Sugden preamp WAL AC Farnell.
 

Are there any Sugden fans who might be able to shed some light on this unit?

Neat wiring, soldering and the feeling throughout of a hand assembled unit but would appreciate some more insight and background.

I think WAL stands for Wellington Acoustic Laboratories, more than that I don’t know.

Would be grateful if anyone can comment on its likely sound quality.

To work as a phono preamp would it require an outboard RIAA?

What would be its best role in a system? Could it work as just a sitting box?

I haven’t yet fired connected it up, are there any readings I could check with a DMM?

Re: Sugden preamp wal ac farnell
 

First thing: check earth continuity. If you have a PAT tester, that's a good idea.

Do you have a variac? I would strongly recommend switching it on by gently ramping up the voltage on one.

'Disc' input suggests that it has some kind of replay EQ in it. As to whether it's the conventional type of RIAA, you will only be able to find out either using a reverse-RIAA filter (easy to make, and probably cheap on evilbay); or using a test record (the latter won't be accurate, as you'll be measuring anomalies / resonances in the cart / stylus / preamp combination ).

If it's easy to do, you could detach the PSU from the rest of the circuitry and power the PSU on its own. You could measure its output, and you could also try powering the PCBs from a current-limiting lab PSU (while watching its output on a scope) on their own. As an early solid-state preamp, I would very much doubt if it takes more than 50mA per PCB. Be cautious with I-limiting to begin with.

Some of those yellow axial caps will need checking out. They can start to pass DC at this age. If it's easy to do without hurting the PCB, you can lift a leg and measure their R. It ought to be high: preferably in the Meg Ohm range.

It is designed to connect to some kind of control amp or level control, so you'll need to make something up to go between it and a power amp. Try it on a line input on an integrated amp first.

Before you connect it to anything, check all the inputs and outputs for DC offset. Look at them on a scope as well.

edit: This is quite likely designed for a ceramic cartridge, in which case a typical reverse RIAA won't work with it, nor will a modern cartridge. My expertise doesn't extend to ceramic carts, but there are many members here who will know how to handle it.

NB - I think it's quite elegant. I look forward to finding how it works out.

And another edit: Sugden is still going. Why not shoot them an email? I'm a fan of their work. They seem like a good company to me.

Re: Sugden preamp wal ac farnell
 

The yellow axial caps look like Mullard Mustards to me. I'd be surprised if they were leaky and even more surprised if they were leaky enough to matter in a relatively low impedance solid state circuit.

Re: Sugden preamp wal ac farnell
 

Unusual unit with it having a microphone input as well as disc and tape, the microphone has left and right too, the case with the outward facing wings for screwing down to hold it in situ, maybe used in an educational, theatrical or something similar setting.

Re: Sugden preamp wal ac farnell
 

Anyone got a Farnell catalogue of that era? I don't know when the company changed from A.C. Farnell to Farnell Electronic Components or whatever it became next. Might it have been a special commission for Alan Farnell?

The Erie / Hunts electrolytic cap is interesting in having a date code of YYA = 009. It must be a YMM code rather than WWY as there is no week 00, and if it has Erie branding it's late enough to be YMM anyway. That puts it at September 1970, which tallies with the only Philips / Mullard code I can see in the pics B0S which is April-June 1970. Perhaps you can read others. As per Herald1960 it is most unlikely there is anything wrong with mustards.

Re: Sugden preamp wal ac farnell
 

The mullard mustards are polyester dielectric and very unlikely to be a problem. The axial electrolytic caps could do with checking, particularly since the superb construction unit is over half a century old (eek!)

Craig

Re: Sugden preamp WAL AC Farnell.
 

A.C. Farnell were based in Sheffield, where as Farnell Electronic Components were based in Leeds and were totally seperate companies, although they were set up by members of the same Farnell family. A.C. Farnell were more into brown goods and service spares, I used to buy PL519 and PY500A from them, as their valves were g'teed and seemed to be of a higher quality than a lot of others at the time. I think that A.C. Farnell ceased trading a lot of years back. Farnell Electronic Components did and still do mainly electronic components.

The preamp of the OP was probably built for factory usuage to supply music and announcements over the 'in house' entertainment system for the factory workers. It may also have been used in warehouses, larger offices and shops for similar purposes.
Dave

Re: Sugden preamp wal ac farnell
 

I did think that they could be the much-fabled Mustard caps (desirable in much vintage audio), but I have seen similar looking caps go virtually short in valve gear, so automatically leaned on the side of caution.

Craig makes a good point re: electrolytics. More reason to use a variac when turning it on, unless you plan to shotgun re-cap them (which could irk some around here!).

I haven't encountered a ceramic cart since my age was in single figures. Am I right in thinking it most likely is for ceramic?

Re: Sugden preamp WAL AC Farnell.
 

Well there are two polystyrene capacitors in there of clearly different value. So I suspect that it *might* have RIAA correction - implying it equally *might* be moving magnet and not ceramic.

Without tracing the circuit, or measuring its frequency response it is difficult to be certain

Craig

Re: Sugden preamp WAL AC Farnell.
 

The gain will be different for ceramic, right? They are a lot louder than the typical 4mV from a MM. I think you are probably right, though. You can make a fairly effective RIAA with 2 caps.

Re: Sugden preamp WAL AC Farnell.
 

I think that is quite probable.

No tone controls, Jack sockets on the front, no Tuner input wouldn`t be a great spec for a domestic Hi Fi pre amp, even in the sixties.

Re: Sugden preamp WAL AC Farnell.
 

I thought they were jack sockets, but looking closely, they look more like phono type, top row of sockets, the far right one, you can see a gap around the edge through fascia, and the shadowing of said socket.

Re: Sugden preamp WAL AC Farnell.
 

It seems WAL is Wellington Acoustic Laboratories. Seems to be for music / PA rather than home as others have suggested.

Re: Sugden preamp WAL AC Farnell.
 

What a superb forum! Just excellent.
Thanks to everyone who's contributed so far.
I now know a great deal more than I did yesterday..
Further contributions of course welcome.

Re: Sugden preamp WAL AC Farnell.
 

Looking at what I can see of the board, it looks like this could be based on the Bailey three transistor design, which appeared in December 1966 WW. This had the innovation of feeding the frequency selective feedback from an emitter follower rather than the two transistor gain cell. (In addition, one of those transistors looks like a Ferranti E-line, now made by Diodes Inc. One of the secrets of low voltage noise designs are the E-line devices)

https://worldradiohistory.com/UK/Wir...ld-1966-12.pdf

It was further improved byWalker WW May 1972

https://worldradiohistory.com/UK/Wir...ld-1972-05.pdf

But that post-dates the OP's unit.

Craig

Re: Sugden preamp WAL AC Farnell.
 

Thanks for the clarification, I had an incorrect recollection that one became part of the other.

In those applications I would have expected a mono output, even with stereo inputs, separate preset gain controls, and balanced input at least for the mic(s). While its purpose might well have been within a commercial installation, perhaps one more along the lines of demonstration or testing of audio equipment?

Re: Sugden preamp WAL AC Farnell.
 

To most users, Ferranti had evolved some quite outstanding transistors with particularly good current handling for their package size. Thismade them great for motor control... EG switching to drive stepper motors and bridges for switching direction of DC brushed motors.

This was done by designing in excellent current sharing mechanisms and low base-spreading resistance.

Coincidentally, this also made them rather good for low noise capabilities in low impedance environments. It took a while for this to be recognised, but it's real.

Low noise people designing dynamic microphone inputs eventually found that Rohm made a range of low spreading resistance transistors for the motor drive market, and that these parts were about the best for their work. Of course, Rohm obsoleted them when they saw the motor market drop off as it changed to MOSFETs and IGBTs.

Who'd have thought that tough motor drive transistors would have a sideline in the most delicate applications?

David

Re: Sugden preamp WAL AC Farnell.
 

The other characteristic is low Vce(sat). I have measured 6mV on some of the current E-line devices even at a few mA Ic. Of course this is a needed characteristic for applications like stepper-motor drive. There is a definite correlation between Vce(sat) and en.

The rbb' of some of the E-line devices has been measured (HH Ed 3) at sub 2-ohms with very low 1/f noise corner, better even than the legendary and long obsolete Rohm parts.

Diodes Inc have now recognised the low noise performance of their E-line devices, and list as one of the applications low noise audio.

The disadvantage is of course high capacitance, because of the extended (interdigitaged) junction area.

Craig

Re: Sugden preamp WAL AC Farnell.
 

Just found my measurements. Cobo is in the range 60-100pF at 10V Vce, which means that they really need to be cascoded, or used common base.

Craig

Re: Sugden preamp WAL AC Farnell.
 

The history of Farnell is really quite complicated and I've always thought that A C Farnell was originally based in Leeds. This potted history is interesting:

https://advanceproductservices.co.uk...s/our-history/

Not hard to imagine that there could have been a business relationship between Sugden and Farnell in view of their close geographic proximity. Worth noting too that R E Sugden was very much focused on good quality audio equpment.

Alan

Re: Sugden preamp WAL AC Farnell.
 

The manufacturing rights to WAL products were sold to A.C. Farnell circa 1963 by the founders widow, the founder was Roy N. Wellington.

Lawrence.

Re: Sugden preamp WAL AC Farnell.
 

Thanks everyone, such a torrent of illumination.
Initial response on the unit from the manufacturer:
- The unit hasn't been seen before.
- The circuit boards are not from another Sugden product.
- It was built for a special purpose, possibly part of a test rig.
- The circuit boards are estimated at 1967-8.
Curiouser and curiouser.

Re: Sugden preamp WAL AC Farnell.
 

So AC Farnell may well have commissioned J.E. Sugden to produce this WAL unit.
But to what purpose? As a prototype for further manufacturing?
And how good is the sound quality likely to be? Some of the comments on the excellence of some of the components suggest that it might be surprisingly good.

Re: Sugden preamp WAL AC Farnell.
 

I'm glad to know that Sugden replied to you. They make good stuff (I scrutinised one of their current offerings with my R+S analyser), and it's nice to know that they took time to reply to you. I have pieces from several OEMs that are off-radar and either they don't reply, or when they do, they simply tell you it's discontinued and suggest that you ought to take a look at their latest offering.

I think you have several options:

i) Plug it in and have a listen. I'd suggest powering it with a variac before doing this, as the caps may not have been powered for decades. Although it's most likely cap-coupled everywhere and is unlikely to harm anything connected to it, if you want to be careful, run around all inputs and outs with a DVM and check that nothing resembling DC is coming out. If you like the sound, does it matter what anyone here says? My feeling is that it'll likely sound ok, assuming you connect it to the right type of cartridge. As Craig suggested, the old filter caps could mean hum performance isn't great.

ii) Are you looking to learn about audio electronics? If so, get yourself a generator (soundcard + freeware will also do it) and a scope. You can then test it for yourself and do some basic measurements. It'll take a little time, but you'll learn plenty.

iii) Find someone with an audio analyser. This will tell you exactly what its functions are in about 2 minutes: whether the output is flat, noise level, gain etc. But where would the fun be in that? And it'll bias your attitude towards listening to it.

Audio electronics have been good for quite a few years now.. They had discrete transistors in the late 60s that could be used to make signal paths that are quiet enough to be used with modern digital gear. The late, great Rupert Neve used the BC184C and BC109 in his designs, and these preamps are more desirable today than ever.

Re: Sugden preamp WAL AC Farnell.
 

WAL preamplifiers were listed in Hi Fi Year Book 1967-68, then under Elstone Electronics.

Attachment 227392

These were battery-operated units for matching tape, microphone, or pickup inputs. That suggests that they were intended for use with amplifiers or control units that did not have low-level inputs, not too uncommon at the time. And there were other makers of this kind of preamplifier for domestic use.

Evidently WAL moved on to mains powered units of the same basic type. I imagine that the three-way selector was less intended for daily use than to preset the unit for specific applications. Magnetic cartridge matching and equalization may have bene the main objective, but as the same basic circuit could easily be configured for use as microphone or tape head preamplifier, it would have been easy enough to include those facilities.

Re Sugden’s involvement, the disc preamplifier section of its C51 control unit, although mostly intended to do the RIAA job, was configurable for microphone, and tape head inputs, as well as for different disc equalization curves. I think that there was also a plug-in for the A.R. Sugden ceramic cartridge, which was something of a maverick amongst higher quality ceramics in terms of its characteristics and required loading (it was outside of the range of the Burrows parameters.)

So perhaps the design of the subject WAL unit drew from that of the Sugden C51.


Cheers,

Re: Sugden preamp WAL AC Farnell.
 

It seems that WAL was transferred to Elstone Electronics by 1963 (the Studio Sound advert) and Elstone Electronics had been taken over by AC Farnell by 1966 at the latest. Presumably Farnell gave up manufacturing electronic devices and got J.E. Sugden to produce a new version of the WAL Gain but the crucial questinm is when? The J.E. Sugden C51 preamp didn't come out until 1969. A.R. Sugden (manufacturer of the Connoisseur turntable) was a complelely different company.

Re: Sugden preamp WAL AC Farnell.
 

Has it got a ground post for the TT chassis / arm? Did TTs from this era common chassis GND to the cartridge -v side?

Re: Sugden preamp WAL AC Farnell.
 

Thanks everyone for the new contributions, really excellent.
Can confirm that it doesn't have a ground post for the TT chassis /arm.
Looked at some Sugden C51 pictures and can see some overlap of components on the boards, others may be able to discern more.

Re: Sugden preamp WAL AC Farnell.
 

Although the C51 had a prior life as the C41, under the Richard Allan name, this having been announced in 1968 April, along with the A21 integrated amplifier and A41 power amplifier.

Sugden seemed to have been particularly interested the matching and equalizing of pickup cartridges at an individual model level, as evidenced by his fairly well-known article in Hi Fi News for 1968 April, “Flatten Your Head”. The individual cartridges mentioned therein also appear in the C51 data as being catered for by special input circuit arrangements. I suspect that it was the same for the C41. Inclusion of the A.R. Sugden Connoisseur cartridge in that list may have been an artefact of the “Yorkshire Triangle”. Anyway, one could say that c.1968, Sugden was well-positioned to design and supply a third-party disc/mic/tape preamplifier, and that one might expect such to include some of its own thinking as to how this task should be addressed.

In the absence of other evidence, the circumstantial case points to 1968 as the introduction date for the Sugden-built WAL preamplifier, but it might have preceded the C41, so 1967 is not outruled.


Cheers,

Re: Sugden preamp WAL AC Farnell.
 

It's at the point where I think the circuit needs tracing out. Then it can be compared to various published designs and that Hifi News article. I wonder if 'Tape" means tape head?

Without any controls, I think this is really a pre-pre-amplifier to add high sensitivity for low output sources like dynamic mikes, magnetic cartridges and tape heads.... things not normally included in most preamps.

David

Re: Sugden preamp WAL AC Farnell.
 

It could have been designed for a Bingo Hall ;-)

I once had a mixer from the early 70s from one. It was in beautiful nick, as the only pot that had seen any use was the mic -)

Re: Sugden preamp WAL AC Farnell.
 

The original WAL Gain was certainly meant to be used in a hi-fi system rather than a bingo hall as this advert from The Gramophone in 1958 proves.

Re: Sugden preamp WAL AC Farnell.
 

Thanks again for these contributions.
So we can say that ten years after this advert from 1958 a version of the WAL Gain pre-amplifier was still considered to produce sound quality sufficient to merit its selection for incorporation into a test rig unit built by J.E. Sugden and commissioned by A.C. Farnell. Fair to say that there was probably excellent oversight available in both companies.
Is it possible that this particular unit’s WAL Gain design was seen as something special?
Would key personnel in either of these eminent companies have been content with putting effort and expense into designing and building a new device that was likely to provide, by 1968, second rate output or be judged as technologically somewhat behind the curve?

Re: Sugden preamp WAL AC Farnell.
 

If the 1958 version used silicon transistors, it must have been really early - the first silicon transistors only became available three or four years earlier.

I suspect it might have gone through at least one design revision.

Re: Sugden preamp WAL AC Farnell.
 

Why do you think the 1958 version might have used silicon transistors?
The first version was mono ; a stereo version came out a few months later.
I have discovered that Elstone Electronics was incorporated into Farnell in 1945(!) so the transfer to Elstone was also a transfer to Farnell as an earlier post stated.

Re: Sugden preamp WAL AC Farnell.
 

This is a typical WAL device a little in line battery powered amplifier.

Unfortunately the label has peeled a little but it used to say Elstone.

Date late 50's early 60's at a guess.

The case size was determined by the battery (PP7).

The Sugden unit is way more sophisticated and higher quality.

Cheers

Mike T

Re: Sugden preamp WAL AC Farnell.
 

I think that's an original 1958 mono WAL Gain which has been "badge" engineered by Elstone.

Re: Sugden preamp WAL AC Farnell.
 

Germanium transistor apparently

Re: Sugden preamp WAL AC Farnell.
 

It's an STC TK45C also marked ACY29

According to Mr Transistor this happened around 1962/63

http://www.wylie.org.uk/technology/semics/STC/STC.htm

So its a little later than I first thought.

Cheers

Mike T

Re: Sugden preamp WAL AC Farnell.
 

Your pictures show a remarkable resemblance to the original mono WAL Gain pictured in the Gramophone in June 1958. Perhaps Elstone bought all the remaining cases as well as the manufacturing rights.

Re: Sugden preamp WAL AC Farnell.
 

Very tempted to see how the the Sugden sounds as a phono preamp, or even a pre-preamp. However, no ground screw is present on the unit. Any suggestions as to the best way to go about remedying this, perhaps just as a temporary measure in order to see how it sounds.

Re: Sugden preamp WAL AC Farnell.
 

There's no photo of the back panel in the set posted, but does it have a screw you could replace with a binding post, or with a thread sticking out and a terminal nut?

David

Re: Sugden preamp WAL AC Farnell.
 

Thanks David.
The previous interior images 2 and 5 show a fixing for the mains cable.
Detaching the grey cover at the rear reveals the holding screw. Might there be a way to utilise this as a ground?
Back panel photos attached.

Re: Sugden preamp WAL AC Farnell.
 

Back panel.

Re: Sugden preamp WAL AC Farnell.
 

Latest update.
Delighted to hear that the manufacturers are sure that it was designed by Jim Sugden.
Advised that a variac can sometimes cause instability issues.
Plugged it in to the mains and no smoke or pops to report.
However, can anyone suggest some DMM readings that I could perhaps take from inputs and outputs that might offer me some reassurance prior to connecting it to source, amplifier, and speakers?

Re: Sugden preamp WAL AC Farnell.
 

As we've ascertained that the preamp is built using what appears to be good quality parts (i.e. Mustard caps), and most, if not all of the I/O are likely to be cap-coupled, I reckon there is little likelihood of it hurting anything. However, just to be safe, put your DMM into the DC range and look for anything above about 50mV DC on any I/O. If there is DC present, it ought to go down with the small loading the meter presents it with (totally normal).

Ideally, you ought to test it with an oscillator + scope (or analyser), but if you haven't got one, it'll take less than a minute to check I/O for DC (which may not be 'DC' in some designs, but high-frequency oscillation, that looks like it to a meter), and it'll give some peace of mind.

NB - I ought to have said that the variac should be used without audio connections. If the reservoir caps have started to pass DC, simply turning it on will put a load on the transformer and rectifier. Ramping up with a variac is not as good as reforming them externally with a DC bench PSU, but it's better than nothing. An alternative is the light bulb limiter method. The variac method is not recommended for valve designs, and designs that have logic circuits might object to it. But in this case, I think there is a fair reason to suspect that the preamp has a simple, conventional PSU, probably with a single rail. Ramping it with a variac after a layoff, potentially decades long, is better than nothing.

edit - seeing as you've already powered it, the last paragraph is redundant!

Re: Sugden preamp WAL AC Farnell.
 

Just adding some info and readings to this thread, my apologies for the long radio silence.
Looking at these readings below, can anyone advise as to whether they look fine or are there any issues about which I should be concerned? Naturally, I don't want to risk any damge to my amplifiers or speakers (vintage Celestion Ditton 66's with hard to source replacements..)

My intention is to try it out as a phono amp which will then be connected to a pre amp (NAD 3020A pre section) which will in turn be connected to a power amp.
I realise that an RIAA circuit of some sort may have to be added to make this work satisfactorily.



Does any one particular channel look to have better readings than the rest?
And any to be avoided?



MIC TAPE DISC OUTPUT CHANNEL
2.7 ~ 3.0 1.0 ~ -0.3 1.5 ~ 0.2 1 Mic left
1.0 ~ -0.3 2.5 0 ~ 1.2 1 Tape left
1.0 ~ -0.3 0.9 ~ -0.2 2.9 1 Disc left

4.8 0.7 ~ -0.2 1.2 ~ -0.2 1 Mic right
8.0~ -0.2 3.9 1.3 ~ -0.2 1 Tape right
0.9 ~ -0.2 0.8 ~ -0.1 4.8 ~ 4.5 1 Disc right

The above chart displays the DMM DC readings in mV for each of the I/O sockets.
The I/O socket from which the reading was taken are written in capitals at the top of the columns.
The position setting on the rotary lever switch are written in lower case at the right hand end of the rows.
When the rotary switch was turned a higher reading (90mV, 70mV, even a 170mV) would briefly flicker in between the selector registering in the new setting. Is this a concern?

Re: Sugden preamp WAL AC Farnell.
 

This is the same table, which may be easier to read..

Re: Sugden preamp WAL AC Farnell.
 

...

Re: Sugden preamp WAL AC Farnell.
 

I suspect this to be a re-laid out derivative of circuitry used in Sugdens then domestic hi fi range. IME of repairing and restoring such gear for customers the most likely issue will be noisy carbon composition resistors. They used these for quite a long time after everyone else had ceased to. They must have known about their dodgy noise performance (in a correctly functioning resistor rather than one "gone noisy") as in the most sensitive parts of the low level circuitry (RIAA amp) they used carbon film and even a few metal films for some production.

OP. I wouldn't worry about it damaging other equipment etc... VERY unlikely. If you have contact cleaner then a bit in the selector and sockets and then "work them" for a while and you should be good to go. If you find either initially or after a few days/weeks use that you get "bacon frying" noises, sometimes intermittently, it's probably those resistors. I've also known BC109's to go noisy in this vintage of Sugden equipment.