Fender amp volume / tone configuration?

[Veenture]

My friend and band mate has a late 90's Fender "Deluxe 112 Plus" solid state amp which is much the same as my 90's solid state "Princeton 112 Plus" ...or so I thought!
There's a difference in operation in the volume- and tone department: when I cut back treble and bass settings on mine completely down to zero, the master volume remains unaffected, irrespective of the level of volume that was dialed in. I sometimes do this -in combination with my Boss GE-10 Equalizer- to get a certain vintage 'studio sound' for solo electric guitar a-la Hank Marvin and to cut through the mix much better …I have no problem leaving the heavier tones to the Bass player!

My band mate wanted to try the same thing on his amp and to our amazement we discovered that when he cuts back his treble-, mid- and bass settings, the master volume is killed…completely, as in dead! i.e. his tone knobs work also as volume knobs!

Did Fender design it this way or could it be due to faulty wiring? He did have a repair on it at one time…perhaps a "Friday repair"?
I find it strange; my other Fender amp (Custom Vibrolux Reverb RI -tube) operates in the same way as my solid state Princeton 112 –leaving the volume level unaltered -at any given chosen setting.

Thus far, I have not yet managed to find an answer googling on the internet and paging through owners’ manuals, online.

I guess I need some amp education…anybody?

[sleeperNY]

Paul, my Twin Reverb is that way. If you kill all the tone controls the volume also falls off to almost nothing. I also have a Stage 160 Fender SS amp and it does the same thing.

Jim

[Veenture]

Hey, thanks Jim, ...a new discovery for me then

[Mr. Bill]

Traditional Fender tone circuits are all cut or subtractive tone stacks, meaning they operate by shunting certain frequencies to ground.

When you have a 3-band tone control set, treble/middle/bass, and you turn all of the controls to "1" (minimum setting) you basically shunt all of the signal to ground.

When you have a 2-band tone control set, treble/bass, there is a resistor that replaces the mid control in the circuit that keeps all of the signal from being grounded out. It would be like having the mid control set to "4", if I remember correctly.

So if your amp has 2 tone controls it will operate differently from one with 3 tone controls.

[Veenture]

Learning all the time...thank you for your excellent explanation Mr. Bill.
I think I prefer the 2 tone controls that I'm so used to but the 3 tone configuration certainly offers more options...it just needs some time to adjust to it, I guess.

[olrocknroller]

I've got a SS Fender twin twelve "DSP" model, which I bought for the noisy gigs, and was surprised to find how little the tone controls actually do...from "0" to "10" not much real difference. All the amp models with this one weren't worth the extra $100.00 over the 212R. Loud though When I get home I'll have to play with all three controls set to "0".