Steve's Amps - Amplifier Repairs in Godalming, Surrey - Convenient for Surrey / Hampshire / Sussex / London areas
Tel: 01483 417576          Mobile: 07775 908191
Valve and solid state, vintage and modern amps for guitar, harp etc serviced, repaired,customised and constructed


Frequently Asked Questions


 

 

 


What if it’s not broken but just sounds crap?

Glad to help.

Components drift in value on old amps – sometimes this makes them sound nicer, sometimes not. Old AC30s can lose all their bottom end this way – nothing broken but horrible nasal tone with no warmth.

This can be put right, and it doesn’t always mean replacing everything in sight at huge cost. It can however often mean it’s best to do a ‘cap job’ – replacing all the electrolytic capacitors in the amp – as these are the components most likely to drift and affect tone, and if one’s gone the others will soon follow.

Can I get more distortion/crunch?

Oh yes.

I can’t turn your AC15 into a Mesa without a total rebuild, but you can generally find a bit more gain than manufacturers build in quite readily.

The limiting factor in going for more gain and crunch is usually oscillation (a kind of internal feedback which high-gain circuits are prone to - symptoms include motorboat chugging, crackling sounds following notes, momentary volume dropout after you hit a big chord as well as various squeals and howls). Manufacturers build in a safety factor to avoid such problems – which we can nibble into a bit, or maybe a lot, depends...

Er, mate, what it is, I like bought this amp on Ebay and, er...?

...and the wife said what was actually rather a hurtful thing when you unwrapped the parcel, about it matching all the other bits of old crap that don't work that you've been filling the house with. The 'investment' argument doesn't seem to wash with her, and actually, it really doesn't work, does it, and that's going to be a little bit hard to explain.

But that's ok! I can fix it! ...Probably!

Really, buying a pre-printed circuit valve amp that's bust isn't really all that stupid (though some of the prices are). Worst case scenario - one or another of the transformers burned up, and it took some stuff with it, including whatever shorted out and burned it up in the first place. Then someone put it in a skip, then someone else took it out and put it in his shed in a sack with a load of other stuff he got out of skips (he wasn't married, obviously). Twenty years go by, time takes its toll, and the executor of his will finds it in the shed and puts it on Ebay with all his other bits and pieces, and is amazed to find it's worth only slightly less than a house. (From what I've seen this is a very typical Ebay amp sale scenario.) But it's still not a tragedy if your bidding finger ran away with you a bit. Even if absolutely everything I've just mentioned has happened to it, it might cost you, say, 300 quid or so for me to fix it - a lot less to raise your average dead amp up from the dead. Now then, to buy a new amp that good's going to cost you a grand, and a fixed-up secondhand one probably not much less... so, within limits, and after doing your sums, go for it. If you're transfixed by something bust on the 'bay, drop me an email and I'll tell you what I can about it. Good old Brit valve amps to splash out on even if they're bust include Burman (any Burman), White, some early Carlsbros especially the old 50 Top and 100 Top, and Roost, as well as the more well-known and thus expensive types.

Do you fix solid state amps?

All the time.

Big modern tranny amps are generally quite fixable, which is a good job as they go pop so often. Older ones are often well-built and also readily fixable.

And many old or new tranny amp problems are peripheral - switches, fuses, pots - and things like that can be sorted quite economically.

If it's a high-wattage amp - like many modern bass heads over 200 watts - and there's no output at all, then the chances are we have shorted output devices, the product of overheating or shorting out the speaker connections. There may well be some collateral damage to go with it. This sort of job can easily cost over £200 I'm afraid.

We just need to avoid situations where you end up giving me more than it would have cost to buy a new amp. Remember that you can get a good quality old tranny combo like an H/H or a Sessionette for under a ton- so please do your sums before you call me in.

Can you modify my amp for harp so it sounds good and doesn't feed back? Or build me a harp amp?

Yes I can. I'm a blues harp player myself and I build my own gear.

So, I could build you one from scratch. For sound economical reasons, however, most people prefer me to modify an existing amp.

Many old valve PA amps are good for harp - they were built to amplify exactly the same high-impedance, high-output microphones that harp players love to use.

Some modern guitar amps are good for harp. The Fender Blues Junior, Blues Deluxe, Blues Deville and Bassman Reissue are particular favourites of mine for adaptation. They need gain reduction and a flatter EQ curve with no mid scoop.

What I generally do is a while-you-wait job, so you can try it out and we can get things just right. It usually takes 2-3 hours, which costs £60-£90 for labour, plus £10 each for any preamp valves we swap in from my stock (two is the usual maximum we'll need).

Can you give it more top-end bite? Or tighten the bass? Or...

Yes indeedy. This sort of tonal tweaking is quite easy to do and doesn't stretch the parameters of the amp's reliability or stability as much as going for gain does. What I'm not so comfortable with is - 'can you make it more like on this record', or '...kind of browner', or '...more musical', or '...less creamy'. I mean don't be afraid to ask about tonal changes, and if I can translate your wishes into electronics I will, but in the end I'm a repairman not a guru.

Can you transform my amp into a custom high-gain Stevie Special?

Lots of mods are possible. More gain can often be found. Extra gain stages can be inserted. It's easier to do this sort of thing with old point-to-point amps than with circuit boards, but even on boards some things can be changed. We need to talk this kind of thing over pretty thoroughly though, so we both know what I'm going to do.

Do you buy/sell amps?

It’s been known. But no, not really – it’s a funny old market – everybody seems to want an immense amount of cash for their old amp – and I’m never sure who’s actually going to want to pay it. Not me, usually. I don't keep a stock, nor do I have a wonderful treasure-house of amps I bought for a fiver in the early seventies all piled up in the garage and secured with a padlock out of a christmas cracker. Sorry, burglars.

Can you make my Fender 112 sound like a Marshall?

Yeah, for about the cost of a Marshall. It might be better to say that I could move a Fender a little towards a Marshall by pepping up the drive whilst preserving the top-end.

I can make Marshalls more like Fenders too. And there's usually more gain to be found. Oh there's no end to it.

My silverface Champ is a bit boring...

There are a few things I like to do to these basically nice old amps to liven them up and make them get out more.

One is to fit a reissue Jensen P8R 4 ohm speaker. They are made for the amp and sound great in there. The other is to tune the negative feedback circuit to bring up the gain and liveliness.

These amps can be made to sound absolutely wonderful - a chimey, clean sound that leaps off your fingers, and past 7 or 8 a nice fat crunch. The speaker costs about 75 quid, but the specific work that makes all the difference is only £30. (This price doesn't include any other faults / problems you may be experiencing!)

Hello Steve.

Hi there.

Do you offer amp valuations?

Well, that would be a moneyspinner... but why not do what I'd do and have a look on Ebay? (that's enough about Ebay - Ed.)

Are some components better than others?

Well they certainly vary.

Capacitors cause a lot of debate in this area. It's quite subjective, but I like to use Sprague Orange Drops. I think I can hear the difference and so will you, especially in high gain amps with plenty of stages for the signal to pass through.

Otherwise I use good quality modern mainstream components. Filter caps, for instance. Older amps often have those big cylindrical can caps sticking up from the chassis, and they do get tired. Modern direct replacements are available and I used to fit them, until I had a few go wrong and gave the matter some thought. These large can-type replacements are manufactured in very small numbers for the guitar amp repair market only. Equivalent values are available in smaller modern caps that are manufactured in their millions for all sorts of circuits and mass-produced products. Which are likely to have better design and quality control, the ones that were just made for guys like me, or the ones they make for Sony? So nowadays I fit the modern smaller filter caps on a little tagboard inside the chassis, leaving the old ones in situ for appearance's sake. Much more reliable.

(For more on this, see below for the old valves, speakers issue and go to the blog page)

Can I damage my amp if I don't match the output impedance with the speaker impedance?

Certainly you can.

With transistor amps you generally have a free choice of speaker impedance so long as it's above 4 ohms. Some will go down to 2 ohms. Even so, shorting out the speaker connections on a tranny amp is very likely to cause major damage.

The real danger to valve amps is too high a speaker impedance, not, as most people think, too low. Plugging a 4 ohm output into a 16 ohm speaker is more dangerous than plugging a 16 ohm output into a 4 ohm speaker.

So yes, always try to match up output and speaker ohms with valve amps. Having said that, you can often get away with a one-step difference in an emergency, say 8 into 4, just don't push it too hard.

Can I come round and watch you fix it?

While-you-wait is possible if we can find a convenient time.

If it's a 'tone consultancy' thing then I'd actually prefer it if you could come so we can listen together to the problem and the proposed solution. Your mileage may vary, as the yanks like to say, and what I think sounds fab may be ear-torture to you.

Can you hear that funny noise?

What, kind of a hummy whistley noise? That's the Russians again, trying to fry our brains. Oh, I see, from your amp. 

I am patient and understanding about this sort of thing. I may well not be able to hear your funny noise, but I will as a first principle take your word for it and, if it seems realistic to do so, try to do something about it. On the other hand, if I say there's not much point me fiddling around it's not that I think you're imagining things, I'm just trying to save you money.

Do you accept credit cards?

Sorry, I don't – too much infrastructure hassle. Cheques... well, you understand... can't really do that. Payment in cash on collection makes sense for me, so I make that my formal 'terms of business'. 

Blimey, that’s expensive!

Valve amps aren't cheap to build, buy or service - but there'll be no nasty surprises if I can help it - I'll always give you a warning to avoid getting you into a money-pit situation.

I believe I offer good value compared to others in terms of my hourly rate (and I do work fast).

I will be decent and sensible and not get you into uneconomical repair costs when you'd rather have given it up and bought a new amp.

Don't be afraid of asking me about costs, we're all on budget these days.

Will you fit firecracker Chinese valves if I ask you...

Whatever. Reliable valves are available new, at reasonable prices. I'm not xenophobic. Chinese valves get better all the time.

Do you guarantee your work?

I guarantee that:

  • What I've charged you for is what I've done,
  • I use reliable parts and that I do things properly
  • The bits I've fixed won't come unfixed because I didn't fix them properly
  • I didn't unfix anything else while I was fixing it
  • If I do fail you in any of these ways I will put it right for nothing if you bring the amp back to me.

I can't guarantee that something different won't go wrong tomorrow - old amps are like that - but if you ask for a service I will, in addition, pick up anything that looks close to its sell-by date and let you know.

Basically think of it as like the relationship you have with a good garage who look after your car.

Aren’t old valves better?

I don't especially recommend 'NOS' ('new old stock' or ancient but unused) valves, unless you're interested in collecting them or seeing how they sound for the fun of it.

Which valves sound best? Which ones should I buy? Whose reviews should I trust?

I put some of what I know on my blog page. I wouldn't glorify it by calling it a review as thanks to GUITARISTS my ears aint what they used to be, but then at least you won't have to read about 'detailed soundstages' etc etc. Most reviews on the web are honest but biased, ie not a lot of use to you. I'm not biased but then I can't usually tell the difference between types of valve anyway so what do i know?

I would recommend buying valves stamped by the manufacturer, simply because it cuts out the middleman. There aren't that many factories in the world. Here are the ones I know about:

JJ - the old Tesla factory, in the Czech Republic. Good name for quality.

Sovtek - the old soviet Reflektor factory, now owned by Electro-Harmonix. they churn out plenty of Sovtek and EH labelled valves, and are also responsible for the current rash of 'reissues' - labelled Mullard, Tungsol etc. They are also 'reissuing' Svetlana valves (S-logo not flying C) but are not now allowed to sell them over here, no doubt because of

Svetlana - still making valves inSt Peresburg but a little bit hard to get due to lack of distributors.

Shuguang - in China. They make lots of valves and the quality seem to be good now.

Do you supply valves?

I keep small stocks of the common types to use in repairs or revalves - stocking my idea of the best current-production lines available. I have a flat charge of £10 per preamp valve, £15 for the common power valves and rectifiers.

These will be the best valves I can get hold of at reasonable prices. Sometimes JJ, sometimes Sovtek, often the excellent 'Billington Gold' labelled valves supplied by my wholesaler (I will explain to you the origin of these - for instance their 5881/6L6 and EL84 at the moment are the bomb-proof pre-'91 Russian military types, which are far more reliable than any modern manufacture alternatives, and sound great). Sometimes I use Chinese valves, but always with an eye to quality and reliability. If a valve I have fitted fails on you I will replace it free.

I will sell valves to you, matched if you like, at these prices if you want.

If you'd rather plug your own in that's fine. You can give valves to me to fit/bias if you like. If you have some old valves hanging around I can test and match them up for you easy.

Do I need matched pairs of power valves?

No you don't, is the simple answer, unless your driver circuits and (above all) output transformer are balanced too. Which they hardly ever are.

Balanced valves give less hum. End of list of benefits given by matched pairs of output valves in guitar amps.

I do try to balance valves IN THE AMP while biasing it up - and if you give me any extra valves you have hanging around I'll try to balance up the currents for maximum efficiency, if that's what you want.

I wish I could come up with an idea like balanced pairs of valves, I'd make a fortune.

(For more on biasing, see my blog page...)

Yes but I'm a sucker, ok? Can you match valves?

Yes. I have a good tester and can match up pairs for you from a batch, if you're the sort of person who can afford a batch of new valves.

If you have some old valves you're not sure about, leave them with me when you leave your amp and I'll check them out. I usually test valves in any amp that comes in and I will try to get some kind of balance going in your amp.

I bought new EL84s for my Laney VC30 but when I plugged them in they went pop. Wassup?

John from Champ Electronics in Nottingham (see Links) reminded me of this one.

The sockets in the VC30 are wired up to accept only one type of EL84. They use a pin that has no connection on some valves as part of the circuit - however other EL84s do have a connection there - and pop they go when you plug them in. Not too hard to rewire the sockets if you have this problem.

The advice is to get this job done before plugging in any new power valves except those Laney supply.

While we're on the subject, John pointed out another issue on a VC30 he had in. He'd sorted the wiring thing, but still found that one of the power valves glowed red on the plates however many times he checked the bias. Then he noticed it was very close to the speaker magnet. The magnetic field was helping the current flow, overheating the valve.

Well spotted John. Tricky little amps, VC30s.

Is biasing necessary?

Aha, the issue of issues.

It's wise to have it done when you change power valves, yes, though not always an urgent necessity - depends on the situation.

Usually I bias for power and clarity. But it's your choice. If you want me to go for less volume and a browner, distorted sound, let me know - some amps suit this approach better than others.

Timescale? It's not going to take me long to adjust your bias in most cases. See blog for more on this controversial issue.

What are the best speakers? Are old speakers better?

What replacement speakers do you fit? Aren't old speakers better?

I'm a bit heterodox on this. There is an immense confusion of voodoo out there about 'vintage' speakers. All the disagreements are a sure sign to me that there's really not much difference anyway… So, unless you specify otherwise, I'll replace clapped out speakers with a decent modern ceramic. Good new ceramics are cheap, sound good and handle 'loud' with aplomb.

Y'see, for me the best thing about valves is the lovely mix of harmonics that makes a guitar really chime. Valves make distortion musical. So, I like a speaker that doesn't get in the way of that.

But of course I'll fit anything you want fitted. If you like, I'll offer a view on what you've already got and how we might get it to sound more like you want.