Kalamazoo Amp Field Guide: Bass Amps

Kalamazoo Amp Field Guide: Bass Amps

Technical Overview

[ Technical Overview ] [ Schematic ] [ Photos ]

For more information on the Kalamazoo line, see the Kalamazoo web pages at http://www.rru.com/~meo/Guitar/Amps/Kalamazoo/ .
NOTE: I finally own a Kalamazoo Bass 30- the later, upright style. I also have a chassis which I have gone over and done the safety tricks to- a bit more complex on these with the existing wiring since the control panel is separate from the amp and power supply. Other information has been gleaned from other owners and sources.
Externally, the only differences in the early models are on the badge and the control face. These will either be marked "Bass 30", "Bass 50", or "Bass" on the control face and nothing on the badge. Amps without a number after the word "Bass" may be solid state or tube; you'll have to verify this on an amp by amp basis. I believe the later model was only avalable in a 30 watt version.
Like the Fender Bassman, this works well as a guitar amp. It does a tolerable job as a bass practice amp, though it farts out from about the low G down to the E. It's pretty bad below that (5 string, detuned, etc.) decent (if quiet) job as a bass amp.
This amp was meant to play clean. Even with a Thunderbird, which has high output pickups for a bass, there's more headroom (and often more volume) to be had. Running a preamp ahead of this can get a lot more volume- or dirt. Running my Thunderbird into my MXR preamp into a Bass 30, I can actually feel the bass in a 12'x15' room, especially with the door shut. At that point it's usable jamming with a guitar player.
Vital Statistics

Model: Bass 30 (tube), Bass 50 (tube), Bass (tube or solid state)
Year manufactured: 1965 - ~1970
Controls:
FLIP TOP:

Two inputs (one channel)
Loudness (volume)
Treble (with on/off switch)
Bass
On/off switch may be on treble control or separate rotary switch (which may have polarity setting as well)

Tubes:

Bass 30: Two 7591s in push-pull^[1]
Bass 50: Two EL34/6CA7s in push-pull
6EU7 (preamp,. phase splitter)
6EU7 (post phase splitter drivers)
solid state diodes for rectifier
one other diode (bias supply)

Output Transformer:

Bass 30: Woodward-Schumacher 606921 / 955-003511
Bass 50: Unknown

Speaker: Per marketing material:

two 10" Jensens, front loaded in sealed cabinet:

C10P with 17 oz magnets (Bass 30)[2]
C10? with 27 oz magnets (Bass 50) [almost certainly a C10N]
C10? for solid state Bass model

A correspondent has sent me photos of what are almost certainly factory installed CTS speakers in an early model Bass 30.
Cabinet:

25.5" wide x 19.625" high x 10" deep

Miscellaneous:

schematic and tube layout chart pasted inside amp

Notes:

At least one Bass 30 was shipped with a schematic showing the output tubes in parallel, even though the amp is push-pull and seems to have come from the factory that way.
The same amp referenced above has C10Q speakers installed in it, presumably from the factory.

[ Technical Overview ] [ Schematic ] [ Photos ]
Last updated: 31 August 2019
Copyright Y2K++,Y2K+7 Miles O'Neal, Austin, TX. All rights reserved. Amp photos courtesy of Kagang on eBay .
Miles O'Neal <roadkills.r.us@XYZZY.gmail.com> [remove the "XYZZY." to make things work!] c/o RNN / 1705 Oak Forest Dr / Round Rock, TX / 78681-1514