Active crossovers

This is a question regarding bias pots in general. My experience has been that they don't hold their adjustment for very long. This is the case for all the amps I've owned. They may stay close to the mark, but still drift. The issue is not that they drift per se, but that they drift to different values from each other so that you lose channel balance, whether you're dealing with monos or an integrated. I'm speaking strictly of SS amps here.

With a line-level xover you will always need an amp on each channel. More specifically, you need amp inputs on each channel. I say that because a multi-channel amp would only work if it also had independent inputs on each channel.

I use 2440's, EV15b mid-bass, and JBL 2240Hs for bass. Tweets are fostex t500amkii's. I used a different approach. No digital crossovers or amps though. Two, Marchand analog xovers, a couple of ~70 watt PP, and a 500watt SS amp. The tweets run with a simple cap off of one of the PP amps.

I am a little confused by your question regarding the resistor. You say these are bias pots (?) but I've not heard of stepped biasing. Are these stepped attenuators?

Sorry guys. I've been away. I hope this thread isn't dead. I have to apologize as I'm out of the loop in regards to this entire conversation and completely illiterate to the jargon. I have a pair of JBL 2440 compression drivers with horns and Hartsfield lenses, a pair of JBL C1200(12") mid-bass drivers and a pair of JBL 2245H(18") bass drivers. I want to cross the 2440's over at 700hz, the C1200's at around 300hz. I have the specs and requirements for the drivers and intend to build the cabs. Efficiency for the 2440's is 117db, for the C1200's 93db and the 2245's 95db. I just love the sound of the Ampzillas and have a bunch of them. The best ones IMO are the Son Of Ampzillas at 80w.min. per ch. I have three that are rebuilt and want to tri-amp, hence the Behringer. But it would be great to be able to use just one amp without the need for a passive crossover. Another question I have is whether it's possible to install a fixed resistor in conjunction with a lesser value bias pot in an amp in order to achieve a finer adjustment since you would now have a larger space of adjustment for the
wiper to rest on the pad. Multi-turn pots are such only because there is a step-down gear attached to the adjusting
screw but the actual pad is the same relative length as any other single turn mechanism. It simply allows you to arrive at the adjustment more easily but does not improve it's ability to hold the adjustment. It seems a wider place of adjustment on the pad would accomplish this. Is this a worthwhile exercise?

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I am triamping and Pure Music has a built in crossover that works seamlessly with the RME. Crossover points and slopes are adjustable along with polarity and gain. Very flexible. You can add whatever plugins you want if you want EQ or whatever. I play around Fab Filter ProQ for EQ.

I did it myself. The transformers are 1:1 that Dave wound specifically for this purpose. If you contact him he can give you a quote. http://www.intactaudio.com/index.html Probabaly around $200 each so you'll have as much or more in transformers as you do the RME. There are cheaper transformer options but Dave's are very, very good.

The tricky part is you are soldering on surface mount components which is very easy to mess up, and of course you void your warranty. I bought a used RME on eBay.

The RME has 8 channels of audio output with 4 stereo DAC chips. The chips have balanced outputs which are cap coupled to opamps. The mod bypasses the opamps by soldering the transformer primary directly to the outputs of the chip. Hook whatever connectors you need to the secondary running balanced or single ended as needed.

The traces are teeny tiny so very easy to burn up a trace which I did. Fortunately I only need 6 of the 8 channels so I'm still good to go.

I am an electronic tech but really no experience or expertise in dealing with SMT soldering. If you find a repair shop that is they should be able to do the work for you.

The RME sounds very good stock so you could start there, or explore other pro audio interfaces; Apogee, Lynx, and many others. Bear in mind the RME is Firewire and some others are USB.

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Herman, do you out souce your mods or do them yourself? Also, would you talk some about the transformers you purchased from Dave Slagle?

I am in the discovery phase about the RME. I have read through the website description and found a local store which stocks the product. I have a Galibier TT and triplanar arm and several hundred pristine lp's. Lp's have not been as magic since the driver rack came along.

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I used a Behringer before I switched to this set up. It was highly modified and did sound pretty good. The output opamps were bypassed and I used Dave Slagle (Intact Audio) transformers, the clock was replaced, and a linear power supply used. I'm using the same transformers in the RME. I was thinking about replacing the DAC chips which is supposed to be a big improvement when I decided to go with the RME.

I could have lived with it but the RME is better and allowed me to use Pure Vinyl software without having to have a phono preamp. If not for that I would probably still have the Behringer. The RME is not a LOT better than the modified unit but is a LOT better than the stock unit.

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Csontos, I have been using a Driver Rack Pa.This unit is in the same league as the Behringer.I have had this active system for two years. I highly encourage you to do so as well.

Herman, have you any expierence with other cross overs? ASi-tek mods the Behringer, I have spent some time considering that unit or maybe a Marchand.

Asi-tek has a upgrade option to mod the Behriger with transformer coupled outputs. i guess this is similar to the modded RME.

Csontos, I hope I am not redirecting your line of questioning. i am most interested in all discussions about active systems.

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You don't mention a budget but you could go the computer route like I did. Take a look at my system.

The Behringer is amazing for what it costs but you'll get a LOT better performance with a pro audio interface like RME and others.

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Please divulge your equipment, set-up and anticipated results desired to achieve.
A wealth of knowledge abounds here.

http://www.madisoundspeakerstore.com/digmoda-amplifiers/digmoda-ddc552-mono-plate-amplifier-3-channel/

How can you think of using an electronic crossover in an active configuration without multiple amps? Impossible.

If you mean getting one multichannel amp to replace all of your amps, sure. There are amps with many channels. Just define your power needs.

If you mean getting integrated amps/crossover, Linn offers this in their Majik range.

Kal