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previous: Margaret Wilson I've been having some trouble with ... -- 5/30/2000 7:25 PM

Re: Bass "Flubbing Out" in SFPR!

5/30/2000 8:39 PM
MBSetzer	Re: Bass "Flubbing Out" in SFPR! Hi Margaret: I'm not so sure I've got an answer, maybe if I did, my SFPR would be here in the lab instead of still stored away the last few years. It might help to post what kind of guitar & settings you are having the most trouble with, and if you are pluging straight into the amp, which input? Without real facts to back it up, I have always thought that Leo Fender followed the example hifi circuits from tube manuals of his day a little too closely. That resulted in too wide a frequency response compared to what might be considered optimum for guitar, especially since the 1950's came & went, and guitarists tastes evolved since then. The speakers have always rolled off the highs without much audible side-effect, since there is much less energy than in the bass notes. The speakers roll off the bass, too, but since the signal is still passing through the voice coil even if it is a frequency below those capable of being audibly reproduced, all remaining audible information is superimposed on what can be quite a flubby signal, since the cone's inability to follow the lowest frequencies is the reason for the natural rolloff below a certain Hz anyway. I don't think this was as much a problem when the early Fender amps were intended mainly for use with Fender guitars, which are usually considered the least bass-heavy (some say shrill or thin) guitars in any pickup position. Who knows, the amps might have first been made operational according to radio/hifi design conventions, then the guitars & pickups could have been logically voiced to match the amps. Still a vintage Fender guitar & amp is a hard combination to beat, but people have always accepted some kind of compromise when using other guitars, especially bass-heavy ones like humbucking Gibsons in the neck position. One answer I have pursued somewhat is to reduce the frequency response (especially bass) that is available to the speaker's voice coil to begin with, trying to supply it with only the signal that IMHO it is capable of reproducing tonefully. Electrically this is easiest for me by reducing the values of the coupling caps between tube stages, and by reducing the values of the bypass caps at the preamp cathodes. The possibilities are endless, and it would best be tweaked by ear, so trial & error are more effective than calculation & prediction, neither seems as good as proven experience though. Only after I have done mine will I have real world results, though at this point I'm sure that for me, before I am done with my SFPR, both the 0.02 & 0.1 coupling caps will be reduced, and also the three 25mf/25V cathode bypass caps will be no greater than 15mf. Hope this helps, Mike

5/30/2000 8:39 PM

MBSetzer

Re: Bass "Flubbing Out" in SFPR!

Hi Margaret:

I'm not so sure I've got an answer, maybe if I did, my SFPR would be here in the lab instead of still stored away the last few years.

It might help to post what kind of guitar & settings you are having the most trouble with, and if you are pluging straight into the amp, which input?

Without real facts to back it up, I have always thought that Leo Fender followed the example hifi circuits from tube manuals of his day a little too closely. That resulted in too wide a frequency response compared to what might be considered optimum for guitar, especially since the 1950's came & went, and guitarists tastes evolved since then.

The speakers have always rolled off the highs without much audible side-effect, since there is much less energy than in the bass notes.

The speakers roll off the bass, too, but since the signal is still passing through the voice coil even if it is a frequency below those capable of being audibly reproduced, all remaining audible information is superimposed on what can be quite a flubby signal, since the cone's inability to follow the lowest frequencies is the reason for the natural rolloff below a certain Hz anyway.

I don't think this was as much a problem when the early Fender amps were intended mainly for use with Fender guitars, which are usually considered the least bass-heavy (some say shrill or thin) guitars in any pickup position. Who knows, the amps might have first been made operational according to radio/hifi design conventions, then the guitars & pickups could have been logically voiced to match the amps. Still a vintage Fender guitar & amp is a hard combination to beat, but people have always accepted some kind of compromise when using other guitars, especially bass-heavy ones like humbucking Gibsons in the neck position.

One answer I have pursued somewhat is to reduce the frequency response (especially bass) that is available to the speaker's voice coil to begin with, trying to supply it with only the signal that IMHO it is capable of reproducing tonefully. Electrically this is easiest for me by reducing the values of the coupling caps between tube stages, and by reducing the values of the bypass caps at the preamp cathodes. The possibilities are endless, and it would best be tweaked by ear, so trial & error are more effective than calculation & prediction, neither seems as good as proven experience though. Only after I have done mine will I have real world results, though at this point I'm sure that for me, before I am done with my SFPR, both the 0.02 & 0.1 coupling caps will be reduced, and also the three 25mf/25V cathode bypass caps will be no greater than 15mf.

Hope this helps,
Mike

Replies:

Margaret Wilson Hi Mike,I play a US... -- 5/30/2000 9:39 PM
Steve Ahola Mike: -- 5/31/2000 1:30 AM