HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

Hello all.

I'm a full NVA user save my Rega Brio-R CD player.

I'm curious about stepped attenuator, but confess I don't fully understand why this may (should) increase musicality (or whatever).

Can someone explain?

The technical bods will explain it better, but the SA has separate sets of resistors for each volume level. The volume control switches from level to level. A normal rotary pot is one continuous variable resistor that gradually varies the output level.
SA is a more direct and stable connection that allows a clearer signal path for better control.

The obvious thing to do is to try it and see. It's a long time since I took that particular journey and I didn't make any comment about the differences at the time.

As I understand it, it is about there being less in the signal path. So the in the stepped attenuator, the potentiometer (variable resistor) is replaced by a series of resistors so, at each step a different set of resistors is put into the signal path and the wipers that provide the contact to the variable resistor are replaced by a click in mechanism. I thought this had been explained in other posts here but I can't find them.

It is down to the quality of the material making the resistance. A resistor is not just a resistor which is why different ones sound different especially in a stepped attenuator. We use two different ones, one much more expensive than the other. The stereo in the P50 uses Takman metal film which are extremely good, but the mono SA in the P90 use Shinkoh tantalum resistors which are the best sounding resistor ever made and silly expensive. I can only justify them in the stepped attenuator, not on PCBs. Shinkoh has closed and stock are very difficult to find, but my SA maker has access still to stock but slowly as values run out they are having to be switched for Audio Note tantalums which are not quite as good. The standard potentiometer uses a metal film track for the variable resistance, a pad follows around the track as the knob is turned changing the resistance in the path to the signal - quite simply it doesn't sound as good.

I think I should add please, that a film pot as used in NVA preamps is better than a carbon film generally (I think they last longer too) and it's not just a linear resistance that changes as the control is turned, the resistance 'across' the load changes too, in an attempt to maintain an impedance balance I think. A stepped attenuator of the type the Doc uses, may well fine tune this loading further and they certainly look the business.

Also, stepped attenuators are not simply just that. There are three basic designs. Series, shunt and ladder. Generally ladder is regarded as best with shunt not far behind because these two designs allow the signal to pass through just two resisters in the signal path. Series design involves increasing or decreasing number of resistors in the signal path depending on volume setting which can significantly affect the sound. I like steppers, but a poor mans or even intelligent mans solution is using a standard pot but in a psuedo shunt mode. This is a cheap simple mod involving soldering in just a pair of resistors and rewiring the pot. An easy DIY job that seriously improves the overall sound quality.

A good guide here........

http://www.world-designs.co.uk/forum/sh ... php?t=5795

Thanks everyone. Very informative.

Can an existing P50 be upgraded to the stepped pot, or is it the 'normal' upgrade route?

Dingsking wrote:Also, stepped attenuators are not simply just that. There are three basic designs. Series, shunt and ladder. Generally ladder is regarded as best with shunt not far behind because these two designs allow the signal to pass through just two resisters in the signal path. Series design involves increasing or decreasing number of resistors in the signal path depending on volume setting which can significantly affect the sound. I like steppers, but a poor mans or even intelligent mans solution is using a standard pot but in a psuedo shunt mode. This is a cheap simple mod involving soldering in just a pair of resistors and rewiring the pot. An easy DIY job that seriously improves the overall sound quality.

A good guide here........

http://www.world-designs.co.uk/forum/sh ... php?t=5795

Ta for that, o goody something for me to easily try .

kimangelis wrote:Thanks everyone. Very informative.

Can an existing P50 be upgraded to the stepped pot, or is it the 'normal' upgrade route?

Either same price. The difference.