guitar speaker/was Re: Tube challenge!

Paul R. Higgins higg0008 at tc.umn.edu
Fri Nov 26 06:23:07 CET 1999


>>    Read any guitar magazine, and you'll hear professional players
>>    talking about how they love their Marshalls, but they go through
>>    them like water.

> Guitar players also throw amplifiers around, drop them onto concrete,
> store pedals and random crap inside the amplifier, run the amp into a
> short because they haven't noticed that the speaker cable is frayed,
> run the amp into an open load by forgetting to connect the cable,
> connect some device with a severe grounding problem to the amp thus
> applying the ac line voltage directly to an input, and, of course,
> they routinely dump beers into their amps.
> I wouldn't say that a manufacturer like Marshall is cheaping out just
> because some amps die under these conditions.

Notice that I said PROFESSIONAL players in my description of DOA Marshalls.  The
kind of behavior you cited is not characteristic of a professional.  But amps do
have to be designed to take a certain amount of abuse under real-world 
conditions, and some Marshalls are not up to the job.  A good example of this is
George Lynch (of Lynch Mob--great name!) who literally blows up his Marshalls.  
He's one of the aforementioned musicians who "go through amps like water".  

Most modern tube amps have inadequate output trannies, and I'm certainly not the
first to say so.  Dave Funk of Thunderfunk Amplifiers has a great discussion of 
this in his "Tube Amp Workbook".  Kevin O'Connor also discusses this in his 
excellent book "The Ultimate Tone, Vol. 1".  (Buy these books!).  Here's a 
direct quote from O'Connor, who makes amps for a living:

"One would suppose that all transformers are of equal quality, when made by 
reputable companies.  Unfortunately, this is not the case...we have encountered 
many defective English transformers, most of them in Marshall amps...based on 
our own observations, we are reluctant to recommend English replacements for 
failed English transformers.  Our first-choice replacements for guitar amp 
transformers are from Hammond Manufacturing, Ltd. in Guelph, Canada.  Hammond 
transformers are very conservatively rated and have proven themselves extremely 
tolerant to tube failures."

I'm not suggesting Marshall is "cheaping out" per se; what I am saying is that 
routine operating conditions for Marshalls in fact constitute abuse.  This is 
especially true when players redline the amps and send near-squarewaves through 
the entire output stage.  I've seen spectacular failures under such conditions.

>>    As an example of this, take a look at a 100W Marshall (or Fender)
>>    output transformer; then compare it to a 30W tranny made by a good
>>    manufacturer like Hammond.  The 100W Marshall/Fender tranny will be
>>    the SAME size as a 30W Hammond!!  
 
> Such a transformer size is not necessarily a sign of inadaquate
> design.  A transformer needs to be large for the low-end frequency
> range, right?  The lowest note on a Hammond organ is 32.7 Hz, the
> lowest note on a guitar is 82.4 Hz.  That's a sizable difference.

Yes, and there's a sizable difference between equivalently rated trannies from 
Fender/Marshall/etc. vs. those made by Hammond.  The difference in size is 
crucial, as are the specs.  Hammond's frequency response specs are given at full
power, not 1W as in lesser trannies.  That's why they cost so much.  Also, what 
about players who use drop-D tuning, or use 7-string instruments with a low B?  
They'd be interested in the response of the amp below 82 Hz.  

The good news in all of this for synth-diy people is that none of this matters 
for tubesynth purposes, since the circuits don't involve power amps, output 
trannies, etc.  (At least not the tubesynths I've seen from Eric Barbour).  

OTOH, if you wanted to play your tubesynth through a tube power amp...  :)

-PRH

_____________________________________________
Paul Higgins
email: higg0008 at tc.umn.edu
University College, University of Minnesota
_____________________________________________




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