Mid Freq EQ - Possible replacements for LM741

[Whoops]

I would recommend OPA134, because it is very tolerant on its environment (layout, rail decoupling) and doesn't draw more current

Abbey I will follow your advise and use the OPA134, I should have quite a few around the workshop.
I was just worried that I could get into instability or oscillation in the circuit because the OPA134 is much faster than the 741

 

[abbey road d enfer]

Well, if I'm saying that it's because I know, when I don't know I ask.
The EQ section was turned off

Turned off how? If you by-passed it, you by-passed not only the 741, but more significantly the single-transistor stage struggling with the task of providing enough gain for the EQ to work AND driving the output and the NFB network.

 

[Michael Tibes]

I can't really understand the mid EQ at first glance, but why don't you just give it a try to swap the 741 and see what happens? I've had good experiences with kicking them out, it is actually the only opamp I know which really sounds 'bad' to me. It is hard to explain, somewhat choked and grainy.
Do you have the schematics of the rest of the console's audio circuit? Just curious, up until the mid eq it seems to be the most minimalistic channel design I've ever seen. I could imagine that Teds sonic description might be right, even though I also find his other claims regarding headroom rather obscure.

Michael

 

[Whoops]

Turned off how? If you by-passed it, you by-passed not only the 741, but more significantly the single-transistor stage struggling with the task of providing enough gain for the EQ to work AND driving the output and the NFB network.

The EQ section was turned off because I didn't press the "EQ IN" switch

 

[Whoops]

I can't really understand the mid EQ at first glance, but why don't you just give it a try to swap the 741 and see what happens? I've had good experiences with kicking them out, it is actually the only opamp I know which really sounds 'bad' to me. It is hard to explain, somewhat choked and grainy.
Do you have the schematics of the rest of the console's audio circuit? Just curious, up until the mid eq it seems to be the most minimalistic channel design I've ever seen. I could imagine that Teds sonic description might be right, even though I also find his other claims regarding headroom rather obscure.

Michael

Hello Michael,
I don't have the schematics of the other parts of the console, even this schematic for the Channel's circuit might have mistakes.
But the circuit is so simple that I will trace it when I have the time.
Yes I can confirm that Ted is right in is sonic description of this console. Thats why I bought mine, at that time I didnt even know that there were a lot of people still using this desk, and knew nothing on the circuit or it's history.

It's a simple 8 channel mixer with a stereo "Echo Return"
Every channel has unbalanced Direct Out, you can select pre or post fader with a jumper on the PCB
EQ has High, Low, and semi-parametric Mids
1x Aux Pre fader
1xAux Post Fader
Summing is passive
Then it Feeds a Stereo Limiter in the Master Section
Unbalanced LR Outs

As for the 741 Opamp yes It's quite an horrible device,  I already binned all the 741's yesterday.
I wil try OPA134, if I encounter any problems I move to the TL071. I have both at the workshop

Thank you

 

[abbey road d enfer]

The EQ section was turned off because I didn't press the "EQ IN" switch

So how do you know the 741 is the culprit? Not pressing the EQ switch by-passes several other things than the 741.

 

[Whoops]

So how do you know the 741 is the culprit? Not pressing the EQ switch by-passes several other things than the 741.

Sorry Abbey, I dont understand. Culprit of what?

 

[abbey road d enfer]

Sorry Abbey, I dont understand. Culprit of what?

Culprit of whatever you don't like in the 741 sound.

 

[Whoops]

Culprit of whatever you don't like in the 741 sound.

there's no 741 anymore, are on the trash can.

let's move on please.

Thanks

 

[radardoug]

So you dont like the 741 but you didn't know you weren't listening to it? This is why you need to do double blind tests, but none of the golden ears ever do!

 

[Whoops]

So you dont like the 741 but you didn't know you weren't listening to it? This is why you need to do double blind tests, but none of the golden ears ever do!

Well you need to read the thread otherwise you will just write ridiculous comments like your last one.

I never said I didn't like the 741 on the Alice 828, I said I didnt like it, period.
And I said I really like the sound of the Alice 828 channel and I know that changing the 741 will not alter what I like about the sound because when I recorded with the console the EQ  section turned off, and if you have read instead of writing absurd comments you will know that the 741 is in the EQ section.

I never said I wanted to improve something, I said I wanted to change one Opamp and asked for help in knowing if I could replaced ,
Just that.

 

[ricardo]

I was a real DBLT guru in my previous life.

741 is easily detected even by non-true golden pinnae run at -10dBu nominal level (with 20dB headroom) as were most domestic preamp outs in late 1970s.  Modern Red Book CD output would be about right.

Most telling is piano music .. Beethoven for preference.  It's a harsh clangy quality that gives it away if the noise doesn't.  Use good uncompressed stuff.  We had one of the first Sony PCM F1s in the country which was a revelation as a recorder though we tweaked the mike inputs.

The first OPA to be marginally (un)detectable was Raytheon 4136 but it wasn't until TDA1034 (which became 5534) that we felt confident that any extra circuitry & buffers we added wouldn't upset the DBLT results.  We were beta testers for TDA1034 before they even had a name for it.

Until then, we spent a lot of time trying to splice discrete BJTs to LM301 (bypassing the i/p stage) to try & get something to use as a building block with limited success.

 

[Whoops]

thanks for the info Ricardo

 

[radardoug]

Hmm, well 741s were used in the record and repro amps on the legendary 3M 79 recorders. Lots of hit records made on those machines. Some say they were one of the best sounding multitracks.

 

[ricardo]

Hmm, well 741s were used in the record and repro amps on the legendary 3M 79 recorders. Lots of hit records made on those machines. Some say they were one of the best sounding multitracks.

;D  ;D

And there are celebrated machines/mixers etc using 709s as well    Hands up those who actually designed these into gear.

I'm just reporting on what we found for DBLTs.

 

[PRR]

> I really like the sound.

Then why change anything??

 

[Whoops]

> I really like the sound.

Then why change anything??

PRR, I already explained my honest reasons in Post 12:

- Because it's cheap and easy to stick an opamp with better spces
- Because changing it will not alter what I like about the Alice 828 channels sound
- Because I really dislike the LM741 and psychologically I will fell better if I spend 10 euros putting there something better, even if the benefits are marginal because the costs are also marginal.

 

[abbey road d enfer]

Well you need to read the thread otherwise you will just write ridiculous comments like your last one.

No need to ride your high horses. Your original post was written in such a manner that it attracted these answers. Had you been more accurate in the description of the conditions of your observations, this wouldn't have happened.
We try to keep this group courteous (albeit animated) and open to all opinions, as long as they are properly substantiated.

 

[Whoops]

No need to ride your high horses. Your original post was written in such a manner that it attracted these answers. Had you been more accurate in the description of the conditions of your observations, this wouldn't have happened.
We try to keep this group courteous (albeit animated) and open to all opinions, as long as they are properly substantiated.

I strongly disagree, I'm always courteous but Radardoug didn't read what I wrote and rose his high horses by assuming something that was simple not true, and making  umproper comments, while not helping in the subject manner in any way.

I got the info I needed, so this is solved for me.
I would to thank you and everyone that helped in this thread.

 

[radardoug]

Sorry I dont have any horses high or low.