Tips For Purchasing Vintage Amplifiers

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Tips For Purchasing Vintage Amplifiers

Written by vintage on June 13, 2009 – 4:47 am -

There are some fun and funky amps out there that can still be had for a steal, as well as a few bargains remaining in good vintage amps that come out from under the bed now and then, but you need to know what you’re looking at to determine whether that tweed suitcase is a tone machine in the rough, or just an old sparky that’s about ready to pop. Take this checklist with you when shopping, and you’ll be a few steps ahead of the game.

1. Play your own guitar through it. You want to be in familiar territory to judge an amp objectively, and it’s difficult to assess an amp’s suitability if you’re testing it with an unfamiliar instrument. Work from your comfort zone, and you’ll better know whether this one could be of use to you, or is just way out of the sonic ballpark.

2. Start with an external visual check:
• Is the amp reasonably clean, or does it appear to have been neglected? If the latter, does it look like it will clean up okay, or is this deep-down grunge?
• Do the tubes look old (is the lettering faded and discolored from excessive heat?), or do they appear to be fairly fresh, even if they are NOS (new old stock) types? It’s cool to find an old amp with its original tubes, or very old replacements, if they are still in decent playable condition. An amp that carries old, burnt-out (or nearly so) tubes, however, just indicates gear that has been neglected.
• Are the tubes reasonably tight in their sockets?
• Does the speaker look sound, tightly mounted, and in good condition, even if it’s an old one? Or is it dusty, discolored, have a brittle cone, or loose mounting bolts/screws/nuts?
• Are the cabinet’s edges and corners tight and solid?
• Your assessment of all of the above will give you a general idea of the amp’s condition before you have even plugged it in. An amp that is old and a little dusty and grimy, but basically in decent condition underneath, is possibly one that was cared for well, but just stored for years and left untouched. An amp that was cared for poorly or not serviced at all, or serviced poorly, while in use for many years is a riskier proposition.

3. Has the seller installed a safe grounded, three-prong AC cord? If not, don’t touch any other electrical equipment while testing, and ask them if they will have one correctly installed (if it’s a guitar store) before selling the amp, or make a concession on the price so that you can do so. If you buy it as-is, have a three-prong cord properly and professionally installed asap. This is a safety issue, and it won’t be safe to gig or record with the amp until you have done so.

4. Turn the amp’s volume control(s) down to 0, switch the power on and let it warm up. Does the pilot light work? Are the tubes glowing as normal? Switch the standby on if it has one, and/or turn up the volume control(s) slightly. You should hear a slight — but not excessive — hum through the speaker. If there are any loud hums, squeals or oscillations in the amp at any stage in this process, switch off immediately and unplug from the AC socket.

5. If all is well, plug in and play. Start at lower volumes, try all the other control knobs for function and scratchiness. If you get a little “static” style scratchy sound when you turn any of the potentiometers but they still function much as they should, this isn’t a big deal. A tech can clean these with a squirt of contact cleaner for a minimum bench charge. If you get any major volume jumps or dead spots, that might mean the pot needs replacing. Still not too big a deal if the price is right and it’s an amp you are really interested in, but it means more of a repair investment.

6. Turn up, and play louder. If the seller insists that you test it at quiet volumes only, explain that you need to at least play it briefly at or near full volume, or the deal is off. You don’t have to crank it for hours, and it’s unreasonable to expect others to tolerate that, but play it at a fairly advanced volume for 30 seconds or a minute or so at least, and listen to how the whole amp, and the speaker in particular, reacts to the wattage you’re putting through it.

7. If you get “ringing” or “pinging” sounds or microphonics at medium or higher volumes, this could be the sign of a bad tube (as well as a number of other things that are more difficult to suspect). You can sometimes check this by gently tapping each tube in succession with a pen or pencil — with the volume at around 10 o’clock — while listening for the one that reacts excessively (note that you will get a little sound out of any good tube by doing this), ask the seller if they have a replacement tube you can try in that position. Switch off the amp, let it cool down for a few minutes, and make the swap, using a dust cloth or other protection to remove the suspect tube if it’s still hot. If the tubes are old and worn anyway, you’ll need to figure a replacement set into the purchase price (details of which below).

8. If the amp sounds intermittently fine, but emits odd rasping or scratching or vibrating sounds from time to time, it might have a faulty speaker. If you suspect the speaker at all, ask the seller if you can patch the amplifier’s output — if at all possible — into another cabinet of a similar impedance rating with a speaker that is known to be good, to test further. If all is well in the new cab, you have a speaker issue to consider, and need to figure a replacement into the purchase price (details of which below).

9. All well and good? You like the tone? You might have a groovy new amp, if the price is right. Even so, it’s still a very good idea to have a professional amp tech check and service any “new” used amp you acquire, especially if it’s old and looks at all worn or neglected.

10. All not so good, but you think you’d like to have it if it can be made right? If the seller doesn’t have the facilities to fix any problems for you, here’s a list of approximately replacement costs for major components that are likely to need attention.
• A full new set of tubes for a small to medium amp (two or three preamp tubes, two output tubes, rectifier tube) will cost a minimum of $80 for decent, tested tubes.
• One new 12-inch speaker will cost around $40-$50 for a fairly generic replacement of passable quality, $60-$80 for a mid-quality speaker with more character, and $100-$250 for a top-notch, high-end replacement.
• Potentiometers and worn or faulty tube sockets will cost $5-$8 per item, plus the cost of labor to replace them.
• Filter capacitors (a common weak point in older amps) will cost $4-$10 per item (multiples of this, for “multi-cap” can types), depending upon size and quality, plus the cost of labor to replace them.
• Cosmetic issues such as vinyl (Tolex, tweed) and grille cloth … well, that’s up to you, and depends on how much of a “lived in” look you can live with.
11. Extra attention: If it’s a vintage amp, and one with any value in particular, and you feel you like the tone and performance enough that you’re ready to make the purchase, it’s a good idea to “look under the hood” to see how much the original circuit has been messed with. Don’t do this all on your own, especially if you have no experience working safely with tube amps. If the seller is experienced with amps, or has an in-house tech, ask them to — having unplugged the amp and let it cool — remove the chassis from the cab so you can see the components on the board, the wiring and the undersides of the transformers. DON’T TOUCH ANYTHING! Tube amps can carry dangerous voltages even after they have been switched off and unplugged. Just make a visual assessment, to the best of your ability, of how much the amp appears to be original, and how much has been changed or modified (often an honest dealer or amp tech will walk you through this and help with such an assessment). If you’re not in a position to make this judgment, or can’t safely have the chassis removed, ask to let a qualified amp tech explore this for you before you make the purchase, especially if the amp is of any elevated vintage or collector’s value.