I'm toying around with a new idea.

For a while now I've been kicking an idea around. Over at this other forum I frequent, alot of folks have been upgrading the crossovers to their vintage models with better caps and, in some cases, resistors. (As a matter of fact, I have a set of parts to do one of either two pair I have. I just haven't gotten off my butt and done it. I think it's time, though. I just need to decide which ones.)

Anywhoo, a while back, I had my Plat's crossovers sent out, because I developed a bad problem in one of them. (At that time, unknown to me, I think they effed up one of my amps. Different story...) I had both of them done, so they would match up. But I think the parts were kind of run of the mill, ya know? Same thing as they would have used in production runs.

Well, I am thinking of building all new crossovers. I would keep all of the same specs, but use all high grade parts. New inductors, film and oil caps, wire wound resistors. All tight tolerances, yadda yadda. This is going to be pricey, but I think the end result would be worth it. I hope so, anyway.

One thing I was wondering is would air core inductors perform better than iron core? Does anyone have any good souces for parts? Should I try to keep them inside or just go seperate?

Any opinions? Any input?

They may sound COMPLETELY different (not necessarily better or worse), however, they will sound ALIKE. YMMV. The thing about close tolerance parts is that they will be closer to one another. Better parts (especially caps) can be more "musical" (whatever that means to you). Better hookup wire can help too.

....
Well, I am thinking of building all new crossovers.....

I was planning on re-building the crossovers in My Klipsch Cornwall IIs; doing research, looking at parts, etc. Then I had the idea that as long as I was spending money, the worst thing about a speaker crossover is that it exists.

Power is wasted in the passive components, phase shift through the passband, and interference patterns from multiple speakers playing the same frequnecies that are physically separate from each other; and more.

So I decided to go active. In the case of Amazing Plats they're basically a full range ribbon with a built-in sub (they cross over at 100Hz). There's also a notch filter in the high pass to tame a resonance in the ribbon due to it's enclosure (acts like a resonant cavity).

For Amazing's you'd need:

1. Another two channel amp

2. A two-way active crossover like the Rane AC22b (there's a raffle going on right now: viewtopic.php?f=110&t=5341) it's a 4th order (24dB/ooctoave) phase aligned (butterworth) two way stereo crossover.

3. A two channel notch filter at 7KHz (like two Rane PE-15s)

An AC22b goes for between $75 and $125, depending on condition
A PE 15 is about the same (you'd need two)
An amp (if you go with Carver) seems to run $300-$500, depending

My $0.02

Just a point, if you go with the Rane AC-22B, your amp will need balanced inputs, and your preamp will need balanced outputs. With the non-B version your preamp outputs can be either balanced or unbalanced, and your amplifier inputs MUST be unbalanced.. I use the non-B version with balanced outputs from my TGP-III (XLR) terminating in ¼ inch stereo phone plug (TRS) inputs to the Rane, and mono ¼ inch phone plug (TS) outputs from the Rane terminated by RCA inputs into my amp.

I chose the B (XLR) model because I didn't like the way the Tip/Ring/Sleeve (TRS) connectors of the non-B model were looking at me

Thinking of headphones, it seems they'd be noisier; so I went with the B model and am using XLR to RCA adapters

Well, I had a long run between my Sunfire TGP and the Rane (behind all the components, TV, etc - about 8 feet) so I wanted that balanced (and have the Rane do the magic to eliminate the noise. From the Rane to the 400 x 7 is one shelf down (less than a meter), so unbalanced was fine I didn't think those XLR to RCA connectors did anything except take the hot leg. Are the 10k and 3.9k resistors necessary to go from the +4dBm balanced to a -10dBv unbalanced output in place in those connectors?

......Are the 10k and 3.9k resistors necessary to go from the +4dBm balanced to a -10dBv unbalanced output in place in those connectors?

I haven't powered up yet, first time for me going balanced to unbalanced; on the XLR to RCA pin 2 is center and pins 1 and three are shield.

Rich, it will work with what you say, but to get the signal right, I've heard (I haven't done it) that the connection should be something like this.

BaltoUnbal.gif (1.51 KiB) Viewed 926 times

* connection needed for transformer developed balanced. Might cause problems with transformerless connections.

I've been working on a balanced to unbalanced project using op-amps. I'll PM you sometime later.

Might cause problems with transformerless connections.

Just to be perfectly clear for anybody running across this thread in the future...this wiring CAN blow output op-amps!! This drawing is anticipating that the output is servo-balanced or transformered and not directly driven by an op-amp.

Most op-amp outputs should be protected by an output resistor and not immediately harm anything, but even thats suspect to count on. The resistor value might not be enough for a permanent short or might in the long term stess the resistor and change value or open. You really gotta keep that magic smoke inside the chips...it makes 'em work!!

So again, good drawing for transformered or servo-balanced! Disclaimer complete...Now back to your regular show....

Mark

.....I've been working on a balanced to unbalanced project using op-amps. I'll PM you sometime later.

Sounds good...thanks I've been wondering about pin 1 and 3 ....sure wish there was a switch on these adapters in case there's hum; if there is I'll have to open them up and break the connection.

I'm relatively certain that Sunfire XLR connections use pin #1 for the +,and the center & 3rd pins for - and common. Is center pin positive the normal XLR connection??

I'm relatively certain that Sunfire XLR connections use pin #1 for the +,and the center & 3rd pins for - and common. Is center pin positive the normal XLR connection??

For XLR outputs, the pins are in a V shape, starting from the left and going clockwise 1,2,3 so center is pin 3, usually ground, pin one (left) is usually common and pin 2 (right) is usually high.

For XLR inputs pin 1 is on the right and going counterclockwise 1,2,3 so center is still pin 3, but common and high are reversed.

As far as what's normal, pin 3 is always ground, but some manufacturers sometimes switch pins 1 and 2 (I've heard)

[edit] Bill's post below is correct; I had 1 and 3 reversed in my mind]

300px-XLR_pinouts.svg.png (24.46 KiB) Viewed 859 times

Pin Function
1 Chassis ground (cable shield)
2 Normal polarity ("hot")
3 Inverted polarity ("cold")

300px-XLR_pinouts.svg.png

Pin Function
1 Chassis ground (cable shield)
2 Normal polarity ("hot")
3 Inverted polarity ("cold")

Bill, I was looking through the TG-IV manual and this is the exact opposite of the Sunfire XLR setup. They use Pin 1 as Pin 2 and Pin 2 as Pin 1 in your example. Pin 3 is still the negative though.

Wow Gary! That's crazy!

I wonder if it's possible thats a misprint or something? That would force using or building special cables. Using a conventional cable, you'd wind up with the shield carrying the hot signal.

In 30 years of dealing with professional equipment every day, I've never run across pin 1 used that way. In the pro sound world, pin 2 is hot and it's been common in the broadcast world for pin 3 to be the hot. But that really doesn't make too much difference in most cases. And it has seemed to begin to be more common for pin 2. But this pin 1 thing just doesn't compute....