OP-AMP VIRGIN

bimasta

bimasta

Addicted Member
I know nothing about op-amps. The entire extent of my knowledge is: I know one when I see one. So talk down to me like Denzel’s 5-year old — can a different op-amp truly improve the sound?

Item: an old Phono Preamp (1986). Cost me pocket change. Broadcast unit, designed/built to a high standard, almost overbuilt — everything about it has serious intentions, and it sounds great. From deepest bass to high treble, it sounds perfect.

I had a “high end” SS preamp in my system at the time, one of the superstar brands. Comparing phono sections, they sounded identical. I could fine-quibble little things, but I could substitute the cheap little b’cast unit without “settling for less”.

So I didn’t keep the superstar (though its looks and prestige — and MC stage — were appealing). But I also didn’t really love it. Admirable, but more analytic than ‘musical’. Emotional music didn’t move me, and it couldn’t cut loose and Rock, too controlled. Since my good old cheapie sounds the same, I don’t use it — love having it as a back-up, but not main listening.

So that’s my question: can we get it to do what it’s missing? Or is this just how it sounds, and only minor improvements can be had?

It uses three Signetics NE5532AN op-amps. Will someone guide me a bit, preferably who knows them and others comparatively, for SQ, and for the low signals of Phono?
 
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the 5532 is a good opamp dating back decades. in recent years there have been advances in
opamp designs, extending bandwidth and all the features we love to hear about.

you can try different ones as long as (generally) the new opamp's maximum voltage is
not exceed by your device, and does not need compensation, and what the opamp
does in the original circuit. the key is whether the new opamp is not unity gain stable
and the circuit uses it with filtering that approaches unity gain at some frequency.
the RIAA (phono) curves dip to 0 (or unity gain) and this opamp may not work.

the flip side is that newer opamps have wider frequency bandwidths to handle
today's digital frequencies. this means there can be oscillation due to the original
design not being designed to newer opamps or higher bandwidth requirements.

then there's the decoupling that may be necessary, these are typically wired
right the pin and connects to the dual PS voltages to ground. occasionally you
see mention of decoupling between the dual voltage rails.

you are somewhat safe if you see a Zobel at the output (NADs have this)
which is a resistor in series with a cap that goes between the signal line
and ground. this passes the high frequencies to ground. otherwise
your wide-band power amp amplifies the oscillation. one of the few clues
is that your amp (and/or preamp) gets warmer. and you cannot hear
these oscillations but if the gain is up you can damage your tweeters.

you can look at the datasheets and scan for compensation and unity gain.

you are somewhat safe if you search for opamp replacements for the
gear you have. let others play the oscillation roulette.
 
The 5532 is a 99 cent part. Plenty of options from Burr Brown/TI etc, or analog devices. the BB 2134 would be a good starting point.
And if you really want to step up, you can go with discrete op amps from Sparkos labs dot com.
 
mcgjohn said:
The 5532 is a 99 cent part. Plenty of options from Burr Brown/TI etc, or analog devices. the BB 2134 would be a good starting point.
And if you really want to step up, you can go with discrete op amps from Sparkos labs dot com.
Click to expand...

Wow, it can get expensive fast. Especially if you have multiple op-amps in the circuit.
 
Previously i used OPA2134 Op-Amps in my DIY project and CD/DVD modification and after abou year ago i start to use OPA1612. It is more open sounding and clearer sound from OPA1612 then OPA2134. Anyway, OPA2134 is pleasure sounding Op-Amp. Inside CD/DVDs most manufacturer uses M4580 OP-Amps but when it change to OPA1612, any CD/DVD start to singing after that.
 
Not forgetting that while the 5532 is old, its still pretty well regarded by many.

I have replaced other opamps in some circuits on client's equipment, but left the 5532 in place in some equipment as I think it sounds good.

You would need to weigh up whether switching it out of a circuit (as Bob says above) will likely introduce some parasitic oscillation (by using a newer, faster device) that will need some suppression measures.

I did put a newer opamp in a Technics SU-V6 pre-stage with spectacular results.

Rolling is where its at, these things are usually cheap.
 
I'm learning a crash course here. Thanks for the info and ideas.

@Bob Your warnings of what could go wrong almost decided me "Forget it!" But love to experiment. Your idea to learn from others' trials and tribulations is smart, but there's nothing online. No one has played with this unit; few mentions at all in fact, even of its existence. And neat phrase "Oscillation Roulette" — is that like Monte Carlo roulette where you sink vast sums, but might win? Or Russian Roulette?

@mcgjohn I looked at Sparko and Burson awhile back. Bursons won't fit, Sparkos might. But even the cheaper Sparkos would cost 20-times what I paid for the preamp. Worth every penny if the results are there, but only one way to find out: roulette.

@FileFixer Interesting news on the OPA 1612: 'singing' is what's missing. But Bob's admonition "look at the datasheets and scan for compensation and unity gain" is an advanced class in foreign language for me, and that's just to see if a new op-amp is compatible in the circuit. 1612s might sing like the angels, but not if they don't work.

As is, it gives all the accuracy, details, dynamics I could want: I just want to add heart and soul. It may be foolish think those come in a chip. But the foundation is so good, not just its excellence at what it does right, but its construction. Just the case: a case is a minor thing, but this one isn't thin sheetmetal screwed together; or even solid slabs of aluminum bolted together — it's solid slabs welded into a uni-body. Just makes me think there's more potential.

No decisions yet, and more ideas may come in. Thanks for the education!
 
Most, if not all, of the opamps under discussion operate in class AB. None of them are ideal in small signal audio applications, IMO.
 
Jfets have worked very well in phono preamps over the years. Heck, one of my tube phono stages uses a Jfet in the first gain stage. I would think the OP amps having Jfets inside the chip could sound just as good.
 
oscillation roulette like monte Carlo simulations have game theory outcomes. the easy way
out is to put a wide bandwidth scope on the output. you'll see spikes if there is a high
frequency oscillation.

you could simply buy a bunch, look up in the data sheet if there are any "caveats".

lastly you could look underneath the current opamps to see whether they been
decoupled. Maybe the schematic shows this. maybe a previous owner did this.

and look inside the opamps may not be socketed. as my Dahlquist DQ-LP1 was
not, and I had to take it apart to find the problem when a bass channel in
the crossover went quiet.

and yes, mostly those who do the opamp "rolling" don't mention anything so
it's all in the trying.

it is my opinion that you can do this without having anything explode
(with the one exception that if your unit is overdue for a recap by being
original and over 20 YO and never having its oil changed which could
at any time have a minor/major failure that may be blamed on that
new opamp).
 
Frank Van Alstine uses TL-1028 opamps in his award winning VisionQ phono preamp. I have not owned or used better (I have 3 of these now). For $499, it can run any cartridge, including LOMC, and has loading options, small chassis size and wall wart powered.
 
bimasta said:
So that’s my question: can we get it to do what it’s missing? Or is this just how it sounds, and only minor improvements can be had?
Click to expand...
The first widely available and commonly used op-amp was the 741 which was seen a lot in the 1970s. It wasn't a spectacular device and was probably responsible for op-amps getting a bad reputation. Better op-amps came along later and the NE5534 (1980s?) was aimed specifically at audio applications. The NE5532 is a dual version of the 5534. It was an expensive op-amp at the time and was highly regarded. These days they are cheap and because they've been around a long time they're often seen as cheap-and-cheerful and scoffed at by audiophiles. However, Douglas Self (well-known designer) regards them very highly. Yes, you can pay a lot more for an op-amp but will it sound any better?

As for improving the sound of your phonostage ... :dunno: There are so many different ways to design a phonostage that it's hard for me to believe that simply changing one op-amp type for another will alter its sonic characteristic. There are lots of other design choices within a phonostage - even the way the circuit board is laid out - and I think they're responsible for the sound of the finished design more than the type of op-amp used.
Having said that, there's no reason why you can't try some different op-amps to find out for yourself. Yes, some op-amps might do odd things at ultrasonic frequencies so it's not 100% guaranteed safe to swap op-amps willy-nilly, but you might as well have a go. You can always put the old ones back in.

Just a word of caution: are the op-amps in sockets? If they're soldered directly to the board they can be difficult to remove without damaging the PCB tracks.
 
In my opinion unless the circuit for the OP amp is designed for it, you almost certainly won't see the maximum advantage in using it. I do think that changing an original OP amp for a more modern replacement can sometimes yield an improvement, because I've done it and seen the effects (replaced M5219L with OPA2604). This was in an Integrated amplifier, there may be more subtle gains to be had in the case of a stand alone phono pre-amp.
 
If I'm not mistaken Dr audio had a thread a while back about replacing certain OP amps in somewhat pedestrian CD players to very good effect.
If you wander down this path , the first thing I'd do is install sockets.
 
Any chance for a schematic? The broadcast phono amp I have uses op-amps, but something about the way it is designed requires the particular part number it originally came with. I forget which mine uses, and honestly without looking at it I can't recall what it even is. Smarter people than me explained this, and my fix was to just replace the bad op-amp with another of the same type to make it work again. Considering it went from one channel to two, there was significant improvement to be had.
 
@bimasta Depends on purpose and for what and where I use another Op-Amp instead of old Op-Amp. Sometime I use OPA1612, OPA1642 and OPA1622. These three Op-Amps sounds great. OPA2134 is basic hi quality Op-Amp and all rounder Op-Amp with great sound. Before any modifications I use shematics to see what i need to choose between these four Op-Amps.
One good example is XU09 portable headphone amplifier. XU09 have Mitsubishi M5218 Op-Amp on input and Ti OPA2604 at output. Changing this Op-Amps with OPA1612 on input and OPA1622 at output this headphone amplifier show real strength. Also if change R14 and R16 resistors (4.7 KOhm) with 100 KOhm resistors, volume on output is much louder then before when output was realy low. ;)
 
The NJM2068 is another "cheap and cheerful" opamp that is surprisingly good. NWAvGuy tested it as the quietest opamp in a shootout he did before disappearing. They're used by the millions in Japanese origin HiFi/home theater and pro-audio gear. Basically the Japanese equivalent to the 5532 in that they pop up everywhere you look in audio gear.

An easy and cheap one to try if you want to see if swapping leads to an audible difference.

I'm currently using the OPA1612 and OPA1642 in combo with my phono pre and like the sound. They require a SOIC-8 to DIP-8 adapter though. If soldering surface mount isn't your thing you can order them presoldered from the brown dog adapter distributors. :)
 
Forgot to mention. When swapping into older equipment, look at the slew rate of the opamp. If it's way higher than the original part you might need to do some additional decoupling on the power rails to prevent oscillation vs a slower part.
 
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