The audio issue may consider the OPA2132 (BurrBrown/TI)

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JohnInTX

Joined Jun 26, 2012
3,799
Mod edit:
This thread was split from #9 of the below thread:
CD4066 off state not off enough

http://forum.allaboutcircuits.com/threads/cd4066-off-state-not-off-enough.116866/#post-915544



With the resistor to ground it works perfectly now!
Regarding the TL07x I'll keep it in mind for my next supply run.
If you're doing audio, consider the OPA2132 (BurrBrown/TI). A bit more expensive than the TL07x but way better for audio - on the datasheet and in the ears. Less noise, higher slew rate and bandwidth. I've been toying with a guitar preamp design and that's what I've found so far.
The OPA2134 is similar and spec'd specifically for audio but I (and my test listeners) like the 2132 better.
Just my .02
 

#12

Joined Nov 30, 2010
18,076
If you're doing audio, consider the OPA2132 (BurrBrown/TI).
I missed them. :( My excuses: They had just recently been invented when I did my last low noise audio design, most people were still using Windows 3.something, and I hadn't found AAC yet. :oops:
 

Thread Starter

JohnInTX

Joined Jun 26, 2012
3,799
I missed them. :( My excuses: They had just recently been invented when I did my last low noise audio design, most people were still using Windows 3.something, and I hadn't found AAC yet. :oops:
I only wish I knew what you and others around here do in this area. This kind of my first 'serious' one. I culled all of the 'best dual IC amp' listings from sites like DIYauto, ESP etc as well as schematics from amps I like (and don't) and distilled them to a few PNs to try. So far so good. Apparently the MUSES stuff is even better - more BW and slew rate. Bought some but haven't tried them yet. But I thought I'd pass along what I've learned about the amps so far..
 
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#12

Joined Nov 30, 2010
18,076
I only wish I knew what you and others around here do in this area.
I'm so old that I still have some LM833's @4.5 nV, but I changed to the TL082. Can't remember why. o_O My primary audiophool likes a JRC 4558 because it doesn't have a latch-up hesitation when under volted on the power supply and over driven in the output amplitude. Eventually I changed to a single j-fet pre-amp of my own design (excellent bandwidth, low noise, no latch-up) and he's still waxing poetic about what a God I am. :eek: Of course, that means nothing when you consider I used 4 op-amps and a single ended jfet input for one of his fantasy projects, and he asked me if it would need software updates.:D

Edit: Took all day to remember that chip number was JRC4558. Anyway, it's about the same as the NE5532.
 
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hrs

Joined Jun 13, 2014
179
If you need good isolation, its common to use a pair of transmission gates. The control is fed directly to one and through an inverter to the other - one gate passes the signal, the second gate is shunt connected and switched on to short the signal when the series pass gate is off.
That's interesting, I'll have to research that, though I'm at a very basic level of understanding right now.

If you're doing audio, consider the OPA2132 (BurrBrown/TI). A bit more expensive than the TL07x but way better for audio - on the datasheet and in the ears. Less noise, higher slew rate and bandwidth. I've been toying with a guitar preamp design and that's what I've found so far.
The OPA2134 is similar and spec'd specifically for audio but I (and my test listeners) like the 2132 better.
Just my .02
I've read about those on the pages of Rod Elliott at ESP. He also recommends the NE5532 and I have a few of those. Prices from the webshop that I use are as follows for DIP8 packages:
Code:
TL082    $0.18
NE5532   $0.26
TL072    $0.29
OPA2134  $2.45
By the time I have something that works I'll make sure it's socketed and do some blindfolded listening tests :). Looking at the datasheets the NE5532 seems to be much better than the TL072 but maybe I'm missing something.
 

ian field

Joined Oct 27, 2012
6,543
That's interesting, I'll have to research that, though I'm at a very basic level of understanding right now.


.

Its rather like combining a series pass regulator with a shunt regulator - except they don't regulate like linear regulator, they're either on or off. One is on while the other is off and vice-versa.

When the pass gate is on, the shunt gate is off so it doesn't interfere with the signal - when the pass gate is off, the shunt gate is on so it shuts off any residual signal getting through.

Depending on the configuration of your circuit, you may need a second pass gate to isolate the load from the shunt gate, but in most cases you only need pass and shunt.
 

Thread Starter

JohnInTX

Joined Jun 26, 2012
3,799
I've read about those on the pages of Rod Elliott at ESP. He also recommends the NE5532 and I have a few of those. Prices from the webshop that I use are as follows for DIP8 packages:
The 5532 is a bipolar input amp so its input impedance is less - 300K typical. That's kind of low for a typical guitar maybe.. Its a great amp otherwise but you might want to stay FET for the preamp. I am using the 5532 as a reverb driver and may use it in later stages.. Don't know.

The OPA2132 is a little cheaper than the purpose-spec'd 2134 FWIW and as noted, sounds marginally better. From your pricing, you can see why most guitar amps I've seen use the TL072 all over the circuit. I'm only building one so don't care. The MUSES8920 was close to $20.00! It better be good.
 
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dl324

Joined Mar 30, 2015
8,877
I'll make sure it's socketed and do some blindfolded listening tests :).
I don't want to start a heated debate, but do you consider yourself a hardcore audiophile? Such a person would not tolerate distortion/noise introduced by an analog switch, a socketed part, or a semiconductor...:eek:
 

Veracohr

Joined Jan 3, 2011
688
I just read about the dual gate method, although using JFETs instead of CMOS gates, and tried it out. Worked quite nicely. The source that described it (Small Signal Audio Design by Douglas Self) showed 120dB+ off isolation at low frequencies, way better than the best claimed by analog switch ICs. That's beyond the capability of my equipment to measure, but I didn't see anything to contradict it.
 

Thread Starter

JohnInTX

Joined Jun 26, 2012
3,799
I think you aren't telling the truth in this moment.;)
NO worries. I have some 14ga. super de-oxiginated fine-stranded speaker cable made from the finest Chilean copper annealed on the thighs of... Anyway, since I can't tell the difference between that and the orange extension cord from Home Depot, we can use it as a noose if things get out of hand. :D
 

Veracohr

Joined Jan 3, 2011
688
Looking at the datasheets the NE5532 seems to be much better than the TL072 but maybe I'm missing something.
You're missing the effects of input bias currents. JFET input opamps like the TL07x series have essentially zero, and sometimes this is necessary.
 
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#12

Joined Nov 30, 2010
18,076
JFET noise doubles for every 10C increase.
Yebbut...does the bias current double?

Please. I keep my audiophools off this site as a courtesy to others. It just makes me too crazy to imagine a few dozen nerds dancing around a sacred cow with spears in the firelight.:D
 

ian field

Joined Oct 27, 2012
6,543
I just read about the dual gate method, although using JFETs instead of CMOS gates, and tried it out. Worked quite nicely. The source that described it (Small Signal Audio Design by Douglas Self) showed 120dB+ off isolation at low frequencies, way better than the best claimed by analog switch ICs. That's beyond the capability of my equipment to measure, but I didn't see anything to contradict it.
JFET series and shunt gates are fairly common in bypass circuits in guitar effects pedals.

If you search out schematics on that area, you'll also find examples of the 4007 MOSFET array used for the same function.

For RF work, the component of choice is the P.I.N. diode.
 

AnalogKid

Joined Aug 1, 2013
8,102
National's 833 was a very interesting part with single-supply capability and relatively low noise for opamps at that time, but I always found it to be a bit quirky. So in my head the 5532 was the first true grown-from-the-ground-up audio opamp. It has a partly-deserved reputation for its sound being a bit harsh, which is why everyone luuuuvs the later Burr Brown parts. A 2132/34 with a resistor from the output to the negative rail is a very smooth little puppy.

ak
 

Lestraveled

Joined May 19, 2014
1,943
Since we are dipping into the audio-idiotrocy of electronics, has anyone used the MC33078? It is the equivalent of the NE5534 with lower distortion and will accept much higher differential input voltages, and it is a cheap part. I recently repaired several Crown CE1000 and CE2000 amplifiers that used the MC33078 and the MC33079. Looks like a better part than the NE5534 in some ways.
 

Thread Starter

JohnInTX

Joined Jun 26, 2012
3,799
which is why everyone luuuuvs the later Burr Brown parts. A 2132/34 with a resistor from the output to the negative rail is a very smooth little puppy.
What does the R do to make it smoother and by smoother do you mean less crossover distortion? What value R?

Kind of a novice in this area...
 

AnalogKid

Joined Aug 1, 2013
8,102
By creating a current load to the negative rail that is related to but separate from the audio signal amplitude, the output stage never moves out of class A operation. Example: 2 Vpp output signal centered about GND, 1K load resistor to GND, and a 5K bias resistor to the -12 rail. Here are the peak output currents:

+2 V +2 mA into the load resistor and 2.8 mA into the bias resistor. Total current is +4.8 mA.
-2 V -2 mA into the load resistor and +2 mA into the bias resistor. Total current is 0 mA.

So even at the negative signal peaks, the output stage never sinks current from GND. With a smaller bias resistor the output stage is solidly in class A operation, hence no crossover, hence zero crossover distortion.

ak
 
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