Relay based stabs are ruled out for reasons explained. Sevo Stab is a different animal. I have a
KryKard 3 KVA Servo Stab that regulates voltage to
+/- 1%, that is output voltage is always between 227 V to 233 V sharp, I think this is fair enough. Voltage correction rate is 20 V / Second which also a good rating. In normal state mains voltage don't fluctuate that rapidly. KryKard comes with Surge suprresion and both Under / Over voltage cut offs as well as over current (110% of rated) switch off and auto restart. All these features are standard.
One can order
RFI-EMI protection module at an extra cost of Rs 800. That will take care of most EMI/RFI realted problems.
KryKard, Vertex , Argo etc are very good Servo Stabs and can be used with any HiFi system without any worries of degrading the quaility
BUT care should be taken while selecting the rating of the Servo Stab. Sevo should be capable of delivering at least
2.5 to 3 times the fuse rating of your Integrated / Power amp!
During complex / Dynamic / Heavy Bass music sections Amp draws large current while steady state current is much lower. That's why most Amps are fitted with 'Slow Blow' type fuses. That is they can momentarly withstand over load (by a factor of 1.5 - 2 times) . So if your amp's fuse rating is 3.5 Amp then your Servo Stab must provide minimum 10 Amp , means it should be rated min 2.5 KVA - 3 KVA. (and not 1.5 KVA as the fuse rating might suggests).
For further protection you might want to add
an Ulta Isolation Trasformer in the chain. So the wiring plan should be :
AC Mains (wall socket) -> Servo Stab -> Ultra Isolation Transformer -> Terminal Strip -> Audio equipments.
CVT is no good for HiFI, will write on this later.
If you really want to go first class then bring in some AC Regenerators like
PS AUDIO but those are way expensive. Another (
expensive) solution is to use a
TRUE SINE WAVE (OFF LINE) UPS. First charge the Batteries then disconnect UPS from AC mains and then use it to power your HiFi gear ,
Remember Red Wine Audio ? (Charged batteries should last for 2-3 hours , fair enough for a typical listening session.)
Areas where Voltage fluctuations are not a big issues (Mumbai for example) , do not use anything (even Sevo) for Integrated / Power Amp, while provide protection for source component . Even a TURE SINE WAVE UPS can be considered here as Source component draws very little power.
Terminal strips available at your Computer shops are known to create problems with HIFI gear because of improper use of MOVs and RC networks. Avoide such ready made Terminal strips . Better ask your electrician to make one for you using some good quality (brass) sockets and switches, insist on good quality wires and cables , e.g. Finolex .
Check Earthing in your hosue wiring system. In most cases it is not done at all! Or it is connected to Water pipes! Call your electrician and get this aspect checked and corrected. If possible try to shift Refrigerators, TV, Fluroscent lamps, Air Conditioners, Fans with Electronic regulatiors etc on another circuit / phase.
Avoid using HiFI system during lightening . thunder storms (typical in mansoon) , disconnect the system from AC mains during such period.
For critical listening , best time is around mid night and onwards.
Hope this helps.
Becuase it does not give a stable output. The ouput voltage is controlled by relays with different taps on the transformer and keeps varying with varying input voltage. The voltage correction time is also high. Further, it offers NO protection against Surges, Spikes, etc. and the relay switching can actually induce spikes and noise (if contacts are dirty).
A servo gives a constant output within the input range and the better ones have high/low voltage cut off. The correction time is in milliseconds but depends on how much correction is required. It however offers no surge and noise supression and needs to be coupled with a UIT or similar for this.
A CVT gives the most constant output with negligible correction time. It also offers surge and spike suppresion. Disadvantage is that it is noisy, large and expensive.
Ideally, there should not be any filter/transformer/regulator between the wall and equipment. However, given the quality and state of our power supply this is mostly not possible and some AC protection / filtering is required.
