| Author |
Topic: Alembic F2b |
Kevin Raymer
From:
Chalybeate, Kentucky, USA
|
|
|
|
Pete Burak
From:
Portland, OR USA
|
Posted 3 Aug 2014 7:37 am |
|
I have one and use it for Steel sometimes.
I have it in a 2-space rack with a Lexicon LXP-1, which is a Stereo Delay unit from a similar era.
I typically use a MosValve 962, which is a stereo power amp with 80W per side, to power it.
They really sound great for any instrument/application.
Mine is an early one more like the one described here.
http://www.darkstarpalace.com/2010/03/phil-leshs-alembic-f-2b-tube-preamp.html |
|
|
|
Brad Sarno
From:
St. Louis, MO USA
|
Posted 3 Aug 2014 7:46 am
|
|
Alembic's is the "normal", non-reverb channel from a Fender. It's a classic workhorse, but its design has issues in my opinion. The output stage and impedance and heater supply hum aren't the greatest. But it is a tank.
My SMS Classic is the "reverb" channel from a Fender, but we gave it a much quieter DC heater supply and a modified output stage to halve the output impedance, double the drive capability. I've got a ton of F2B converts that now prefer the SMS Classic. Not only is the SMS Classic arguably a quieter, better and improved design, it's also far less expensive.
http://www.sarnomusicsolutions.com/products/ctp.html
Brad
 |
|
|
|
Pete Burak
From:
Portland, OR USA
|
Posted 3 Aug 2014 8:01 am
|
|
I've got one of Brads unit, too.
Nice!
 |
|
|
|
Kevin Raymer
From:
Chalybeate, Kentucky, USA
|
Posted 3 Aug 2014 2:30 pm
|
|
Well.... I'm liking the revelation I got.
Can't imagine the alembic being better..
I would however like to try one of those octal preamps.
I wish there was a octal option for the revelation ..
_________________
Kevin Raymer
Zum / Knaggs / Breedlove
Fractal Audio |
|
|
|
Brad Sarno
From:
St. Louis, MO USA
|
Posted 3 Aug 2014 7:19 pm
|
|
| Kevin Raymer wrote: |
I wish there was a octal option for the revelation ..
|
Keep your dream alive... 
B |
|
|
|
Bill Hatcher
From:
Atlanta Ga. USA
|
Posted 5 Aug 2014 6:44 am
|
|
the f2b is the greatest piece of gear i ever bought!!! i used it for electric bass since it came out. i have 5 or 6 of them. anytime since i got my first one in i think the later 70s that i saw one for sale used i bought it.
sarno. if your unit is even close to the sound of the f2b with verb, then it is a deal for sure!! maybe one day i will get one.
the only real issue i have had with the f2b is the mounting of the filter caps. back in the day they used those big sprague atom caps with a piece of foam wrapped around them to reduce the movement. the mounting is sideways with the cap end soldered to the board and the other leg of the cap bought around to the board. basically the cap is suspended sideways. when the foam degrades over time the cap flexes and the wire end that is closest to the board either breaks out of the board tracing or can brake off the cap. smaller caps with the same value with both wires coming from the bottom are a solution and also i ad some hot melt around the base of the caps to keep them from moving when being hauled to the gig.
can you post an interior shot of your preamp?? i sure would like to see it. |
|
|
|
Brad Sarno
From:
St. Louis, MO USA
|
Posted 5 Aug 2014 9:02 am
|
|
Bill,
I'll take some shots of the guts of my SMS Classic next time I get one rolling on the bench. Keep in mind that mine is a single channel, not dual like the F2B. The F2B is a real benchmark, and Ron Wickersham smartly used very good military pots and those fantastic Allen Bradley carbon comp resistors, so the thing is a tank. And yeah, I've seen that foam issue, but like you found, you can hot glue or even better, silicone adhesive to hold them still.
The SMS Classic has a much quieter DC heater supply, and since it's the reverb channel, it requires 3 tube stages unlike the 2 in the F2B. That final stage serves as the reverb mixer and output driver. SInce I'm left with a 4th triode stage, I parallel that with the other so that tube #2 has double the output drive capability (half the output impedance). The Alembic's output driver section is just a single triode stage with an output Z that's pretty high, about 40kOhm. That's normally ok because there's plenty of swing, but some power amps or loads can really bog it down. Then Alembic has a resistor network for mixing the two channels and that added resistance can induce some tone loss if your output cable run is too long. In practice, it's obviously not a big deal though. The F2B delivers nicely.
We also use quieter, non-inductive plate resistors to keep the hiss down, and we also have some pretty tasty selections of signal capacitors and voicing tweaks that are very friendly to pedal steel. But all in all, the SMS Classic and the F2B draw from the old AB763 Fender circuit from the blackface amps. The F2B is a virtual clone of the "normal" channel from a Showman or just about any of those amps in the line. Our SMS Classic has made quite a few moves on that design, but still at heart is that same general idea of the reverb preamp channel and is very familiar to anyone who likes to use Twin Reverbs or similar.
B |
|
|
|
Bill Hatcher
From:
Atlanta Ga. USA
|
Posted 6 Aug 2014 5:09 am
|
|
| wow!! nice sounding design. are you using verb springs???!!! |
|
|
|
Brad Sarno
From:
St. Louis, MO USA
|
Posted 6 Aug 2014 8:13 am
|
|
No, mine is a 24bit digital processor instead of a real spring, but it's circuit topology, the way it returns the reverb effect into the circuit is identical to a Fender circuit. The dry path remains entirely tube-analog and the reverb is blended in parallel. I can program it for a spring or a hall or a room algorithm. This all keeps it in a single rackspace unit. The digital reverb factor is the main deviation from the classic Fender preamp.
B |
|
|
|
Kevin Raymer
From:
Chalybeate, Kentucky, USA
|
Posted 6 Aug 2014 8:17 am
|
|
They make no bones about it..
It's a fender showman preamp with a few mods...
Straight from the Alembic WebSite...
http://www.alembic.com/prod/f2b.html
Circuit detail
The F-2B was inspired by the Fender Dual Showman amplifier. In the late '60's, we routinely added preamp output jacks to Dual Showman amplifiers and substituted an external power amplifier for the built-in quad 6L6's, most usually a MacIntosh 75.
The F-2B came about to provide the same preamp functionality in a rack-mounting package, as the Dual Showman was considerably wider than the standard 19 inch rack.
We took the opportunity to make a small improvement in the input jack circuit, while providing identical functionality. Plugging into Jack 1 alone gives full sensitivity, while Jack 2 alone is attenuated 6 dB. If signals are plugged into both jacks simultaneously, mixing resistors combine the signals and give isolation to the two input sources. In the original circuit, the mixing resistors are always in series with the grid of the first stage, and contribute a small amount of Johnson (thermal) noise. Our jacks have additional contacts which completely switch out the mixing resistors when using Jack 1 and the ultimate quietness of the tube is preserved.
_________________
Kevin Raymer
Zum / Knaggs / Breedlove
Fractal Audio |
|
|
|
Bill Hatcher
From:
Atlanta Ga. USA
|
Posted 6 Aug 2014 8:54 am
|
|
| Brad Sarno wrote: |
No, mine is a 24bit digital processor instead of a real spring, but it's circuit topology, the way it returns the reverb effect into the circuit is identical to a Fender circuit. The dry path remains entirely tube-analog and the reverb is blended in parallel. I can program it for a spring or a hall or a room algorithm. This all keeps it in a single rackspace unit. The digital reverb factor is the main deviation from the classic Fender preamp.
B |
smart! i didnt think it was spring, but had to ask. your preamp just appears to be a very nice piece of gear. do you have any way to grind it up some for the underarm guitar players. they dont seem to buy much these days that they cant get some distortion out of! |
|
|
|
Brad Sarno
From:
St. Louis, MO USA
|
Posted 27 Aug 2014 8:16 am
|
|
| Bill Hatcher wrote: |
| ...can you post an interior shot of your preamp?? i sure would like to see it. |
All copper on the pcb is 2oz thick trace, 100% oxygen free. You can see that the reverb section takes up quite a bit of real estate. The preamp section is pretty minimal.
Sure.
 |
|
|
|
