[Jaypee]

thank god I haven't ordered the parts yet then ... I'll haveto consider going with conventional passive ground β22 amp with 2xσ22 PSU's. I know that setup would cost a bit more, so do you think it's worth the extra buck?
For driving speakers:
2xβ22 board (conventional 2 channel passive ground) + 2xσ22 PSU's
OR
2xM³ board (bridged) + 2xσ11 PSU's

thanks for your input

EDIT: or even a β24...

 

[johnwmclean]

I know what my moneys on

 

[Beefy]

Yeah, once you are at the point of two S11's, it may be worth considering to go up a step.

For headphones, the balanced M3 can be done easily and cheaply. But when you start looking at two chassis, two transformers, and all the other modifications for speakers...... it makes less sense.

And I would wager that the B22/S22 combo would be able to supply more juice.

 

[grawk]

I dunno, for my money, the balanced m3 I had is still on the very short list of the best dynamic headphone amps I've ever had, for quite a bit less than even a simple balanced b22 build.

 

[Beefy]

Oh absolutely - I've read opinions from heaps of folk who have heard your amp that were very impressed.

But for speaker use, it just doesn't have the same legs as the B22.

 

[Jaypee]

I might still go with 2xM³ + 2xσ11, since I'm on a budget. The amount of components is far less than 2xβ22 + 2xσ22 combo (especially since I can ignore the ground channel completely on the M³'s) + the transformers will be considerably cheaper for σ11 as opposed to σ22. Thanks for your help so far!

 

[Beefy]

Are you aware of Glass Jar Audio? You might be able to get kits that could save you some money.

Jeff used to do M3 kits as well, even though they aren't listed on the website. Not sure if he would have the alternate parts for speaker use though.

 

[grawk]

My m3 was briefly set up for speakers (28 watts) but I have decide it's better to just use a speaker amp

. Even b22s are prone to melting down when used that way.

 

[Jaypee]

So, if I'll use two σ11, each powering their own M³ board intended to drive speakers, to what voltage and current should the σ11's be set to? AMB.org says:
Quote:

For even more power, two M³ boards can be used in a balanced configuration. This is commonly known as "bridged" outputs and will give about 20Wrms per channel (into 8Ω) when used with a 36V, 5A power supply

but 36V 5A each seems a bit much..

 

[Beefy]

Quote:

Originally Posted by Jaypee /img/forum/go_quote.gif So, if I'll use two σ11, each powering their own M³ board intended to drive speakers, to what voltage and current should the σ11's be set to? AMB.org says: but 36V 5A each seems a bit much..

Current would be limited by whatever transformers you put in there, and how much heat you can get rid of. I doubt you would need to supply 5A constantly though - only on transients. While your typical low-end linear power supply will crap out on those transients, a pair of S11/22's would not.

If it were me, I would use a pair of transformers for 36V, 1A each. So maybe Amveco 62073, or 62083. The 15+15V secondaries should be sufficient for good regulation (particularly if you go for the 50VA model, the 62083), and much less heat than if you were to use an 18+18V. I would also use 2 or 2.5" sinks on the S11 to help manage the heat. And 2 or 2.5" sinks on the M3 as well, of course.

Or as Grawk says, make an amp specifically designed for speakers......

 

[Steve Eddy]

Quote:

Originally Posted by amb /img/forum/go_quote.gif In a bridged configuration, the speaker load impedance "seen" by each of the "hot" and "cold" amps is half the real speaker impedance, increasing the current further (this is why you get theoretically four times the maximum output power bridged, the voltage swing is doubled, and the current is also doubled due to halving of the impedance).

No, the current isn't also doubled due to halving of the impedance. There is no halving of the impedance. The impedance remains the same. Doubling of current is due to doubling the voltage swing. Period.

se

 

[amb]

Quote:

No, the current isn't also doubled due to halving of the impedance. There is no halving of the impedance. The impedance remains the same. Doubling of current is due to doubling the voltage swing. Period.

OK, true, but you're arguing semantics. V = I * R, when V is doubled, and R is fixed, I has to double. When you're pumping double the current into the load, then as seen from each of the hot and cold amps, it looks like it's driving half the impedance because each amp is still swinging halt the total voltage. Simple Ohm's Law.

 

[FallenAngel]

Why go with 2x Beta22 boards with 2x Sigma22 for passive ground? Makes more sense with 2x Beta22 and 1x Sigma22 or 3x Beta22 and 1x Sigma22 for active.

On the M3 front, a single Sigma11 should be plenty, make sure you have good heatsinks and air flow

 

[Steve Eddy]

Quote:

Originally Posted by amb /img/forum/go_quote.gif OK, true, but you're arguing semantics.

I'm arguing against your statement that "the voltage swing is doubled, and the current is also doubled due to halving of the impedance."

You're saying the voltage swing is doubled. Doubling the voltage swing doubles the current. But then you say "the current is also doubled due to halving the impedance."

As stated, this implies that current is quadrupled. Doubled first by doubling the voltage swing, and doubled again by halving the impedance.

Quote:

V = I * R, when V is doubled, and R is fixed, I has to double. When you're pumping double the current into the load, then as seen from each of the hot and cold amps, it looks like it's driving half the impedance because each amp is still swinging halt the total voltage. Simple Ohm's Law.

Yes, it's simple Ohm's Law. But "halving the impedance" isn't a good way of describing what's going on. It just leads to confusion and misunderstanding because that's not what's actually going on.

Current is doubling due to a doubling of voltage. Not any halving of the impedance.

se

 

[Steve Eddy]

Quote:

Originally Posted by FallenAngel /img/forum/go_quote.gif Why go with 2x Beta22 boards with 2x Sigma22 for passive ground? Makes more sense with 2x Beta22 and 1x Sigma22 or 3x Beta22 and 1x Sigma22 for active.

3x Beta22 and 1x Sigma22 for active?

What's the third Beta22 for?

se