New B4 active crossover

[Nelson Pass]

The owner's manual to the newly revised B4 active crossover is posted on the First Watt site.

www.firstwatt.com/pdf/prod_b4_man.pdf

It's been two years getting the revisions out, and not that I thought you would
buy one, rather that you might enjoy the pretty curves and witty commentary.

 

[Zen Mod]

.... witty commentary.
..

that's the part I'm enjoying most

 

[Zero D]

@ Nelson Pass

Shame, if it went from 24Hz - 6276 Hz i might consider one

Each of the four filters offers 1, 2, 3 or 4 “poles” for each filter, corresponding to 6, 12, 18 or 24dB/octave slopes. Each of these filter poles is independently adjustable within each filter, allowing wide customization of the character of the filter.

That's as it should be If only more products had done that in the past !

I'm surprised you're using a SM PS though ?

 

[Nelson Pass]

The XVR1 is similar, and offers balanced lines, but costs more than twice.

Nice shiny separate supply and four knobs, though.

 

[edwyun]

Thank you. Can't wait.

 

[Zero D]

@ Nelson Pass

Hi, i couldn't see XVR1 on your www ?

 

[Nelson Pass]

@ Nelson Pass

Hi, i couldn't see XVR1 on your www ?

www.passlabs.com and then under products and then preamps and then
"specialty"

 

[Zero D]

Ahh, i was looking @ FIRST WATT that's why i didn't see it

Thanx

 

[Michael Rothacher]

Really great stuff! Always fun to read a Pass owner manual

 

[edwyun]

They have a common input, and an input switch on the left decides which filter will have level attenuation. The other filter will see the direct input.

The high pass filter and the low pass filter are each independently buffered from the input
and the input attenuator. This assures that the attenuator and the impedance of the signal
source do not influence the performance of the filters.

Thank you. This is a welcome update.

The L setting is provided to switch a capacitor on each filter so as to implement a “Linkwitz-Riley” value set when you are using 24 dB/octave setting

So the new B4 can create a LR4 crossover. Is there a way to create a LR2 crossover?

 

[Nelson Pass]

The LR2 is the SK 12 dB/octave filter using equal RC values and unity gain
buffers, so you simply operate from the "S" column on the frequency values.

 

[AndrewT]

LR2 is a pair of cascaded RC (single pole) filters.
The B1 Follower can be used as a Buffer for each part of the cascaded pair.

LR4 is a pair of cascaded Butterworth 2pole filters. The B1 is included inside the active feedback loop to create the active 2pole filter.

 

[vdi_nenna]

Just ordered two B4s! My first (and second) official Pass products! So exciting!! I swore I'd not build another active crossover!
Can't wait...!!!!

 

[Michael Rothacher]

You're going to love them!

 

[vdi_nenna]

It's going to be great. I've some reading to do!

 

[2 picoDumbs]

www.passlabs.com and then under products and then preamps and then
"specialty"

I'll trade you my B5 for one of those.
You're getting the slightly better end of the deal, but I'm I'm a generous guy.
Hehehehe

 

[vdi_nenna]

I read the manual a couple of times. Do I have it right that the attenuator is switched between Lo and Hi sections, allowing the amp with the higher gain the be lowered by the attenutor?

In the low pass 800hz, 18db slope example, what's the purpose of multiplying the first 2 poles by 2x frequency and last pole 1x frequency? The high pass section is set the opposite.
The proceeding paragraph says to "sum flat". Not sure what that means.
Is it because having poles 1,2 and 3 at 800hz will create a bump in frequency at the crossover point?

Thanks

Vince

 

[vdi_nenna]

Missing RCA washer is normal

If you pick up a B4, you'll notice one of the RCA plastic washers on the inside is missing and the chassis paint removed in that area. Don't panic.
This is normal, and is used for chassis ground. Verified with vendor Reno Hi-Fi.

 

[edwyun]

Reviving an old thread. How easy is it to convert the captive SMPS on the B4 to a linear power supply?

 

[Nelson Pass]

Easy. Just give it a simple RC power supply filter to take out the ripple at 120 Hz and above.