[Harp-L] Differences in Same-Model Amplifiers

["John Balding" <John.Balding@xxxxxxxxx>]

On Friday, September 15, 2006 , in response to the "Audix Fireball (V)
vs Blues Blaster" thread, Steve Klein wrote, in part:

 

" I use the mics for 2 Kalamazoo Model One amps. I thought that they
would sound the same but they do not. Even though both are "identical"
amps the sound is different from each amp. I am told that the reason for
this is that the older amps were not made to exact specs but were only
checked to see if they were within a general tolerance and would be
passed as acceptable if it hit the right area in the meters they used to
verify general compliance with the specs. That's why identical vintage
amps can sound different."

 

Here's a point which helps to support/explain your statements:

 

Leaving all of the other variables out of the equation for now, I wanted
to point out something about resistors.

 

Most of the resistors used in vintage amps were the carbon composition
type, and had a tolerance of +/- 20%. This means that the 470 ohm plate
load resistor of a Fender Champ could have a legitimate rating of
anywhere between 376 and 564 ohms! Two Champs side-by-side, one biased
using 376 ohms and the other biased with 564 ohms would certainly sound
different. VERY different.

Tossing all the technical mish-mash aside, consider that the tweed 5F-1
Champ had 12 resistors in it, and that EACH of these had the potential
to very by 

+/- 20% . The potential existed for an incredible amount of variance
from amp-to-amp, all things else being equal. The '59 Bassman 5F6-A had
about 28 resistors!  I am no math genius, but I can say that the odds of
two identical amps rolling off the assembly line were not too good. And
that is solely based on the resistors' inherent discrepancies, and
doesn't take into consideration the multitude of other contributing
factors.

 

John Balding