I wasn’t surprised that the Stadium amp had very little circuitry when I opened her up, she sounds very direct and uncomplicated.
A real point to point beauty laid out intelligently and very little of the ‘rat’s nest’ jumble to deal with.
This little thing has a few wiring surprises such as the inputs going directly to the volume control before hitting any tubes or resistors. More on that later as I plan to open up and analyze the circuitry of each amp that has been presented here to date.
There are no markings at all on the speaker of the 400-T. It’s an odd choice of speaker given the size of the cabinet and I have to admit to never having seen an oval shaped one in a guitar amp before. It looks like something intended for a car stereo setup but I can’t argue with the results of the sound.
The tube setup is a bit unusual as well. The 35W4 rectifier is coupled with the 50C5 output for what looks like a the classic old radio trio but instead of the usual preamp companion of a 12AV6, we have a 12AX7! The 12AX7 provides more bite here than is generally found in amps that feature the radio tune lineup.
A fried hard drive has canceled part two of the look at the circuitry of the Estey T-12, so we move right along.
This is a 1958 Stadium 400-T, a rare bird that is difficult to dig up documentation for, either online or in books. As can be seen from the slightly warped rear panel that adjoins the control plate, the wood on the amp is plenty thin.
I’ve never seen nobs like these and they are either plastic or perhaps bakelite. The handle and its mounting look to be straight off a piece of late 1950’s luggage.
The brushed steel panel is somewhat like that of a vintage Fender but the lesser grade of metal doesn’t have quite the same shine. There are three inputs but it’s the middle port that provides the highest gain.
As can be seen when the chassis is pulled, there ain’t a whole lot of circuitry to the Estey-T12.
The choke in the foreground looks shot to hell in person but the old guffer still does it’s job at 42 without a hitch.
This gets us a wee bit closer to things and as can be seen from the preamp and output tube assemblies, it’s true point to point wiring between the components.
For once, one of my amps has the schematic still attached! It’s a bit hard to see here but it’s all drawn up very nicely and also indicates that the amp design was approved for manufacture in December, 1964.
The tubes aren’t the average choices for most amps and that’s something I like; it sounds great while not featuring the same old 12ax7 and el84 lineup.
The preamp duties are performed by a 20ez7 with a 45b5 handling the output tube chores and a 36am3a serving as the rectifier.
Not sure if this is really the case, but I’ve read that a 20ez7 is a 12ax7 with a 20 volt heater. It’s definitely an uncommo valve and shows up in few tube radio applications in the early/mid 1960’s.
The 45b5 is known as a ul84 in Europe and was used in some mid 1950’s tube radio designs.
The 36am3a is a 7 pin vale developed in 1940 that was popular in the early and mid- 60’s for tube radio sets.
The Estey T-12 is as humble around the back as she is up front.
And here’s a big reason why she sounds so sweet – Chicago’s finest – a blue label Jensen speaker.
Date codes on the magnet cover peg this example from the 37th week of 1966, likely manufactured in September of that year.
This little number was made by Estey Electronics of Torrance, CA in 1967. The T-12 is pretty simple, just the way I like my amps, with only two inputs, three nobs and a power switch featured on the front panel.
Pilot light, carrying strap and really sweet grill-cloth material pretty much sums up the remaining external aspects of this amp.
With a touch of boost added.
