Voltage regulators for line level circuits

From 1995:
 

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Nicke

Member
2001-06-20 11:27 am
Sweden

ALW

Member
2001-06-12 10:15 am
UK
Good post Harry

Nice collection to play with.

For Nicke,

I'm currently awaiting some professionally produced PCB's for the updated Jung reg's (with the tracking pre-reg).

I've built about 10 units as prototypes and they are fantastic, transforming everything they've been used with, from preamp supplies to portable MD units.

The differences between the circuits are interesting. The op-amp based units all offer lower output impedance, owing to the large small-signal gains available. The downside is that op-amp compensation being what it is open-loop BW drops with frequency, hence impedance at the reg o/p rises.

The discrete circuits have the potential to offer much wider OL BW, the POOGE one, for example offers flat o/p impedance to >100kHz.

This can, subjectively, be preferable in certain applications (primarily where noise is not the major concern) as it gives a neutral sound. Impedance is nearly always higher in these designs though, without some exceptional amplifier design.

Newer op-amps offer some hope here (Ad817 / AD825) offering much wider OL BW (to approx 10kHz). It's again at the expense of impedance and noise.

The other thing to bear in mind, as Walt mentions in his 2k update, the low-noise non-degenerated front ends of units like the AD797 can easily be driven into non-linearity in certain applications (notably digital designs with high levels of HF noise). As always careful selection for application is beneficial.

For my 0.02, the op-amp suppplies are marvellous for limited supply voltages, offering the lowest noise, low o/p impedance and stunning line rejections, discrete is the only option at higher V for power amps etc.
I recommend everyone to try the POOGE (with my updates) as it's easy to trial using prototype board (or even HH's beloved p2p!) and is such an order of magnitude better sounding than a 3-terminal reg. They're stable, cheap and fun!

Andy.
 

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Re: Good post Harry

ALW said:

I recommend everyone to try the POOGE (with my updates) as it's easy to trial using prototype board (or even HH's beloved p2p!) and is such an order of magnitude better sounding than a 3-terminal reg. They're stable, cheap and fun!

Andy.

Are they much better sounding than LT1085 types?
I'm asking because I'm still looking for good regulators for my CD Pro 2 project. I'm almost settled on LT1085, but still hoping to find something better.
 

ALW

Member
2001-06-12 10:15 am
UK
PCB Artwork

RonS,

I'm not keen to distribute the artwork at present, as I'm planning to sell professionally produced PCB's - sorry!

I put a massive investment in time and parts into the prototype units, and hope to recoup some of my costs to invest in future projects.

Also, the +ve reg's are the only ones I have at present, negative ones are now in the prototype build stage.

Andy.
 
Let me rephrase my questions. All those regulators seem to be delivering 14V. What should be done to modify them into 5V?;)

ALW, I would be also interested in purchasing your boards if they come available. I've seen your previous posts and can imagine the amount of work you invested. But it's hard for me to imagine that those reg. are better than LT1085 (just kidding;) ).
 
What should be done to modify them into 5V

Not quite than simple when supplying the opamp supply with the regulators output voltage. Also the reference voltage must sit inside the common mode limit of the opamp as well as the output
of the opamp being level shifted to drive the base of the output transistor. The first step would be to find a good op amp that runs on a single 5V supply. Also what are you current demands and preferred input voltage?

Op Amp gurus?........

H.H.
 
Re: What should be done to modify them into 5V

HarryHaller said:
Not quite than simple when supplying the opamp supply with the regulators output voltage. Op Amp gurus?........

H.H.
HI,
I did not find the time yet to draw and post my schematic.
I am using a 5V reference and this is "amplified" by the opamp-follower combination to 5V (gain = 1). The opamps are powered from the raw 20 V supply. For a 15 V regulator I am using a gain of 3.
For the negative regulator the reference voltage is inverted by a opamp to -5V. The positive regulator opamp is powered from +20V and the negative supply regulator opamp is powered from -20V.
It is all very simple and very good working without oscillations.
Note that for a +/-5V and +/-15V supply used in my KWAK-DAC only one reference is used.;)
It all fits just on one Eurocard (100x160mm PCB) including heatsinks.;)
More later.;)