Randall RG75 G3

[Mick Bailey]

Has anyone got the schematic for this amp? - this is the one with the 12AT7 in the power amp. The schematic is one of those that got lost a few years back.

[g1]

This one?
http://music-electronics-forum.com/a...ll-rg75-g3.zip

[Mick Bailey]

I'd already looked at that one, but didn't notice the power amp was over two pages first time round. How dumb is that? Thanks for the reply. Interesting filter section feeding the tube (IC3/IC4) with the simulated inductors. Funnily, the owner of the amp complains that it sounds like a filter or wah is engaged all the time. I guess it is.

[MarkusBass]

I think that this is the same as in L5 Lab Series amp. But in the amp there was a pot to adjust the filtered signal (or disable it).

Mark

[teemuk]

I think that this is the same as in L5 Lab Series amp. But in the amp there was a pot to adjust the filtered signal (or disable it).

Randall's filter simulates the response of an amp with high output impedance driving a speaker load: Basically upper high frequencies are boosted, and low frequencies at somewhat narrow band.
Lab Series "Multifilter" was a comb filter that mimicked "cone nodes" of loudspeakers: The uneven frequency response the driver starts to introduce near its response's high frequency limit.
So no, not the same function.

I wonder... Has anyone else noticed that these newer "OEM:ed" Randall preamp designs are cloned from Fender's SS amps? Fender has been relying and following that preamp architecture for over 30 years.

[darkfenriz]

Randall's filter simulates the response of an amp with high output impedance driving a speaker load: Basically upper high frequencies are boosted, and low frequencies at somewhat narrow band.
Lab Series "Multifilter" was a comb filter that mimicked "cone nodes" of loudspeakers: The uneven frequency response the driver starts to introduce near its response's high frequency limit.
So no, not the same function.

I wonder... Has anyone else noticed that these newer "OEM:ed" Randall preamp designs are cloned from Fender's SS amps? Fender has been relying and following that preamp architecture for over 30 years.

Ha ha, exactly.

Not only it looks copied circuitry (with some changes to switching channels and they forgot to redraw one crucial resistor in fender's input bootstaping stage), but also drawn in a similar style, which would suggest redrawing without understanding. Checked side-by-side with Fender Stage schematic, which is very typical for Fender solid state circuitry past decades.

[MarkusBass]

Checked side-by-side with Fender Stage schematic, which is very typical for Fender solid state circuitry past decades.

I'm not able to find the filter that we are talking about on the Fender Stage schematic. Can you post a schematic of the amp with this filter?

Mark

[darkfenriz]

Mark,

Fender and Randall preamps are similar - that's what I mocked on.
I believe that you're talking about the filter in the power amp section that I honestly didn't look at.