(Nearly) Universal Mods?

[HumanJHawkins]

Tastes vary widely, which is why we have mods... One person wants more treble. Someone else wants less, etc.

But if you pulled together a bunch of amp techs for gold and platinum level artists (meaning, people for whom money is no object and quality is a top priority), are there any mods more than half of them would probably be choosing to do? (Particularly for Marshalls of course)

 

[chadjwil]

Upgrade the flimsy stock tranny's in the newer Marshalls and probably nine out of ten would replace the sag resistor with a choke if theirs didn't have one.

Just my 2 cents

 

[iron broadsword]

Doesn't the 'sag resistor' instead of a choke help to remove sag? Sag sucks, keepin' my resistor, yo.

 

[Alabama Thunderpussy]

No, what he means by sag resistor is that there is a voltage drop across that resistor that varies with the amount of current that is being drawn from the supply, which does so depending on the level of signal the amp is passing. This voltage sag doesn't occur with a power choke, which is an inductor, which smooths the DC ripple by keeping voltage constant during the half cycle's off swing.

 

[Micky]

But sag can be a GOOD thing...

 

[Alabama Thunderpussy]

No, what he means by sag resistor is that there is a voltage drop across that resistor that varies with the amount of current that is being drawn from the supply, which does so depending on the level of signal the amp is passing. This voltage sag doesn't occur with a power choke, which is an inductor, which smooths the DC ripple by keeping voltage constant during the half cycle's off swing.

Actually after looking at this a second time, this is a more apt description of the supply capacitors' role in the filtering. A more accurate description of the choke's role as a filtering component is more related to its resistivity to changes in current. This is what the "sag resistor" attempts to mimic, but with far less cost on the manufacturing side. And by contrast the resistor resists current change but also causes a voltage drop in the process. The choke theoretically doesn't have this issue. This is important because the difference in current can vary greatly over the span of an amp's power, especially push-pull amps. At full swing, the voltage drop across the resistor will create significant sag, whereas the choke smoothes the residual AC ripple without significant voltage drop, because of it's extremely low DC resistance.

 

[chadjwil]

Yup. It also adds a little bit of protection from transient current spikes due to it's resistance to instantaneous current changes. I've heard some people say they prefer the sound of the resistor though...can't really imagine why, but to each his own.

 

[GIBSON67]

I would think that adding the 1 ohm 1 watt resistor for biasing, and adding the bias points and trim pot to the rear so it can be adjusted, very easily.

 

[Tüßermensch]

I think this is what they call the loaded question the question seems to negate the answer

- Heinrich

 

[Tüßermensch]

Yup. It also adds a little bit of protection from transient current spikes due to it's resistance to instantaneous current changes. I've heard some people say they prefer the sound of the resistor though...can't really imagine why, but to each his own.

It is transient voltage spike due to sudden magnetic field collapse, called back emf, which implies a resistance to changes to the current. But not how you describe...

-Heinrich

 

[MKB]

Another would be a post phase inverter master volume on most non master volume amps (1987, 1959), or some sort of power attenuator, especially on the 100w amps. 100 Marshall watts is just too much most places these days.

I'd also guess most would like more gain in a standard 2203/2204 circuit, as most artists use some sort of boost with nearly all of them.

 

[chadjwil]

Just trying to keep it simple Tubermensch.