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The Alembic F-1X Megathread

#282
Jeff Scott said:
Keep in mind the EQ controls are highly interactive, but great tones lurk within!
Click to expand...

Very true! Remember, too, that the “flat” setting on the EQ is 2-10-2 (bass-mid-treble). Start from there. This tone stack simulator is worth playing around with as it will help you understand the interactive nature of the EQ (thanks to Alembic Bill for the link):

TSC
To simulate the F-1X, use the Fender tone stack and swap the C2 and C3 values (make C2=47n, C3=100n).

Enjoy!
 
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#283
Well, received the unit yesterday and I was impressed by the quality. I plugged it in and started with a setting of 2-10-2 as suggested, I immediately heard that valve warmth in the sound and once I got to tweaking the settings I could go from molasses thick bottom to glass-shattering highs and everywhere in between.

Up to this point I had only read reviews on the F-1X and they all spoke very highly of the sound, confirmed: it sounds awesome! I'm mounting it in a rack this week so I can take if for a spin on the weekend.

Thanks to all for the great advice. :)
 
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#285
quickervicar said:
Wouldn't swapping C1 and C2 values make C1=100nF, C2=250pF, and C3=47nF? Then again, I'm easily confused when it comes to this stuff.
Click to expand...

You are correct, sir! Here's the correct tweak to simulate an F-1X:

When you first run the TSC, click on the Fender tab. Next you need to make two changes:
Double click on C2 and change its value from 100 to 47.
Double click on C3 and change its value from 47 to 100.

That's work :)
 
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#288
20190205_192741.jpg
 
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#291
Jeff Scott said:
Keep in mind the EQ controls are highly interactive, but great tones lurk within! I've had two, and keep thinking about another one.
Click to expand...
  1. There are really two separate sections in the circuit. The first section involves the BASS and MID pots, two caps and a fixed resistor. When the BASS control is at 0, the MID control is essentially a level control for all frequencies for this section of the circuit. When the BASS control is turned up, more low frequencies are *added* to the output of this section, increasing the overall level.

    The second section consists of the TREBLE pot and a cap. One side of the cap connects directly to the input of the tone stack. The value of this cap is such that only high frequencies will pass through it. The TREBLE pot provides the final output from the tone stack and is connected such that at one extreme setting (10) it passes *mostly* the output from the treble cap and at the other extreme setting (0) it passes *mostly* the output from the BASS/MID section.

    Now here's the observation I haven't seen anyone else make...

    The TREBLE knob is actually a *blend* control between the output of BASS/MID section and the output of the treble cap !

    So when you turn up the TREBLE, you're actually *reducing* the level that's coming from the BASS/MID section at the same time you're *increasing* the amount of signal coming from the treble cap.

    Realizing this made it easier for me to think about how the knobs work. For example, if you want to add more highs and keep the lows and mids the same, you need to not only turn up the TREBLE knob, but also turn up the BASS and MID knob to compensate. I've seen descriptions of this circuit that say the BASS and TREBLE controls are "boost only" and the MID control is "cut only", but that's somewhat misleading. I tend to think of the MID control as a "direct" level, the BASS as a low-frequency boost and the TREBLE knob as a "blend" control as described above.

    Hope this is helpful and not too confusing :)

    doctec, Nov 27, 2008
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    markorbit
    Apr 16, 2004
    IIRC something else is worth noting... increasing the treble control MOVES the actual mid frequency lower to incorporate more high mids whereas the bass control doesn't move the mid frequency likewise.
In my view the tone stack is a low pass network and a high pass network in parallel. The low pass is slightly modified to become a shelving network by the addition of the mid control such that as frequency increases, a maximum amount of attenuation is reached and this point is controled by the mid control. The Treble control is not a blend control per se but as it is turned up the bass does reduce slightly by about 2dB. If it was truly a blend control, the Bass and Mid controls would have no affect when the Treble control is all the way up.

A neat (and free) program that graphically demonstrates what many common tone controls do can be found here:TSC

turning up the TREBLE knob adds highs *and* reduces lows

This is true. If both the BASS and TREBLE controls are at or near '0', the frequency response if fairly flat and MID knob acts like a gain control.
start at all "0", turn up the mids to about 5-7 (it now gets obvious that this is a kind of "direct" level as opposed to a midrange-boost, as this will not honk or sound telephone-isa the way mid-only boost EQs will), add bass according to taste/needs (basically to "fatten" the direct sound), tweak maybe the treble a notch. Then, if necessary, give some more bass/mids.
 
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#294
Fantastic preamp. My standard for about 10 years, mid 90’s to mid 00’s, after which I spent the last 15 years with Demeter. But, I decided I wanted to jump back in a year ago. Here is the current rack.

D9D35071-E10C-40A2-BB5C-9BC6B56BCB81.jpeg


My last (really) upgrade will be to replace the wonderful PLX 1804 with a GX7, due in the end of this week. I think I’m done at that point. (I know, famous last words.)
 
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#295
IIRC the F 1X is the Normal channel from a Fender Bassman. I wonder how they got permission to do that?

In 1968 I started to use a Leak TL50 Plus HiFi 50W tube power amp for my bass. To drive it I built the equivalent to the Normal channel. The pre-amp plugged into the power amp and was powered by it. It worked well. :D
 
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