Sean Killback 5E3/5F4 ?

[crashtm1]

I was diggin' through some old schematics I found in a box..
 Came across this from Sean Killback. I'm sure some of you may remember this one from 10 years ago.
Is anyone aware if there is a "layout" of this?
I get a bit confused around the 2nd 12ax7 when trying to lay it out over a 5E3 layout.,

[Willabe]

I don't know of a layout drawing for it. But I think you can draw one for it.

He added a NFB loop so a few extra parts, resistor, cap and pot. Added a MV with a small by-pass cap and a 2nd coupling cap to keep dcv off of the MV. Then a -bias instead of cathode bias for the output stage.

Get a copy of the 5E3 layout and cut and past in the new stuff.

Here's a couple of links for the 6L6GB power amp section (schemo and layout) without the MV. It should help you. 1st likn is for the Super 5F4, 2nd is for a tweed bassman 5D6a.

http://www.el34world.com/charts/Schematics/files/fender/SUPER_5F4.pdf

http://www.el34world.com/charts/Schematics/files/fender/Fender_Bassman_5d6a_schematic_+_layout.pdf

                  Brad    

[stratele52]

I don't know of a layout drawing for it. But I think you can draw one for it.

 Get a copy of the 5E3 layout and cut and past in the new stuff.

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                  Brad    

+1

[Tone Junkie]

Looks like it could be promising the gain stage before the master will give it a little more grunt. could be a kick ass amp.
 Bill

[Tone Junkie]

Question for all my knowledgeable brethren what type of bias is this. Is it an adjustable bias with a fixed resister. I'm looking at building the 5D6-A bassman and it has a bias supply kind of like this.
But I want to use the Valco Iron which doesn't have a 50 volt bias tap like this one. How would I adjust this for maximum efficiency. Obviously a 1 ohm off of the 8.2k and 100uf tail to measure.
But what should I adjust, or which resister do I stick a pot on to dial in what I want.
Sorry for being long winded had a couple of good drinks with my guitar playing tonight.(LOL)
Thanks Bill
                                                 

[Ed_Chambley]

Question for all my knowledgeable brethren what type of bias is this. Is it an adjustable bias with a fixed resister. I'm looking at building the 5D6-A bassman and it has a bias supply kind of like this.
But I want to use the Valco Iron which doesn't have a 50 volt bias tap like this one. How would I adjust this for maximum efficiency. Obviously a 1 ohm off of the 8.2k and 100uf tail to measure.
But what should I adjust, or which resister do I stick a pot on to dial in what I want.
Sorry for being long winded had a couple of good drinks with my guitar playing tonight.(LOL)
Thanks Bill
                                                 

Bill, in this case if I want fixed bias with an adjustable pot I borrow a bias section from a Marshall JTM 45 with kt66, which will get you very close.  May have to make 1 resistor adjustment if your voltage is slightly different.

[Tone Junkie]

Thanks Ed, yes I used that bias supply a few times. I guess my real question should have been, why you thought they used the bias supply that way. just seems odd not to make it adjustable.
Bill

[sluckey]

I guess my real question should have been, why you thought they used the bias supply that way. just seems odd not to make it adjustable.

None of the Fender 5XX or even 6XX series amps had adjustable bias. Adjustable bias came in a later series.

[Ed_Chambley]

Thanks Ed, yes I used that bias supply a few times. I guess my real question should have been, why you thought they used the bias supply that way. just seems odd not to make it adjustable.
Bill

I have no idea why the resistor was changed to a pot.  I have fixed bias amps made before the introduction of the adjustment pot and have not changed them.  It is really not a big deal either way.  It is easier with a pot, but it is not difficult to determine the resistor value either.  I would guess the pot was added so bias could be set faster reducing bench time.

It could have had something to do with Bias Vary tremolo and keeping it functioning strong.  Seems the adjustment pot arrived about the same time as the roach.  Just a guess.