silvertone 1484

[johnfromcyrene]

I came across a silvertone 1484 that mojotone put out. they eliminated the trem and reverb.

Can someone confirm that they modified the voltage doubler? Im not to familiar with this type of circuit.

Did they just use a different power transformer?

[sluckey]

The original weird stacked voltage doublers have been replaced with a more common power supply using a standard power transformer.

[johnfromcyrene]

Would it have any effect on the sound? was just thinking of building this one instead of the doubler one.

[passaloutre]

This Mojotone kit was the first amp I built, 14 years ago.

The preamp and phase inverter are true to the original Silvertone design, without the effects of course. The power section, including the power transformer, is very Marshall-inspired. The PT is the same unit they sell for their JTM45 kit.

It’s a great sounding amp, but different from the originals that I’ve played. Cleaner and punchier, which I attribute to the Marshally power amp. I think the low screen voltage from the Silvertone voltage doubler contributes to the originals’ signature tone, which is a bit mushier.

[johnfromcyrene]

Do you need a special transformer for the voltage doubler? or do u just use a lower powered one.

[passaloutre]

I think it requires a different transformer spec.

It may be possible to use a more traditional power supply and just drop more voltage to the screen node for the same effect? I’ve never tried.

[johnfromcyrene]

which one sounds better then?

[kagliostro]

Do you need a special transformer for the voltage doubler

When you use a voltage double you double the voltage at the expence of the current

Si if you require a 100mA you must use a doubled current transformer (200mA)

Franco

[passaloutre]

which one sounds better then?

Well that's pretty subjective. I may be one of the few who've played both, and I'd say they both sound great. The "tone" is quite similar, as the preamp hasn't changed, while the changes to the power supply affect more the "feel" of the amp. I would say the Silvertone has a spongier, compressed feel with less headroom, and the Mojotone version is more punchy and dynamic, loud.

It was my first amp build, so I followed Mojotone's circuit faithfully. Knowing more now, many years later, the Mojotone design almost seems a step between the original Silvertone and something like a 1970s Orange amp: https://el34world.com/charts/Schematics/files/Orange/Orange_graphic_mkii_or120.pdf, the chief difference being negative feedback.

[johnfromcyrene]

I think the mojotone uses diodes instead of a rectifier. what about adding a gz34 to create sag for the amp?

[passaloutre]

You can definitely use a tube rectifier to get more sag, but you'd be building yet a third different version of this power supply, so no one here can tell you what it will sound like. It won't be a 1484, but it may be something you like