Peter Wade - Revalver

Paul White Hello, and welcome to this Sound On Sound podcast. I'm Paul White, and this time I'll be talking to Peter Wade, who's had a very interesting career, mostly within the music industry, doing electronics, but now his passion is repairing valve amplifiers. So Peter, can you tell me about your background as an electronic engineer, and how your career progressed? Peter Wade Okay, so I actually qualified as a radio and TV engineer, but my first proper job was with a musical instrument importer. called Coppock of Leeds. Among other things, they imported Randall amps, um, Elgin organs and keyboards, and Ibanez effects. And I was lucky enough to work on all of them while being able to consult with their design engineers, which was brilliant for, um, learning. I caught another break there, career wise, when Elgin brought out a computer based synthesizer and I was sent to their factory in Italy to study how it worked. I didn't realize at the time, but this would really help me to move into the computer industry a few years later. Unfortunately, Cop Hooks went out of business. So me and the marketing manager, Stuart Field, we set up a company to take over importing the Randall amps. And Don Randall himself arranged for us to import Leo Fender's new GNL guitar line, which was a real bonus. Incidentally, our company was called Everbimes. Uh, not my choice of name. It's, uh, Semibreve Backwoods, apparently. Anyway, after Everbimes, I moved into the computer world with, uh, a company called SysTime, where I ended up fixing DEC processor boards and, uh, CDC disk drives down to chip level. Uh, and I then took a job with DEC, who are also known as Digital Equipment Corporation, uh, as a field engineer. Um, the technical training at DEC was excellent. I was able to, uh, move up to senior technical support engineer, before moving into software as a VMS specialist. After 20 years with DEC, I was lucky enough to get a job with AMS Neve as their London based service engineer, working on recording consoles at the likes of Abbey Road, Air Studios. The BBC, Pinewood, all the big London studios in fact. But after a couple of years of London rent and Yorkshire mortgage, I decided to move back home, uh, and start my own business. So my business is called Revalver, and I repair and modify valve amps, guitars and other band equipment. See if you've come back through all the developments in electronics since what, the 60s or wherever, and then gone back to where it all started with fixing valve circuitry. Mainly guitar and bass amps, with the odd mixing desk and PA amp maybe. I much prefer to work on valve amps, but I will do solid state amps out of push. I do keyboards as well. I'm Roland authorised and Cassie authorised. But, don't get that much, they're obviously too reliable. Yeah, well that's a problem you won't have with guitar amps, and valves were. Because they get a hard life, don't they? They get chipped around a lot and left in vans. That brings up the question of valve availability, because of course a lot of them were made in Russia. Um, there was a sort of a brief period where they were quite difficult to get hold of. I think maybe there was a bit of panic buying went on. But then I don't know if the Chinese stepped up or, I think there's another factory in Eastern Europe. So although they went up quite a bit, I think you can get most of the common ones now quite easily. So yeah, it's not too bad at the moment, touch wood. So, other than the valves themselves, what are the most common problems with, uh, with valve guitar amplifiers? Like you say, they get thrown around a lot and they run hot. Um, I would say capacitors are the next biggest issue. Uh, they tend to dry out over time. Uh, so it's particularly bad with vintage amps. Power supply's smoothing caps on the main culprit. If they go open circuit, the amp will develop a really loud hum. If they go short circuit and the fuse doesn't blow, then you'll Get smoke. Uh, coupling capacitors also become leaky. They can cause all sorts of strange noises. Oh, and ribbon cables are a bit of a Also used to be issues with, uh, old Bakelite valve bases, which used to sort of carbonize. Yeah, oh yes, for tracking on the valve bases, yeah. So what would you do with those? Replace it with a modern porcelain one? Try cleaning them first, but, I mean, if it is tracked, then yeah, the new, um, Ceramic or porcelain are good. They're not very expensive, it's just a bit of a fiddly job really, so. So what's your view on all these tyre kicking debates over whether point to point wiring is better or circuit boards or tag strips? I mean, I always liked tag strips because you could get at everything. Exactly, they're much better to work on. I think PCB's got a bad name early on because they weren't very good. I think they were, the tracks were too thin and got lots of problems and they got a really bad wrap. I think some of the modern ones now are fine, you know. But people do still prefer the, uh, point to point wiring. I guess ultimately, with the circuit boards, the main problem was the cheap designs that mounted the valve bases straight on the circuit board and then that would overheat the board. Exactly. Unbelievable. Some people have mounted power resistors too close to the board and they'd get so hot that it would actually melt the solder and it'd become loose on the circuit board and then you get all sorts of intermittent problems. But from your point of view as a repairer, um, safety is also an issue of course, because you can get a hell of a belt off of a valve amplifier, as I've experienced. Some people are asking you to bias the amplifiers harder, try and get more gain out of them. Is that just a matter of re biasing, or do people actually want circuit mods? Um, there are circuit mods, because there's so much info on the internet these days. There's a brilliant site called Rob Robinette, and he's got a host of, um, Mods to do on Valve Apps on there, which people will read and they'll say could you do this, or could you do that? Yeah, I mean biasing hot and cold is, well biasing hot is really what people like. You have to point out that the valves might not last as long, and you don't want to go too hot. But negative feedback's a good one. I think one of his mods is to put a switch in so he can either have, um, heavy negative feedback, or, or light, or none at all. Uh, which changes the sound quite a bit. Apparently if you take the negative feedback away, you get much more of the second harmonic distortion, which gives you that nice singing overtone sort of thing. Um, so yeah, that's a good one. Also, some apps don't have a bias adjustment pot, probably in order to encourage us to use their own brand selected vowels. Uh, it's not a bad idea in theory, but the branded premium vowels tend to come at a premium price. Thanks. So one really useful mod is to fit a bias adjustment pot so that any valve can be fitted and people can experiment with various makes. Any special problems with Vox designs like the AC 15 and AC 30 which were essentially class A? Uh, no, not really. I haven't had one in for repair for quite a few years. I'm guessing not many people gig them anymore. Because they're very heavy and bulky for a 30 watt amp. They're also very collectible again, so, uh, probably all taking it easy in studios. Uh, class A biasing thing is a bit misleading these days. Marketing people have gone to the term and used it when it's not always true. Even the Vox AC30. Is that a class A or is that class AB? It's still a class AB push pull output stage. Biased quite hot. And cathode biased. If it was true Class A, the output valves would be hotter than one of those old McDonald's apple pies in the 80s. Yeah, because they can get into trouble where you end up with the output valves glowing like room heaters. Are there any that are particularly difficult to get into? Because I remember trying to fix, um, I think it was a PV Delta Blues amplifier. And the way that all the circuit boards were folded in on themselves, you couldn't get to anything. I had a similar problem with another PV, a PV Ultra 22. Uh, it took me about 30 minutes to get the chassis out of the box. And then it's even harder to get it back in when you've fixed it. Are you able to get circuit diagrams, most of the things that you need to fix? Yeah, getting hold of circuit diagrams used to be a real problem years ago. But now we've got the internet. Um, you can get most things with a bit of Google searching. In the past, if you wanted an authorised service centre, you'd You couldn't get the diagrams you needed. Old vintage valve amps are okay, because they're loosely, well they're all loosely based around the original RCA data sheets. Generally fairly simple, so you can usually get by without a schematic. Have you seen Aspen Pittman's book of valve amp circuits? I've got that book myself in my collection, and it's invaluable. Highly recommended. I suppose that we should explore the debate about whether valve amplifiers really do sound very different from solid state designs these days. Although I think some of the digital emulations are getting closer. But there are things like the presence circuit, which, in most of the amps I've looked at, is a feedback path taken from the output of the output transformer. That's right, the negative feedback. That's one of the modifications I mentioned earlier. The AC 30 doesn't use negative feedback, which is one reason for its unique tone, I think. Without negative feedback, the amp produces mainly second harmonic distortion, which is associated with that sweet, creamy valve amp sound. Odd harmonic distortion can make amps sound thin or brittle. Solid state amps tend to produce mainly odd harmonics. Increasing negative feedback does flatten the frequency response and tighten the bass, but also reduces even harmonics. So it definitely has a big effect on the valve sound. Well there's certainly something very punchy and weighty about the valve amp sound and I always put that down to having a low damping factor and allowing the speakers to flop around a little more. And it takes us back to the negative feedback mod. Uh, reducing the NFB also reduces the damping factor Uh. So definitely a mod worth considering. I think the, um, the early, like the Fender Champ. Everybody loves the sound of that, they're going for thousands of pounds now. And it was designed as a student amp, so they used cheap components and the output transformer's probably actually underrated. And as a result it saturates, compresses naturally, and gives you, by accident, this really nice sound that guitar players like. You probably must know Bob Gatts, the Marshall engineer. I was just reading an article, I don't know where this is from, but, Um, he's designed something called a blender, which uses new Vista valves. From what I can gather, he adds, or blends, a tiny amount of second harmonic distortion to a state of the art transistor preamp. And the results are said to be spectacular. So, the article's definitely worth a read, I would say. There are a lot of pedals that have started using valves, probably again for a marketing thing. I've seen one preamp that had a preamp valve that was lit by an LED to make it glow. Yeah, and it was running off about, I can't remember, 20 or 30 volts. It's obviously not really working like a valve should. But people have got the valve is better now, and marketing are taking advantage now. More just to have the tick box. So Peter, what are you working on at the moment? I'm Uh, at the moment, a Miles Platting amp, and it's quite amusing because reading on the internet about, oh, people say, oh, Miles Platting was brilliant, what an amazing amplifier designer. Turns out that Miles Platting is a railway station near Manchester. And the, I think it was Hornby Skews, the, um, one of the directors or something, was going through the station and he thought, oh, Miles Platting, that's a good name. And when they commissioned They're actually made in Doncaster by Wilsik. Don't know if you might have come across them, probably in the 70s I think. So it's a Wilsik design. It looks very similar to old Marshalls really. It's got Drake transforms in it. It's all good quality stuff. But it was then a marketing thing to put Miles Platting on it. I suppose you thought it sounded better than Wilsik, which isn't the best name, is it, really? Um, other than that, um, I've also got a fairly new Vox VT 100 in bits, with a really horrible intermittent fault. Uh, the problem seems to be caused by the built in add on Multi Effects Board, but it's really difficult to work on. It's crammed full of these modern miniature components. So yeah, give me the old fashioned ones, the vintage ones. I can hardly see surface mount components now. How do you feel about the future for valve amplifiers? Well, it looks like they're not going to go away any time soon, as long as they're still being made and reasonably affordable. But at some point the design gurus might just finally nail the valve sound. Then who knows? But I think it could be a while. It's the same with, like, pianos. The electric pianos now, they've got a really good grand piano sound. But it's that last few percent where you'd never find some classical concert pianist playing an electronic grand piano. Steinway, really. And I think it's just the last two or three percent that's never going to get there, you know. Well, let's hope you get a steady stream of dodgy guitar amps to fix to keep you busy. Not too many, I don't want to work too hard. That's great, Peter. Thanks very much for talking to us. It's so nice to speak to you too. Thank you for listening, and be sure to check out the show notes page for this episode, where you'll find further information, along with web links and details of all the other episodes. Oh, and just before you go, let me point you to the soundonsound. com forward slash podcasts website page, where you can explore what's playing on our other channels.