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Author Topic: Zener vs IC regulator for the preamp section  (Read 336 times)

Aleksandar

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Zener vs IC regulator for the preamp section
« on: August 30, 2019, 08:50:45 AM »
What would you choose between Zener and IC regulator for the preamp section and why? I read that zener regulated power supply is unstable, but then, would that make the amplifier feel more "organic" and "touch responsive" compared to the IC regulated one.

My goal is to build an amp with TL072 or TLE2072. The power supply would be +-15-18V. I want it to be as clean as possible, with as low noise as possible, because I will be using it for jazz. So, the greatest concern for me for now is how to regulate the power supply for a maximally clean and quiet preamp, but then again, I don't want a sterile Hi-Fi amp sounding either.

phatt

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Re: Zener vs IC regulator for the preamp section
« Reply #1 on: August 30, 2019, 10:22:48 AM »
Zener or IC reg will make no difference to any *Organic mojo*
These are SS amps and without any form of OD the amp will have no feel.
these trick have to be done in the preamp stages.
to get power stage rattle in SS power amps you need to have years of practice at building gear.
I use an old Laney keyboard amp which is rather basic and *Sterile* by itself but all the tricks are in the pedals I use, easier and cheaper than trying to reinvent the wheel of Valve power stage compression and all the other mojo that goes into that.

I have 6 pedals on my board 3 are brand names and 3 are my own designs.
This covers all my needs from clean to heavy OD. I don't play metal or like so I only need the classic rock which is often just a bit of compression and rattle. Some call this the edge of break up.

as to regs,, IC regs are trouble free and would have better regulation.
Phil

Enzo

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Re: Zener vs IC regulator for the preamp section
« Reply #2 on: August 30, 2019, 04:00:45 PM »
Who told you zeners are unstable?   A zillion guitar amps use zener regulated supplies for the op amps.

Loudthud

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Re: Zener vs IC regulator for the preamp section
« Reply #3 on: August 30, 2019, 07:11:44 PM »
If you want organic and touch sensitive, you don't want opamps and regulated power supplies. Those things are mutually exclusive.  Even a tube preamp can be cold and lifeless with a regulated or isolated power supply. To keep the hum out of a preamp, start with a well laid out ground and adequate filtering.

phatt

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Re: Zener vs IC regulator for the preamp section
« Reply #4 on: August 30, 2019, 11:41:58 PM »
Who told you zeners are unstable?   A zillion guitar amps use zener regulated supplies for the op amps.
Maybe i should have said that generally IC regs are more reliable?
I don't recall having to replace any IC reg circuits I've worked on. But you have many more years of experience than myself.
In my limited experience I've had to fix a few Zener regulated circuits.
Maybe not so much the fault of the Zener but the way it's implimented.
I can't recall exacts now but I recall a couple of SS Amps where the zeners have run so hot it delamed the copper track,,Overheating and killing the Electro beside it.
If only a little more thought went into layout and stand off the zener from the PCB it would have been ok?

Also after replacing the Zeners in my old faithful SS Laney twice in the first~5 years I ripped them out, replaced with ICreg and has given no issues in the last 10+ years.
Phil.

Enzo

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Re: Zener vs IC regulator for the preamp section
« Reply #5 on: August 31, 2019, 01:30:47 PM »
And IC regulators have to be properly mounted and heat sunk.  I have drawers full of 7800/7900 Vreg parts, mainly 15v but also 12v, 18v, 5v and others.   I surely do have to replace them.  And I have found some without heat sinks that failed in commercial products.  I replace zeners too of course.  I used to buy 1N4744 by the hundred.  Like anything else, it isn't the zener's fault if the part is underspec'd or not mounted properly.  You are correct, the engineers who did the design needed to put sufficient thought into it.

Scott Novak

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Re: Zener vs IC regulator for the preamp section
« Reply #6 on: September 01, 2019, 01:27:38 PM »
Zener diodes are NOISY!  I suspect that they are also much faster reacting than any op amp based regulator, so in that regard they may have some advantages.

Another approach is to use a zener diode as a reference for a series pass transistor.  You filter the zener diode well so that it's noise is reduced, then the transistor handles most of the load.  Select a fast transistor and you may well have a better sounding regulator than many, if not most op amp based designs.

But if you are using an op amp based design, keep in mind that at higher frequencies it's the decoupling capacitors on the output of the regulator that are going to be supplying the transient currents to the amplifiers, so pay special attention to power supply decoupling.

Don't forget that capacitors have series inductance and a natural resonance.  You might use a 10µF electrolytic with a low ESR capacitor bypassed with a 1uF polypropylene film cap, bypassed with a 0.1µF polypropylene film cap.  If your amp runs cool enough you may get by using polystyrene capacitors which are even better sounding, but more expensive and physically larger.

Also pay close attention to avoid ground loops within your layout.  Pay attention to where the decoupling capacitors are grounded.  You don't want the transient currents flowing through the capacitor ground connections to modulate another part of the circuit.

Scott Novak

mandu

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Re: Zener vs IC regulator for the preamp section
« Reply #7 on: September 01, 2019, 10:22:40 PM »
You can get Zener diodes for almost any voltage and wattage. They work as shunt regulators. Don't get easily damaged by over voltages like the 78xx. But voltage will dip on over current by load. Very widely used in many instrument amplifiers to drop from higher voltages above 35V DC. 78xx/79xx are Series regulators limited to selected voltages and prone to damage by higher supply voltages and some tend to oscillate under less load. Application to use 7xxx or Zener depends on the designer. All diode/transistor junctions are noisy when reverse biased. 78xx/ 79xx use zeners internally.

 

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