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Amp Technician Theo Argiriadis
Words and Pics: Andy Hall

During a recent editorial staff meeting in the pub, BiL's resident guitar gear geek Dave informed me that my early 80s (Paul Rivera-era) Fender Concert amplifier had become a quite a collectable item. Sadly it had been living in neglect under my stairs for the last 5 years (after a half-arsed attempt at repair by Arbiter), so I decided it needed some love. Which is how I came to get in touch with Theo Argiriadis, a north London based tube amp and analogue electronics specialist. I dropped off my amplifier and we had a chat about the world of tubes...

BiL: So where did this all start, how did you end up in this particular niche?

It started as a hobby as a child and over the years I became more interested in science, and physics which was what made me get into electrical stuff. The physics had many parts; thermodynamics, the mechanics, electricity and magnetism and so on. I used to make little experiments and things, and then I got into music and playing guitar. I sort of played off an on with a bands and eventually started to use my electronics skills more.

Then, later in life I did an electronics degree course at North London Polytechnic, but I was still playing guitar and I guessed I would probably have to go and get a proper job. I went to the careers centre and they really freaked me out, they basically told me I'd have to do a lot of arse-licking to get myself a job. I didn't wanna do that! (laughs) Also, a lot of what I specialised in - semi-conductor switch mode power supplies - were particularly applicable to the Ministry of Defence, and I just didn't want to get into that.

So I started repairing televisions, then in the late 80s/early 90s I got a job at a studio in West London as the electronics maintenance guy, looking after the amplifiers and PA. Then I gravitated more into the 'electronics of sound' as I call it, and I started designing circuits, and getting into amplifiers, and testing and it just went on and on from there.

And now, I'm really keen on doing my own thing and producing my own amplifiers, mainly for guitars, but I also work on other stuff as well. What you see on the bench is a Hi-Fi using valves. I also do studio stuff like equalisers, spring reverbs, bespoke distortion units, things like that. But I'm mainly focussing on guitar amps at the moment.

BiL: So the dream is for you to launch your own range of amplifiers?

Yes, they'll be made in a special way – it's quite big in America at the moment – they call them 'boutique.'

BiL: Whether it's guitars, amps, effects, a lot of people seem to get very obsessive about vintage gear. Was there ever a golden age of amplification? When we last spoke you mentioned about how advances in tube technology went hand in hand with early Rock 'n' Roll, and maybe that's why we have such positive associations with that sort of sound.

Well... Both during and straight after World War II, there were a lot of advances and developments in electronics and amplification. When it was all over, there were a lot of new ideas around ready for the start of Rock n Roll. (Incidentally I think Blues, Jazz, gospel and honky tonk were being amplified long before Rock n Roll, with those little pickups on guitars). Anyway, there was a boom after the war and the Beam Tetrode 6L6 valve started being used in these early amplifiers. And they've got what you call (electronically speaking) a very characteristic range of harmonics, especially when being overdriven.

Together with the 12AX7 which is the traditional pre-amp tube, and depending on how you design the circuit of course, they tend to generate a certain type of harmonic distortion which really goes well with the string of the guitar. So we became used to that kind of sound. Let's assume for moment though that transistors were somehow invented first, now they produce a lot of high harmonics of the odd type. Valves produce odd harmonics but not of such a high order. In electronics, when we say harmonics, we mean multiples of the original frequency. An even harmonic would be say twice the original frequency, 2000/4000 Hz etc. where odd would be 3000 / 5000 / 7000 Hz... Transistor amps produce this type of high i.e odd harmonics so the guitar sound is a bit more brittle. But if that sound had come first, maybe that would be what people today would aspire to...? We just don't know.

I don't believe in this 'traditional' or classic thing, I think our taste in music and our taste in sound is being formed as we go along.

BiL: It's not a static thing.

No, it's not. A classic example is contemporary RnB and Hip Hop. In the 1980s, a lot of these guys used to hang out with those ghetto blasters. They used to turn them up really loud and what did they get - transistor distortion! And what do they do these days in studios? They actually distort stuff to sound a bit farty. I just don't believe in all this traditional... whatever....

BiL: So you obviously don't buy into the fascination with vintage gear, or achieving that magical sound?

There is no 'right' sound, I mean people are fascinated with everything and anything these days. Elton John sells a pair of old stinky shoes, and people will go and buy them because Elton John used to wear them! Yes, some old amplifiers do sound good, but you can make something new which also sounds good.

Like I said before, the tube amp is compatible with the guitar sound. If we had a spectrum analyser here, and we were to play a guitar string on its own, you'd see the harmonics generated and the valve amp when turned up loud with a high signal (not even over-driven) also produces similar types of harmonics. Pre-amp tubes like the 12AX7 produce 2nd harmonic distortion. The beam tetrode of the 606 type in push-pull circuits produces low order odd harmonics. The combination of these harmonics give a certain flavour to the sound. There's no way you can get that with transistors. They've tried, a lot of people have tried...

BiL: It's an over used analogy, but take someone who drives a 50 year old 'classic' car. It may sound and look good, but there must be contemporary components and technologies that would make it perform better if it were given an overhaul or rebuild? So surely it should be possible to make an even better amplifier nowadays?

Of course it is and that's what I'm trying to do now, but as you say, there are still those people so fascinated by 'the old' that they'll say, "put carbon composition resistors in my amplifier" (similar to the ones Fender used to have), and claim that it sounds a lot better, "the highs are better", "there's better definition" and so on.

As an engineer, if I think the electrical specification of the component they want is acceptable, of course I'll put it in, but it's not the sort of ultra faithful renovation project I'm really into. But one thing I have to say about the tubes of the 1950s is that they were better for the very simple reason that they were used not only in sound but everywhere. The mainstream electronics industry was vacuum tube orientated, so the quality control, testing and also the building and materials were far superior.

These days it has become a specialised market, and the quality is not as good. There used to be thousands on the market, they even used valves in the first computers, all sorts of things. However, there are still good suppliers around, people such as Watford Valves who do in-house testing for reliability and sound. The other components though, I think are better now. Capacitors didn't die, resistors didn't die, so they make much better quality components nowadays, and that also includes some transformers funnily enough.

BiL: Tell me a bit more about the idea behind your own 'boutique' amps?

Well, about 10-15 years ago, people thought guitars were on the way out. Everyone thought music would be made on computers. Then of course Brit Pop happened and suddenly there's hell of a lot of guitar music around. So there's a corresponding great demand for guitar amplifiers. But these manufacturers are trying to build these things like toasters, someone designs it here, emails it there, it gets built in China or in some other part of the world, and there is no connection between the people involved. 

Also, they are recycling old designs, and they've taken Marshalls, Voxs, Fenders, whatever, and tried to copy them. But no matter how good these original amps sounded, they were built in an era of fierce competition and they inevitably contained mistakes. So these new guys are making the same mistakes all over again! Some of them, they don't even try to make circuit changes or increase component ratings for better reliability.

Of course, what makes it harder is that the whole electronics industry today is geared toward low voltages, even flat screen televisions now are low voltage. But these valve amplifiers deal in high voltages and high temperatures, whereas contemporary electronics is all about high efficiency – getting 500W of output with very little heat generated. So the expertise is just not there in the mainstream industry.

I even refuse to work on some of these new amps because they do really stupid things in them, both in mechanical and in electrical terms. I had a customer who had an amp from a well known company that was built in China which was rattling. It turned out that the sound was not coming from the speaker but the transformer which was mechanically rattling! I was reluctant to fix it, but I ended up wedging a piece of wood in there which stopped the rattle, but it was just so badly built.

So this frustration is partly what has made me decide to build my own amplifiers, which are mechanically and electronically sound. The first is a parallel single-ended amp. Most guitar amps split the signal into two parts, and the only amplifiers I can think of that does not do this is the Fender Champ and the Vox AC2. There is a big thing in America at the moment with people trying to beef them up with two 6V6s which they say gives 10W. My parallel single-ended amp will easily generate 22W. It'll be a bit like the Champ or the Vox AC2, but with a lot more power.

BiL: Using my 80s Fender Concert as an example, can you explain how you approach a renovation job?

Your amp is not that old, but first thing I do is a visual inspection. Electrical safety is really important as these amps often deal in very high voltages. I check for corrosion and wear... did you know when they first started using plastics, they thought they'd last forever. Now we know that plastic deteriorates just like anything else...

I check the fuses and fuse holders, and the switches. The mains switch makes the valves glow but the second one is a high voltage switch responsible for about 480v so it really has to be looked at thoroughly. Then we get into things like the terminals which again have high voltages running through them.

Another thing is the valve sockets, Fender valve sockets don’t hold the valves that well so I'll replace them which, is quite a bit of work as I have to modify the diameter of the holes to hold the replacement sockets. A big part of the job is to remove solder from old deteriorated joints, grinding and cleaning the terminal until I see clean metal, use a little bit of solder paste and then resolder. I also look for cracks, blisters or other structural problems.

Then I check the bias circuit, which won't effect the sound but prolongs the life of the valves. Another thing to replace is the control grid resistors because Fender used a 220k grid resistor where the valve manufacturer specification called for a 100k. Too high control grid resistance could lead to thermal runaway. Then basically I replace the valves, fire it up and see how it performs. I do a series of bench tests, overdrive and so on. I don't use a speaker, just check resistors, bias and how each valve performs. The earthing and electrical insulation has to be checked.

I may have to change the position of certain components away from components that are heat sensitive. I also replace some resistors for ones with a higher power rating. I check the condition of high voltage electrolytic capacitors, and I may have to change some of them if they have blisters. I check switches, sockets and the whole amplifier has to be cleaned with special electrochemicals. It’s also possible that we may have to reject some of the new valves.

Then I do a sound test which leads us on to the small valves. And of course when you start to use the amp, you may discover other little problems which we can then deal with.  Overall your amp is okay but I'm not sure how it'll be in 20-30 years time. I'm very fussy when it comes to mechanical stability as the last thing you want is a short to the chassis!

Amen to that.