Bassman 100 - Should it be louder?

[nwguy]

Jest recently bought a 1976 Bassman 100. Posts on the net say that this sounds like a twin or Showman without the tremelo or reverb. Well my Deluxe Reverb is louder. The Bassman sounds ok, just not very loud. Any ideas of where to look first

[J M Fahey]

*First* of all, change all 4 output tubes, they must be worn out.
Keep the old ones as spares for an emergency, you never know.

[Jazz P Bass]

Not Loud

Can you try to measure the AC signal at the speaker terminals?
Amp full on, play your instrument hard.
With the AC output voltage in hand we will have something to discuss, other than "not loud".

[nwguy]

measured the output

I finally measured the output on the bassman and got a reading of 21 volts on the high end into 4 ohms. As a test, I did the same with my deluxe reverb and got 20 volts into 8 ohms

[nwguy]

measured the output

I finally measured the output on the bassman and got a reading of 21 volts on the high end into 4 ohms. As a test, I did the same with my deluxe reverb and got 20 volts into 8 ohms

[Albert Kreuzer]

How did you do the measurements?
Are these Volts RMS or peak or peak-to-peak?
Sine wave or square?

21V RMS into 4 Ohms would be 110 Watts, perfectly OK for a Bassman 100.
OTOH, 20V RMS into 8 Ohms would be 50 Watts, can't believe that coming from a Deluxe Reverb.

Cheers,
Albert

[J M Fahey]

Hi, agree with Albert's calculations and add:
whether they are RMS, Peak to Peak, average, or whatever, they were measured approximately the same way, and they clearly show that your Bassman has *twice* the electrical power of your Deluxe Reverb, *so*, we have a speaker problem here.
I guess your Deluxe has an original "Fender" speaker, which would be a Jensen in an old one or an Eminence in a newer one. Good, average, standard speakers, adequate to fullfill what's asked from them.
Obviously that is not happening with your Bassman.
What are you using there?
Although twice the Deluxe power is nothing to write home about (to put it mildly), it should still be apreciably louder, not softer.
The good thing is that your Bassman is alive and reasonably well , although it should put out *much more* than the Deluxe, not only twice as much.
We now know that very probably it needs new tubes, *and a new/better speaker*

[Jazz P Bass]

Deluxe Reverb

I want to know how you got a 20 volt signal out of a Deluxe Reverb.
It is a 22 watt amp.
Care to share the name & model of your DVM?
It still points to something wrong with the Bassman 100.
4 6L6's & it cannot keep up.

[nwguy]

Bassman 100

Guys
Thanks for the input. Tubes have been tested and all test good. I used a standard digital VOM to measure the output. The speakers being used in both are Celestian and actually my mistake. On the Deluxe, I am using a 16 ohm speaker

[Jazz P Bass]

DVM

16 ohms makes a little more sense.
The reason that I asked for the name & model of the DVM was to ascertain whether you are reading an RMS voltage or not.
It matters.

[nwguy]

Bassman 100

Model: 30XR-A
Brand: Amprobe

[Jazz P Bass]

True RMS meter

Thanks for the info.
It is a nice meter.
It is not a true RMS meter.
Munufacturers quote:
"Full Size Manual Ranging Multimeters (30XR, 33XR)
The XR series of multimeters is designed for electronic, electrical, plant maintenance and HVAC use. Two XR meters are average sensing: 30XR and 33XR."
When dealing with ampifier power equations, you must use true RMS.
So, multiply what your meter reads x 0.707
For more info:Audio power - Wikipedia, the free encyclopedia

[J M Fahey]

Hi. sorry for having to repeat it, but I must set clear two things=
1)RMS voltage is 1.1 times Average voltage, *for a sine wave*
2) A "common" multimeter, be it analog (needle) or digital, measures *average* voltage, *but* the scale is already corrected, and written in RMS values, at the factory, so you don't need to multiply by 1.1 what you read, it's already done.
Example:
sine wave 10V peak
meter reads 6.37 Volts.
The scale *should* indicate that, but those ckever guys at the factory print a corrected scale (or move a little gain trimmer or reference voltage) multiplying that by 1.1 and:
meter shows 7.07 Volts.
All this holds true for sine waves-
Bottom line is: you don't need an expensive RMS voltmeter to make accurate audio voltage measurements, if you stick to sinewaves (and work within its bandwidth)
---------------------------------------
Going back to the Bassman:
if it shows 21Volts into 4 ohms and the deluxe shows 20 Volts into 16 ohms, we are talking an approximate 4:1 power difference, yet it has less volume than the little one:
"whenever you have discarded everything else, what remains must be the truth, however improbable it may look"
In this case, although the measuring method does not (yet) give us a RMS power, both values are comparable, being the same method, the same operator, presumably short time between one and the other.
If we measure 4:1 power in favor of the bassman , yet it sounds less, the only variable left is the speaker; there's no other option.
Forgot link: http://www.sfu.ca/sonic-studio/handb...an_Square.html

[nwguy]

Bassman 100

First off I want to thank all of you guys that have added your thoughts and experiances here. If nothing else, I have bennifitted from all of you. How does one determine the efficiency of a speaker (s). There is nothing in the specs that say anything.

My original statement about the overall loudness of this amp comes in part to what I remember a friends twin reverb sounds like. Both 100 watt tube amps by Fender, should sound close.......right? I thought so. Anyway, I am bringing my baseman over to my friends house for an A/B comparison with the same speaker cab and same guitar. This ought to prove me right or wrong

Again my thanks to you all and I will report back my findings

[pdf64]

Speaker efficiency is measured in decibels per watt (dB/W).
celestion.com has this spec for all current speakers.
If yours is an obsolete one, assume 97dB/W for smaller 35oz magnet types, 100dB/W for larger 50oz magnet types.
The way this translates into the sound pressure level that we hear, is that a 50 watt amp into a 100dB/W speaker is as loud as a 100 watt amp into a 97dB/W speaker, all else being equal, ie if the power input to a speaker is doubled, the sound pressure level goes up 3dB.