Pro-Ject Head-Box - The Amazing Headphone Amplifier

Not really vintage but an interesting little box nevertheless. I have little experience with headphone amplifiers, even headphones in general but this unit was very surprising indeed.



I picked this up at a boot fair a few years back and its just sat around in a cardboard box ever since. However the other day I was refurbishing my cherished Cambridge CD1 and felt the need to go hunting for op-amps. This lead me to the Pro-Ject Head Box but sadly it used dual op-amps, not what I was looking for. But upon opening the unit I was so impressed with its design I felt I should take a closer look.



I came across a thread where someone had also been impressed with it and modified theirs with great results. I could feel me figures twitching for the soldering iron, I wanted to get stuck in, it was Lampizator all over again!

I plugged the unit in for the first time and was shocked, it sounded better than my Sansui Ca-2000 on headphones! How can this be, my world has been crushed. Cheap and cheerful op-amps never sounded so good!


So lets gets started!

First off, new caps
470uf   35V   x2  main power supply, after ac-dc conversion
330uf   16V   x2  main power after regulator
10uf     63V   x2  op-amps (no need for such high voltage surely?)
4.7uf    100v  x4  decoupling (by volume pots)

Main power supply caps can be increased but I kept original values as space is at a premium and very little current drain in this amplifier. I used Sanyo oscon on op-amp and 1uf polyester for decoupling. The polyester are by no means the best thing to use but its all I had. Polypropylene should be used instead, wima ect.

Second, op-amp sockets for easy swapping!



Above we have the finished article, or so I thought. After plugging my phones in I had too much mid-range, very crisp and transparent but it was hurting my ears! Hmmm I felt the polyesters may have given this effect but I wasn't sure. So now I had to get those op-amps out and start swapping!

The 4580 came out and the LM833 went in, not much difference on paper but the 833 is used in a lot of the good old TDA1541 Philips players.

Headphones went in and BAM! there it was, perfect. The LM833 sounded lush, shimmery mid with very realistic vocals and as a bonus it had less distortion at higher levels. Anyone who says op-amps have no impact on sound is talking rubbish!

I had to play the whole London Grammer album, start to finish, I was helpless. So this is me signing off in a state of bliss, until the next time folks!

Speaker Cabinet Restoration, Oil or Varnish?

I've been asked by a couple of people whether they should Oil or Varnish their speaker cabs.

Well the answer depends on what state your cabs are already in but ultimately you want Oil not Varnish. Varnish is a quick and cheap way to give a hard wearing protective surface but over long periods of time can flake and crack. It also doesn't feed the wood, the veneer is left underneath getting dryer and dryer. This can result in the veneer itself flaking off. Oil will feed the veneer, help prevent flaking and enrich the colour tone and depth. However oil will require more work and regular polishing to keep it at its best.

If your speakers are already varnished but in good condition with no flakes coming off, then there is little to be done. You can oil them, they will go shiny but then dull as the oil drys. The oil will sit on top of the varnish and wont feed the wood. You can varnish them again but in my opinion the best option here is to leave them alone, a regular polish will keep them nice.

If you have cabs with old varnish flaking off then you can strip the old varnish, rub them down (very lightly) and then build up layers of oil. When stripping I tend to go less paint stripper and more elbow grease. You can find elbow grease at any local hardware store... If that sounds like too much work for you then adding oil to the flakes and cracks will help the general appearance and the use of a good bees wax polish after will do wonders.

The speakers below had slight cracking in the varnish but the oil and bees wax helped a lot.

If your cabs have no varnish on them, the fun can begin straight away. A quick rub down is still advised as this will freshen the surface ready for the oil to soak in. It can also help hide any light marks and scratches.

But which oil should I use? I hear you cry.

Teak oil: Its good stuff but tends to be a bit expensive and is quite thin.

Danish oil: Another good one, very poplar, again, can be expensive but buying in bulk helps.

Linseed oil - Double Boiled: The oil of school workshops, its thick, its good value, its safe.

Personally I use Linseed Oil, it must be the double boiled stuff for the best results though. Its the thickest oil I've found and really gives a good finish. After oil the veneer has more depth, 3 dimensional glistening and improved colour tone. It also leaves a film over the whole speaker which helps protect and continues to feed the veneer. Any of the above oils, and others, will work well but after a few coats have been applied and set we must move to the next stage.

Beeswax Polish.

This is were we receive the fruits of our labor. Apply a small coating over the speaker and leave it for 10 minutes. Now buff away the residue to reveal a glorious shine, buff in the order you waxed. The longer you leave the wax on the more elbow grease you will need, hopefully you have some left from earlier.

So there you have it, bye bye varnish and hello oil. You cant beat oiling speakers on a hot sunny day!

Goldring Lenco GL75 DIY V-Blocks

Ah the good old GL75, my trusty companion. Quite long in the tooth now but I love it, and personally I find its sound reproduction quite good for a table from 1972! Im not a huge record head but I have a big collection of vinyl and the Lenco is usually the deck I reach for. However, this particular deck has the common v-block issue.

Im not going into too much detail about dismantling your lenco but hopefully the pictures will give you an idea. Below you can see the v-blocks, a mustard coloured rubber material which has perished with age, especially the one on the right.

The best option is to buy a new pair online for around £20 + p&p. However, I have a little trick which is easy to try, non destructive and its free! All you need is: some super glue, scissors and an old drinks can.

I propose we keep the original v-blocks but add an aluminium skin over the top.

You will need to cut a strip of metal from a drinks can. Make it the width of the "inside" of the v-block. The longer you make the strips, the easier it is to see if they are sitting square latter on.



You then bend it into a right angle, make sure your fold is straight and true, I used a straight edge to bend against. You can now pop it in the v-block to check it sits well and is the correct size. Hopefully you have something like the picture above. If so make another one to match.

You should now have two strips in place, one for each block. Now this is the tricky bit! You need to apply a tiny dab of glue to the lower part of the strips, pop them in place and then get your arm seated as quickly as possible. Make sure your arm is seated correctly as the glue will dry fast! Hopefully you now have something like above.

Once the strips have bonded to the blocks you can remove the arm and the v-blocks. You now simply trim the excess metal from the blocks. Hopefully it looks like the above.

Now put it back together and fold the little strips over the tone arm. This will keep the arm sitting in the crisp metal groove we have made. Put the rest back together and your ready to go!



Before the arm would loose tracking about half way in a disc and do all sorts of jumping ect but now with my super high precision v-blocks in place she plays solid and true. The wobble in the arm is all gone, before you could rotate the arm and it used to lean to one side.

All in all I'm very pleased with my creation but I certainly wouldn't recommend it instead of new blocks. This should only be tried if you don't have the money or simply cant wait for new blocks to arrive. You need good eyes and a steady hand and the success of the project depends on how accurately you fit your strips in place.

Until the next time guys...

Choosing the Best Vintage Drive Units for DIY Speakers.

How on earth do you choose which drivers to use when you have little to no technical information on the units you have available?

This is a tough one because everybody has their own taste and may require their speakers to do different things. Some may be looking for volume, others may want accuracy or maybe you'd rather an easy listening setup you can enjoy for hours. There are also other factors to consider, like budget, time frame and the physical size. Also there is a question of wood-working/electronics skills and available tools.

So lets assume you are somebody who has a fair collection of drivers and you want to build a musical system with good bass at low volumes and you don't want to spend your life savings on it. Lets say you have basic wood working skills and you have a ruff idea about speaker cross overs.

I'm of the opinion that a very good two way speaker can be achieved, and quite easily too, if you have a good source of drivers to experiment with and you don't crave a perfect flat response.

My ideal two way would be something like an 8" bass/mid in a tl and an open back tweeter sitting on top. I'd simply use a first order crossover but this will make choosing your drivers quite difficult. You want the tweeter to go fairly low aswell so you can take advantage of the "open back sound".

I think most of us would agree that a three way is going to achieve the best results so I will focus on this design method. However I'm going to suggest a rather unorthodox method for choosing drivers.

First driver to pick is the mid-range. you need to play it naked, no crossover, no cabinet. Try to keep in mind that its the mid-range were listening for, if you like the sound as it is you have a good starting point. If you don't like the sound then don't waste time on it, smash it up with a hammer and find another driver.



If you play a kef B110 naked it sounds fairly naff, well, it is a bass driver after all. However if you play an old Philips AlNiCo or an EMI ect, you should find it quite satisfying. Please don't use dome mid-ranges here unless you really like them for some reason. You want to try and go paper cone, with paper surround and AlNiCo if you like.

Now you need a tweeter. I do a similar thing as the mid but I use a single capacitor in series with the tweeter to protect it. I would start with a 4.7uf for 8ohm tweeter and keep the volume low. Try and pick several tweeter options from this test so you can choose the "perfect one" latter on. A Kef T27 sounds like crap here but a pair of decent paper cone open backs should sound glorious. Open back tweeters can be hard to find but a decent AlNiCo dome like the one below will work very well in most cases.



PLEASE NOTE: If you have a 16ohm tweeter the 4.7uf cap wont filter as well so I would use a 2uf. Likewise, if you have a 4ohm tweeter the 4.7uf could filter too much and you wont get the natural sound of the tweeter.

Now you need a bass driver. Go no smaller than an 8" and personally I would use a kef b200 if your other drivers are of similar sensitivity. When choosing a bass driver you want a very low resonance. If you hold the speaker to your ear and tap the edge of the cone you will hear a nice bass thud. The lower the tone the better. I always look for something around 20-30hz but the cabinet you place it in later will change this value. A small sealed box will increase the resonant frequency. So if your building a small bookshelf speaker, a driver with 60hz resonance will be fine. I personally would only ever use a transmission line for the bass because I can't resist that deep rumble organ bass.

Now you have at least three drivers, you can have a quick listen to them all together using an existing 3-way crossover network from an old speaker system. If you hear peaks in the spectrum, try reversing the polarity of the drivers until it sounds right. This is only ruff but you should be getting an idea of how well matched your selected drivers are in terms of sensitivity.

From this you should now have three drivers your happy with. Now you need to build your enclosure and I'm leaving that part up to you. But lets say you are using a transmission line for the bass and the mid and tweeter will sit on top open back.

Fit your drivers in place and start the lengthy process of making your crossover, by ear if you're feeling brave. Building a speaker in this way means you are constantly  playing with values and you really get a feel for what the individual components are doing. I have been playing with crossovers for months in some cases. You can of course use a cross-over calculator which are plentiful online. These don't allow for the sound you will actually hear in your listening room but are certainly a very good starting point.

Im sure many will disagree with this method of building speakers but Its more fun and you can tailor the sound to your preference. Would you rather sit on the computer looking at numbers or sit on the floor surrounded with vintage drivers?

Let the MUSIC flow!

The Capacitor Clock is Ticking

I'm afraid I bring bad news for all vintage hi-fi enthusiasts. We are reaching an apocalypses moment and it is vital we all recognize this problem and address it before its too late.

All of your Hi-Fi components contain electronic components and one of the most common and important components are: CAPACITOR components...

I won't get bogged down in explaining what capacitors are because I don't have the time or anywhere near enough technical knowledge. But basically, they are used to smooth out currents in power supplies, frequency filtering, oscillation ect.

They come in many different types but the most common is the Electrolytic Capacitor. Again, Im not going into too much detail here but an electrolytic capacitor is essentially a metal can filled with paper soaked in Electrolyte.

Electrolyte is a chemical, a liquid, and liquids will dry up over time. When the electrolyte in a capacitor dries up, the value of the capacitor will change and eventually the capacitor will fail.

If a capacitor fails, it could have devastating effects on your equipment, damaging other comments in the circuit. This means high repair bills and in some cases, where replacement components are not available, can lead to you owning a rather expensive door stop.

If you own an amplifier from the 70's, its now reaching 40 years old and the capacitors inside will be way past their best. So the clock is ticking and if you do nothing the amp will eventually fail.

Do not fear though, there is light at the end of the tunnel, two lights in fact.

You can have an amplifier "re-capped", in other words, new capacitors through-out. It is a little expensive but there are two plus sides.

One: you have saved your amplifier from failing and hopefully this cherished gem will give another 40 years of faithful service.
Two: The sound improvement will be considerable and you will be able to enjoy your music like never before.

So there you have it guys and the same goes for capacitors in passive speaker crossovers. So pick up a soldering iron and do those ya self. You simply replace like for like, there's no high voltages to fry yourself with, and the sound improvements will be appreciated.

Amazing Alnico Speakers

First off, what are we even talking about?

Well, we mean the type of magnet used in a speaker drive unit. Any conventional driver will use a magnet. There are two types commonly used: AlNiCo and Ceramic.

There's quite a fan base for these vintage drive units and many claim they sound better than ceramic speakers. The question is do they actually sound better and if so why? This stir in the HiFi underworld appears to have been noticed by today's companies, who now offer their own AlNiCo units. So is there something in it?

What is Al-Ni-Co (Aluminum-Nickel-Cobalt)

Its an alloy magnet system and was very common in the 60s. Its more expensive than ceramic magnet material, so logic would dictate that it was used for a reason. Saba, Isophon, Goodmans, all top manufactures back in the day and all of them used AlNiCo magnets in many of their drive units.

"the AlNiCo sound"

This is all about compression and it only happens due to the nature of the AlNiCo magnet.


AlNiCo magnet has a delicate magnetic field, easilly drained by other forces. So when you send a signal to the voice coil in a speaker, you are generating an opposite magnetic field. The field generated in the coil pushes away from the AlNiCo field, causing the cone to push out. When you swap the polarity, the reversal happens.

The field in the coil is also interacting with the AlNiCo, it looses some of its power as the coils field is present.

When playing music, the louder the volume the greater the field in the coil. The AlNiCo magnet is constant but the coils field is jumping around and switching direction. The bigger the coils field, the more power sapped from the AlNiCo.








So to recap, when the fields are interfering, the voice coil field weakens the AlNiCo magnets field. As you increase the signal, the greater you weaken the AlNiCo.

If you weaken the magnet on a speaker, it becomes less efficient (you get less output volume). This is happening with every movement of the voice coil, tiny tiny amounts and at extremely high speeds.

So the AlNiCo magnet system is smoothing the sound, or, to be more accurate, compressing.

So there is a difference with AlNiCo speakers and to my ears they do sound "better" but of course there are many other elements to a speaker and a well designed ceramic speaker will sound better than a poorly designed AlNiCo.