Retro Vintage - World Audio Designs PHONO II and PSU II

World Audio Designs PHONO II and PSU II

After the success of the Fostex horns I worked up the courage to have a go at the now defunct World Audio Design (WAD) PHONO II and PSU II kits. I hadn’t really used a soldering iron before but was encouraged by the supposedly easily construction thanks to the pcbs and reassured by the thriving community on the old WAD BB.

The kits consisted of an RIAA stage using 3no. ECC83 double triodes remotely powered from a solid state power supply. A matching PRE II preamp was also available using a 6922 double triode.

Everything required was included in the kits, from chassis, brushed aluminium front plates and cables to pcbs, components and valves. Being somewhat cautious with my first build I followed the instructions closely and took my time. Construction was pretty straightforward: populate the pcbs and solder the components on both sides of the pcbs. Even a novice like me managed. No problems.

Having read the warning in the instructions that electrolytic caps wired up with incorrect polarity can explode I was rather nervous the first time I switched on. Fortunately my trepidation was unfounded and it worked first time! This was a bit of a surprise, though, in reality, following the instructions and taking plenty of time is all that was needed to complete a successful build.

Listening Impressions

These kits make a very nice sound, no doubt about it, and are an improvement over the inbuilt stage in my Exposure IIV pre amp. Having heard other valve phono stages since, to make a significant improvement requires significant expenditure.

Improvements

There are a number of improvements that could be made, from valve rolling to a complete rebuild with fancy bits. The only changes I have made so far (apart from adding Lundahl LL9206 MC step-ups) are to the valves, which I guess is a measure of how good the phono stage is in its basic form.

Perhaps fortuitously, one of the originally supplied Ei ECC83s died after about a year, so I replaced it and another of the remaining good Eis with Svetlana 12AX7s. This improved the sound – more detailed and perhaps a little tauter and refined. The improvement left me thinking the Eis were rather uninspiring.

A much bigger improvement was changing all three valves for some old 5751s. These are similar to ECC83s but with less gain. They are also reputed to have a nicer sound and they certainly improved my PHONO II. I have some Mullard ECC83s, I should compare them to the 5751s sometime...

Future Improvements

In its standard form the PHONO II does not correct for the 3.18us RIAA equalisation time constant. This is sometimes used to protect the cutting head during recording, and there is an FAQ on the World Designs forum for correcting this. Reported results are mixed; some hear a small improvement others hear none. I have the resistors, just waiting for a period of stability in my system (ha!) so I can see if it makes any improvement.

The caps in the PHONO II are prime candidates for upgrade and I really must get around to trying some fancy ones.

Lundahl LL9206 MC Step-ups

As I experimented with my Garrard 401 the time came where I had to try the infamous Denon 103. As my existing cartridge, a Dynavector 10X4, is a high output MC I didn't have any step-ups. Initial experimentation with the 103 without step-ups was promising: a good sound but the system ran out of gain on quieter pressings. Looking on the WD forum the LL9206 MC step-ups had some good feedback and didn't cost the earth. There is no Lundahl supplier in the UK so I got mine direct from Sweden. There are suppliers in Europe, but it seemed easier to go direct to Lundahl.

The LL9206 have an amorphous core and mu metal can. The datasheet says that the primary side must have a ground reference. From experience I can confirm this, unless you like listening to lots and lots of hum! They can be configured 1:5, 1:10 and 1:20 for gain. 1:10 seemed to fit my system best, so I used schematic C (no center tap).

The small pins protruding from the cans are frustratingly fiddly to solder to, a right royal pain in the posterior. I had seen on a couple of websites that small pcbs are available to facilitate installation. Not appreciating how difficult it would be to solder them I didn't bother, but if I was soldering them for the first time again I would be sorely tempted to get a couple of the pcbs. Once soldered I attached each one to the chassis with a zip tie.

For cartridge loading, the 103 has an output impedance of 40R but wants to see, say, 6 to 10 times this, or 240R to 400R. Some 103 users report good result up to 1000R. The 1:10 ratio transforms the impedance by 100 (the gain squared i.e. 10 x 10), so the stock 47k resistor at R13/R14 should be replaced by one between 24k and 40k. As this is pretty close I have left the 47k resistors alone, but will eventually try 20k and 100k, and tune from there if there is an improvement.

December 2025 Update

I still use the PHONO II and PSU II. That can't be a bad sign. I have been working on a C3g-E88CC Aikido on and mostly off for 20 years, but that's another story. I don't remember ever implementing the 3.18us RIAA equalisation time constant, but I did change the two coupling caps. Not to anything fancy, just cheap PP. I should probably investigate some "better" caps, but life's perhaps too short.

I must have written this before 2008 as I bought a Denon 103pro in Japan that year and it hasn't been supplanted since.

I used the Lundahl MC step ups until earlier this year. I started playing with JFETs a year or so ago and after a couple of iterations I drew up a pcb for the front end of Wayne's Pearl 3 phono stage, using 4no. paralleled LSK170s rather than 2SK170s. I was really quite surprised how much better this was than the Lundahls, at least with the PHONO II. It will be interesting to see how it matches with the C3g-E88CC Aikido, if I ever get it finished......

Lenco L75 Replinth

Goodness, 8 months since my last blog. The Google servers must have thought I'd given up. Life just gets in the way sometimes. And even this isn't a blog about something I've done, it's about a rather special plinth that Anthony Cresswell made for my Lenco L75. And here it is, playing REM's New Adventures in Hi Fi, rather appropriate but completely unintentional.

I've had a Goldring Lenco for a few years waiting for the right moment to be redeveloped. I'd been leaning towards a solid replacement plinth, either slate or constrained layer damped with various timber sheet materials, which would do away with the slightly tinny top plate. Something along the lines of Pieter's Top Plate looks to have some merit in its approach to me.

So I was starting to do a little more detailed research about the Lenco itself and how it would need taking apart, chopping down and rebuilding when Ant posted on the Audio Talk forum that he'd just done something very similar. Given my somewhat glacial timescale for audio projects commissioning Ant seemed a pragmatic choice. Besides, he knows what he's doing and I knew he'd make a much better job than I would...

The Lenco is an idler drive turntable - it doesn't use a soft belt around the rim of the platter, and doesn't drive the spindle directly. It's a mechanically sophisticated method of spinning the platter, but can be affected by poor setup, just like any turntable.

Unlike Garrards, like a 301 or 401, which drive the inside of the platter rim with a horizontal idler wheel, the Lenco uses a vertical idler wheel which drives the underside of the platter top. Idler drive proponents will discuss at length pros and cons of different drive systems, the quality of the motors, and even whether a grease bearing 301 is better than one with an oil bearing. I'll leave that discussion to others with more time and inclination, but those that have taken these things apart are impressed with the build quality - they're Swiss and the build quality shows.

Here are a series of photos that Ant took during the build, for which I'm very grateful. The first is when Ant had initially stripped the deck down. It's nearly as old as I am and cosmetically in excellent shape, much better than me. In a way it was a shame it was going under the angle grinder, but some things have to be done.

No going back now...

I think this is something akin to the PTP mod mentioned earlier (with apologies to Pieter if it isn't!)

And now with the idler wheel, spindle and linkages refitted.

Next job was the plinth with lots of routing of a sandwich of a number of layers of mdf and plywood. The theory of constrained layer damping (CLD) is that a different layer of material is used between others materials to damp vibration that the outer materials can't. Rubber is often used, but as we know, audio is a mysterious beast with many different ways to succeed.

Here we can see the differing cutouts in each layer - just enough is removed to house the mechanism, this way the mass is maintained.

Those with a keen eye that know their Lencos will have noted that Ant has been rather clever in the way he's mounted the mechanics. One of the biggest drawbacks with the L75 for me is that the on/off lever is located virtually under the cartridge. I can't imagine how many styluses have been destroyed by unfortunate accident over the years. So Ant reoriented the mechanism with the on/off lever at the back - this is a compromise as it doesn't want to be too close to the arm collar either. This puts the variable speed lever at the front, and the idler wheel at the opposite side of the platter from the arm, which is probably a good thing.

And here it is with my old Linn Ekos mounted. I'd wanted to try an Audiomods arm but Ant suggested trying the Ekos - it has a very slightly different effective length than the Rega-derived Audiomods so will need an arm board should I change in the future, but using the Ekos was a "zero cost option", additional cost anyway, as it was sat on a shelf unused. And for that matter I had a Kontrapunkt b with low hours also sat in a box, so why not use that too.

Next job was sanding. Lots and lots of sanding, after the plinth was cut roughly to shape.

Next was paint time, starting with the underside.

Just 5 coats of black on the rim. It does look good I have to say.

It turns out the mechanics weren't quite as good as thought. Somehow it had seized "on" - even though the platter wasn't turning the motor was turning. Must have been like this for some time before I obtained it. Previously I'd only listened to about a side of one record - I'd lashed up an old Linn K18 just to try it and was surprised by just how "together" it sounded. Enough to know a full rebuild was worthwhile ;-). So at least I didn't make it any worse. So Ant stripped it down, which saved me a job.

Note the pit the spindle has worn in the bottom plate. Ant simply turned the plate over. Testament to the Swiss build quality really.

Back to the plinth, and it was veneer time - a simple English oak. It's difficult to see but Ant managed to salvage the original Lenco sticker for provenance - it's located on the left hand side of the remaining part of the platter.

And here it is with a couple of coats of danish oil (I think)

And finally at home with the the Kontra b fitted, this time playing the Living Stereo release of Reiner's Chicago Philharmonic performance of Pictures at an Exhibition.

I must say I'm very pleased with how it's turned out. I'm always a little reluctant to wax lyrical as one day I'll probably look back and think I was talking rubbish, and well, we've all read those oh-so fawning reviews that mean nothing.

But Ant's done a terrific job, much better than I would. It strikes an excellent compromise - it has the drive of an idler (obviously), and the effortlessness of a good direct drive. Compared to my 401 in twin deck slate plinth with 12" ebony Schroeder-a-like arm and Denon 103pro cartridge this has the edge. The bass is firm and controlled, and better balanced than the 401 I think, which tends to tank-on. Coupled with the fluid mid that reminds me of direct drive this is an excellent turntable.

One day I should try an alternative arm and cartridge as I've never been a huge fan of the Kontra b - at least the 103pro should get a run out. That might squeeze a little more musicality out, but for now I'm very happy with it as it is.

I should add that I have no connection with Ant other than as an audio friend through Audio Talk. We live about half an hour away which makes it easier too. But I have no financial interest. With that said, make no mistake - in the crazy world of audio, if you were to find yourself a half decent Lenco (cosmetics aren't important) and get Ant to build you a plinth you'd have a killer turntable for pretty cheap. Ant has a website where you can read his own thoughts. Cheers Ant.