Sound of LM741 op amp?

[jdurango]

I'm looking for a VERY vintage, vibey, warm, fuzzy almost lo-fi sounding circuit. I've found a console with metal can 741 op amps driven by peerless transformers.

I know many here consider them terrible op amps, but I'm not at all going for a clean, fast, low noise sound. Quite the opposite. I need something with some nice smooth HF distortion and slow slew rate to tame harsh cymbals and transients....think 50's/60's kinda vibe.

Anyway, is the 741 a good choice for this? Anything else I should consider? Any good discrete options? Thanks!

 

[gswan]

The 741 is an op-amp which will give a low-fi output. It will have noise/hiss and a fuzzy top end. I would not consider it 'warm', just not an accurate signal path, so you will get the kind of effect of a cheap 1970's desk (eg a Jands JM5).

 

[Michael Tibes]

In my experience the 741 doesn't sound 'good' but 'bad vintage' - at least for my taste. Maybe a very simple transistor circuit would do the magic?

Michael 

 

[jdurango]

Thanks for your replies. Could you be more specific about the sound quality (or lack thereof)? Qualities or characteristics? Thanks!

 

[gswan]

Sounds a bit like cheap no-name brand cassette tape. Plenty of noise and no real transients. I was glad to get rid of them.
Remember. Not all vintage is good. A lot of it was bad, simply because it's all there was at the time.

 

[gar381]

You can play with the old LM301.  If memory serves me Eventide Clockworks used these
in the real old DAZE.  They are a bit faster.

GARY

 

[JohnRoberts]

Thanks for your replies. Could you be more specific about the sound quality (or lack thereof)? Qualities or characteristics? Thanks!

When the 741 was designed they made it as good as they could. It is not very fast, around 0.5V/uSec so if you slew rate limit it will sound like slew rate limiting.  If you operate it with lower nominal signal voltage (like -10dBV instead of +4dBu ), and at modest gains, it will probably not slew limit and sound OK.

JR

 

[midwayfair]

They sound pretty good in a RAT pedal where lots of "good" op amps won't!

Is a breadboard to try it out of the question?

 

[Whoops]

.think 50's/60's kinda vibe.

Anyway, is the 741 a good choice for this? Anything else I should consider? Any good discrete options? Thanks!

Simply put, No.
You will not get a 50/60s vibe with the 741.
The 741 was not even available at that time, it was introduced in 1968 and not even specifically for audio.

As I wrote you in the other thread if you want a 50/60s  vibe, you should get something from that period.
It starts with the music, the instruments used, the preamps and microphones of that era, the type of effects and mixing choices, etc.

 

[CJ]

install a socket, plug and play,

they still sell them at digikey, cans are not cheap, but saves offshore drama from evilbay,

get some Melcor opamps if you want mellow vintage,

no wait, don't get those, leave them for me!

 

[jdurango]

install a socket, plug and play,

they still sell them at digikey, cans are not cheap, but saves offshore drama from evilbay,

get some Melcor opamps if you want mellow vintage,

no wait, don't get those, leave them for me!

I'd love to use Melcors. The console I have uses Peerless 15356 line xformers for line and mic ins. They can go 1:2 with input impedance of 630 @ 10k, which isn't ideal for mics but will probably work with a 990 DOA circuit @ 24v.....not sure if those 1:2 t Randy's are a good way to drive Melcors though. What do you think? Any existing circuit or schematics I should consider? Thanks!

 

[CJ]

there should be some stuff in the META on rolling your own Melcors, used to be a lot of that going on around here, boards for sale, parts in the Black Market,

 

[jdurango]

there should be some stuff in the META on rolling your own Melcors, used to be a lot of that going on around here, boards for sale, parts in the Black Market,

Awesome! Will check it out! Thanks!

 

[Monte McGuire]

You can play with the old LM301.  If memory serves me Eventide Clockworks used these
in the real old DAZE.  They are a bit faster.

The LM301 can be faster, but the LM741 was the "already unity gain compensated" version of the LM301. So, the LM301 would only be faster if you're using it above unity gain, with your own-provided compensation cap (or lack thereof).

Yeah, both of these amps are really slow, but still, it's worth mentioning that 3M was able to 'almost' successfully use them in the repro amps of some of their '70s tape machines by using custom wound transformers to step down the signal voltage around these hobbled amps, and then use even more custom wound transformers and some discrete stages to get an output that was suitable for a professional audio device. My point is that if you carefully engineer the "context" of such a slow amp to limit the voltage swing, you can get it to pass 20kHz without slew limiting, and almost make it worthy of professional use. Not such an awful tradeoff, given the high noise floor of tape re. IC amplifiers, and the inability of IC amplifiers then to slew voltage.

That said, 3M later released a bunch of retrofits to these machines, once the TDA1034 and NE5534 became available, so that owners of these tape machines could use an amp that actually worked well.

Oddly enough, 3M's discrete electronics machines (M56?) also used amplifiers with really low collector currents and very large compensation caps, so their discrete designs were pretty much equivalent or worse than a 741 in terms of slew problems, for reasons that I cannot understand. I think they were fixated on the current noise that results from a high collector current, without considering that a high collector current lets you reduce voltage noise by using lower circuit resistances, which also makes current noise less relevant. But again, using their odd step-down and step-up transformers, they seemed to get the thing to pass 20kHz.

Such are the awesomenesses of "vintage circuits"! Nobody would do any of that now, so, to  the original poster, if you want "vintage sound", you should try to find a device whose flavor you like and then study the circuit. There are too many versions of "vintage sound" to be able to sort it out easily, without ending up with something that simply doesn't sound that good.

 

[jdurango]

The LM301 can be faster, but the LM741 was the "already unity gain compensated" version of the LM301. So, the LM301 would only be faster if you're using it above unity gain, with your own-provided compensation cap (or lack thereof).

Yeah, both of these amps are really slow, but still, it's worth mentioning that 3M was able to 'almost' successfully use them in the repro amps of some of their '70s tape machines by using custom wound transformers to step down the signal voltage around these hobbled amps, and then use even more custom wound transformers and some discrete stages to get an output that was suitable for a professional audio device. My point is that if you carefully engineer the "context" of such a slow amp to limit the voltage swing, you can get it to pass 20kHz without slew limiting, and almost make it worthy of professional use. Not such an awful tradeoff, given the high noise floor of tape re. IC amplifiers, and the inability of IC amplifiers then to slew voltage.

That said, 3M later released a bunch of retrofits to these machines, once the TDA1034 and NE5534 became available, so that owners of these tape machines could use an amp that actually worked well.

Oddly enough, 3M's discrete electronics machines (M56?) also used amplifiers with really low collector currents and very large compensation caps, so their discrete designs were pretty much equivalent or worse than a 741 in terms of slew problems, for reasons that I cannot understand. I think they were fixated on the current noise that results from a high collector current, without considering that a high collector current lets you reduce voltage noise by using lower circuit resistances, which also makes current noise less relevant. But again, using their odd step-down and step-up transformers, they seemed to get the thing to pass 20kHz.

Such are the awesomenesses of "vintage circuits"! Nobody would do any of that now, so, to  the original poster, if you want "vintage sound", you should try to find a device whose flavor you like and then study the circuit. There are too many versions of "vintage sound" to be able to sort it out easily, without ending up with something that simply doesn't sound that good.

This is great info. I've heard those 3M 79 tape machines had them, but I but didn't know how well their limitations were compensated for.

I know the very popular and highly regarded  Studer 169 uses LM301 IC's (even though it's often described as "all discrete"). If the LM301 shares some of the poor characteristics with the LM741, I'm surprised it works so well in the Studer. Then again, it's a Studer, so not that surprising.

 

[gridcurrent]

Yeah, both of these amps are really slow, but still, it's worth mentioning that 3M was able to 'almost' successfully use them in the repro amps of some of their '70s tape machines by using custom wound transformers to step down the signal voltage around these hobbled amps, and then use even more custom wound transformers and some discrete stages to get an output that was suitable for a professional audio device.

the 3M79 employs a 1:2 output transformer with the741 based line amplifer in order to achieve  "pro spec" +24 dBm;
this from a single ended +28 VDC power supply.
The 741 was also integral to the record circuitry.
Line input transformers were an option, the unbalanced input impedance listed at 2500 ohms.
The reproduce amplifier only employed head transformers in sync mode, the play head being high Z.

 

[jensenmann]

If you want to play with 741s then try the Harris/Intersil version of these if you can find them. They had better specs. But then they don´t sound "bad vintage".
Melcors are a good call, give them a try.

 

[emrr]

Or you can try any of the vintage 2520 footprint instrumentation opamps which are typically slow and start to lose treble by 10kHz. 

 

[ricardo]

If you want some music that will reveal the (yucky) sound of 741s, try well recorded Beethoven Piano Sonatas.

That's assuming you know what they sound in real life  8)

That's good for other stuff too .. like proper dither.