Brown Bassman Transformers
From tim6l–(at)–lonline.com Wed Oct 16 23:01:05 CDT 1996
>On the subject of speakers: Prior to sometime in ’62, the cabinet used a
While this is right in 90% of the cases, it is not always
Also, I would disagree that it is “very important” to make
>Personally, I have a ’62, double-speaker, blond bassman rig that sounds
I’ll agree. A limited amp, but what a sound it makes!!!
Just my 0.02
Article: 24910 of alt.guitar.amps
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From: tim6l–(at)–lonline.com (Timothy J. Richter)
Newsgroups: alt.guitar.amps
Subject: Re: Fender Bassman Heads
Date: Wed, 16 Oct 1996 05:38:51 GMT
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>single speaker mounted on a “tone ring”, an interesting way of porting the
>speaker. After ’62, Fender went to a 2-speaker configuration. It’s very
>important to make sure the head matches the cabinet, since >the heads
>designed for the single speaker have an 8-ohm output transformer and the
>heads designed for the two-speaker configuration have a 4-ohm output
>transformer. There is an EASY way to tell which head you have: If it has a
>tube rectifier, it’s an early 8-ohm, single-speaker head; If the amp uses a
>solid state rectifier circuit (no tube rectifier, but a round plug where the
>tube would go), it was designed to go with a 4-ohm, 2-speaker output. This
>is, of course assuming that someone hasn’t replaced the output transformers.
the case that a Bassman with a tube rectifier has an 8 ohm
output transformer. I have a 100% stock Blonde tolex
Bassman. The date code is “LA” (Jan. 1962), and I have a
silicon diode (SS) rectifier. BUT, my amp has an 8 ohm
transformer. Here is a 100% test that cannot fail. (I
think) Each output transformer (if original) has a part
number stamped (or sometimes inked) onto the metal end bell
encasing the wiring. It will have 6 digits and begin with
125… If it is a 125A5A it is definitely an 8 ohm tranny.
If the number is 125A13A it is a 4 ohm tranny.
sure that the cabinet matches the speakers. In 90% of the
cases, you will have a non 1961 Bassman and it wants to see
a 4 ohm load. Most common are 8 ohm 12″s. (fender rarely
used 16 or 4 ohm speakers), so it is likely that a 2×12″ box
will match with 90% of Bassman heads. BUT…Wait!!
an 8 ohm load will not be optimal for a later Bassman, but
it will not be disasterous. Fender amps are tolerant
(moreso than Marshalls) and many times throughout Fender
History a speaker load mismatched the amp. (Think of the
EXT SPKR jack–c’mon, did anyone realty change out their
Deluxe Reverb 8 ohm speaker to a 16 ohm and use a 16 ohm ext
cab??!!)…
Anyway. I too have a 1962 Bassman (2 in fact, one with the
8 ohm OT and one with the four). Just tonight I used the
4 ohm 62 Bassman with a Marshall 8 ohm 4×10″ and got the
most KILLER tone I have gotten from that amp. Anyway, many
will tell you that mismatching ohms will kill a tube amp,
but in my experience, a 100% mismatch is OK (8 ohm load on a
4 ohm OT, or a 16 ohm load on a 8 ohm OT, or even a 4 ohm
load on a 8 ohm tranny)
>great with a guitar. It has that one sound, but it’s a nice one.
Also, if you doen’t mind modding an amp (gosh!! eeek!)
If you like the NORMAL channel and want to rewire the
BASS channel, you’ve got three knobs and 2 tubes (4 gain
stages) to work with. (I built a Marshall pre-amp into the
BASS side of a BF Bassman –now it’s a versitile amp!)
Tim
