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Incognito Rewiring the RB-300

Prima Vera!

Adding to the DL-103

Figuring SRA

Author: Werner Ogiers

[Italian version]

Incognito Rewiring the RB-300

[Incognito-rewired RB-300 tonearm, presented by little Sam]

Product: Incognito Rega rewire kit
Dealer (among others): British Audio Products
Price: UKP 125

Many years ago, long before it became fashionable, I decided to rewire my Rega RB-300 tonearm. Following the example set by Pink Triangle's Anniversary, I wanted to use an extremely flexible cable, so as not to upset the suspension of my GyroDec. In addition, I intended to design and build a balanced-input phonostage which was to be positioned right under the turntable's plinth. So I wanted a very short, fully balanced loom with matching, but small, connectors.

Back then there wasn't a lot of information on Rega modding: internet was still in its infancy (*), TNT wasn't born yet, and I was writing for printed audio rags. I took my questions to the local distributor and promptly got into a fight for claiming I could improve on something so holy as the RB-300! I then took my same questions to the source and promptly got answered by Roy Gandy himself (**), who told me everything I thought I needed to know to bring this project to a success.

Which wasn't enough ...

I opted for Deskadel stranded silver wires from cartridge tags to a first connector 20 cm below the arm base. This connector was a sexy Hirose balanced thingy, the intention being to mate it to a Hirose receptacle on my forthcoming phonostage. But for the time being I added a 50 cm piece of copper cable terminated in Hiroses at the input and RCA at the output, allowing me to connected my modified Rega to any standard preamp. (For completists: that Deskadel wire still is essentially what is now used in the Michell TecnoArm 'a').

This all worked, but the rewiring process cost me a full night, and a rather frustrating one at that. Moreover, the final result looked positively awkward and had questionable mechanical integrity. Ten years later my balanced pre still hadn't materialised (I had lost all interest in balanced inputs, concentrating on single-ended folded cascode JFETs), my main arm had become the SME IV (on another GyroDec), and the Rega was moved to the study, just for experiments with turntables and the odd transfer of LP to CD.

The Deskadel + Prefer hybrid sounded well enough, but last month I decided I wanted cabling of an uncompromised mechanical nature, and ripped everything out, to be replaced with the well-known Incognito kit.

And then I learned something: it is darn easy to remove the arm tube of the RB-300600/700/900/1000. Had I known that over a decade ago, I could have finished my own wiring job within a hour, with less grey hairs resulting, and entirely without fits of fury and sustained damage to my psyche. That's why I wrote this article: not as a review of the Incognito, but rather as a guide to taking Regas apart.

[Take out the two Allen screws below the VTF dial] [Remove the big nut at the opposite side of the dial]

Start with putting the Vertical Tracking Force to its neutral position of 3 g. Then remove the two small Allen screws that reside below the VTF dial. Turn over the arm, and remove the large nut at the opposite side of the dial. Then you can lift off the main arm tube (and cut the old wiring or do whatever pleases you).

[Remove the arm tube, and feed in the new wires]

Having the main tube apart allows easy access to the tiny hole the wires are supposed to go through. Believe me, this sure beats messing around with a pull cable (as still is required for the RB-250, by the way!). And while you're at it: with the arm tube removed from its craddle this is the ideal opportunity to screw in, very tightly, the new arm stub that came with your Michell TecnoWeight without having to fear for the arm's precious bearings.

Reverse the process to re-assemble the arm. The big nut should be snug, but not over-tight (those bearings again!), but the two Allens can be very tight indeed, as these constitute a large part of the arm's rigidity.

[Carefully solder on the cartridge tags]

The Incognito loom is a continuous run from cartridge to RCA plugs. There are essentially four continuous copper stranded wires insulated in what appears to be PTFE (I may be wrong), and for the last 1.2m of their length sheated in a conductive shield and a strong plastic mesh hose. The four signal wires are not connected to any other part of the loom, while a fifth wire serves as ground connection, being connected to the cable's shield and to the main arm structure itself. The signal RCA plugs (of standard gold quality) again connect only each to two of the signal wires, not touching ground or shield. This configuration means that the Incognito, contrary to the original Rega wiring, allows to run the cartridge floating, in a pseudo-balanced way. This is good news for those who employ that rare animal, the balanced-input phonostage (I'll be reviewing the AQVOX Phono 2 Ci soon).

The wires come with the cartridge tags de-attached, in order to feed the four wires through the arm. So you have to solder on the tags yourself. This is the only finicky part of the process: the wires are too thin and slippery to allow mechanical stripping (believe me, don't try!), so one has to revert to heating the insulation directly with a soldering iron to melt/shrink it away from the conductor. I hate this, as this invariably brings the iron's tip in contact with polutants. Don't forget to clean it afterwards and before you proceed with the actual soldering works.

Luckily Incognito redeem themselves by supplying the very best cartridge tags I have ever encountered: fairly large, easy to solder, and with a positive clamping action over the cartridge pins. I wished these tags were made available separately, as they could be an upgrade to just about any tone arm! Likewise, the armbase plug that separates the four individual wires in the arm tube from the shielded and protected external cables is of solid brass and has a perfect fit. (In my own re-wiring effort this was Rega's original plastic plug, drilled, and finished with elegant globs of ... blutack, so you'll understand why this makes me happy.)

I mentioned before that this was not going to be a real review of the Incognito rewiring kit. I'm not a cable guy anyway. Suffice it to say that the arm now sounds a little bit smoother than before with the silver-copper cabling, which, if I remember correctly from 10 years ago, sounded a lot more detailed and integrated than the stock Rega wiring. 125 pounds is a lot of money for a piece of wire, but the Incognito package is well thought-through, has peerless build quality, and comes with instructions of such excellence that literally anybody who can handle a solder iron can succeed in doing this modification.

Prima Vera!

[Rega RB-300 VTF spring damped with felt]

If you happen to speak Italian, English, and Dutch then this is probably the perfect title for what follows ...

It is not a secret that the spring used for applying the vertical tracking force in the Rega RB-300 to 1000 series of arms rings like a bell. If you want a demonstration of this, then take up a tonearm and remove the counterweight. Push the end stub firmly against the piece of cartilage that sits in front of your ear hole and then lightly tap the arm tube with a hard object. Hear?

Some people put the spring in its neutral position, at 3g, to try and defeat this. But this doesn't work: the spring remains attached to the arm proper, and it remains just as ringy as before.

In the past I tackled this with grease, but in the long run this gets messy. An easier solution comprises of putting one or two slim pieces of felt between two or three windings of the coil, as you can see in the above picture. (The spring can be accessed by removing the two Allen screws below the VTF dial, as well as the big nut in the middle of the dial.) If you don't like or need the effect this modification can easily be undone. Unlike the grease ...

Adding to the DL-103

[Modified Denon DL-103 cartridge]

Despite being an Allaerts-owning Jag-driving capitalist pig I have developed a certain fondness for the Denon DL-103 cartridge since I reviewed it here in 2002. It is a dirt-cheap moving coil cartridge with the sort of sample to sample consistency that reveals its pro-market origins. The DL-103 sounds like music, as opposed to hi-fi, is easy to align, and sturdy enough to be virtually indestructible. It likes heavy arms, but works well enough in the 11 g Regas and in the 12 g arms typically used on 1970s Japanese direct drives.

But the 103 is, of course, not perfect. For starters, this cartridge is decidedly less tall than the average modern model. Mounting it in arms of fixed height often results in an excessive VTA/SRA. Yes, the 103 has a conical stylus and thus is totally insensitive to SRA errors, but a VTA that is way off only adds to distortion. It would be better to avoid this.

Then there is the lack of threaded mounting holes, the plastic body only sporting open lugs. This is a shame, as otherwise the smart stylus protector and the square lines of the body make this cartridge a dream to align.

And finally there is always the desire to have it push against a bit more mass.

[Modified Denon DL-103 cartridge] [Modified Denon DL-103 cartridge]

So I came with a solution that in one stroke addresses all three problems: a 3 mm thick aluminium top plate with threaded holes for M2.5 bolts, weighting 3 g, glued on top of a DL-103. This may seem sacrilegious, weakening the bond between cartridge and headshell. But it isn't. Like so many MCs, even exalted ones like the mighty EMT, the DL-103 internally consists of various parts that are also just glued together. This often applies to the magnetic circuit itself. The result is a non-totally rigid, slightly lossy cartridge frame. According to the Swiss cartridge guru R.L.Andreoli this is even a good thing, as long as it has been calculated into the design itself. So I don't think that super-glueing (I use Pattex Power Glue which is compatible with metals and most plastics) a large slab of aluminium on top of a large box of plastic is going to detract much from the overall system rigidity.

Figuring SRA

I've always been fascinated by the claims of some that microscopic changes in VTA/SRA can make huge differences in perceived sound quality. I'm also utterly sure of the fact that if something sounds different, then it can be measured. After all, what are our ears and brains other than a pretty advanced (but also pretty sloppy and forgetful) signal analyser?

So I set out on a quest for tangible manifestations of the VTA/SRA spectre.

Vertical Tracking Angle concerns whether the cartridge's stylus suspended from the cantilever traverses the same arc as the cutting stylus did during the LP's production. A failure in this respect manifests itself as harmonic distortion on vertical (i.e. out-of-phase, stereo) modulations.

Stylus Rake Angle concerns whether the stylus' sharp edge has the same alignment with respect to the groove, and thus to the ondulating signal in the groove, as the cutter's edge. It is a bit (a lot!) like head azimuth in tape recordings. A failure leads to progressive loss of treble.

Conical/spherical styli have no sharp edge, and thus such cartridges only have a VTA, and no SRA.

I tackled the VTA problem with distortion measurements on vertically-modulated tracks (from the HFN&RR and the Cardas test discs), using a DL-103. The result was, insofar proper readins were possible as the limited number of modulation levels present on these discs, that lowering the armbase always lowered the vertical distortion. No sweet spot was unambiguously identified.

Then I hunted for SRA artefacts with my old Benz Micro MC Scheu cartridge. This one has an FGS stylus, which is a pretty extreme line contact type. The only test signal that could provoke a measurable difference was the -20dB pink noise track on the HFN&RR disc. With rising arm base the output rose for a total of 0.5dB over the 10-20kHz band, the arm travelling over a 6 mm range. Again, no sweet spot existed.

To be continued.

(* When I got to see the very first html browser, Mosaic, in 1993, my reaction was "Gee, FTP with a graphical user interface. Nobody's ever going to need that"!)

(** Much later John Michell properly introduced me to Roy. A nice bloke who is probably wealthy enough so that he can afford to be nice.)

© Copyright 2005 Werner Ogiers - www.tnt-audio.com

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