Fender 400PS Tube bass head circa 1970

Discussion in 'Amps and Cabs [BG]' started by PAguy, Oct 1, 2005.

  1. PAguy


    Aug 19, 2005
    Anyone know anything about these? A local shop here has one for sale.


    Front Control Layout: Power Sw, Standby Sw, Pilot Lamp - Bass: In, In, Deep
    Sw, Vol, Treb, Bass - Normal: In, In, Bright Sw, Vol, Treb, Mid, Bass, Reverb, Speed, Intensity - Master Volume

    Rear Control Layout: Speaker Out, Speaker Out, Speaker Out, Output Tubes Matching, Tremolo Sw Jack, Reverb Sw Jack, Fuse, Ground Sw

    Knobs: Chrome skirted w/ black "F" center, numbered 1 - 10

    Head: 11½" x 28" x 12¾" (29.2 x 71.1 x 32.4 cm)

    Head Hardware: Black strap handle, corner protectors

    Head Covering: Black Tolex

    Head Grille: Blue grille cloth (70-72)

    Grille mounted, raised, chrome & black script "Fender" w/tail (head and cab)

    Weight: Head: 84 lbs. (38.1 Kg)

    Speakers/Load: 4 ohms

    Effects: Tremolo, Reverb

    Output: 435 Watts (3 x 145 Watts)

    Preamp: 2 x 7025

    Power: 6 x 6550

    Bias: Fixed Bias

    Rectifier: Solid State

    Phase Inverter: 12AX7, 6L6GC, Transformer

    Reverb Driver: 12AT7

    Reverb Recovery: 7025

    Tremolo: 12AX7 (photo resistor)

    Comments: The output was divided into three 145 Watt outputs,
    so three cabs were needed to get the entire 435
  2. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    It's amazing that they used a POWER TUBE for the driver tube. That tells you how much juice was on the 6550s, and how you couldn't use crappy tubes on this amp.
  3. BassGreaser


    Aug 22, 2002
    Austin, TX
    yep I had a Fender 300PS that was a sweet amp, but it was HEAVY!!! had to have been 100lbs. +
  4. Fealach

    Fealach Guest

    Apr 23, 2003
    Gone to a better place
    I have one, but know little about it, the web site above and
    the Yahoo list are the only sources I've found. There's little
    activity on the list, and it's run by the guy who has the
    website, so it's pretty much the same thing I think.

    Are they really as fragile as the site makes them out to be?
    Reading there, it's like a mystical superstitious thing, and only
    one man in the world can even bias them. I've been reluctant
    to put much use on mine, since I can't spare the shipping $
    never mind the fees. And then there's the impression that
    only GE6550A tubes are suitable, and anything else will
    ultimately lead to catastrophe. Is it really that bad? And I've
    read the preamp tube chart inside the amp lists one tube as
    incorrect. Don't know which one. It's my understanding that
    in other amps similar preamp tubes can be substituted -
    I mean if it calls for a 12AU7 a 12AX7 can be used without
    damage but perhaps with unpleasant sonic results. Would
    loading it with quiet 12AX7 preamp tubes harm it, if the result
    was sonically acceptable, not noisy etc?

    Don't mean to overwhelm you with questions, and hopefully
    these are some of the questions the original poster should
    know the answers to before purchasing. My work schedule
    prevents me from phoning Time Electronics, and they have
    not responded to my emails. It'd be nice to have a second
    opinion from someone who knows what they are talking
    about, as I'm sure you do.
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    With tremolo and reverb it's not a bass head, though it certainly could be used as such. As a guitar amp it was a failure in the marketplace, as guitar players didn't want super clean 400 watt amps, the wanted super dirty 50 watters. You don't have to use GE tubes, all 6550 types are interchangeable, though you're best off with matched sets. 12ax and 12aU, as well as 7025 and a number of other tube types are also interchangeable, but they do have different gain structures and sonic signatures. Sites devoted to bottles will give you more information there.
  6. jondog


    Mar 14, 2002
    NYC metro area
    I've met the Time Electronics guy. He's a good bassist and did some high quality work for me but it cost more than I was expecting. He is a reputable businessman who gets a lot of random questions via email. If you put in your subject heading that you have cash and are seriously interested in buying, I'm sure he'll respond.
  7. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    Trust me, the tube chart isn't incorrect. It uses a 6L6 power tube to drive the 6550As extremely hard. How else would you manage to get 435 clean watts out of only 6 6550s?!?
  8. protoz


    Nov 30, 2000
    Can I have one for x-mas? I've been a good boy!
  9. They're not fragile, just not hack-tech wannabe proof. The picture of the melted tubes came from someone who tried to bias it using plate current diassappation.

    Not really, but with the proliferation of "instant expert techs" who have only read a book by Dan Torres or Gerald Weber and, armed with a multimeter, are ready to take on any amp they come across, it's a beast that deserves more caution and expertise.

    That was written in the days when crap Chinese 6550's were the only option. While I wouldn't use Svetlana 6550C's or some Chinese KT88's, there are a lot more possibilities now.

    Mine's right.

    I wouldn't. You'll get significantly more gain and the preamp will distort and lack low end.

    It's supposed to be an 'all purpose' amp with separate bass and guitar channels meant to compete with Ampeg's SVT/V9. Heart used them onstage in the 70's.

    ...not in the 400PS. You HAVE to use 6550A's or tubes that meet their specs. Not all 6550's do.
  10. Fealach

    Fealach Guest

    Apr 23, 2003
    Gone to a better place
    Thanks for the info. I was afraid getting it properly serviced was going to be trouble, and it is. Just finding an honest, competent tech (and, importantly, honest about his limitations!) within reasonable driving distance has taken years.