What's the deal with tube amps? Why all the fuss?
Yes, they do have a special sound, one that digital 'modeling' can't quite get right... It's actually the limitations of tubes that impart that special tone--that natural compression and smooth breakup. Sure, they keep improving solid-state amplifiers--but a look at the majority of mid-range to high-quality amps, the current models (mostly all tube, tube/ss hybrids, etc.) should convince you that it's very difficult to capture 'that sound' without tubes.
Does a 'rebuild' ruin the value of my vintage equipment?
No. Maybe. I don't know. Does changing the tubes mean the amp is not longer 'vintage?' Every old amp will need a rebuild at one point or another. If this negates it's 'vintage' status, then there is no such thing as a vintage amp! Functional amps, anyway--o.k. for nutso collectors who don't actually use 'em.... Who cares about them!
This little jem is a 1961 Kay 503A instrument (guitar, harp) amplifier. Output is in the 3-4 watt range. A nice studio, or "living room amp."
Here's a taste, and there's more video on the last step:
#1 -- Mod A (my first attempt--If you only have patience to listen to one clip, play #2):
(recognize the Trash-o-caster?)
#2 -- This is Mod B, IMHO, a much better sound:
(pickups switched from middle to middle/neck phased mix, about half way)
#3 -- Quick one added, with a Gibson Les Paul, just to show the amp has some bluesy distortion..
(pretty 'raggedy' playing on this one, but it's enough to catch the sound...)
All the videos are 'clean'--guitar and amp only, no FX.
Danger! Danger! No, really, DANGER!!!!!
A tube amp, even an unplugged tube amp, stores enough electrical energy in it's capacitors to kill you! YES, KILL YOU. Don't touch it unless you take precautions. See the section on DISCHARGE THOSE CAPS!!!!!
I'm not a tube repair technician, or an expert electrician. I'm just a hobbyist. Don't take my word, do your own research, and please be careful !
Step 1: Symptoms: How do I know my amp needs a rebuild?
--Weak signal: Bad tubes, failing output transformer.
--No highs/loss of tone: Bad tubes, coupling or bypass caps.
--Unpleasant distortion (not the kind you want): Often, this is bad tubes. Also could be the coupling caps or cathode bypass caps. Or could be filter caps, if the signal is modulated with 60 hz noise.
--Weird noises (squeals, crackles, etc.): Probably bad tubes. Sometimes failing coupling caps.
--In each case, look to the speaker, also. A torn or worn speaker cone could be the culprit. In rare cases the output transformer may be failing.
This amp had the following problems:
--good tone for 5 minutes, then a nasty, harsh clipping distortion on louder notes (yep, bad tubes were the cause.)
--Nasty hum (filter caps and routing problems.)
--Dull, muddy tone (needed new caps and tubes.)
--The original two-prong power cord needed replacing.