I remember a time BEFORE the three pin regulators,a time where building a regulated power supply took a damn lot of work and as for cost effectiveness ?
HAH !
Then came the LM317/337 and the like and now EVERYONE could have a low ripple stable voltage supply and for most a godsend but others ?
Once a design passed a certain level of SQ it was discovered that many time the regulator chips were the main culprits in holding back the full potential of the supply so some went to ther "methods" such as "SUPER" regulators,discrete regs,or in some cases (me
)
NO closed loop supply voltage regulation but parallel networks (shunt regs) or a better DC source using multiple CLC and CRC "Pi" filters to clean up but
not regulate the DC feed on the theory that most modern audio designs are either chip based or if discrete making using of cascoding and/or active current sourcing creating a situation where the AUDIO CIRCUIT takes care of the PSSR which in turn relegates the regulation stage to a non-essential as long as the main DC feed is a clean one (no hum,no noise,no ripple) making the AC in effect a "virtual battery" but without the wonky impedance profile.
Where regulation (and if cost/complexity is to be kept down means chip based regulation or at best a hybrid ) becomes essential is when the audio design is a simple circuit,simple as in single ended class-A gain stage with a discrete resistor current source.These circuits have the advantage in that they sound GREAT but the disadvantage in that the power supply becomes THE make or break circuit and will almost always be for more complex and far more costly than the actual audio signal amplifying stage due to the universally piss-poor PSRR of the discrete single ended amplifier,a condition where the power supply is so
audible most of the "circuit tweaking" takes place either at the PSU or by modifying the circuit itself to make the power supply take a back seat role :
1-Differential Cancellation
B-Active Current Sources
C-Cascoding
The problem is,by using ANY of the above techniques you change the very nature of the audio circuit from the original "Simple Single Ended Class-A Audio Signal Amplifier" to something else entirely so while you correct the one thing you at the same time change the very essence of the circuit with those changes being ALL to the negative if you happen to be one of those who feels the original SE Class-A sound whips the sh*t out of any attempts to better it,as I do (a personal taste thing
)
So what to do ?
Either go with the modern "fix the circuit,optimize it,make it
better " whichmeans CHANGE THE SONICS or sharpen your pencil,get out your data sheets and a pad and DESIGN a
proper power supply with an eye to simplifying where possible a simple circuit
almost always being more predictable and reliable long term (easier to TS too
),usually means less actually chassis real estate will be required and lastly will more often than not be cost effective so my way ?
Use the tool available then BEAT THEM into shape for my needs and if that means three pin regulators then for my money/time it means using either an LDO,a Jung type regulator or for higher currents an LM350.Dual supplies ?
Two identical power supplies with the "-" of supply "B" tied to the "COM" of supply "A" rather than diddle around with plus/minus versions of the chips which in my experience fall short of identical SQ any damn way.
Careful design along with smart choices in the supporting parts (the passives) plus PAYING ATTENTION to the actual data sheets showing how the part can be expected to function under a dynamic load into a know impedance will usually get you there in fine fashion but again,it eans WORK rather than the typical "plug 'n play" way most regulator chips are used which means mostly choosing the right resistor value to obtain the desired output voltage then using WAAAAAAAY too much capacitance on the output node (read the ferkin data sheets jerkweeds !) to have ANY shot at a good sounding voltage regulator !
Think "stable voltage ripple reducer without adding noise" when thinking about series regulators and you are half way there unlike the norm of "well if a lot of capacitance is good then MORE
must be better" train of thought that usually works out just fine when we are talking about UN regulated current hungry (ripple creating
) power amplifier output stages.
Oh and BTW-If you must,the Motorola branded 12 and 15 volt FIXED VOLTAGE 3-Terminal V-Regs kick the hell out of the offerings from other vendors.Why ? Fkn magic for all I know ,
but only if you keep the output capacitance low or you fk up any gains.
at least that is my experience.Your Mileage may vary.......and probably will