Fender Studio Bass Club!

Discussion in 'Amps [BG]' started by gjesse, Sep 18, 2011.


  1. gjesse

    gjesse

    Joined:
    Aug 12, 2011
    Location:
    Cleveland Ohio
    Anyone rocking a Fender Studio Bass amp, Super Twin, or some variant thereof? If so, reply and let's show em off! I can't say enough about this amp...I've had mine for the last 4 years, and I'll never let it go. It sounded great in the very original combo it came in, but was a little thin sounding, so I recently pulled the head out, and I'm running it through an Ampeg 15/10 cab. Absolute BUTTA!

    Attached Files:

  2. pgk

    pgk

    Joined:
    Aug 19, 2007
    wish i was a member
  3. emblymouse

    emblymouse I Dig A Pony Supporting Member

    Joined:
    Jan 22, 2006
    Location:
    W' Sconsin
    Disclosures:
    Endorsing Artist Lakland**Bag End**Schroeder
    Supa Twin waiting for it's cab. I haven't begun to explore yet. More to come....:bassist:
  4. pbass888

    pbass888 Supporting Member

    Joined:
    Jul 8, 2009
    Location:
    New York, NY
    Looks lovely! Two decades or so ago Ive played a bassman and a showman (really havent found anything close). Love to hear sound clips of any of these if you guys have them. I see em on the bay from time to time and just sit and stare....
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  6. Boot Soul

    Boot Soul

    Joined:
    Feb 10, 2009
    I own two of these amps, one in its original combo form, and another that was re-cased as a separate head, and that is "souped-up" with NOS Philips 7581A's in place of the specified 6L6GC power tubes.

    It is important that anyone who owns one of these understands a strange part of the layout of the preamp tube sockets. The preamp tubes from left to right (if viewing the amp from the front) go in this order: V1, V3, V2 , as they relate to their labeling on the schematic. They DO NOT go V1, V2, V3.
    link to schematic: http://img.photobucket.com/albums/v18/jetsetvet/bassrig/studiobassschematic.gif

    In other words, the 12AU7 tube is correctly placed in the third socket from the left. The first and second sockets from the left are specified for a 7025 or 12AX7A (pretty much the same tubes as each other...the 7025 is reportedly more "hi-fi", but they are the same gain factor).

    I don't know why the sockets are arranged this way, but what I am saying here is true.

    Realize that if one puts the 12AU7 where a 12AX7A is supposed to be, and a 12AX7A where the 12AU7 is supposed to be, the gain structure of the preamp is VERY different.

    A 12AX7A tube has more than five times the gain factor as a 12AU7 tube, as can be seen depicted in these charts:

    Fuzzy's Dead Mouse - 12AX7 Family Tube Substitution
    Guitar amp tweak - change the gain factor of your pre-amp

    If you happen to have these two tubes switched with each other (as simple logic would lead you to do), then you will have about five times too much gain for the five-band EQ section, and about one-fifth the gain specified for the V3 socket (the SECOND from the left) of the preamp.

    If you have this wrong and then make it right the preamp will have dramatically more gain (as it is supposed to!).

    On my amps, I rarely have the Volume (which is the Gain) turned up higher than 7 or 8 on the dial. I get a mildly warm overdrive beginning around 5 (when using a passive bass like a regular P or J). A higher output bass, like a G&L L2000e that I have, will get more overdrive at a given Volume setting. I never need to turn the Master Volume Output knob (on the far right) past 6 or 7, even when using a Bag End 4x10 cab that is rated to take 800 Watts (it is a pretty efficient cab, however).

    A possible tube swap is to try a 5751 tube in V1 and/or V3. These have slightly less gain than a 12AX7A, and may be more to ones liking. Just give it a try. It is never harmful to an amp to replace a preamp tube with another tube of lesser gain. Rolling (switching between brands and gain factors) of preamp tubes is kind of fun in these amps, because they are sensitive to subtle changes (more so than in something like an Ampeg V4, in my opinion/experience).

    No matter what, these amps are not going to grind/fuzz like an Ampeg, and they are not meant to. What they are is basically the ultimate Fender Bassman. I have read several comments here on TB where someone says that they love the tone of their old Fender Bassman, but wish it could go louder and keep up with a loud drummer and/or loud guitar player. The solution to that problem is the Fender Studio Bass. And, these amps do indeed pair up nicely with a dirt box between one's bass and the input, for those that prefer more grit/grind/fuzz/crunch to their sound.

    In the combo, one might consider replacing the original EVM-15B (relabeled as a Fender) with a more modern and efficient (and lighter weight) driver like an Eminence Kappalite 3015. The highs may not be quite as sweet, but you will get quite a bit more volume at any given setting of the Gain and Master Vol. Output.....and more solid lows as well.

    Another great feature of this amp is the line level output, because it comes off the output transformer, and thus carries the tone of the power section as well as the preamp section (unlike many amps that have their line out between the pre and power sections). It is a hot enough output that it can feed a slave power amp, and drive as many more cabinets as one cares to chain. I have tried this amp driving a single 15 cab and then hooked-up a Crest CA9 to the line out driving an Acme Low B4. Hence, all of the tube tone and power tube sag, and volume to part the Red Sea. Holy Moses!

    It is also cool to use the line output as a DI, by using a DI box such as a Countryman, (which is made to handle line-level inputs with no problem), and then send the balanced signal to a FOH/mix board. It allows one to DI their power tube tone, without needing to mic their cab.

    There are only two down-sides to this amp as I see it. First, it only has an 8 Ohm tap on its output transformer. I think it would be safe to run a 4 Ohm load, but it would likely have a little less power, and might wear out the power tubes a bit faster. Second, it would be nice if it had an effects loop between the preamp and power section, and a tuner out. That is hardly a realistic complaint though, since these were made from about 1978 to 1981 (I think), and that kind of pre-dates the era when these features became commonplace on amp heads.

    Fantastic Amp!

    [​IMG]
    [​IMG]
    [​IMG]
  7. gjesse

    gjesse

    Joined:
    Aug 12, 2011
    Location:
    Cleveland Ohio
    Welcome Boot Soul! Great info again! This is exactly the reason I started this thread, to get a better understanding of my gear and share the love of it with other like minded folks...I knew that head and cab looked familiar! I saw it on John's website, but didn't realize it was for sale! It's inspired me to break my head out of the combo as well, but I don't have the funds right now to do it right, so I just built a cab out of scrap wood in my garage....certainly a lot easier to transport now, even if it's not much of a looker. I'll post pics later. Let's just say it looks unique.
    Anyways, I got mine for about the same price on Craig's List, but I had to replace two power tubes and recap it to the tune of 300$, so I've got a lot in it at this point. I did have a rough spot last year and almost let her go for 800. SOOOO glad I didn't. Once I started running it into the Ampeg 15/10 cab it really showed off what this thing can do. It is worlds apart from the cab in the combo. It must have something to do with the shallowness of the Fender cab or something. Anyways, I think I'm gonna put it in a proper 'Fender' head cab eventually.
  8. Remus_Redbone

    Remus_Redbone

    Joined:
    Dec 27, 2010
    YES; I'm the proud owner of a Studio Bass and I pulled the amp section and built a cabinet to convert to a head. I played mine into a single 15 for a few years (an EV like the original, but not the original). My goal was to get the 15 into a larger ported cabinet to see if I could get more out of the amp and it was a very successful venture. I built the cabinet for the 15, and had the Thiel parameters for the speaker so I could calculate the proper porting. The single 15 has it's limitation, so I eased into playing through two 4 ohm cabinets using a series cable. After consulting with a few amp mechanics, I finally got brave enough to try the amp with a 4 ohm load. The head sounded great through an old Peavey 410, but I finally went big and bought an Ampeg 810. I thought that was almost the holy grail (just an SVT head short). The Studio Bass did great with the 810, but the sealed cabinet wants a little more power than the SB can produce (and I grew tired of moving a refrigerator every gig), so now the SB sits atop a new Ampeg 410 HLF. I think the new ported 410 HLF outperforms the 810 with this amp; more bottom with the same power. The Studio Bass and the 410 HLF spent their first weekend together this past 9/16 & 9/17; it was near perfect for my taste. Wish I had another gig this weekend....
  9. Boot Soul

    Boot Soul

    Joined:
    Feb 10, 2009
    Well, actually I bought the head and cab from JohnK about three years ago, and he still keeps the info about it, and how he restored and re-cased it on his web site......which is perfectly fine by me. It is really the last amp I would sell of the ones I have. The head case is a bit shallower front to back than in the original combo, and with the NOS Philips 7581A's (which each put out about 5 watts more than a 6L6GC), I found that it generated enough heat that it was melting the glue that held the Tolex on the back. So, I installed two ultra-quiet computer fans in it with a DC power supply that plugs into the power outlet in the back, and I shielded the inside of the back cover with thin aluminum sheet metal (a plate from a printing press at my Aunt's print shop). This works like a charm and I cannot even hear the fans. I also replaced the JJ preamp tubes with NOS JAN Philips 12AX7As and a NOS RCA Clear top 12AU7. This was a subtle improvement....I think that the JJ tubes were quite good as well, and a great value for how inexpensive they are.

    The whole thing is pretty compact and only weighs around 45 pounds (maybe 50). It will drive an 8 Ohm Bag End 4x10 just fine...loud as I could want. When I have brought it to a few jams most people think it is just an older blackface Bassman....until I (or they) plug into it. Then a few heads turn. Then they see all that glass glowing in the back. Then they smile. :cool:

    The thing looks like it is brand new (the case is new....from Mojo). I feel really lucky to have been able to buy this from JohnK. He probably never would have let it go if it weren't for the fact that he owns many, many other incredible vintage amps. More cool tube heads than even Tom Bowlus, and that is saying something!

    Here are the deets on his web site:
    Fender Studio Bass

    Thanks JohnK !
  10. johnk_10

    johnk_10 vintage bass nut Supporting Member

    Joined:
    Feb 16, 2008
    Location:
    Thousand Oaks, CA
    Disclosures:
    John K Custom Basses
    yep, that particular Studio Bass was a beauty! ( & i actually regret selling that one ;) )

    i ended up replacing it with a super twin (converted to a head) since it's basically the same exact amp (only with a funky distortion control which i never use). It has a 4 ohm output tranny so i run it with 2x15 JBL K140's in a '70's fender bassman cab. i love it, so lately, it's become my main gigging amp.

    [​IMG]
  11. will33

    will33

    Joined:
    May 22, 2006
    Location:
    austin,tx
    Disclosures:
    Use of this field for any other purpose is prohibited
    Drooling over here........

    Haven't seen one for sale locally yet, when it happens it will be mine. The bassman is my alltime favorite tone amp, just need one with this kind of power.
  12. gjesse

    gjesse

    Joined:
    Aug 12, 2011
    Location:
    Cleveland Ohio
    So about my lack of preamp drive...I just checked, and the V2 position (third from left looking from the front) is indeed a 12AU7. I was really hoping the tubes would be switched up, as it would explain the lack of drive in the preamp. Maybe I should just replace the 12AX7's...the ones I've got are the originals. I don't get evidence of overdrive until about 9 on the gain dial. I can pin it at 10 and it's still almost a completely clean signal. I'll try some other tubes and post the results...
  13. Remus_Redbone

    Remus_Redbone

    Joined:
    Dec 27, 2010
    Mine is clean up to about 8 with my "P" bass that has an SD Antiquity II pup, but it starts getting gritty at about 6 when I use my T-Bird. Input level makes all the difference in the world.
  14. gjesse

    gjesse

    Joined:
    Aug 12, 2011
    Location:
    Cleveland Ohio
    maybe I'll just add a preamp to my input chain...just would rather juice up the onboard pre if possible with hotter 12ax7's...started reading reviews of the different 12ax7's in current production..seems the JJ golds are a good choice for high gain and low noise. That or the Tung-Sols.
  15. johnk_10

    johnk_10 vintage bass nut Supporting Member

    Joined:
    Feb 16, 2008
    Location:
    Thousand Oaks, CA
    Disclosures:
    John K Custom Basses
    my supertwin starts getting gritty at around 5-6 on the input volume.
  16. gjesse

    gjesse

    Joined:
    Aug 12, 2011
    Location:
    Cleveland Ohio
    what are you using in the V1 and V3 positions?
  17. johnk_10

    johnk_10 vintage bass nut Supporting Member

    Joined:
    Feb 16, 2008
    Location:
    Thousand Oaks, CA
    Disclosures:
    John K Custom Basses
    RCA 12AX7's
  18. gjesse

    gjesse

    Joined:
    Aug 12, 2011
    Location:
    Cleveland Ohio
    I've got the original fender labelled sovteks in mine. I guess I'll just have to experiment with some other brands...probably start with the JJ golds.
  19. johnk_10

    johnk_10 vintage bass nut Supporting Member

    Joined:
    Feb 16, 2008
    Location:
    Thousand Oaks, CA
    Disclosures:
    John K Custom Basses
    the original fender tubes wouldn't have been sovteks, but either GE's or RCA's. IMO, sovteks are okay, but i prefer their either their LPS version or JJ ECC83's and/or ECC803's.
  20. Boot Soul

    Boot Soul

    Joined:
    Feb 10, 2009
    I don't believe there were Fender labeled Sovteks in these amps or anywhere else. The original Fender labeled preamp tubes are RCA, at least I'm pretty sure that they are in my original combo Studio Bass, as shown in pic above.

    My combo has all its original tubes, except for two of its six power tubes, which are labeled Peavey, but otherwise identical in appearance to the other four power tubes that are labeled Fender. All of these power tubes are grey plate RCA 6L6GC tubes, as far as I can tell. The info regarding the originality of most of these tubes (and that they were rebranded RCA tubes) came from the original owner from whom I bought the combo, about five years ago or so. I really can't see why he wouldn't have been honest about that information because I had already won the Ebay auction that it was sold through, before I learned those details from him.

    With respect to your desire for more overdrive, I agree with others that you would be better off just increasing your input signal a bit, than trying to find a brand of 12AX7A tube that might be a little hotter than other brands.

    Barge Concepts makes a little box that I would like to get for this purpose, which is unique because it will boost the input signal while still giving the ability to adjust the impedance of that input signal, so that the passive tonality isn't changed (so they say). It can also be used to tame the output of an active bass, and lower its output impedance to be more like that from a passive bass. It just seems like such a smart idea, and I have never seen any other box with this set of features.

    "The GLZ’s variable impedance control alters the resistive output of the buffering stage, to make the output signal appear more like a passive signal."

    Check out the GLZ-1
    [[...Barge Concepts GLZ-1 & BV-1...]]
  21. gjesse

    gjesse

    Joined:
    Aug 12, 2011
    Location:
    Cleveland Ohio
    I was assuming they were Sovteks, based on something I read online...shows what that'll get ya.
    Good to know they're RCA/GE's. I'll look into the GLZ-1, BootSoul. Could be just what I need.
    I already ordered the JJ gold 12ax7 to try out in V1. If there's no improvement over the originals, I 'll find another place to use it I'm sure.

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