Pro Jr - What are they based on?

Been quite a few Pro Jr threads around here lately.

Which has me wondering - what would they be closest to circuit-wise of the tweed-era amps (Fender, Gibson, Valco - whoever)?

Or are they really their own thing?

A buddy has a very early one. Which are supposedly "better", or at least different, from later ones. Can anybody tell me what, if anything was changed?

Cheers,
Geoff

There's no difference between the early and later version except that the earlier versions came with an Eminence Alnico blue frame speaker.
The current version III has been redesigned, apart from a cosmetic change, I'm not exactly sure what they've done to them.

Haven't seen a schematic but IIRC the pre-amp is similar to a fender tweed.

IT is closer to a the 5G9 Tremolux that anything else in the tweed stable....and that makes it sort of a miniature 5F6A Bassman with a simpler tone treatment. Long-tailed pair PI, fixed biasing. IT is much different when compared to a 5E3 Deluxe, which has a cathodyne PI and cathode biased power tubes. There are quite a few different 'tweed sounds'......it is very easy to count at least 6 tweed sounds from 1955 through 1960.

I have no idea what it was based on, or what's going on inside it, but I have an old one with the blue speaker and it sounds great. Love that little beast.

A Fender version of the 18 Watt. A little lower tail resistor and negative feedback.

Re: the Marshall thing... As with any Marshall from 1980 and earlier, without the Fender TWeed-eraroots, there is no Marshall amp. Irregardless of the power tube choice, the oldest circuit that the PRo Jr. resembles somewhat closely is the 5G9 Tremolux...which predates that little Marshall. It is the circuit rather than the power tube choice that has the major impact on the sonics of the circuit, ime....and this circuit has its roots in the tweed Tremolux 5G9..ultimately. Adn...that amp has a lot in common with its larger brother teh 5F6A that preceeded it in production. Now, did the fellows at 'modern' FEnder forget their tweed history and look to the Marshall 18-watter for inspiration??? Maybe..... but I am going to think that Jim Marshall and Co. looked to the FEnder tweeds for their small amp inspiration...just as they did for the larger amps.

Not that any of this matters.....

Re: the Marshall thing... As with any Marshall from 1980 and earlier, without the Fender TWeed-eraroots, there is no Marshall amp. Irregardless of the power tube choice, the oldest circuit that the PRo Jr. resembles somewhat closely is the 5G9 Tremolux...which predates that little Marshall. It is the circuit rather than the power tube choice that has the major impact on the sonics of the circuit, ime....and this circuit has its roots in the tweed Tremolux 5G9..ultimately. Adn...that amp has a lot in common with its larger brother teh 5F6A that preceeded it in production. Now, did the fellows at 'modern' FEnder forget their tweed history and look to the Marshall 18-watter for inspiration??? Maybe..... but I am going to think that Jim Marshall and Co. looked to the FEnder tweeds for their small amp inspiration...just as they did for the larger amps.

Not that any of this matters.....

Right, but the Marshall 18 watter is supposedly inspired by the Watkins Dominator circuit. So, is the Pro Jr. then closer to that circuit than it is to any of the tweed Fenders of the 50s?

Agreed that none of it matters - just curious.

Cheers,
Geoff

Right, but the Marshall 18 watter is supposedly inspired by the Watkins Dominator circuit. So, is the Pro Jr. then closer to that circuit than it is to any of the tweed Fenders of the 50s?

Agreed that none of it matters - just curious.

Cheers,
Geoff

Lets be honest, not a lot of this REALLY matters anyway, but it is fun! :grin:

In a very old Fender Frontline, the person who was responsible for that amp and the then new Hot Rod line (cannot remember his name sadly, but he has since passed away, way too young), stated that the Pro Jr. had a setup where as you turned up the volume, the gain for the amp was also turned up at the same time. Don't know if that is still the case today, so many years hence...

Or are they really their own thing?
Geoff

I think that they really are their own thing.

In a very old Fender Frontline, the person who was responsible for that amp and the then new Hot Rod line (cannot remember his name sadly, but he has since passed away, way too young), stated that the Pro Jr. had a setup where as you turned up the volume, the gain for the amp was also turned up at the same time. Don't know if that is still the case today, so many years hence...

That's it in a nutshell.

The Marshall 18 watt amps and the Pro Junior both have EL84 power tubes and both break up when you crank them. Is that the connection that some are describing?

I think that the Fender cleans (and dirt) are warmer and rounder than the Marshall.

If only someone did a handwired Pro Junior in a real solid pine cabinet.

Do you build your own amps valiant?

Right, but the Marshall 18 watter is supposedly inspired by the Watkins Dominator circuit. So, is the Pro Jr. then closer to that circuit than it is to any of the tweed Fenders of the 50s?

Agreed that none of it matters - just curious.

Cheers,
Geoff

Well, the Watkins Dominator is a cathode bias design whereas the 5G9 Tremolux, the Pro JR. and the Marshall 18-watter are fixed bias designs. Big difference there.

Maybe we should just thank RCA/Westinghouse for ALL of the basic designs that have mutated into ALL of our guitar amps.