#1
Reading up on the Blues Junior, I got that the Fat Switch is a mid booster, but the other source say that it is a cathode follower. So is that basically the same (using a SS cathode follower for mid boost)?

On another note: how is the sound difference between having the FAT at the 1st gain stage (rev B) compare to having it in 2nd gain stage (rev D and later)?
Ibanez SA-120 (ed.2006)
BluesJr 1996-B + cathode follower + texas Heat
Crate CPB150
Homemade 4 x 10 cab Bass closeback
Metal Muff
#2
A cathode "follower" in this case is probably a capacitor in parallel with the cathode resistor on the preamp tube introduced into the circuit with the fat switch. I don't know what you mean by "SS cathode follower," since it's just a capacitor. It doesn't have anything to do with solid state, and you couldn't possibly have a tube follower if you wanted to.
Depending on the size of the capacitor, it could be a low-mid or a bass boost, but I wouldn't call it a mid-boost; it's more like a slight gain boost with added bass response.
The difference between having the switch at the 1st gain stage vs. the second is that the added bass signal is less likely to make the amp flabby or farty since it's only being amplified once, vs. twice in rev.B.

If you link me a schematic I can tell you more.
#3
I saw a Bjr schematic a while back, and it's a switchable JFET set as a cathode follower on V1.
The Laney Thread are big and clever. No exceptions.
#4
Quote by MrCarrot
I saw a Bjr schematic a while back, and it's a switchable JFET set as a cathode follower on V1.

Eww. Why would you do that?
#5
No idea, but I presume it must change the cathode's frequency response... You can't really get much extra boost over 22uF with the regular cap/resistor method so it must have some effect somehow.
The Laney Thread are big and clever. No exceptions.
#6
It serves a good solo boost, i dont really like having it on when I'm playing rythym
My Strat/Modded '69 RI Mustang
Ovation 1117-4 c. '75
Fender Blues Jr. [JJ Power Tubes, White Grille, Warehouse Speakers Greenback Clone]
BOARDZILLA 2.0

#? of EHX Guild
#7
i found it too harsh and in most cases, more than the speaker could handle.
Jenneh

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#8
I usually will only use it at lower volumes as a solo boost, i should have made that clear

Once I do a speaker swap, tube swap and build another 1x12 hopefully it will be more useful
My Strat/Modded '69 RI Mustang
Ovation 1117-4 c. '75
Fender Blues Jr. [JJ Power Tubes, White Grille, Warehouse Speakers Greenback Clone]
BOARDZILLA 2.0

#? of EHX Guild
#9
Quote by Roc8995


If you link me a schematic I can tell you more.


Rev B (1996), the version I have (I actually opened it up): http://www.schematicheaven.com/fenderamps/blues_jr.pdf

Rev D and MIM Rev A:
http://www.fender.com/support/amp_schematics/pdfs/Blues_Junior_Schematic.pdf.

I need this information to determine how to mod the Blues Jr, particularly in using the "spare triode". I can either use it as an extra channel, an extra gain stage, or a tube cathode follower for the tone stack. I have an idea of what the extra channel option and the extra gain stage COULD sound like, but I have no idea how a tube cathode follower before eq will affect the tone. As well, since I already have FAT switch, I am wondering if the tube CF is even needed at all.
Ibanez SA-120 (ed.2006)
BluesJr 1996-B + cathode follower + texas Heat
Crate CPB150
Homemade 4 x 10 cab Bass closeback
Metal Muff
#10
The cathode resistor and optional capacitor are normal for the fender fat switch. The rest of the circuit is a high-headroom SS follower. If I were modding the amp, I'd just have the capacitor hooked up to the switch and take the boost stage out. Then you could have another switch to use that extra triode for more gain. A tube cathode follower would have a smaller effect than another gain stage. You can also have the option of having the fat switch and/or the extra gain, instead of only both, where it might get muddy.
#11
Yeah the fat switch is a JFET booster. It sounds great in the amp with the Greenback, but terrible in the amp with the Weber. I think it adds a bit of a marshall-style boost to the amp.
Fender MIM Stratocaster
Ibanez TS-9 Tube Screamer
Fulltone OCD
Dallas-Arbiter Wah Baby
Home-Built Germanium Fuzz Face
MXR Carbon Copy Analog Delay
2 Fender Blues Juniors
#12
Thanks to all for the reply. No, I am not planning to get rid of the fat switch, but whether another CF is needed in Blues Junior.

A question remain: How is parallel channel selection (most of the amplifiers) compare with serial channel selection (ala Mesa Mk I) differtiate?
Ibanez SA-120 (ed.2006)
BluesJr 1996-B + cathode follower + texas Heat
Crate CPB150
Homemade 4 x 10 cab Bass closeback
Metal Muff