BRPD: Most bizarre tube preamp ever! :O

Discussion in 'Gear & Equipment' started by Emperoff, Jan 24, 2021.

  1. Emperoff

    Emperoff Not using 5150s Contributor

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    I love rack preamps. They're old, cheap, and sound awesome. So I'm always looking up for new specimens. But man, this one it's just one of a kind. Let me introduce you to the Exef 6-Shooter preamp. Exef is a defunct company from (west) Germany ran by Jochen Köckler, a mad genius that pioneered programmable amplifier designs in Germany. And I can tell you this preamp was really ahead of its time ('89)...

    [​IMG]

    What? That's just your average 2-channel tube preamp. What's so weird about it? As always, devil is in the details...

    Preamp has two channels: MA(rshall) and MB(oogie). But not only that, each channel has their own separate modes as if they were independent preamps:

    Mesa channel is 100% Mark DNA. It has pre-gain EQ and two gain knobs, and it shines at typical Mark "B0,M3,T10" settings. On top of the three modes (clean, crunch, lead), it has a mid-shift option that resembles the "pull knob" effect on Marks, while also adding a touch more gain.

    Marshall channel has "Vintage" and "Getuned" (I suspect a german word for modded, or hot-rodded). The gain is controlled via two gain knobs "normal" and "bright", like a Plexi. This allows you to fine-tune the overall character of the gain. The Getuned mode gets a kick in the lows, highs, and gain department. I don't know if it tries to be a JCM800, since honestly I'm no Marshall expert.

    [​IMG]

    But wait, what are those "Boost", "Wah", "Limit" and "Distortion" LEDs I see? Well, those are indeed onboard analog FX. To be specific based on a Dallas Rangemaster, a Dunlop Crybaby and a MXR Distortion+ (and its dedicated gain knob and two distortion voicings).

    And how do I control all this shit? I don't even see any front panel switches! Answer is via MIDI. In fact, that is the only way you can access to all the inner functions of the preamp. In case you don't have a MIDI controller, the preamp has built-in midi knob with 15 factory presets. How cool is that?

    [​IMG]

    With a MIDI controller, you can set it up with up to 99 combinations, IIRC. It would have been great to be able to overwrite those 15 positions, but sadly you can't. There are plenty of really cool sounds to be explored:
    - The treble booster (known as "Fortin Grind" on this place) will make any distortion mode a rythm machine. With the Getuned Marshall is basically insta-Djent. But with the Mesa sounds absolutely punishing.
    - The wah can be controlled by an external pedal, and sounds pretty good. You can just leave it on for leads if you want as well.
    - The distortion with the Marshall Vintage sounds pretty cool, very 70-80s. Not a sound I would use much, but it's there.
    - The limiter is garbage. It's not a compressor, so if you play hard you can hear the volume lowering down (instead of evening everything out like a compressor would), so its basically unuseable except for clean arpeggios, etc.

    So you can basically have a MIDI controller with Fender cleans, Plexi crunch, boosted Mark rythm tones and use the mid-shift option for leads. Each with their own master volume. Isn't that awesome?

    To wrap it up, it has an FX loop, emulated recording out (disabled if running it in stereo), and two inputs (front and back). All in a tiny 18cm deep enclosure. How can it do all of that? Well, let's take a look inside... @Deadpool_25, @technomancer

    [​IMG]

    Hmm, it looks cramped for sure. Input section seems to host the boost and distortion FX. Separating the tube preamplification stages with a spacer.

    [​IMG]

    Build quality is great. Wima capacitors are used throughout the whole preamp, along with Siemens electrolytic capactiors rated at 350V. Pots are chassis mounted and soldered between them. Transformers are covered so no idea.

    [​IMG]

    Three NOS RSD branded tubes that happen to be EI Yugoslavia long plate tubes. VERY nice sounding tubes, but bad choice for 1st stages on hi-gain amps. Two of them were quite worn but the last was super strong. Ended up at V5 on my Triaxis and re-tubed this one with 3x Siemens ECC83 which are basically my favourite preamp tubes ever. Sounds amazing now.

    [​IMG]

    This is when things get... risky. See those big fat blue capacitors? Well, those things can easily shock you if you try to change a tube. They're too close. Worst part is that they retain voltage even when powered off. 70V, to be exact. It discharges at a rate of 3V per day so you have to discharge the thing with a resistor before attempting a tube change otherwise you're at high risk of shock.

    Also, the tube at the top also has a poorly placed relay that is literally touching the tube. This means you're forced to use NOS tubes in there (they're smaller), otherwise they won't fit.

    Phew! That was long. After a while the "Getuned" mode started to hum, so I suspect a recap might be necessary since the device is 32 years old. I already ordered some F&T caps which are also way smaller and will make tube changes easier in the future.

    Stay (ge)tuned for part 2. More Exef threads coming soon!... :wavey:
     
    Last edited: Jan 24, 2021
  2. budda

    budda Do not criticize as this Contributor

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    Well!
     
  3. Deadpool_25

    Deadpool_25 SS.org Regular

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    Damn that sounds like an awesome piece of gear. I haven’t gotten into tack stuff myself but I have to say that shit is pretty cool. HNRPAD!
     
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  4. youngthrasher9

    youngthrasher9 SS.org Regular

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    I gotta say, it actually lives up to the title. I wasn’t expecting that.
     
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  5. Gmork

    Gmork SS.org Regular

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    Neat! Would love to take that for a run!
     
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  6. boltzthrower

    boltzthrower SS.org Regular

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    I've owned over 50 preamps and I've never heard of this thing. Badass. I bet I would've shocked the shit out of myself with it.
     
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  7. laxu

    laxu SS.org Regular

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    Would love to hear some clips!

    It's amazing something like this was built in 1989 yet here we are 30 years later and somehow having MIDI control on most amps with more complex switching is too much to ask.
     
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  8. narad

    narad Progressive metal and politics

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    Exef stuff has always had my interest and looked a bit crazy:

    [​IMG]

    But now knowing it's crazy inside has me backing off.
     
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  9. laxu

    laxu SS.org Regular

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    Well it's not exactly a Peavey Classic 30 tri-fold PCB so it's fine. Rack units are always going to be a bit cramped if they are 1U and most people should not be poking inside their amps in the first place.
     
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  10. Emperoff

    Emperoff Not using 5150s Contributor

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    Mine is their most cramped preamp. There are others way less crowded.

    Exactly. Also:
    It puzzles me that something like the Mesa Badlander doesn't have damn MIDI integration. I don't buy any amp/preamp without MIDI nowadays since, I control everything with my Multi-Fx units.
     
    Last edited: Jan 25, 2021
  11. Shask

    Shask SS.org Regular

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    Everyone got stupid in the year 2000 and cant operate anything with more than 3 knobs, lol.
     
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  12. Mourguitars

    Mourguitars SS.org Regular

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    I missed this thread, but that pre is pretty awesome !

    Yes it is cramped and im sure i would have got zapped changing tubes with those caps , I've learned a lot in the last few years...lol...look , study then leap rule..

    Those RSD tubes are East German right ? maybe from the RFT factory...ive never seen that Brand/Re-branded EEC83 before

    So much to look at and study in the gut shots, im kinda in Awe...hope it sounds as good as it looks...built quality for sure

    Congrats !

    Mike
     
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  13. Emperoff

    Emperoff Not using 5150s Contributor

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    Thanks mate! I'm sure that if you had opened it and saw the big caps so close to the tubes you would have at least google'd before putting your hands in... Or so I hope! Haha

    RSD rebranded tubes from Europe mostly, these in particular are EI (Yugoslavia) tubes. Very, very nice sounding tubes, but prone to microphonics. Changing them made the preamp quieter.

    I'm glad you like the gut shots. I always have curiosity what is cooking inside these noise machines we plug into!
     
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  14. TheWarAgainstTime

    TheWarAgainstTime "TWAT" for short

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    Gnarly! Definitely ahead of its time with all those extra options :metal:
     
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