what defines "high output" vary depending on the efficiency of the speakers and the size and acoustics of the room. For most moderately-sized rooms and relatively efficient speakers, and with enough heatsinking, and reasonable playback volumes with occasional high peaks, it should be fine. Just don't have any expectations that this amp would be able to serve as a pro-grade PA or concert amp!

The β24 on the other hand, is designed from the outset to be a speaker power amp, with larger TO-247 output MOSFETs and large heatsinks. Also, in the β24, the σ22 PSU provides power to everything except the output stage, so it's relieved of the high-current and high power dissipation burden that's present in the β22. Thus, β24 would be much more adept at high sustained outputs.

 

[FallenAngel]

Thanks again amb, a beautiful distinction.

I have been holding off building a Beta22 because ever since I saw it released in design over a year ago on HeadWize, I've been seeing it as the King of headphone amps. Therefore I wanted to build the other headphone amps before I reach this level.

After reading it can drive speakers in balanced mode to 50Watts, lets say it's very hard to resist. Your post about the 630VA 2x30V transformer for $75 pretty much sealed my fate into wanting to build it for my speakers as well.

Well, that is definitely if I can sell off my latest experience with an over-the-top maxed out all-in-one with 4-input switchbox with 3x RCA and USB AlienDAC source, CKK-III preamp/headphone amp with custom PSU and LM3886 Gainclones amp for hopefully most of the parts cost, oh and very much THANK YOU for your help in the ground wiring scheme, it reduced the transformer hum to non-existent!

My speakers at the moment are 6Ohm Wharfedale 9.2 and I like them, but as with all great things, they don't last and I will likely upgrade sooner or later, which means they will be floor-standers and will likely want more power than the 50Watts the Beta22 can produce in balanced mode.

Having said that, it's just so hard to decide between a speaker-enabled Beta22 and Beta22 + Beta24. Oooh, here comes the little devil on the shoulder saying build both

and I think I'm going to listen.

Any recommendations on a cheap yet good transformer to drive a balanced Beta22 headphone amp? The $75 for 630VA knocked my socks off!

 

[amb]

Quote:

Originally Posted by FallenAngel Any recommendations on a cheap yet good transformer to drive a balanced Beta22 headphone amp? The $75 for 630VA knocked my socks off!

In terms of VA per dollar it's hard to beat that transformer, and it's shielded to boot. But, it is BIG and a bit overkill for four β22 boards, but if you've got the space... why not. Use it to drive four σ22 PSUs and you'll have quite a monster. It's even got a couple extra secondary windings that might be useful for other gizmos.

For those who are wondering what we're talking about, it's this one.

Other than that, Parts Express carries some Avel-Lindberg transformers at excellent prices (cheaper than you could buy them directly from A-V for at single-quantities).

 

[FallenAngel]

Quote:

Originally Posted by amb /img/forum/go_quote.gif In terms of VA per dollar it's hard to beat that transformer, and it's shielded to boot. But, it is BIG and a bit overkill for four β22 boards, but if you've got the space... why not. Use it to drive four σ22 PSUs and you'll have quite a monster. It's even got a couple extra secondary windings that might be useful for other gizmos. For those who are wondering what we're talking about, it's this one. Other than that, Parts Express carries some Avel-Lindberg transformers at excellent prices (cheaper than you could buy them directly from A-V for at single-quantities).

Oh completely, I was thinking of an OPUS and receiver off the 1A 16V-0V 1A secondary running off a TREAD, it's a fantastic find, thank you.

Now I just have to find a new Programmer Analyst job in the next 10 days to get a TN-1 Visa and stay in the country so I can continue this hobby.

 

[el_matt0]

could i use that big ol 630VA trafo to power both my sigma22s for my 4 channel balanced b22, or would i be better off just buying another 100VA avel-lindberg for the 2nd s22 to match the one I currently have? I'm terrible with this kind of stuff so any advice you guys can offer would be much appreciated - will the 630VA one just be overkill, no harm done though? will i be losing anything perse going this route as opposed to getting two separate 100VA trafos, or is the 630VA single trafo still going to far overpower the 2 individual ones?

 

[amb]

el_matt0, you can use the 630VA transformer for both σ22s and it will be way overkill but no harm done (provided that you have room for a 6.5" diameter lump). Otherwise, using a second 100VA transformer is probably a more sensible solution.

 

[el_matt0]

ok, i THINK thats what im seeing in the pictures of that 630VA trafo, but is that a second set of secondaries (ie for hooking up a second sigma 22 board without needing to splice) or am i a bit off base in my labelling of the wires....?

 

[amb]

el_matt0, look at the transformer label. There is only one 30V-0-30V secondary so you must splice the wires. The other secondaries are 13V-0-13V and 0-16V.

 

[vixr]

WOO HOO!!!

 

[el_matt0]

niiiiiiice vixr!

 

[fault151]

Whats the main difference in the 3 channel option over the 4 channel version of the b22, apart from the obvious?

Do they sound similar?

 

[el_matt0]

single ended with active ground (3 board) versus fully balanced configuration (4 boards)

 

[fault151]

Quote:

Originally Posted by el_matt0 /img/forum/go_quote.gif single ended with active ground (3 board) versus fully balanced configuration (4 boards)

You mean the input being single ended and balanced out put?

Is one better than the other or is it just preference depending on your set up?

 

[amb]

Quote:

Originally Posted by fault151 /img/forum/go_quote.gif You mean the input being single ended and balanced out put?

Sort of, but not really. In a 3-channel active-ground amp, the output ground is actively driven by an amplifier just like the stereo channels, but the ground amp does not swing voltage (only source/sink return load current). It allows you to get most of the benefits of balanced output without the need to modify the 3-wire headphone. It also does not require a balanced source to make full-use of its capabilities. See the "tech highlights" section at the β22 website for more detailed info.

 

[el_matt0]

yea, to clarify my earlier post, 3 channel board = single ended inputs and single ended outputs. its a 3 channel single ended amp. if you go with the 4 board version, youd need (ideally) balanced dual XLR inputs and likewise for the outputs, although you can set a 4 board up to also run single ended outputs in addition to the balanced ones (just using 2 boards instead of 4).