Active Crossover Problem

Hello,
In the process of taking apart an active crossover to decide what type of mods I could do to it, I think I messed it up. I have been thinking of modifying the op amps in it and also replacing all of the capacitors with black gate models. I wasnt very careful when i pulled a couple of the op amps out to take a look at them, and i bent the pins on two of them. I straightened them and put them back, but now the thing makes really strange noises. This is almost good because i wanted to replace them anyway, but kinda scary at the same time. I am hoping this is the only problem with it and replacing the op amps will fix it. I want to put new op amps in it, and now that i think that is the problem with the unit I guess I will take advantage of this opportunity and replace all of them. There are 26 op amps inside of it and they are all JRC 2068D op amps. This is an Image Dynamics IDX24 crossover, in case anyone is familiar with it, and I want to modify it for ultimate sound quality. I was reading around and I noticed that opa627's are pretty kick ***...but they seem kinda pricey, especially considering how I would have to make little riser boards to convert the 8 pin sockets to accept two of these single op amps. The candidates for replacement so far are OPA2134, OPA2132, or the LM6172. I was reading a post earlier where someone rated certain op amps and the LM6172 fell into the same bracket as the OPA627. At 15 bucks each, and since they are single i would need 52 of them, i'm pretty sure that the opa627's are out of the picture. lol. So could someone please try to steer me in the right direction as to a really kick *** op amp that doesnt cost more than say 5 bucks? I am pretty sure that the LM6172 is only about 4.80 each, and right now that's what I'm thinking of going with. Thanks in advance.
 
redisign it

I dont really want to redesign the thing...But it wouldnt be the end of the world. I realize that 26 op amps is a TON but it is a three way 24DB/octave crossover. And it is an incredibally high quality one, at that. Until recently I have been running my setup with the crossover crossing my tweeters, midranges, and subs all separately, but now I have decided that i want to actively cross the subs from the mids and then use a passive for the mids to the high. I will then have one amp for the left and one amp for the right (also one for the subs) and use a passive crossover. So if it were at all feasable to make a new two way 24db/octave adjustable active crossover using only the absolute very totally 110% best components so that the thing is more transparent than anything ever, then i would be extatic (not to mention i would feel like a total johnny for doing it myself lol) But if it would not be very easy to do something liek that then I would really like some guidance as to how to modify this thing to make it perform the way I want.
 
I have been doing alot of searching on this forum and on the web for a few different crossover designs that are simple, yet high quality...But I dont really know exactly what I am looking for. Jocko, you said that you dont think that schematic shown will give desired performance, but it will get me started in the right direction. I would rather go all out the first time and make a perfect XO and just use it. Perhaps you could tell me of a design that will deliver hi performance? I would really like to also be able to adjust the crossover point very easily. The design I was looking at you had to replace many components to do this. Also, do you know of any that have balanced XLR in and out?
 
Never mind......having a senior citizen moment. My brain was not awake, and it somehow locked in on the last L-R I did, which was 2nd order, and 3-way. In retrospect, 4th order would have been easier. (There are phase reversals need in 2nd order, and there can be a problem with bleedover if you pick the frequencies too close together. I'm innocent........I had to do what the speaker designer told me.........!)

Tuning can be a bear. Do your homework first, and hopefully you won't have to mess with it.

As for balanced.............a real pain unless you convert to SE, and then back. I started one once, all balanced..........

You note I said "started".

The problem with converting is all the commercial units I've worked on use those SSM-2141/2/3 things AD makes. They sound OK. They do a great job of doing what a balanced setup should, but sonically they are just OK.

But since you asked.........

You might want to consider using a buffer, as opposed to an op-amp. Op-amps usually don't sound good as unity-gain stages. Lots of buffer circuits out there. Could be a parts farm though.

Jocko
 
I have the IDX24 (and IDQ31s) and have found the IDX24 to be one of the best xovers made. The JRC 2069Ds are some of the finest opamps designed for audio, with minimal distortion and a very high slew rate.

If I were you, I'd look to replace the JRC 2068Ds with the same part.

I'm going to look into the IDQ31s for possible upgrades now.
 

djk

R.I.P
2001-02-04 4:23 am
USA
A 2068D is a step below a 5532 in terms of speed.

I would suggest the AD823

Digi-Key Part Number AD823AN-ND Price Break

[email protected]$4
[email protected]$3.37
Unit Price

Manufacturer Part Number AD823AN
Description IC OPAMP FET DUAL 16MHZ R-R 8DIP
Quantity Available 3682
All prices are in US dollars

While expensive, it is reputed to sound better than the OPA2134 and OPA2604 (both of which are quite good).