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Need some advice, does anyone have any experience, ideas on how these amps sound? I'm thinking of making it some sort of a "hobby" amp and have it modded, etc. From what I know about the amp, its a Kent Model 20A with 3 KT66 power tubes.
 

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3 Tubes?

Chito said:
Need some advice, does anyone have any experience, ideas on how these amps sound? I'm thinking of making it some sort of a "hobby" amp and have it modded, etc. From what I know about the amp, its a Kent Model 20A with 3 KT66 power tubes.
Just finished a '57 Kent amp for a mandolin player. Pair of 6V6's, tremolo - the head snapped onto a speaker cab with an old 15". Really vintage!

Kent was an old Canadian manufacturer. It was never a well-known name so it's not surprising I searched the main schematic websites and found nothing on a model 20A. If the tech knows his stuff a schematic is not absolutely necessary, it just makes things go faster. Unfortunately, it means I have no way of knowing how your amp is wired up from the info you've given.

Using 3 KT66's is rather bizarre! It's like finding a 5 cylinder car engine. More likely there's a mistake somewhere. Usually an amp will use one output tube, a pair of tubes or multiple pairs of tubes. Except for a small one output tube amp you would never see an odd number of output tubes.

Sometimes an amp will run in what's known as Class AB2 or Class B. It may use a large tube as a driver so it's possible that would account for an extra KT66. Still, that would be strange because a much smaller and less expensive output tube like a 6V6 would easily drive a pair of KT66's in this type of amp.

Maybe that 3rd tube is not a KT66 at all? It might be a rectifier tube like a 5Y3 or a 5U4. The shape might be the same or similar.

Many amps glue a schematic somewhere inside. If you could find it and scan it you could post it or email it to me and I'd be able to offer more specific advice.

If the amp indeed runs a pair of KT66's then if you tell me the preamp tube lineup I could make some suggestions. You can change an amp into any type you want, depending on what you have to work with. It would mean you have to have some experience working with hundreds of volts without zapping or killing yourself, of course!

Give us some more info!
 

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Discussion Starter #3
Thanks Bill. Just shows how much I know about amp circuitry. The only information I got plus that the tubes were KT-66s which I'm not really sure now is this:

Kent model 20A tube amp circa 1960. About 15W with 4 inputs, bass/treble pot and working tremolo.

BTW, thanks, I really appreciate the help. Here are pics.



 

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They look different on the outside...

Ok, judging by pictures is like guessing horsepower without ever popping the hood but here's my guesses!

I don't believe that the output tubes are KT66's. The shape is wrong and besides, it doesn't jive with the rest of what I see. It's possible someone jammed KT66's in the amp 'cuz they will work (with some drawbacks) but I would say that the actual tube lineup is:

12AX7--->12AX7-->pair of 6V6's--->5Y3 rectifier tube

It's hard to judge size from the pix so maybe the 6V6's are in fact larger tubes like KT66's but Kent would more likely have designed in 6L6's, a more common and cheaper tube will similar specs in the same family and the same pinout connections. If so the 5Y3 rectifier would almost certainly be the larger 5U4, to handle the higher power.

If you're lucky the ink will still be readable on the outside glass of the tubes and you will be able to read the tube numbers yourself. There may also be a tube location chart pasted inside the amp's cabinet that will also tell you what you've got to work with.

A pair of 6V6's gives 15-20 watts and a pair of 6L6's gives 30-50 watts. Kent designed on the conservative side so I'll bet on the lower wattage figures.

With that kind of tube lineup you could do a lot of single channel Fender mods. Although you see 4 inputs if you looked inside you'd most likely see that there aren't actually 4 channels, just 4 input jacks tacked together in parallel.

There are no cheap and simple mods to turn this into a 50watt Plexi Marshall. Myself, I wouldn't bother! As it is, this is a sweet vintage blues or country amp and I wouldn't hack it up. Better to get an old Traynor that's already got a lot of rock & roll inside it and mod it instead!
 

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Discussion Starter #6
Thanks Bill. Really appreciate the reply :food-smiley-015:

Decisions, decisions... should I or should I not... A 60's vintage tube amp for the price of a pedal.
 

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Chito said:
Thanks Bill. Really appreciate the reply :food-smiley-015:

Decisions, decisions... should I or should I not... A 60's vintage tube amp for the price of a pedal.
You know, this amp could be made into a FABULOUS down home, greasy, oily sounding Biscuit Boy/James Cotton harp amp...
 

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Chito said:
Decisions, decisions... should I or should I not... A 60's vintage tube amp for the price of a pedal.
You haven't bought it yet? Hell yeah get it.
 

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you can host them at a free site like photobucket ( you'll have to register there )


then upload them to photobucket and paste the path into the reply window....it will link so everyone can see pics
 
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