Re: Fender Bassman 135 question

These amps are real killers, and yes, sound great with guitar.
Several of these ultralinear fenders ive come across with the 4 and 8
ohm taps, ive modded them by removing the special 'switching' extension
jack, and having the older style setup of the two parallel jacks, and I
would install a toggle switch in the ground switch hole to switch
between 8 and 4 ohm taps coming from the OT, feeding that to the pair
of jacks. This way I could have a single 8 ohm load plugged in if
needed.

On Jan 24, 10:56 am, jh <jh-audiop_NOS...@xxxxxxxxxxx> wrote:
The Locum Sysadmin schrieb:

Hi folks, I have a Fender Bassman 135 (apparently aka Super Bassman). The
back speaker outputs say "4 Ohms minimum" - does this mean 4 ohms, or (as
it implies) would the Bassman be fine with 8 ohm speakers?

It's kind of a moot point - the speaker box I've been using with it for
years is actually 8 ohms. It seems fine, but (a) am I doing actual harm and
(b) would I be getting louder output using a 4 ohm speaker?

Side note: recently had the amp repaired, and the mid pots fixed (they never
worked since I got the amp) and suddenly, it sounds pretty awesome as a
guitar amp - chuck it into a Marshall quadbox and boom! Big, rich clean
sound. Should have had it repaired years ago...

Ta.
/LS.hi LS,
if it is a "real" 135W Fender, then it´s got a 4 ohm and an 8 ohm tap
inside.http://www.ampwares.com/ffg/schem/bassman_135_schem.jpg

If you plug in the "external speaker" the switch connects to the 8 ohm
tap and hooks up the speakers in series. The shorting jack at the int.
speaker jack makes the ground connection.
You might figure it out with an ohm meter and a regular speaker cable.
- With the amp powered off, plug in the speaker cable into the internal
speaker jack and measure the ohms (it should read a fracture of an
ohm, but still measurable.
- Then plug into the external speaker jack and take a second
measurement. If it reads a little "higher" (~30%) then the switch
engages the other tap.
- Confirm your measurement by reading the "ground side" of the ext jack
to real chassis ground. It should be the minimum reading, your meter
can provide - the jack should be isolated, but there is a tip to ring
switch in the int. speaker jack. The ground connection is very
important here, to make sure that you don´t get an open load. You
might have the jack inspected/cleaned/replaced.

BTW, the information "4 ohms min" is IMHO a little bit misleading. The
ultralinear Fenders are just normal tube amps. The matching criteria
apply to them as well as to all the other amps.
This means: although the fender power stage is more forgiving than
others, i´d prefer to go into a downward mismatch instead of the other
direction personally.

HTH

Jochen

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