Best low noise regulator?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Spent the last week trying to find something which will power an opamp phono (627->637) and sound better than an ALW-Jung regulator.

In short: nothing came close.

What i tried:

1. 317/337 followed by a cap multiplier. Claim to fame: JC uses the topology in the Vendetta and BT. I was a bit worried about starving the four opamps for current and instead of parallel fets used a bipolar multiplier as Teddy Pardo.
Pleasant, "natural" sound but not much detail or particularly wide soundstage. Diffuse sounding pianos. Still, an obvious improvement upon a 317.

2. Simple 3 transistor regulator using a board from the UGS group buy. A differential amplifier and a pass mosfet (IRF9610). Obviously not so low noise. Similar sound to above.

3. Used a fast opamp (AD811 - 45mA max current) with a low noise voltage reference. Opamp output feeds the phono pre directly. 317/337 used to power opamp.
Interesting sound. Larger than life dynamics, extreme detail in high frequencies. Very impressive on some records but something is obviously not well. Slightly peaky midbass and generally nervous sound. Oscillations that i cannot see on a 60MHz scope? Tried the same using more ordinary opamps. Less nervousness but still not great.


These are not the first regulator experiments i've made. Looks like open loop designs don't attract me too much, at least when powering opamps. This is so uncool :(

Any ideas i've missed? Is the ALW really the best regulator to power an opamp circuit?

Previously i didn't like the sound of simple shunts (CCS feeding a TL431 with a bipolar shunt). Should i re-examine them? Any particular recommendations?

Not surprisingly the ALW is very sensitive to the opamp used. Its sound flavour is very similar to that of the opamp used as an amplifier. I have had best results with AD797 and OPA627 and less pleasant with the AD825.
 
analog_sa said:
Any ideas i've missed? Is the ALW really the best regulator to power an opamp circuit?

Previously i didn't like the sound of simple shunts (CCS feeding a TL431 with a bipolar shunt). Should i re-examine them? Any particular recommendations?

Try this one, you may be very pleased with. I'm using it in my phono preamp. You may replace the resistor with a current source, although I did not find this having any significant impact. Force/sense wiring rules still apply for optimum performance.

http://www.diyaudio.com/forums/showthread.php?postid=1735561#post1735561

Opamp is THS4031, but other high speed low noise models can be used. LED is a red or infrared model (others have larger noise, definitely not blue or violet).
 
analog_sa said:
Thanks. I had something similar in mind, probably with a lower noise voltage reference in order to keep the output cap small. No idea what the specs on the mosfet are but i guess an IRF610 will work just fine. Will report the result soon.

It's a high current (60A if memory serves) MOSFET from ST, in TO220. I had these lying around but any other model will work. You may need to adjust the gate resistor.
 
Hi analog_sa,

Image below represents Walt Jung (positive and negative) SupeRegulators build by a friend of mine, but PCB design is all mine. Both regs PCBs have full rectification and CRC filtration on board prior to regulation, error opamp used in both regs is an Analog Devices OP27. All measurement are done by him, so I really don't know how well/bed setup was, I have never had a scope, but anyway...
DSC00563.jpg


Next image represents residual noise of the scope not connected to anything (top line) and noise at the Jung regulator output with resistive loading (bottom line) measured as stand alone (outside the Marantz CD14 cd player), vertical scale is 5mV on all images.
DSC00568.jpg


Jung regs build in Marantz CD14 powering complete analog section after TDA1547 dac.
DSC00572.jpg


Noise at Jung regs output when they are build in Marantz CD14.
DSC00582.jpg


Output noise at original Marantz CD14 discrete regulator powering HDAM opamp modules.
DSC00578.jpg


Output noise at original Marantz CD14 discrete regulator powering TDA1547 DACs
DSC00584.jpg


Output noise at original Marantz CD14 LM7805 regulator powering other digital circuits
DSC00585.jpg
 
Something's bugging me. There is a large number of opamp driven shunt regulators similar to Syn08's design. No idea who invented the topology but the first implemenation i remember seeing was Allen Wright's SuperReg. All of these bar Manfred Huber's design run the opamp open loop. Is this good? How is overshooting? Performance at high frequencies should obviously suffer. Any comments?
 
analog_sa said:
Something's bugging me. There is a large number of opamp driven shunt regulators similar to Syn08's design. No idea who invented the topology but the first implemenation i remember seeing was Allen Wright's SuperReg. All of these bar Manfred Huber's design run the opamp open loop. Is this good? How is overshooting? Performance at high frequencies should obviously suffer. Any comments?

The HF performance suffers mainly because of the output capacitor! This cap may resonate with the inductive output impedance of the regulator, to create a peak in the output impedance. This peak is also highly dependent on the opamp open loop characteristics. For the THS4031 and 100uF (low ESR) at the output, I was able to measure the resonance at about 900KHz (in good concordance with the simulations). Fortunately, the output impedance peak is only up to under 1miliOhm so everything is fine. Ideally, you should not use any output cap, but usually it's a trade.

The same applies to series regulators, however the parallel regulator seem to be more sensitive to this effect.

I'm not familiar with the Manfred Huber design, any link to?

Anyway, how's the thing working for you?
 
One thing to watch in the linked shuntreg schematic - that opamp is stable only for a gain of 5x or more. You need the OPA627 to stay with the same device family and operate at lower gain of the voltage reference - or another unity -gain-stable opamp

(That reg is also clearly set up for valve B+ voltages - you may need other componenet adjustments for low-volt useage)
 
This is a cool thread. For me, the Superreg was the best reg for phonopres for me as well so far, including a less optimum discrete shunt reg, which gives a more laid back (but no fluffy bass!), and, regrettably, less transparent sound, which nevertheless gives a nice impression at a first (and second) glance.

I simmed syn's proposal with an AD797 and got no less than spectacular results, maybe to good to be true. I will try it the next time I re-build my phonostage.

Rüdiger
 
Onvinyl said:
a less optimum discrete shunt reg, which gives a more laid back (but no fluffy bass!), and, regrettably, less transparent sound, which nevertheless gives a nice impression at a first (and second) glance.




I finished something very similar to syn08's circuit last night, gave it a quick listen and let it burn in during the night. Used IRF610/9610 and OPA627s fed from a preregulated (317/337) 22v for a 15.5v output. Tried a very small output cap and eventually settled for 220uF Nichicon Fine Gold. The LED noise-cleaning electrolytic was moved across the LED as the circuit wasn't stable as shown (probably my grounding).

My subjective impression is very similar to yours: softer, less etched sound than the ALW, probably more suited for acoustic/classical music. Bass has slightly less weight but acoustic bass shows pleasing detail. Overall very high quality sound with possibly better highs than ALW but worse imaging and less PRAT. It then occured to me that these qualities may be attributed to the carbon oxide 50ohm ballast resistor. I am about to make simple CCSs using 317s and replace the resistor.

Needless to say, dropping the raw 30v dc down to 15.5v generates an amazing amount of heat compared to a series regulator.
 
diyAudio Chief Moderator
Joined 2002
Paid Member
After some experiments by member Ikoflexer on my reg for the Simplistic NJFET RIAA that I did in the analogue section, he arrived in a boosted hfe Darlington driver plus op amp buff version that simulated well and performed stably with very good results. Op amp can be your choice as long as the whole thing stays stable. Mosfets can be faster TO220s as well. You may try it if you fancy.
 

Attachments

  • regbuf1.jpg
    regbuf1.jpg
    44.1 KB · Views: 4,768
Shunt reg

Try place shunt reg close powered circuit as close as possible....optimal few mm form it (preferably mosfet source directly to GND point). Also CCS but something better then 317 improves bass. With shunts layout and CCS play major role that's why to the best results shunts regs PCBs can't be universal boards unlike serial regs.
 
Great comments and suggestions but at the moment i am too excited about the difference the simple CCSs made. An almost complete transformation in bass and dynamics. Trouble is the sound now is too similar to the Jung/ALW :) Will have to do some more listening before other improvements.
 
analog_sa said:

The LED noise-cleaning electrolytic was moved across the LED as the circuit wasn't stable as shown (probably my grounding).

This is not good, it changes the HF behaviour a lot. Better fix your grounding, 627 should be unconditionally stable.

Also, use separate grounds and sense the output at the load terminals.

These are things that are 1000 times more important than the output cap model.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.