Just bumped into it looking for quieter alternatives to the ubiquitous TL062 for a battery powered bass guitar tone circuit. Ok, power consumption is higher, but still much lower than the usual audio opamp suspects, noise is decent, THD doesn't look bad. It's expensive but in opamp world that means it costs $5 instead of $0.50 and I only need one, so I think I'll manage. Any reason not to use it or any better alternatives?
Many thanks,
Carlos
The AD822 is a JFET replacement for an LM358 (half of an LM324) or LT1013 single-supply opamp, featuring rail-to-rail outputs. Both the single-supply and rail-to-rail aspects are attractive for some applications (especially with a JFET input), but both involve compromises that degrade the opamp's performance. There are _much_ better choices for high-quality audio JFET opamps.
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Thanks,
- Win
You might want to check out these chips
gg
Would you care to let us have your thoughts on high-quality audio op amps?
Graham Holloway
Looks like the JFET equivalent to the venerable 5534 (performance rated for driving 600 Ohm loads). Nice choice.
But are there any with the sort of power consumption of the AD822 (800 uA/amp), preferably in an 8PDIP package? My first choice would have been the OPA2134 (what I normally use), but as someone else said at 4 mA/amp is on the high side for battery operation.
Many thanks again,
Carlos
Supply current at 4mA / op-amp is somewhat more than a TL062. Not ideal for battery operated.
Graham
I'd say if you want 0.00008% distortion you'll have to pay the 4mA. Perhaps you can afford more distortion? If so, how much?
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Thanks,
- Win
If I recall correctly, I used it in my upgrade for a Music Man StingRay Bass tone circuit.
Here's the article from long ago:
A few weeks back I wrote about how Mabel, my most attractive Ernie Ball Music Man StingRay, had a bit of noticeable hiss when listened to through headphones. When played through a speaker bottom the hiss wasn't noticeable at all, but I sometimes record plugged directly into the mixing board and often practice with my AMP BH420 head driving my Grado HP-1 headphones. Then the hiss was a bit much.
Where did Mabel's hiss come from? Well, the StingRay has an active pre-amp. The key component in the pre-amp is a Motorola TL-082 dual op-amp. While it works very well on a single 9 Volt battery, has an admirably low power consumption and a fast slew rate, the TL-082 does have a fairly high noise level. If I boosted Mabel's high frequency EQ at all, the hiss started to intrude. Luckily, dual op-amps come in a standard 8-pin DIP package with standard pin-outs. I removed the TL-082, installed a high quality socket in its place, and went spelunking through the IC catalogs for potential replacements. When the data sheets pointed to a likely candidate I rounded one up, plugged it in and listened.
It wasn't an easy search but I found just the one: the Analog Devices AD822. It has much better noise specs with only a negligible reduction in battery life. And in addition to its lower noise, it brings an equally important side effect: it sounds better! Considering how much I already love my Mabel's tone, this is *not* a trivial matter.
When I listen very critically to Mabel using top quality 'phones, the TL-082 has a quality that I can only characterize as slightly brittle, or maybe a little glassy, or even like a little bit of momentary flanging on the attack of a picked note, sort of a tap-on-a-window-with-a-glass-rod overtone. The only way to tame it is to cut too much of the StingRay's characteristic clarity and bite with a serious cut of the amp's high frequency EQ. But when I installed the AD822, the brittleness disappeared leaving Mabel's clarity and incredibly forceful low end intact.
Even with the new op-amp, if I boost Mabel's high end a bit too much I can still hear hiss, but it's not close to the TL-082's intrusive level. And to keep me interested, her newly tamed voice is even more enticing than before.
-- Len Moskowitz PDAudio, Binaural Mics, Cables, DPA, M-Audio Core Sound http://www.stealthmicrophones.com Teaneck, New Jersey USA http://www.core-sound.com moskowit@core-sound.com Tel: 201-801-0812, FAX: 201-801-0912
But it's not single supply.
-- Len Moskowitz PDAudio, Binaural Mics, Cables, DPA, M-Audio Core Sound
To be honest I think for this application something like 0.1% would be more than adequate. The circuit is basically a unity gain input buffer followed by the usual negative feedback tone control arragement with
+/- 20 dB boost/cut, so I'd say worst case would be G = 10 @ 5 kHz (harmonics and all I don't expect much life above that freq, if any the 15" speaker will filter it out anyway). Any candidates giving 0.1% THD or better under those conditions plus better noise performance than the TL062?If not, what's the best I can do at or below 1mA/amp consumption?
Tnx+,
Carlos
In many circuits, this won't matter. If the inputs and outputs of the op amp are capacitor-coupled, and there's a resistive-divider biasing network connected between the input and each supply pin, and if the circuit doesn't require the op amp to drive its output particularly close to either voltage rail, then it won't matter whether the op amp is marketed as "single supply" or not.
Since op amps have no ground pin, and really don't know where "ground" is in relation to their supply voltages, what really matters to them is how close to their positive and negative rail voltages the input and output signals have to go.
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Dave Platt AE6EO
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Both are -- or not -- you just bias them differently.
It was daft to use the TL082 in the first place.
The TL072 has the same current draw IIRC but lower noise. It is widely used in quality audio ( whereas the 082 isn't ).
The TL062 has a tiny current draw ( great for battery use ) but is noiser than the 082. Horses for courses.
Graham
He wants the lower noise.
I've been struggling to think of a better device in this application - i.e. noise vs current draw.
If I have any inspiration, I'll post it.
TL071/2 is lower current at 1.4mA typ per amplifer but noise is higher at 18nV / rt Hz than the OPA2134's 8nV / rt Hz although lower than the
062's 42 nV / rt Hz ( with it's 200uA typ per amplifer Icc ).Practice suggests that TL072 is a good compromise choice. It also has good typified distortion figures. It will work pretty well in this application.
I recall incorporating 072s into a product back in 1980 when they were pretty new.
I think the similar LF351/3 from Nat Semi offer 12nV / rt Hz ( subject to memory accuracy here ) but unsure of Icc.
Lol - the book was on the shelp. 1.8mA / amplifier and 16nV / rt Hz.
The LF351/3 have a habit of being a little more 'touchy' though. Prone to oscillating given half a chance.
Graham
The 5535 isn't 'single supply' either.
Graham
The TL072 @ 1.4mA typ per amp Icc is way the best bet IMHO.
It should be a straight drop-in replacement for an 062 too without any further thought.
Not a 'touchy' op-amp ( except as a voltage follower - use a series resistor on the output for driving long lines - use ~ 100 ohms ) well regarded - characterised low THD and low noise for your application ! Note for Hi-Z pickups, the source Z may predominate in noise analysis rather than the input noise of the active stage.
Graham
Hey, it's for a guitar. To get the "tone" it's wrung through a chain of filters, clippers, distorters, echoes and other effects beyond all recognition so why worry about a little bit of distortion at the source?
Having said that, I make and sell a tone filter preamp for a guitar making friend of mine using the TL072. It's basically unity gain, but since the pickup signal normally is rather large (~ 100mV) the subsequent gain is kept low enough to make the noise imperceptible. At least there haven't been any complaints about it.
I have also examined other preamps, some of which were hissy and/or distorty as all hell, those are usually badly designed bjt circuits. They usually come my way because the owner wants to replace it with my quieter version.
- YD.
-- Remove HAT if replying by mail.
[snip]
Many thanks Graham and everyone else for your help. It does look as if the TL072 will be the best option. I must admit I ovelooked it because I assumed the specs would be similar to the 062, just higher power consumption, but it looks more than adequate for this application.
Thanks again,
Carlos
But the AD822 is. And since he's running from a 9VDC battery that's desirable.
-- Len Moskowitz PDAudio, Binaural Mics, Cables, DPA, M-Audio Core Sound http://www.stealthmicrophones.com Teaneck, New Jersey USA http://www.core-sound.com moskowit@core-sound.com Tel: 201-801-0812, FAX: 201-801-0912
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