Fender Blackface Amp Experts - Help!

[Jerry D]

I have a '66 Super Reverb. What is the difference between channels 1 & 2:

(1) in actual electronics, and;

(2) in sound, to your ears.

[Tone Gopher]

Here’s your schematic: https://www.thetubestore.com/lib/the...-Schematic.pdf

The mid control on the “Normal” channel is hardwired to a value of 6800 ohms, vs the range of the mid pot on the “Vibrato” channel that has a max of 10,000 ohms. If you find that you really like a particular setting on the Vibrato mid knob, you can substitute a different resistor - or add a trim pot that you can adjust.

Enjoy. Those are great amps - well worth getting someone to check it out. Don’t be surprised if they recommend replacing the power supply caps and the 100k resistors on the power rail. Fresh tubes will be a nice treat as well.

[Jerry D]

Originally Posted by Tone Gopher

Here’s your schematic: https://www.thetubestore.com/lib/the...-Schematic.pdf

The mid control on the “Normal” channel is hardwired to a value of 6800 ohms, vs the range of the mid pot on the “Vibrato” channel that has a max of 10,000 ohms. If you find that you really like a particular setting on the Vibrato mid knob, you can substitute a different resistor - or add a trim pot that you can adjust.

Enjoy. Those are great amps - well worth getting someone to check it out. Don’t be surprised if they recommend replacing the power supply caps and the 100k resistors on the power rail. Fresh tubes will be a nice treat as well.

Thanks, but there IS NO mid control on the normal channel. There is on the vibrato side, however.

Just had all the caps replaced, one tube replaced and all of them tested, etc., etc., etc.

My real question is, is there supposed to be any difference in the sound between channels 1 & 2.

[stevecuss]

Originally Posted by Jerry D

Thanks, but there IS NO mid control on the normal channel. There is on the vibrato side, however.

Just had all the caps replaced, one tube replaced and all of them tested, etc., etc., etc.

My real question is, is there supposed to be any difference in the sound between channels 1 & 2.

I can't help with the difference between channel tones, but if I am reading the reply to your question correctly, he isn't saying there a mid knob on channel one, he is saying the mid tone is set internally with wiring.

All else being equal, a blackface Fender amp with tremolo - yes please!

[MC5C]

There are two different possible questions being asked here. Each channel has two inputs, input 1 and input 2. On most Fender amps of that generation, and certainly on the amp in question, input one is for lower output pickups so has higher signal level into the first pre-amp stage, with input 2 being for higher output pickups and has a -6dB dropping resistor network in there. So there will be some difference in how the pickup in question "attacks" the first pre-amp stage, and hence signal levels throughout the amp. If you have a big output humbucker and want a clean sound, use input 2 for lower gain and turn the guitar volume pot down, etc. Old timey single coil, use input 1. Edit; I suspect the vast majority of players would plug into input 1 and be done with it. I certainly did. If you plug two instruments in to both 1 and 2 at the same time, they are virtually identical, the difference is bypassed.

Normal channel vs tremelo channel is a very different story. To me, they definitely can have a quite different sound, even taking effects out of the story. The mid-scoop question has already been answered, but the tremelo/vibrato/reverb circuitry has a couple of extra tube stages, and a bunch of other stuff that can have an impact on tone. Which you like is up to you, but I felt they sounded different on my 68 Bandmaster (similar, but not identical member of the AB768 family).

[Pnewsom]

I have a 67 Black Face Vibrolux Reverb, and there is a difference in the sound of the two channels. Basically channel 1 is more scooped sounding than channel 2. Both are good sounds, and some folks will employ an AB pedal to take advantage of the diversity.

I've noticed this in other Black and Silver faced amps.

Great amps, nomatter what channel you use.

[clintj]

For a given channel (Normal or Vibrato), the 2 input is lower sensitivity. One advantage to that is you can use single coils in 1 and humbuckers in 2 without getting a dramatic jump in volume when switching guitars.

Normal vs Vibrato though, that's a little more complex. The biggest difference is the Vibrato channel has one additional gain stage to offset the losses in the tremolo circuitry. This gives that channel a bit more gain, and makes it a little fuller sounding and a touch more likely to break up. This also makes the two channels out of phase with each other, so using both channels simultaneously is going to cancel out a lot of your guitar signal.

[muscmp]

plus 1 on clint's response.

i have a 66 super also. great machine but can't lift it anymore!

play music!

[Jerry D]

Originally Posted by muscmp

i have a 66 super also. great machine but can't lift it anymore!

Tell me about it. I used to gig with the thing and lugged it into many Elks Clubs, etc., with it under my right arm and my Tele in its hard case in my left hand.

Recently, I took it in for repairs. My wife and I set it on a blanket and drug it out of the downstairs den, out into the garage, and then we set it in the trunk of the car. When I got to the shop, I had them bring it in.

Ah, fleeting youth.