Retro Vintage - Bluebell Audio "WE91" Single Ended Valve Amp Monoblocks

Bluebell Audio "WE91" Single Ended Valve Amp Monoblocks

The Loftin White 2A3 has pride of place in my system. After a couple of decades of solid state grain I was enjoying the wonder of direct coupled RCA 2A3s (dualplates admittedly). I'm having to use my old Exposure pre amp to control it unfortunately but it sound's great and I'm really happy with it. Why do I need anything more?

Well, because I'd become hooked... without realising it. That I was happy with the Loftin White was irrelevant, I needed to smell solder fumes. Nobody warned me how addictive this hobby could become. And I was now aware of how many valves I could try in so many configurations; single ended of course!

During the course of one of my conversations with Philip at Bluebell Audio, Philip had raved about a pair of 300B monoblocks based on the old WE91 circuit which he had just finished after sitting incomplete on his shelves for a few years. Over the following few phone calls Philip's enthusiasm for the WE91s didn't wane at all. Here, it seemed, was a 300B SE amp that could do bass and treble as well as the renowned midrange... Here was my next project.

Circuit Description

The actual incarnation of the WE91 is Philip's so it's not appropriate to post it here, but it's very similar to the Angela circuit at www.Angela.com. If you speak to Philip he'll no doubt be very pleased to discuss it with you!

If you have the first issue of Sound Practices the circuit is in there too. You don't have the first issue of Sound Practices? Have a look on ebay and US$30 buys a CD of the entire Sound Practices output from Joe Roberts himself.

Basically, the monoblocks have a 6SJ7 pentode driver stage coupled with a 0.1uF Audio Note copper capacitor to the 300B. Blackgates for both cathode bypass caps, and Cerafines in the PSU. Mains transformers and chokes are Hammond, and I was able to save a few bob by reusing the Hammond 1627SE output transformers from the Loftin White.

As the WE91s are monoblocks some method of control is needed. The beauty of 97dB loudspeakers in a typically sized British living room is that they don't need a lot of power, so I built a simple passive preamp to control them. This was the easiest way (rather than an active preamp) and allowed me to control the headphone amp from the same box too.

Construction

Starting with a Hammond 12" x 10" x 2" black powder coated chassis the first job was to cover the outside surface with 2" wide masking tape. Experience has taught me that with the best will in the world the metal swarf from all the drilling is likely to mark the chassis unless protected.

Then the layout of the iron and valve sockets can be attached. I drew the layout in AutoCAD first , then printed it out and attached to the chassis along two adjacent sides so I could clear the swarf out periodically. Guess I find it easier this way than marking out on the masking tape.

Then it was a matter of labouriously drilling each hole, starting with a 2.5mm drill bit and opening up with increasing diameter bits 0.5mm at a time. Hole punches were used for the larger diameter holes, such as valve sockets etc. I used a captive power lead rather than an IEC socket. It's much easier to use a circular hole punch for a cable gland than mess about fashioning an odd shaped hole for an IEC socket. Here's the chassis drilled and punched...

And with the masking tape removed...

On to the more interesting bit, building the amplifier. First job, install the iron, valve sockets, tag strips and rest of the hardware. The 1627SE output transformer isn't attached to the chassis yet as I was still using them with the Loftin White...

And inside showing the 300B filament transformer and tag strip...

Then start to install the components and wire up. I sketched out the layout of all the components before I even thought about marking out the chassis layout. This allows me to refine the layout to optimise wiring etc. First lay the components out to see how they actually fit...

Then it's a relatively simple job to build the amp and provided I've got the sketched layout correct I have a master plan to compare my build to. Double and triple checking of the sketch helps!

Finally the amp is complete. Now repeat for the second monoblock...

Listening Impressions

After the amps were installed into the system controlled by the passive control unit it was time to plug in the valves. The 300Bs were Chelmer badged - they look a little like Valve Art, but who knows what their heritage actually is? Philip supplied some nice NOS Sylvania 6SJ7s, and a pair of new production JJ GZ34 rectifiers to complete the compliment.

Power up, and fortunately no exploding electrolytic caps! Unfortunately one of the GZ34s was arcing. There have been a number of reports on the web about dodgy new production JJ rectifiers and I can now add my own. So I switched the dodgy JJ for the Mullard GZ33 from the Loftin White and we were away.

Straight away I could hear there was more detail and control than the Loftin White, but it wasn't until the amps had been running for a few days that the bass opened up. Now, in addition to the nice midrange and treble there was real weight and extension to the bass. If the WE91 is the equivalent of FM radio the Loftin White seemed like AM radio. I was quite surprised. Not just that the WE91s sounded so good, but that in comparison the Loftin White sounded rather limited in the frequency extremes. So much so that I'd like to rebuild the Loftin White sometime to see just how good I can make it.

The WE91s had taken me a little further in the journey towards musical reproduction realism. I was very pleased.

Improvements

The easiest place to start is with some valve rolling. Reading on the net suggested that some nice RCA red can 5693 valves would be a decent replacement for the 6SJ7s and some were duly procured through a famous online auction site. Sure enough these were a small but worthwhile improvement. And they look kinda funky in red too.

Weighing up my options for the dodgy GZ34 rectifier I considered a pair of new production Sovteks, but in the end got another Mullard GZ33 from Philip to match the existing one.

Then for the 300Bs. I tried some Electro Harmonix (not the Gold Grid version) first they were a little different but not really any better. Weighing up options, two likely candidates were EH's Gold Grid version (which can be had for under 70 quid a pair) and TJ Meshplates costing a little more. I ummed and ahhed for a while, and after concluding that I could end up spending quite a few quid trying different 300Bs, I took a deep breath and bought some KR 300B XLS from Rod Burman. These are the turbo charged versions and are not cheap, but I really, really like them. These valves have transformed the amps. There is more detail, more control, more tone, more everything.

Lovely KRs

Monoblock with revised valve contingent - KR 300B XLS, RCA 5693 and Mullard GZ33

The only other change I made was different output transformers. I had ordered a pair of 2.5k c cores from AE Europe in the Netherlands as part of a larger order for another 2A3 amp, and whilst I was building the new amp I broke the c cores in with the WE91s. AE have a good reputation amongst DIYers, both for sound quality and value for money. I could tell as soon as thy arrived they were beautifully made, but how did they sound?

When I first clipleaded the c cores in to the WE91s they sounded very similar to the Hammond 1627SEs they replaced. About a week later I had put an album on and disappeared through to the kitchen when I stopped in my tracks, turned around and went back in to the living room. Where had the bass come from? Deeper and more extended, very nice. Treble is also improved. These are very nice output transformers which also happen to be very good value for money. I had to wait 5 months for them as AE was so busy, but I know that one day I'm going to order some amorphous core output transformers from AE. The only question will be silver or copper wired...

Conclusion

I've been listening to these amps for about eighteen months and I really like them. The KRs and AE c cores transform very nice amps to really excellent amps. They aren't particularly cheap to build, probably in the order of 1100 quid, but for those of us not able to design the amps we'd like this is a fine way of achieving really good sound. Just don't try to use them with inefficient speakers.

Future Developments

300Bs seem to need rather a lot of current to drive them properly and I rather suspect that the passive pre I use is not letting the amps achieve their full performance. An active pre amp or another stage may be a worthwhile improvement perhaps. I wonder about an Aikido-style driver between the 6SJ7/5693 and 300B...

And I must try the really nice looking mod that Paul Barker magiced up, adding a voltage regulator tube to the 5693 and doing away with the cathode bypass cap and associated gubbins around the 5693. I haven't plucked up the courage to tweak the amps yet for fear of breaking them. I need another amp so I can have a play without being musicless.

August 2007.

Heaters Update

Over the last few months I've been musing why the WE91s didn't sound as good as when I'd first put the KRs in the amps. I reasoned that it could be that my ears had caught up with the performance and I could now hear the deficiencies in the sound. But I felt that the sound had actually deteriorated quite considerably, to a much greater extent than simply me becoming very familiar with the amps. Specifically, the sound had become laid back to the point of me wanting to push the music along. Not slow exactly, but not pacey as I knew the KRs are.

Thinking about things though, it occurred to me that maybe there was potentially a problem with the heater voltages. Philip had specified a simple CRC DC rectification for the 300B heaters as he had some hum when prototyping. The R of 0.1 ohms was set to give the required 5V. So if the KRs draw more current that cooking 300Bs then the heaters may be under voltage. It would have made more sense to have checked the voltage when I first put the KRs, still, better late than never!

4.4V DC. Not good. It seemed very believable that the under voltage has slowly caused the sound to deteriorate. The question is, would upping the voltage reverse this?

Removing the bridge and CRC filter and AC heating the KRs direct from the 5V Hammond filament transformers gave 5.5V AC. I was a bit surprised that the filament transformers should be so much over the required 5V, but regardless of this I plugged the amps into the system and turned on.

After listening to the amps with completely silent DC heating the tiny amount of hum was something of a surprise. Initially the amps sounded quite thin, plenty of "brightly lit midrange", but the bass was very light. But with time the sound evened up and returned to the wonderful sound I knew. Bodging together the 0.1R resistors and a couple of 0.47R resistors I had in stock I was able to get the voltage down to 5.07V. I think it sounded better at 5.5V but I'm trying not to think about that as burning up the KRs prematurely would make them very expensive valves... Still, it's very pleasing to get the sound back to where it was, fortunately valves seem rather tough and tolerant of misuse.

What has been really interesting about playing with the WE91s again is that I have spent quite a bit of time of late playing with 45s, and whilst 45s have a magical top they seem to be a bit vague in the bass. Maybe it's my amp, and I need to play further, but rediscovering the KRs has been really good and spurred me on to tweak further with the VR tube mod and the driver stage. I'd like to try choke input in the power supply too, but that's going to need a couple of rather large mains transformers.

December 2007

December 2025 Update

These were nice amps, really nice. Yes I worried about it not being a choke input power supply, and a little about the AC heating. But tackling these would have made them very different amps, much bigger, and I would have needed at least new power transformers, and probably another choke.

I might have experimented further but sadly one of the monoblocks met with an accident one Christmas Eve afternoon, in 2016 I think. One of the Alpair 12P MLTLs I built (and are featured in this blog somewhere) thought it would be amusing to fall over, smashing a KR300BXLS, a GZ33, and probably a 5693. I weighed up buying another pair of 300BXLS, but they were already considerably more expensive than the £300 I'd paid for them. I wondered about "lesser" i.e. cheaper 300Bs, but even cheap ones weren't cheap. In the end I did nothing and pursued other valves. 

That's not quite true. The monoblocks are good candidates for using 6CB5s instead of 300Bs, which are dirt cheap, but do have a top cap. I bodged one up to try but was underwhelmed by the sound and put them on the shelf for another day. Maybe. (Thomas Meyer has written about a number versions of 6CB5 amps in his Vinylsavor blog.)

Retro Vintage - TubeCAD two-tube OTL SE headphone amplifier

TubeCAD two-tube OTL SE headphone amplifier.

So I have a lovely direct coupled Loftin White-esque 2A3 SET amplifier which sounds great through my Fostex FE208EΣ rear loaded horns. But I also have neighbours, and, if I'm completely honest, my better half really doesn't enjoy the footy commentaries on my local radio station in the same way that I do... So the next project was to be a headphone amplifier. After discussions with Philip at Bluebell Audio (dead link)he suggested John Broskie's output transformerless single ended headphone amplifier, which appeared on John's website (dead link - try the WayBack Machine) in December 1998.

My implementation of John Broskie's OTL SE headphone amplifier

According to the website, it's an amplifier capable of driving 300Ω Sennheisers as well as 32Ω Grados, and uses 2 number 6922 dual triodes per channel. Philip knocked up a power supply using a small Hammond 369AX 250V centre tapped mains transformer with two IN4007 diodes for rectification and a CRCRC smoothing arrangement after, the final RC being separate to each channel.

Construction

The plan was to use a black powder coated 13.5" x 5" x 2" Hammond chassis longways. Holes were drilled on the back for the input phono sockets, fuse holder, and cable gland. No more cutting IEC connectors for me!

Rear view of headphone amp. Note captive mains lead!

The mains transformer was mounted at the back, with an on/off toggle switch on the right side and a green led on the left. Then some holes to attach the power supply capacitors, and then the four miniature 9 pin Noval sockets. Philip had some concerns that the 6922s may be a little microphonic so supplied the sockets with skirts and spring-loaded cans. Finally, a Switchcraft 1/4" headphone jack was mounted on the front.

Internally, the tag strip was mounted on the fixings for the valve sockets or beneath the transformer to minimise visible fixings on the top surface of the chassis. This needs to be planned otherwise it's pot luck whether the tag strip fixings will mate up.

Internal view

Close-up of audio circuit

Close up of power supply

The compact nature of the chassis helps to make the amplifier look really quite neat and smart, but I had a nightmare building the audio circuit as space and tag strip turned out to be in very short supply. If I was building it again I would try to get some more space for the audio circuit, though I'm very taken with the external look of the amp and wouldn't want to change its appearance greatly.

Switching On

Well, this was the third valve amp I had constructed, but I was still nervous of things going bang. Fortunately nothing did, but, not thinking, I turned it on without headphones plugged in. Inserting the headphone jack with the amp switched on didn't seem to do it any good; I was greeted with loud rustling and then silence. It's probably testimony to the ruggedness of valve amps that after about five minutes of panic I switched on again and had sound! Phew, what a relief. I hadn't trashed the thing before I had started.

Listening Impressions

So the amp's working and my heart rate has started to settle down. The first thing I noticed was the dreaded hum. I checked the voltages which seemed reasonable, although the cathode voltages weren't particularly balanced between channels. I tried moving the four number 6922s around but this only had a small effect on voltage, and none on the hum.

Tackling the hum, I found judicious broddling of the cables inside sorted the worst of it out. Interestingly, it was the shielded cable running from the phono inputs to the input of the audio circuit at the front of the amp that was picking up the hum. Mental note, shielded cable doesn't provide complete immunity from hum. Much better to choose a cable routing regime that avoids the interference altogether. The remaining hum I could perhaps equate to AC heaters; I can hear it if there is no music playing, but as soon as there is (even footy commentary) the hum is no longer noticeable.

I only have a pair of 20 year old Sennheiser HD414s, not a pair of the 650s I fancy, but the sound is very nice. There's that wonderfully fluid grainless sound that valves produce, and that makes it very relaxing to listen to. There's no shortage of detail though, and there's plenty of texture too. I think the 414s are the weak link at the moment, but the combination is a very good alternative to my Loftin White and Fostex horns.

Improvements

Thanks to Steve Shiels I replaced the original Chelmer 6922s with some nice NOS Mullard E88CCs. Very nice, a notable improvement over the Chelmer 6922s. I suppose I really should rebuild the audio circuit too and see if I can balance the cathode voltages, but the amp sounds pretty good as it is and I haven't felt the need to do this yet.

Chelmer 6922 and NOS Mullard E88CC flanked by spring-loaded screening cans

Reading John Broskie's TubeCAD blogs, JRB has published a few Aikido circuits including headphone amps, so I want to try one of these. It's a good excuse to start playing around with the Aikido topology. Then I'll treat myself to a pair of 650s too.

December 2025 Update

Another amp that didn't stand the test of time. I couldn't get rid of the hum sufficiently, I suspect because of my lack of experience of amp building at the time and because it was a more demanding application and layout. It was a useful step on my amp building path though.

The nearly bare chassis sits unloved in a cupboard somewhere.

As the page is no longer available here's JB's circuit.

Retro Vintage - Bluebell Audio "Loftin White" Style 2A3 Single Ended Triode Valve Amplifier

Bluebell Audio "Loftin White" Style 2A3 Single Ended Triode Valve Amplifier

With the WAD PHONO II and PSU II safely under my belt I could get to building what I really wanted - a low powered single ended triode valve amp. The beauty of 97db efficient loudspeakers is that they don't require oodles of power to get a nice sound from them. Still being rather unadventurous and a novice in the amp building game I had intended to build the WAD 2A3PSE kit. Unfortunately as soon as I was in a position to construct one WAD went through an "internal restructure" and the 2A3PSE was dropped.

After a bit of head scratching and a few prompts on the old WAD forum I considered a Loftin White style direct coupled amp, inspired by Keith Garrett's website (dead link). The originator of this take on the original Loftin White amp is Philip Ramsey of Bluebell Audio (dead link - Bluebell Audio is no more). After an initial phonecall in which Philip encouraged and reassured me that I could build an amp from scratch I placed an order, and soon after two big boxes full of strange looking bits arrived. No turning back now. This was the start of a telephone friendship with a man incredibly passionate about valves and music, without whose patience I probably wouldn't be listening to valve amps now. I suppose I should add that I have no connection with Philip or Bluebell Audio other than I provide the cash and they provide the components. Just a happy customer.

Construction

So, I had two big boxes full of bits. One was very heavy and contained all the transformers, the other was smaller and was full of components, valves, fixings etc. Now I had to work out what to do with them.

I spent a long time studying some photographs Philip had sent me of one of his Loftin White builds and sketching out what I thought was going on. It's probably my nature but I wanted to think it all through so I knew what the end would be, not just the beginning. Once I'd got things sorted out, I started to draw the transformers etc. up in AutoCAD and planned how I would lay the amp out. Once happy I printed out the layout and attached it to the 17" x 14" x 4" black powder coated steel Hammond chassis.

Then it was a combination of drilling, filing and hole punches to prepare the chassis. The secret is to be methodical, take your time, and increment the drill size by 0.5mm. The temptation is to jump by a couple of millimeters but a better finish can be achieved by the smaller increment. Generally this creates less swarf so less deburring is needed with a countersink bit. Perhaps more significantly, at bigger diameters an increase of, say, 2 millimeters is quite a lot of material to remove and can result in some work hardening of the steel chassis. Not to be recommended. The worst bit is forming the rectangle-ish shape for the IEC socket. I try to avoid these now and use captive leads that require a simple circle. Much, much easier.

The finished chassis. Philip recommended that I should cover the chassis in masking tape before I started drilling to protect the finish. I rather foolishly thought that by covering it with the printed layout I was doing the same, but all that did was trap swarf between the layout and the surface and inevitably lead to some scuffing. I still use AutoCAD to draft out the layout but I cover the chassis entirely with masking tape and I frequently lift two sides of the layout from the chassis to clean the junk out.

Next job was mounting the transformers, choke and valve sockets. The amp is starting to take shape now. The small 9 pin sockets were probably the most fiddly bit of the whole amp. The holes for the bolts are very close the to hole for the socket and in one case it actually "broke through" when fettling the bolt hole to fit the bolt.

On the rear, the on/off switch, IEC socket (boo!), slow blow fuse holder, phono sockets and speaker terminals.

Internally, the tag strip, Cerafine cap in the PSU, the filament transformers for the 2A3s (AC heated), and the twisted earth bar. I tried to use as many existing valve socket fixings as possible to mount the tag strip, mounting them beneath transformers where there were none.

The first few components connected up - the PSU and output stage.

Now finished, including some mahogany side pieces.

Switching on

Gulp! It's an understatement to say that I was a little nervous the first time I switched the amp on. Thoughts of 400V rippling through incorrectly wired electrolytic capacitors filled me with a little terror, even though I'd checked my wiring, but I thought it important to look confident in front of my better half!

So, standing at arm's length, I flicked the toggle switch and waited. The GZ34 rectifier started to warm up, then there was blue arcing inside and everything went dead. The slow blow fuse had gone. Hmmm, that wasn't supposed to happen.

I tried again, exactly the same thing happened and the fuse blew. Rather frustrating. Over the next few days I had a few conversations, checked all the wiring, scratched my head and waited for Philip to send down another GZ34 and some more fuses.

The following Friday the bits arrived. I got home from work, plugged the new bits in, held my breath and switched on. Success! A smidge of hum from the AC filaments through the Fostex FE208EΣ was very reassuring. I never had another fuse blow after this.

Initial Listening Impressions

It's Friday night, I've been abandoned at home for the weekend, and the neighbours have also gone away. I'm Home Alone with my new amplifier... great! A trawl through all my favourites proved that this amplifier really was as musical as I had been promised. Philip assured me of an "awesome" sound thanks to the direct coupling of the driver stage to the output stage, and that is exactly how it sounded after all those years of solid state amplifiers. The sound seemed so solid, all the grain I heard with solid state gear had been lifted. And even with a seemingly meager 3.5W on tap there was more volume than I could handle at two o'clock in the morning with no-one to wake up. Hell, even Oasis sounded good that night.

Improvements

I had a trip over to see Steve Shiels with the Loftin White. This was the first time I'd heard his Lowthers and rather more esoteric valve amps. Steve has a very nice collection of valves (I'm not doing it justice here) and he was generous enough to try a few different valves. First up was a Mullard GZ32 rectifier which glowed like a light bulb which concerned me a little as I didn't want one of Steve's nice Mullards to expire! It sounded very nice though, quite an obvious difference. I was surprised.

Next up were a few replacements for the ECC83s. Most didn't make much difference to my untrained ear, except for a nice pair of Tungsrams Steve produced. Turns out these were actually made by Mullard. Very nice. Once I got home and heard them in the context of my normal system I could tell they were much nicer than the new production Svetlana 12AX7s they replaced. Result!

Talking to Philip, he said that the components in the amp were already a pretty good spec and without spending significantly there was little to change. He did suggest that I could try some NOS RCA 2A3s though. Which I did...

Dualplates as you can see, don't think I've even seen a photograph of a monoplate. Were they an improvement over the cheap Sovtek monoplate 2A3s? Well, yes I think so, but there's not a lot in it, at least in this amp. The Sovteks are a real bargain though.

Living with the Loftin White

For a year I was really happy with the amp. If it hadn't been for Philip raving about his recent incarnations of the Western Electric WE91 pentode driven 300b monoblocks I might never have listened to another amp. But Philip was so effusive of his new amps I had to try them, and in comparison the Loftin White is limited, particularly in the bass. I had intended to replace the output transformers which I had robbed to build the WE91s and get the Loftin White up and running again. But as time goes by that's not going to happen, slowly I'm taking more bits and it's dying an ignominious death. A little sad really for my "first amp". But it really is a grand little amp, and is so much better than so many commercially available amps it's laughable. Maybe one day in the future I'll rebuild it out of sentimentality. Now, taking inspiration from the Japanese a fully tricked-up Loftin White might be something else entirely...

December 2025 Update

Well I don't think I'll ever rebuild a Loftin White. It's a nice amp for sure, and one that has a special place as the first power amp I built, but it was too limited for my taste compared to other amps.

The chassis lives on though, in my D3A-2A3 amp, which I think is a much better amp. And the output transformers were reused in the WE91 clone 300B amps.

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......

Retro Vintage - Fostex FE208EΣ rear loaded horn loudspeakers

Fostex FE208EΣ rear loaded horn loudspeakers This was the start of my DIY hi fi journey. Finished cabinet with T90A supertweeters. Record added for scale... Background Whilst enjoying the beautiful hills in the Lakes in 2002 I was inspired by Paul Messenger's writings on some commercially available horn loudpeakers using Lowther (updated link) drivers, and was drawn to the positive comments about musicality and communication. Whilst Paul said they were not perfect they did possess a super communication. I started to search the net and quickly came across James Melhuish's Single Driver Website (dead link - did become fullrangedriver.com but this is dead too). This was a revelation and I spent quite some time reading the posts on the old forum and studying the projects. It had never occurred to me that I could actually build my own speakers, AND get a decent result. Lowther (updated link) drivers seemed to attract strongly polarised opinions, a love-em or hate-em reaction. They weren't exactly cheap either, a pair of EX4s cost over £1100 at the time. This was a little too rich for me - I hadn't even heard a pair of horns yet and it seemed a rather large risk as they might not be for me. Reading further, the Americans rated the Fostex (updated link) drivers, some even said they preferred them, but opinions expressed on t'Internet should be taken with a healthy dose of salt... But they were much more affordable. Fostex drivers weren't readily available in the UK at the time, but I got a pair of the new FE208EΣ (updated link) on special order from a Fostex supplier for £320 the pair. Not being used to a drive unit of this expense the construction of the cast frame, size of the magnet and overall weight was reassuring. Rear view of the FE208EΣ driver Whizzer-less banana fibre cone The supplied mounting gasket Choice of speaker I thought about design for some time, considering different flare types and horn lengths etc. I also considered Martin King's mass loaded transmission line (updated link - the old Fostex FE208 project is no longer available) enclosures but Martin felt the new drivers weren't sufficiently suitable and might give less than ideal results. In the end I decided to play it safe and build Fostex's recommended enclosure (updated link). Whilst not perhaps a true horn (more a series of coupled chambers) I figured that the good burghers at Fostex know more about speaker design than I do! Preparation So, looking at the recommended enclosure the first thing I did was convert the cutting list to a sheet size of 2400mm x 1200mm which is available in the UK. This worked out at four sheets for the two cabinets, which is a lot of 18mm thick birch ply. The best part of 10 stones, or 60kg, for each speaker! I weighed up using mdf but decided I only wanted to build them once so birch ply it was. There was a real benefit to rejigging the cutting list. The Fostex plans show a number of panels which are joined: the back, base and sides. Using 2400mm x 1200mm sheets allowed me to use single pieces which I figured had to give better rigidity as well as looking nicer. Cutting the sheets up at the local timber yard took about 10 minutes and saved no end of work. Definitely the way to go, provided the operator makes accurate cuts... The four sheets cost about £150. Two rather large piles of birch ply waiting to be assembled... Back in the shed assembly was pretty straightforward thanks to the square construction. Unlike many horns there are no varying width flares, which means the ends are square. This is supposed to help disperse any unwanted high and mid frequency sound that has entered the horn, so don't radius them. The square ends helped to keep things simple, and fortunately only minimal fitting of the panels was required as the cutting in the timber yard was pretty accurate. However, when working out my cutting list I did allow a few millimeters extra to some of the pieces to allow for trimming to size, particularly the side panels. This gave me the flexibility to make sure that the outside panels were a good flush fit. Construction Using the table saw the first job was to cut the numerous lengths of ply to the required lengths. Then the pieces were glued together in small sections using pva before assembling the small sections together. There were only two areas that required a little more thought. The first was the baffle for the driver. The second was the speaker binding posts, more of which later. The hole for the drive unit marked out prior to cutting out with a jigsaw. The outer circle is for the mounting screws. Beware the filler piece to the top left - used to patch knots. I spent quite a bit of time checking all the pieces of ply to make sure that the impact of any of the filler pieces was minimised. Unfortunately they were quite numerous and their complete avoidance was not possible. So, to start gluing up... First the front baffle and base of the back chamber. I decided to drill pilot holes for the driver mounting screws all the way through the wood to ensure the screws would drive home. I'm glad I did as the screws are a tight fit even so. Next the rear wall of the back chamber (face down on the bench) with the bracing to the first chamber sticking upright. The rear panel. The piece sticking up forms the third and fourth chamber. Note the two holes for the binding posts. I decided I didn't want to use a binding post tray, rather keep the natural birch look. It seemed like a good idea at the time... The internal vertical panel. And then the base panel and bottom front (on the bench). Glued up to one side panel. Note the circle cut from the outside panel for the binding posts. I did this for aesthetic reasons, and I think it looks very nice. 'Course, I'm stuffed if I ever want to change the binding posts or cable inside the cabinet... No, I wouldn't do it exactly the same again but I'd still wouldn't use a black plastic tray. The cabinet construction is easy to see now. Internal wire is two lengths per channel of HU1 (dead link) - silver plated ofc with ptfe dielectric from IPL (dead link). This is the same stuff I use for speaker cables. It's small so fits behind the carpet, and it sounds significantly better than the Linn K400 biwire cable I used to use with the Keilidhs. I only had a puny 18W Antex soldering iron which just wasn't big enough to heat the binding post to get the solder flowing. Fortunately, as I was building the speakers round at my parents I was able to press my mum's cooking blowtorch into service, and without burning too much of the wood either! First speaker almost complete except for the second skin to both sides, the bottom base panel, and proper cleaning up. Finished. Note the over-zealous sanding at 5 o'clock. Fortunately most of this is covered by the drive unit. Phew! Initial impressions Well, the first thing to note is that these are not small loudspeakers. Okay, that may sound obvious but they certainly make a statement in a room. Birch ply isn't everyone's choice, though Mr. Ikea has made a healthy living selling forests of the stuff. But it has the advantage over mdf that it only needs a varnish finish to protect it. And I can live with. Being a pretty impatient person, as soon as both cabinets were finished I moved the speakers in to my parents living room, mounted the drivers, connected my little Teac all-in-one job, and stuck a couple of test CDs on. The drive units were brand new and hadn't loosened up yet, and whilst this was quite audible, so was the open presentation and inherent "rightness" of the sound. My parents living room is a good size and I'm sure this helped the speakers to "breathe", but I was impressed straight away. Much better than the Keilidhs. Setting them up at home Lugging the speakers home was no mean feat at nearly 10 stones each. The speakers are positioned in the corners of my room, either side of a fireplace. There is little alternative, but fortunately they work pretty well here. I have them hard up against the corner, in theory giving better bass response, although the form of the speaker with the mouth in the middle of the baffle perhaps means the speaker doesn't get the full benefit of their location. The recommended enclosure (updated link, but in Japanese) helpfully refers to "sound absorbents" which should be placed in the back chamber, inside the bottom of the speaker, and inside the bottom front baffle. Whilst I thought about what to use for sound absorbents I connected them up the Exposure amps to see what they sounded like. I was still impressed, though the presentation was a little different from my parents' house as my room is half the size and I listen much closer to the speakers at home. Still much better than the Keilidhs. For the "sound absorbent" I got some Dacron-type fibrous pillow stuffing from the market for a couple of quid and filled the bottom of the speakers between the bracing ribs. But all this did was rob the life from the speaker, not at all good. There was an effect on the bass too. By the time I was experimenting with stuffing the drivers had just over 15 hours use. I remember this because at this point I was listening to David Gray's White Ladder and nice deep bass started to come from the horn mouth. When I put the stuffing in the cabinets the newly found bass was severely curtailed. So I took the stuffing out and had a think. I had some 2mm thick laminate floor underlay left over from the kitchen floor which I thought might be worth a try. I cut a number of strips and placed one thickness between each brace. As they were cut slightly oversize they wedged in nicely without any need for fixing. This cleaned the sound up a touch and preserved the life and bass. A good result that I was happy enough with to live with and forget about. I placed a piece of the same foam underlay on the back wall of the compression chamber but it didn't make much difference. I did, however, attach some self adhesive bitumen pads on the back of the magnet. Available from car parts places for a couple of quid a sheet, their principal use is for damping car panel resonances, but with the surface area of the driver's magnet being so large and the high pressures within the compression chamber they really helped damp vibrations reflecting back into the drivers. Although the pads are not easily removed once applied I think this was one of the biggest improvements I made, cleaning the sound up and revealing more detail. And that was as much tweaking as I did initially. I sat back and enjoyed the music. Listening impressions After listening almost exclusively to box loudspeakers for many years the Fostex horns came as quite a revelation. I suddenly (and shockingly) realised how coloured the box loudspeakers I had heard were. Not just the Keildhs, but other well known speakers costing the thick end of £2000. What was so surprising was that I hadn't really noticed the boxy colouration of the speakers when I had heard them, just that the horns stripped it away with a wonderfully organic sound. Bass was fast as you would expect from a horn, the driver coupled directly to the air behind it, though not particularly deep or extended, although the size of my room means I'm unlikely to get very deep bass anyway. Being a single driver there is no crossover. This has the obvious advantage of making the speakers more efficient, and I have come to the conclusion that more efficiency is generally a good thing (especially for SET valve amp enthusiasts). But I think the biggest advantage is having no components in the signal path - this seems to preserve the immediacy, detail and life of the speaker. And not spending money on any crossover components is an added bonus! There are some downsides though. The FE208EΣ is maybe better described as a "wide band" driver rather than "full range" as the treble rolls off from about 7kHz. I lived with the treble quite happily for a couple of years. It's amazing how much the brain can accommodate aural deficiencies, and my enjoyment of the speaker wasn't impaired at all during this time. Eventually though, as I heard other high quality speakers, notably Steve Shiels' Lowther EX4 horns and James D's Quasar open baffles with AER and Supravox drivers I became more aware of the missing treble and eventually added a supertweeter (updated link). The other downside is that due to the large 8" driver the speakers beam, and there is a very narrow sweetspot for the best stereo imaging, literally a few millimeters makes a large difference. How much this might affect you probably depends on whether you can sit in the sweet spot between the two speakers. That said, I can quite happily sit in the next room and listen to the music as the sound is, to my ears anyway, fundamentally right. Instruments just sound like they should. It would take a very good box loudspeaker to tempt me back. So, for under £500 these are a pair of speakers that sound better than anything I have heard commercially for £2000. Not perfect, but a nice balance of compromises that I can easily live with, and have done for nearly four years so far. And perhaps most significantly allowed me to start playing in the world of low powered single ended valve amplifiers... Improvements Well, I did end up adding a supertweeter, and as good as the speakers were the supertweeter improves them no end. See here (dead link). Probably the best value improvement is time. Time allows the drive units to run in and the performance does improve, quite markedly in some respects. Bass can thunder with the right material, given it's only an 8" wide band driver. What has been interesting is that as other components in my system have improved the Fostex horns have responded. For instance, connecting my WE91 type 300B monoblocks revealed lots of bass that hadn't been there before. At a recent meet in a decent sized living room the wooden floor really shook due to the bass energy produced by the speakers. Scottmoose was sufficiently surprised to model the speaker using Martin King's 1/2 space back loaded horn mathcad sheet... The red line shows the response has excellent sensitivity, nominally flat to 38Hz. There is quite a lot of ripple above 100Hz but this is not noticeable in practice: a combination of room acoustics and the internal square edges scattering the medium and high frequency waves in the cabinet helping here. Thanks Scott. The longer I listen to these speakers the more capable they seem to be. It will take something very special to replace them. December 2025 Update Ah these were good speakers. But they went to the recycling centre in the sky a few years ago. Eventually I heard the honk, it was subtle but it was there nevertheless. I tried to damp it with increasing amounts of absorbents, but I found that just robbed the life in the music. And there was a shrill peak around 3.5kHz which was a little uncomfortable if the wrong frequency was hit. Alison Krauss's vocal on Please Read The Letter was guaranteed to set it off. Subsequent experience suggests this is exacerbated by side walls close to the driver - my suspicion is the return wave on the cone makes it worse. My OB experiments changed this character for the better. I also found that if I hadn't listened to them a while they sounded pretty horrid until they'd had a few hours on them again. I love the full range character though and currently triamp so the amp is direct coupled to the 208EZ.

Retro Vintage - Old Web Pages Reborn

I thought my original website was long gone, since my old ISP, Pipex, disappeared. I was rather surprised and more than a little pleased to find a copy two days ago on the Wayback Machine - it was a bit of a trip down memory lane and a little eye-opening. I was a lot younger then, and at the beginning of my DIY journey; some of the words are a little naive reading them now. But valid enough as an account of a journey.

I thought it was worthwhile reproducing some of the more interesting pages in this blog. Well, copying and pasting anyway. The resolution of the photos isn't great sadly, and I've tried to update the links but many of the sites are no longer with us. I've added some thoughts at the end, a reflection looking back a number of years with current context.

So what to call this recreated series of old webpages nearly 20 years old? Antique notionally starts at 100 years, Vintage 20 to 100 years, and Retro less than 20 years. But this is the internet and 20 years is a loooong time. But Retro Vintage sounds about right to me.

Use the Retro Vintage label to find these posts. Ones copied so far include:

• Fostex FE208EZ rear loaded horns
• WAD PHONO II and PSU II
• Bluebell Audio "Loftin White" Style 2A3 Single Ended Triode Valve Amplifier
• TubeCAD two-tube OTL SE headphone amplifier
• Bluebell Audio "WE91" Single Ended Valve Amp Monoblocks