Op-amps vs transistors.

[11-90-an]

Anyone remember the RC4136 quad opamp?

This was the original op-amp in the "Woody" pedal right?

Woody is very interesting
If I remember correct, it is
A) Take original signal and split into 3 parts
B) First part do nothing
C) Second part boost the bass with a resonance
D) Third part Aural Exciter (high pass, distortion, filters)
E) Add all 3 paths back
Maybe use external reverb
Are there any other ways to do Acoustic Sim / Sitar Sim than above idea ?

As far as I remember, the first part does nothing, yes, but when mixed back it cancels out some stuff from the Exciter portion (which has a phase shift stage)

The cheapest "sitar sim" would probably be Tim Escobedo's Jawari and Psychtar:

[Rob Strand]

Why do you think they decided to just flip the power pins around and change the pinouts from the RC4136 type to TL074 type? anyone with ideas?

When I was a kid I always thought it was odd they didn't follow the 74LSxx and CMOS 4000 series power pins which are in the corners pins 14 and 7, sort of like the dual opamp.   

However, as an engineer the TL074 pin-out makes more sense since it keeps the pins of different parts of the opamp separated, and separated by low impedance tracks/pins.   The separation holds all the way from the pins to the internal die.

The RC4136 is clearly an extension of the dual opamp pinout.

Only the TL074 pinout seems like it comes from an engineering perspective.

Sometimes you can find old brochures which rationalize the reasons why things are done.

In the 70's there were a lot of weird parts and part pin-outs.  The companies put them out there but only the strong survived and that's what we see today.

[Vivek]

As far as I remember, the first part does nothing, yes, but when mixed back it cancels out some stuff from the Exciter portion (which has a phase shift stage)

Oops yes, the cancellations Comb filter effect is important for the illusion !!!

> Woody is very interesting
If I remember correct, it is
A) Take original signal and split into 3 parts
B) First part do nothing
C) Second part boost the bass with a resonance
D) Third part Aural Exciter (high pass, distortion,                                 filters )
E) Add all 3 paths back
Maybe use external reverb
Are there any other ways to do Acoustic Sim / Sitar Sim than above idea ?

The filter was a  band pass with a phase shift. It would create cancellations when mixed in with the original signal. Thanks for reminding me !!!

[Fancy Lime]

...
When I was a kid I always thought it was odd they didn't follow the 74LSxx and CMOS 4000 series power pins which are in the corners pins 14 and 7, sort of like the dual opamp.   
...

Really? When I was a kid I always thought it was odd that my parents wouldn't let me just have ice cream for dinner. Pinouts did not start bothering me until much later. We must have been very different kids, you and I...  To think that the always called ME a nerd...

Andy

[Steben]

...
When I was a kid I always thought it was odd they didn't follow the 74LSxx and CMOS 4000 series power pins which are in the corners pins 14 and 7, sort of like the dual opamp.   
...

Really? When I was a kid I always thought it was odd that my parents wouldn't let me just have ice cream for dinner. Pinouts did not start bothering me until much later. We must have been very different kids, you and I...  To think that the always called ME a nerd...

Andy

Rob is talking about when he was 6, not 5 of course.

[Vivek]

When I was a kid I always thought it was odd they didn't follow the 74LSxx and CMOS 4000 series power pins which are in the corners pins 14 and 7, sort of like the dual opamp.

When I was a kid, life was normal, till one of my friends made a little door bell circuit that would chirp like a bird.



He got me interested in building a circuit that was a flipflop driving 2 lamps. After I build it, I kept it running continuously for maybe 6 months !!!


Then in 1980, a kind neighbor gave me a copy of the NATIONAL SEMICONDUCTOR AUDIO HANDBOOK.

My life changed.

[11-90-an]

When I was a kid, I looked at the price of guitar amps and decided that I want to DIY my own.
Bought some parts, a fist sized speaker and a LM386

Long story short, I wasn't able to make any amp at all, ended up using a store bought one.

But then I have already started walking the down long road of DIY...

[Rob Strand]

Really? When I was a kid I always thought it was odd that my parents wouldn't let me just have ice cream for dinner. Pinouts did not start bothering me until much later. We must have been very different kids, you and I...  To think that the always called ME a nerd...

Nah, I was just a silly kid like everyone else, not even nerdy.   Electronics was just something I knew from a young age.

[POTL]

I never use quads for that reason. As I noted here and in "PCB Layout for Musical Effects", I will prefer two duals to one quad because the outputs can be all pointed in the same direction for signal flow.

Also, the power and ground contacts are located in reverse.
However, I recently decided to check whether it is more convenient to have 2 dual amplifiers or one Quad, and I can say that in some cases 4 channels may be more convenient. In particular, in the Madbean analog Octaver circuit, it was more convenient for me to work with four channels.

[ElectricDruid]

When I was a kid I made a "burglar alarm" for my bedroom that consisted of two pieces of tin foil separated by pieces of sponge, connected to a 9V battery and a piezo buzzer. I put it under the carpet in the doorway, so anyone who didn't know it was there would tread on it. Amazingly, it actually worked as intended, although it's true the carpet looked a bit lumpy...

sorry, what were we talking about?

[amptramp]

One specification of op amps is PSRR - power supply rejection ratio.  It is typically in the range of 60 db.  The OP seemed to be interested in using an amplifier stage in a pedal that sounded like it would have too much current drain for a battery.

If you look at a FET or bipolar amplifier, the output impedance of the drain /  collector is fairly high - certainly higher than the drain or collector resistor so variations in power supply voltage add with almost no reduction to the output signal since the voltage division between the output of the device and the output resistor is close to unity.  A typical op amp subjected to 0.1 volt ripple would cut that down to 0.1 millivolt.  Only a common source or common emitter buffer would get any reasonable PSRR and even then, it is not as complete as people would have you believe and you don't have the option of voltage gain..