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Old 08-30-2011, 09:38 PM
fifty8th1 fifty8th1 is offline
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Default LM741 IC Need to replace with faster ..genius's wanted

Guys ..

I have owned a Trident Development Fleximix Mixer since 1984. It works great
except one important thing ... it sounds bad ! It is the chips ... everyone in this
45 channel mixer is the same slow slew rate chip.... the LM 741.

They pull right out .. instantly replaceable ... Can anyone give me good advice on what chip might be available that has a fast slew rate .. and could work in this system ? I know my Protools 9 HD System would sure love to sound great in the monitors ..

Thank you very much ..
John ....
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Old 08-31-2011, 01:52 PM
Pete Gates Pete Gates is offline
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Default Re: LM741 IC Need to replace with faster ..genius's wanted

The standard replacement for years was the NE5534, there are lots of possibilities now: LT1028 / AD8671 / OPA627 and many, many more. I used to be able to keep up but not anymore. The price can vary quite a lot - the OPA627 is one of the best and most expensive, which will add up if you're going to replace throughout the console. If they are actual 741s they will be internally compensated so you will want to use a replacement that is compensated otherwise you'll be soldering in lots of ceramic disc caps.

BTW slew rate is just one issue the 741 has, indifferent input noise voltage, poor input voltage offset, poor gain bandwidth, limited open loop gain compared to newer devices, poor distortion...

Pete
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Old 08-31-2011, 01:55 PM
Pete Gates Pete Gates is offline
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Default Re: LM741 IC Need to replace with faster ..genius's wanted

ps I'd suggest just replacing the op amps in the buses/groups/output and one or two channels to see if the effort is worthwhile before attempting the whole lot!
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Old 08-31-2011, 02:53 PM
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the dude the dude is offline
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Default Re: LM741 IC Need to replace with faster ..genius's wanted

There is a lot more involved than a simple swap out of one amp to another
In a small quantity sure it's fine, the 741 is a j-fet and the 553x is not but will be ok

If you start replacing 10,20,30 or more I would expect issues related around power supply de-coupling and current ratings

You should look at the data sheets to find out a good match

Plus some 741 amp circuits used freq. compinsation in which swapping to a differant amp would not work well
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Old 08-31-2011, 03:15 PM
fifty8th1 fifty8th1 is offline
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Default Re: LM741 IC Need to replace with faster ..genius's wanted

If I find some of these suggested chips .... I would start on a channel or two.
Give it a couple days. I can also compromise. Most of the board is used for monitoring ...and not so critical. I could switch out only those that are used for recording only... Leave it at that for some period of time and decide later if I want to upgrade more.

Do you guys have a suggested place to buy the chips ? ... I can see there are many ... but all are different in some way .. and some confusing.

Most places I visited didn't have a way to check the specs of the chip..

THANKS SO MUCH..

John
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Old 08-31-2011, 03:25 PM
Pete Gates Pete Gates is offline
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Default Re: LM741 IC Need to replace with faster ..genius's wanted

LM741 is bipolar isn't it? Though there are low current jfet versions like the LF441 (not sure I've remembered that number right) or other manufacturer varieties like the good old TL071.

Good point about power supply though - some of the more "esoteric" audiophile op-amps are a bit hungry for current. He will have to compare datasheets to find something comparable with current draw.

Pete
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Old 08-31-2011, 08:03 PM
fifty8th1 fifty8th1 is offline
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Default Re: LM741 IC Need to replace with faster ..genius's wanted

Thanks guys for the help. I will compile everything I have turned up. I know a guy locally who may be able to help me decipher the specs. The soldering I actually don't mind ... it would be worth it to get a good chip. The Trident modules all pull out and are incredibly easy to work on. If I soldered caps for a week I would still be feeling great.

thanks ..
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Old 08-31-2011, 08:16 PM
Craig F Craig F is offline
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Default Re: LM741 IC Need to replace with faster ..genius's wanted

a almost 30 year old desk could probably stand to have it's electrolytic caps replaces as well if it hasn't been done before
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Old 09-01-2011, 09:07 AM
Rich Breen Rich Breen is offline
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Default Re: LM741 IC Need to replace with faster ..genius's wanted

Quote:
Originally Posted by the dude View Post
There is a lot more involved than a simple swap out of one amp to another
In a small quantity sure it's fine, the 741 is a j-fet and the 553x is not but will be ok

If you start replacing 10,20,30 or more I would expect issues related around power supply de-coupling and current ratings

You should look at the data sheets to find out a good match

Plus some 741 amp circuits used freq. compinsation in which swapping to a differant amp would not work well

Hmm - are your sure? IIRC, the 741 is standard BJT, maybe you're thinking of TL071?

In any case, this post is right on otherwise. It's a bad idea - there's so much more to the sound of the mixer than the chip - I would imagine all the support circuitry is equally crappy, plus, as the dude says, power supply will also be an issue if you're dropping in dozens of these things...

best,
rich
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