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Post subject: Interactive channels on a 65' Super Reverb
Posted: Sun Feb 26, 2012 11:50 am
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So, do Super Reverb's have interactive channels as well? I plug into the "Vibrato" channel of the amp and the unused channel, of course, is the "Normal" channel. Does anyone fully understand how your settings, of the unused channel, affect the channel that you are playing through? For example, if I have everything (Volume, Treble, and Bass) in the unused, or in this case the Normal, channel wide open or all the way up then how does that affect the channel being used? I was pretty thrilled to find the previous post about interactive channels here because I was messing around with my amp settings and did notice that the levels in the unused channel did, in fact, have an impact on the sound of the signal coming through the channel I was playing through. Also, how does pulling the 12ax7 tube from the vibrato channel impact the amplifier? I read earlier that it changes the tone of the amp but I'm curious as to what it does overall to the channel as far as frequency goes. Does it boost the signal of the channel or cut it? Is the frequency of the signal more or less responsive? I guess I may not be asking the right questions as I don't fully understand how this stuff works but that's why I'm here, to learn. Thank you for your time to anyone who posts on this topic. Any new information would be greatly appreciated.


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Post subject: Re: Interactive channels on a 65' Super Reverb
Posted: Sun Feb 26, 2012 1:21 pm
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My understanding is this is not a straight forward "linear" kinda interaction. More like a complex one that deals with the tone stack of the unused input and it's 12AX7 (7025) inherent impedance. The closer the stack is to the actual input of the guitar, the greater the interaction between the tone stack and the impedance ratio on that 12AX7.

To translate into English, you'd need to play with the volume/tone controls in the unused channel to fine tune the tonal response of the used channel. Prolly, a lot depends on guitar pups used, stomp boxes, and anything else between the guitar and the amp.

I believe that Leo designed this purposedly into the amps to give them a richer tone quality. Something that has been known about tube amps for a long time.


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Post subject: Re: Interactive channels on a 65' Super Reverb
Posted: Mon Feb 27, 2012 12:51 pm
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BMW2002Ti wrote:
My understanding is this is not a straight forward "linear" kinda interaction. More like a complex one that deals with the tone stack of the unused input and it's 12AX7 (7025) inherent impedance. The closer the stack is to the actual input of the guitar, the greater the interaction between the tone stack and the impedance ratio on that 12AX7.

To translate into English, you'd need to play with the volume/tone controls in the unused channel to fine tune the tonal response of the used channel. Prolly, a lot depends on guitar pups used, stomp boxes, and anything else between the guitar and the amp.

I believe that Leo designed this purposedly into the amps to give them a richer tone quality. Something that has been known about tube amps for a long time.


Beemer, so the Super Reverb does that same kind of a thing as a tweed Bassman does? Am I reading this right? Are the BFSR and Bassman wired similarly?

T2

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Post subject: Re: Interactive channels on a 65' Super Reverb
Posted: Mon Feb 27, 2012 1:42 pm
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T2Stratman wrote:
BMW2002Ti wrote:
My understanding is this is not a straight forward "linear" kinda interaction. More like a complex one that deals with the tone stack of the unused input and it's 12AX7 (7025) inherent impedance. The closer the stack is to the actual input of the guitar, the greater the interaction between the tone stack and the impedance ratio on that 12AX7.

To translate into English, you'd need to play with the volume/tone controls in the unused channel to fine tune the tonal response of the used channel. Prolly, a lot depends on guitar pups used, stomp boxes, and anything else between the guitar and the amp.

I believe that Leo designed this purposedly into the amps to give them a richer tone quality. Something that has been known about tube amps for a long time.


Beemer, so the Super Reverb does that same kind of a thing as a tweed Bassman does? Am I reading this right? Are the BFSR and Bassman wired similarly?

T2


Not even close:

http://ampwares.com/schematics/bassman_5f6a.pdf

http://ampwares.com/schematics/super_reverb_ab763.pdf

The 5F6A Bassman used a cathode follower to drive the tone stack which then fed the PI directly. The cathode follower has in output impedance of around 600 ohms while the load impedance of the PI on the tone stack is about 2M ohms. Ideal conditions to drive the lossy tone stack. There however a fair amount of gain in front of the tone stack from the 12AY7 preamp and 12AX7 voltage amp (the cathode follower is slightly less than unity gain, it acts as a buffer). The net result is a warmer sound, better touch sensitivity, with the chance for a bit more breakup as the signal works its way through the PI and output stages.

The tone stack on the BFSR, on the other hand , is driven by the plate of the first preamp which has an output impedance of about 100K ohms and the load on the tone stack is about 1M ohm. So you have a high impedance driving the tonestack and a high impedance load with a make up gain stage after it. The result here is less gain in front of the tonestack and more after it, resulting in the cleaner, brighter Blackface tone.

I think that comparing the two, there is more interaction in the 5F6A Bassman circuit than there is in the BFSR.

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Post subject: Re: Interactive channels on a 65' Super Reverb
Posted: Mon Feb 27, 2012 6:52 pm
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Thanks Bill. But this post got me thinking so I dug into one of my books, "Fender Amps, The First Fifty Years" and under the Super Reverb section it says the BFSR has more in common architecture wise with the Tweed Bassman that it does with the Tweed Super, which might account for interaction? They basically say that the Tweed Super turned into the Vibroverb.

FWIW

T2

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Post subject: Re: Interactive channels on a 65' Super Reverb
Posted: Mon Feb 27, 2012 8:56 pm
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T2Stratman wrote:
Thanks Bill. But this post got me thinking so I dug into one of my books, "Fender Amps, The First Fifty Years" and under the Super Reverb section it says the BFSR has more in common architecture wise with the Tweed Bassman that it does with the Tweed Super, which might account for interaction? They basically say that the Tweed Super turned into the Vibroverb.

FWIW

T2


I guess it all depends on how you define "common architecture": They both have tubes and four speakers. :lol:

Seriously, though, the preamps and tone stacks are very different. The Super Reverb got rid of the cathode follower which a lot of people feel is the secret to the 5F6A Bassman's tone. Both amps have a long tail pair phase inverter, ignoring the fact that Fender switched from a 12AX7 to a 12AT7 for the PI. The power amp stage is similar except for the tube choice and Fender reinserting the 1500 ohm grid stopper in the BFSR. The 5F6 Bassman had a grid stopper but it was removed for the 5F6A version. All of the changes from the Bassman to the SR were designed to achieve a cleaner tone.

The Tweed Super 5F4 circuit is very similar to the Bassman 5E6A circuit.

http://ampwares.com/schematics/super_5f4.pdf

http://ampwares.com/schematics/bassman_5e6a.pdf

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Post subject: Re: Interactive channels on a 65' Super Reverb
Posted: Thu Mar 01, 2012 1:33 pm
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T2Stratman wrote:
Thanks Bill. But this post got me thinking so I dug into one of my books, "Fender Amps, The First Fifty Years" and under the Super Reverb section it says the BFSR has more in common architecture wise with the Tweed Bassman that it does with the Tweed Super, which might account for interaction? They basically say that the Tweed Super turned into the Vibroverb.

FWIW

T2

What they're really reffering to in that statement is the way Fender seemed to name amps in a haphazard way instead of the later amps being similar to the previous models.....
example...a Tweed Super had 2x10s,the Brown Super had 2x10s...makes sense,then along came the first Brown Vibroverb 2x10s?....the tweed Pro had 1x15,the Brown Pro had 1x15...then the second BF Vibroverb,1x15??...the tweed Bassman had 4x10s,Concert had 4x10s...then the Super Reverb ...yep 4x10s.???
Then the Brown Vibrolux had 1x12,the BF Vibrolux has 2x10s....should be the SUPER Reverb with 2x10s,that would make more sense since Supers had usually had 2x10s....then......of well...get the picture? :lol: :lol:


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Post subject: Re: Interactive channels on a 65' Super Reverb
Posted: Thu Mar 01, 2012 4:37 pm
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Rebelsoul wrote:
T2Stratman wrote:
Thanks Bill. But this post got me thinking so I dug into one of my books, "Fender Amps, The First Fifty Years" and under the Super Reverb section it says the BFSR has more in common architecture wise with the Tweed Bassman that it does with the Tweed Super, which might account for interaction? They basically say that the Tweed Super turned into the Vibroverb.

FWIW

T2

What they're really reffering to in that statement is the way Fender seemed to name amps in a haphazard way instead of the later amps being similar to the previous models.....
example...a Tweed Super had 2x10s,the Brown Super had 2x10s...makes sense,then along came the first Brown Vibroverb 2x10s?....the tweed Pro had 1x15,the Brown Pro had 1x15...then the second BF Vibroverb,1x15??...the tweed Bassman had 4x10s,Concert had 4x10s...then the Super Reverb ...yep 4x10s.???
Then the Brown Vibrolux had 1x12,the BF Vibrolux has 2x10s....should be the SUPER Reverb with 2x10s,that would make more sense since Supers had usually had 2x10s....then......of well...get the picture? :lol: :lol:


Makes perfect sense to me. :? :lol:

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