RIP Jim Marshall

Randy Yates wrote:

> By the way, I've always wondered how Marshall came up with his wattage
> rating system. Matt's Marshall was a "Marshall 50" or 50 watts, but
> that's the loudest 50 watts I ever heard.

Well, these were 'tube watts'. Tube amplifiers create mostly even order 
harmonics when overdriven which sounds nice while solid state amps create 
mostly odd order harmonics which sound awful. This means you can drive a 
tube amp much higher into distortion than a solid state amp before the sound 
gets bad.

This does not explain though why a Marshall amp would sound louder than 
another tube amp (e.g. a Fender). It may be that Marshall amps or cabinets 
used speakers with higher efficiency.

Having played as a drummer in rock bands I can tell though that the best amp 
I've came across was the Vox AC30. Its 30 W tube amp with two 10" speakers 
produced a wonderful distorted sound at a very pleasing low loudness level 
which lead to a very clean stage and concert hall sound. The Marshall racks 
were so loud they ended up in every microphone on stage - and you had to 
play them loud to get their famous sound. Many guitar players who used them 
for a long time are now almost plain deaf; see Eric Clapton.

bye
Andreas
-- 
Andreas H�nnebeck | email: acmh@gmx.de
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On Apr 8, 4:45=A0pm, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote:
> >On 4/8/12 3:18 PM, HardySpicer wrote:
>
> >> The beauty of guitar amps is that the more distortion the better!
>
> >i don't think it's as simple as that.
>
> >Marshall put out some solid-state amps in the 70s and 80s that sounded
> >like canine feces.
>
> >because it has been difficult to emulate exactly what the various tubes
> >are doing (and other parts, like output transformers with hysteresis),
> >it has been difficult to get the kinda soft distortion morphing into the
> >wonderful power chord distortion that we could get from tube amps from
> >Marshall or other manufacturers (like the Fender Twin Reverb or the Mesa
> >Boogie).
>
> >it gets very complicated when the distortion is applied to chords with
> >non-harmonic notes, because then the intermodulation distortion gets
> >messy. =A0play a nicely tuned major chord and it comes out okay, but pla=
y
> >a minor chord and it comes out muddy.
>
> >even when distortion is what you're looking for, not all distortions are
> >equal and it's such a multi-dimensional problem (with both non-linear
> >and non-memoryless components; Volterra series anyone?) that it's hard
> >to get something good without experimentation, alchemy, and luck.
>
> Most of the DSP amp modellers seem addicted to blindly modelling every
> little aspect of what famous tube amps do, like the sag on loud notes due
> to the relatively high impedance of a tube rectifier. I'm surprised there
> isn't at least one modelling developer who has tried to take the best of
> what tubes do, and avoid the bad stuff - like using 6 sensors for the 6
> strings, and separately processing the notes, so any chord with any amoun=
t
> of distortion comes out right. It would make an electric as polyphonic as
> an acoustic instrument.
>
> Steve

Vox has some products which mix Tubes with digital. It's in their
VT20+ series of amplifiers as well as their Tonelab effects boxes. I
have to say I'm impressed with the warm type of distortions I get out
of my VT30 compared to my solid state amplifier.

Some other effects modellers are also using tubes e.g. Zoom and Line
6. The nice thing is the price point in comparison to buying a pure
tube amp.

Cheers,
Dave

On 4/10/2012 3:50 AM, Andreas Huennebeck wrote:
> Randy Yates wrote:
>
>> By the way, I've always wondered how Marshall came up with his wattage
>> rating system. Matt's Marshall was a "Marshall 50" or 50 watts, but
>> that's the loudest 50 watts I ever heard.
>
> Well, these were 'tube watts'. Tube amplifiers create mostly even order
> harmonics when overdriven which sounds nice while solid state amps create
> mostly odd order harmonics which sound awful. This means you can drive a
> tube amp much higher into distortion than a solid state amp before the sound
> gets bad.

...

Andreas,

I don't question the validity of solid-state amps creating mostly odd 
harmonics, but I'd like to know why. It must have something to do with 
the way that the amplifiers are designed. Totem-pole output stages might 
have more asymmetry when overdriven than a tube's transformer-coupled 
output, but H-bridge designs don't. What features of transistor 
amplifiers generate the odd harmonics?

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

On 4/10/12 10:53 AM, Jerry Avins wrote:
>
> I don't question the validity of solid-state amps creating mostly odd
> harmonics, but I'd like to know why. It must have something to do with
> the way that the amplifiers are designed. Totem-pole output stages might
> have more asymmetry when overdriven than a tube's transformer-coupled
> output, but H-bridge designs don't. What features of transistor
> amplifiers generate the odd harmonics?
>
>

i think, Jerry, it's because about the only mechanism for distortion 
with the solid-state amps is the simple clipping at the rails and that 
was pretty symmetrical.  tube amps had all sorts of other subtle 
distortion sources, like the non-linear curve of the tubes, which may or 
may not be symmetrical.

-- 

r b-j                  rbj@audioimagination.com

"Imagination is more important than knowledge."

On 4/10/12 9:07 AM, Dave wrote:
>
> Some other effects modellers are also using tubes e.g. Zoom and Line
> 6. The nice thing is the price point in comparison to buying a pure
> tube amp.
>

and i wonder how well that little 12AX7 in the box models the pentode 
distortion in the "pure tube amp".  surely seems odd to me.


-- 

r b-j                  rbj@audioimagination.com

"Imagination is more important than knowledge."

On 10.4.12 7:26 , robert bristow-johnson wrote:
> On 4/10/12 9:07 AM, Dave wrote:
>>
>> Some other effects modellers are also using tubes e.g. Zoom and Line
>> 6. The nice thing is the price point in comparison to buying a pure
>> tube amp.
>>
>
> and i wonder how well that little 12AX7 in the box models the pentode
> distortion in the "pure tube amp". surely seems odd to me.
>
>

The point is in the heater glow.

-- 

Tauno Voipio

>On 4/10/12 9:07 AM, Dave wrote:
>>
>> Some other effects modellers are also using tubes e.g. Zoom and Line
>> 6. The nice thing is the price point in comparison to buying a pure
>> tube amp.
>>
>
>and i wonder how well that little 12AX7 in the box models the pentode 
>distortion in the "pure tube amp".  surely seems odd to me.

If you get a frosty reception from the audience, at least you have the
cheery glow of your 12AX7 to comfort you.

Steve

Jerry Avins <jya@ieee.org> wrote:

(snip on tube vs. transistor amplifiers)

> I don't question the validity of solid-state amps creating mostly odd 
> harmonics, but I'd like to know why. It must have something to do with 
> the way that the amplifiers are designed. Totem-pole output stages might 
> have more asymmetry when overdriven than a tube's transformer-coupled 
> output, but H-bridge designs don't. What features of transistor 
> amplifiers generate the odd harmonics?

I was trying to figure out the other way around. Why do tubes
generate even harmonics?

It seems to me that if you clip the top and bottom equally,
you get odd harmonics. That would seem to me true for a push-pull
design in either tubes or transistors, but it might be that
transistors are better matched. 

Thinking about it more, it is a nice flat clip that generates
the odd harmonics. If the supply sags while generating the
peak, I believe that will increase the even harmonics. 

In that case, the difference should be more in power supply
design than in the amplifier stage design.

I do remember claims of transistor amplifiers having the
"tube sound" but don't know how they claimed to have done it.

-- glen

glen herrmannsfeldt wrote:
> Jerry Avins<jya@ieee.org>  wrote:
>
> (snip on tube vs. transistor amplifiers)
>
>> I don't question the validity of solid-state amps creating mostly odd
>> harmonics, but I'd like to know why. It must have something to do with
>> the way that the amplifiers are designed. Totem-pole output stages might
>> have more asymmetry when overdriven than a tube's transformer-coupled
>> output, but H-bridge designs don't. What features of transistor
>> amplifiers generate the odd harmonics?
>
> I was trying to figure out the other way around. Why do tubes
> generate even harmonics?
>

they don't. single ended circuits generate them because
they tend to be less symmetric...

> It seems to me that if you clip the top and bottom equally,
> you get odd harmonics. That would seem to me true for a push-pull
> design in either tubes or transistors, but it might be that
> transistors are better matched.
>

And you'd be right in all cases....

> Thinking about it more, it is a nice flat clip that generates
> the odd harmonics. If the supply sags while generating the
> peak, I believe that will increase the even harmonics.
>

Depends on the duration...

> In that case, the difference should be more in power supply
> design than in the amplifier stage design.
>
> I do remember claims of transistor amplifiers having the
> "tube sound" but don't know how they claimed to have done it.
>

FETs. Mainly MOSFETs.

> -- glen

--
Les Cargill

Les Cargill <lcargill99@comcast.com> wrote:

>> (snip on tube vs. transistor amplifiers)

>>> I don't question the validity of solid-state amps creating mostly odd
>>> harmonics, but I'd like to know why. It must have something to do with
>>> the way that the amplifiers are designed. Totem-pole output stages might
>>> have more asymmetry when overdriven than a tube's transformer-coupled
>>> output, but H-bridge designs don't. What features of transistor
>>> amplifiers generate the odd harmonics?

(snip, I wrote)

>> I was trying to figure out the other way around. Why do tubes
>> generate even harmonics?

> they don't. single ended circuits generate them because
> they tend to be less symmetric...

I was remembering push-pull tube amplifiers. When I was in high
school, I inherited a Heathkit tube amp from my grandfather.
The one with the gold colored preamp that plugs into an octal
socket on the power amp. (Jerry might remember that we discussed
that amplifier here before.) I am pretty sure it was push-pull.

However, unlike push-pull transistor amplifiers that use NPN
and PNP transistors and a center-tapped power supply, tubes
need a center tapped output transformer and single-ended
power supply.

>> It seems to me that if you clip the top and bottom equally,
>> you get odd harmonics. That would seem to me true for a push-pull
>> design in either tubes or transistors, but it might be that
>> transistors are better matched.

> And you'd be right in all cases....

>> Thinking about it more, it is a nice flat clip that generates
>> the odd harmonics. If the supply sags while generating the
>> peak, I believe that will increase the even harmonics.

> Depends on the duration...

More specifically, different sag for the positive and negative
peaks. 

>> In that case, the difference should be more in power supply
>> design than in the amplifier stage design.

>> I do remember claims of transistor amplifiers having the
>> "tube sound" but don't know how they claimed to have done it.

> FETs. Mainly MOSFETs.

I suppose, but you also might be able to design a circuit
that had similar clip shape to a tube amplifier. 

Also, the sag could tend to round off the clipped part
instead of the sharp corners from fast transistors and well
regulated power supplies.

-- glen