John Curl's Blowtorch preamplifier part II

[DPH]

Given high end audio could do much much much much much worse than the high end data acquisition/instrumentation space, who cannot get enough performance (see: the entire reason we even have the ad797 today).

Most any of the line-level audio IC's released today were originally for instrumentation.

 

[Markw4]

Let us not forget there are also those who lament the loss of obsoleted parts for use in guitar distortion pedals. It's not just hi-fi enthusiasts who feel the loss. And, yes, seriously. Maybe used on some of your favorite records.

 

[billshurv]

Except that, if your goal is 'closest approach to the original sound' then that is entirely possible with current production parts. Getting that special sound from a pedal is as much woo and foo as design of course.


(obligatory Bill Bailey clip on this subject YouTube )

 

[john curl]

My problem is with designers using audio qualified linear op amps and excessively loading them for whatever reason. For example, a 300 ohm load on a 600ohm spec'd device. How about driving a headphone with a 5534? Apparently the sine wave analysis does not necessarily show much wrong, but what about a transient test?

 

[jcx]

another one bites the dust LM3046 Lifetime buy at TI

LM/CA3046 NPN transistor array used in bias, mirrors and 'translinear' audio signal processing circuits

 

[anatech]

Hi John,
Then they are lacking as far as design skill is concerned.

-Chris

 

[DPH]

Getting that special sound from a pedal is as much woo and foo as design of course.

I give a lot more leverage for what is in essence a musical instrument. Overload is less characterized so understandably a bit more of a shotgun approach.

 

[jcx]

...How about driving a headphone with a 5534?...

if you cut the age of the op amp design by an order of magnitude:

• High-Fidelity Sound Quality
• Ultralow Noise: 2.8 nV/√Hz at 1 kHz
• Ultralow Total Harmonic Distortion + Noise:
–119 dB THD+N (142 mW/Ch into 32 Ω/Ch)
• Wide Gain Bandwidth Product:
32 MHz (G = +1000)
• High Slew Rate: 10 V/μs
• High Capacitive-Load Drive Capability: > 600 pF
• High Open-Loop Gain: 136 dB (600-Ω Load)
• Low Quiescent Current: 2.6 mA per Channel
• Low-Power Shutdown Mode With Reduced Pop
and Click Noise: 5 μA per Channel
• Short-Circuit Protection
• Wide Supply Range: ±2 V to ±18 V
• Available in small VSON-10 μPackage

 

[EUVL]

OPA1622 ?
It is a product most probably targeted at mobile devices (phones or what not).

We built one or two.
Probably OK compared to other opamp headamps.
But no comparison to our other discrete designs.
It has been sitting in my drawer for the last 9 months or so.

http://www.diyaudio.com/forums/vendor-s-bazaar/283672-audio-op-amp-opa1622-25.html#post4747938
http://www.diyaudio.com/forums/vendor-s-bazaar/283672-audio-op-amp-opa1622-27.html#post4789925
http://www.diyaudio.com/forums/vendor-s-bazaar/283672-audio-op-amp-opa1622-30.html#post4953256


Patrick

 

[PMA]

Go composite.

 

[jcx]

yes OPA1622

I particularly like the gnd pin - gives high PSRR to high frequencies, above the usual excess loop gain limit, better than 99% of discrete design I've seen which reference Cdom to a power rail

 

[scott wurcer]

It is a product most probably targeted at mobile devices (phones or what not).

I haven't followed up on how the separate hi-end path in cell phones has worked out. One manufacturer's secret sauce was to pad the output to the earbuds with a resistor, shades of the Carver challenge.

 

[EUVL]

Go composite.

Been there before.


Patrick

 

[EUVL]

One manufacturer's secret sauce was to pad the output to the earbuds with a resistor, shades of the Carver challenge.

AD does not seem to have something specific for headphones ??


Patrick

 

[scott wurcer]

AD does not seem to have something specific for headphones ??

At the time it was repurposed xDSL drivers.

 

[EUVL]

So not interested in the mobile market ?


Patrick

 

[scott wurcer]

So not interested in the mobile market ?

No, I heard there is a part now. You must realize the margins are brutal, then there's the 10M piece orders here today gone tomorrow.

 

[Waly]

My problem is with designers using audio qualified linear op amps and excessively loading them for whatever reason. For example, a 300 ohm load on a 600ohm spec'd device. How about driving a headphone with a 5534? Apparently the sine wave analysis does not necessarily show much wrong, but what about a transient test?

So how is an incompetent designer related to the op amp audio performance?

 

[billshurv]

I give a lot more leverage for what is in essence a musical instrument. Overload is less characterized so understandably a bit more of a shotgun approach.

Yes, but a Luthier understands how to work with the materials at his disposal to get the desired result. A pedal maker to the outside world seems to be several orders of magnitude less 'craftful' . I suspect the punter needs to know about magic vintage leak-a-lot caps and carbon resistors as well.

 

[billshurv]

The OPA1622 'might' have some applications in the field of 'silly low noise preamps' as it can drive enough current so you can keep feedback resistors low. Shame it's not designed for the amateur solder flinger to mount with any reliability. But as ever TIMTOWTDI