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Is there a 2U all-tube bass amp?

Discussion in 'Amps and Cabs [BG]' started by donahue, Jan 16, 2021.

  1. donahue

    donahue Supporting Member

    Jun 10, 2015
    I was just thinking and nothing is really coming to mind? No hybrids etc. All tube. Is there such a thing?
  2. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    No, not with a power amp
    Edit: I stand corrected
    Last edited: Jan 16, 2021
  3. cardinal


    Jan 13, 2016
    Aguilar DB359
  4. Wasnex


    Dec 25, 2011
    (Long Discontinued) Aguilar DB359. 200W, Fender tone stack, 50lbs.
    Here is an image from an old TB Ad.
    Mine measures 17 1/8 from front to back. It's bulky and unwieldy and the front panel is not heavy enough to support the amp IMHO. Because of this, the edges of the front panels are often pretty rough for amps that have been racked and roaded. Probably best if you use some sort of a rack sleever or find a way to attach rear rack rails to support he back of the amp. Mine has a reserved slot on top of a piece of cardboard on a seminar table ;).

    Also a lot of users complained that their amp was noisy and lacked power. I think this may be due to tube rolling or jacking with the internal controls. There are three internal trimmers that are not considered user adjustable. 1. Phase inverter (PI) balance, 2. Clip Level, 3. DI level.

    Mine was noisy and picking AM broadcasts of Rush Limbaugh. I fiddled with the internal factory controls a couple of times and tried to trouble shoot the problem. The last time I must have gotten lucky with the PI balance, because the amp started sounding better, the noise level went down, and the AM radio seems to be gone. I wouldn't say it's the quietest amp now, but it's not too bad.

    A lot of people claim 5751s sound great in this amp. Mine came with a 5751 in V2 and an Aguilar branded 12AX7 in V1. The Clip Level adjust is on the input of the first triode of V2 and the PI adjusts the plate resistance of the second triode of V2. So changing the tube type without properly adjusting these controls could cause a problem. You need test equipment to properly adjust the controls.

    I tried several models of current production and NOS 5751s in the amp. I also tried every possible combination: 5751 in V2, 5751 in V1, 5751 in V1 and V2. I preferred current production Mullard ECC83 in V1 and a JJ ECC803S in V2.

    I was pretty frustrated with the amp until I finally got the PI dialed in. It didn't actually sound bad, it just didn't sound good. Like it had a hollowness to it. Hard to describe, but it relates to the sensation that the amp does not have power. Actually it reminded me of the feeling you get one you have two speakers and one of them is out of phase.

    Now I think it's a decent sounding amp and about as loud as you would expect for 200W. Tonewise it's in the same universe as the Orange AD200B and Sadowsky SA200. The SA200 is way easier to carry despite requiring more rack spaces. It's not very deep so it's not bulky or oddly balanced. The SA200 is also by far the most versatile of these three amps. I would say the DB359 is closer in tone to the SA200 than the AD200B. The AD200B and DB359 have similar tonal versatility. IMHO the Orange tone controls work slight better, but the DB359 has a deep switch which is usable for a thicker sound. The DB359 also has a bright switch, but I can't imagine why anyone would use it, unless they were running a super dark cab. I practically run my Treble control all the way down and the amp is still very bright. Between the three I think I would them 1. SA200, 2. AD200B, 3. DB359. I learning to play through a blackface Fender, so the AD200B sounds and feels like home.

    Also many users comment that this amp is not great for distortion. Mine is better know that I have gotten the internal controls sorted, but I have much better amps for distortion. It does develop a nice tubey quality when pushed, as long as you don't push it too hard. The sound gets a certain sort of harmonic shimmer and the notes develop a certain thickness and bloom.
    bbh, murphy, Kenova and 3 others like this.
  5. donahue

    donahue Supporting Member

    Jun 10, 2015
    Thanks very much. Very informative. Kinda strayed me away from a DB359 coupled how expensive and rare they are.

    I'm surprised no one else tried to cram an all-tube into 2U. Kind of a hard thing to build and design I'm sure but once in a 2U case, hella convenient.
    Wasnex likes this.
  6. gregbackstrom

    gregbackstrom Supporting Member

    Feb 3, 2005
    Tacoma, Washington
    The Ashdown CTM-30 Little Stubby is a two space unit. It’s pretty powerful too. I bought one shortly after they were introduced, and sold it too soon!
    son_of_mogh likes this.
  7. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    There’s a good reason why it’s not done... it doesn’t fit well and the additional materials and labor greatly add to the cost. 3U is a MUCH better package size (at this power level)
  8. Jefenator

    Jefenator Supporting Member

    Aug 22, 2008
    I had a 4U Mesa Bass 400 in a rack case and found that to be pretty convenient.
  9. Wasnex


    Dec 25, 2011
    Price on the DB359 seems to fluctuate drastically. Mine was $956 shipped and its in near mint condition.

    I agree with Agedhorse, two rack spaces is not ideal for a high-powered tube amp. The output tubes have to lay down to fit, and I am pretty sure the height limits the design to toroidal transformers, which are more expensive.

    I think using three rack spaces allow you to develop a more balanced carry with less depth. The DB359 feels heavier than it is, and my guess is the reason is because the mass is spread out so much that you have to deal with rotational inertia. Maybe I would feel different if it were 10-15lbs lighter.

    There were apparently at least two versions of the amp. Here is a gut shot of an amp that has the same circuit cards as mine.


    Here is a gut shot of the other version.

    Another quirky issue I forgot to mention. The output tubes are held in place by a vented rear plate that screws into place. Some sort of spongy heat resistant material is inserted between the top of the tubes and the plate, and this acts as a tube retainer. A problem with this is the height of tubes varies quite a bit, even within a specific brand and model. So in addition to buying a matched set of tubes, you need to be concerned with finding tubes that are a certain height.

    For fun I tried a set of JJ KT88s in the amp and I believe they extended beyond the plane of the rear plate. The amp came with a good set of Aguilar/Svetlana-labeled 6550Cs (pretty sure these are Winged-Cs). I couldn't hear any difference between the JJs and the original tubes.
    Last edited: Jan 17, 2021
  10. donahue

    donahue Supporting Member

    Jun 10, 2015
    Cool pics. Thats an engineering marvel imo but does look like a pain to build and service. I can see why they probably aren't produced any more. The whole thing just looks expensive.

    I didn't want to turn the thread into a DB359 thread but there aren't many other 2U tube amps to discuss I guess.
    Wasnex likes this.
  11. Wow....look at them big toroids!
    Bill Whitehurst, Pocket4 and Wasnex like this.
  12. bassfreakah


    Mar 26, 2011
    Endorsing Artist Ernie ball strings
    It is nice to see an amp with some real parts in it!!!
    Not just a bunch of ic’s.
    Jefenator likes this.
  13. NKBassman

    NKBassman Lvl 10 Nerd

    Jun 16, 2009
    Winnipeg, MB, Canada
    I know there are 1U tube preamps out there, and at least a few low-wattage 1U tube power amps marketed towards guitar players.
    donahue likes this.
  14. Bitterdale

    Bitterdale Natural Born Lurker Supporting Member

    Dec 4, 2010
    Ocala, FL
    Not specifically a bass amp, but the discontinued Peavey Classic 50/50 tube power amp was only 2u.
    Standalone and Bill Whitehurst like this.
  15. Kendescending


    Feb 27, 2020
    The SWR Interstellar Overdrive is a 1U all tube unit with 2 EL84 tubes. It's mainly a preamp, but it does have a 5 watt speaker output (it's actually fairly loud). The speaker out is not ideal in a live band setting, but great for recording. It also worked out well running through the switchable effects loop of my Mesa M2000 bass amp many years ago.

    I realize it's a little off topic, but worth mentioning.
    Last edited: Jan 17, 2021
  16. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    What’s wrong with ICs? Aren’t they real parts too?
    Balog, thetragichero, Geri O and 6 others like this.
  17. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    We alas made some 2U tube power amps, but the power levels are quite a bit lower than 200 watts.
  18. I believe my ADA TS100 tube power amp was also on 2ru. And it was loud. At least the fans were!
  19. 1958Bassman


    Oct 20, 2007
    Many times, picking up radio stations is due to bad solder joints, dirty controls/switches, proximity to the broadcast towers and imperfect ground path. I live very close to several towers and I have had radio interference, but that ended when I resoldered some of the joints. It's important to remember- the ground path extends from the instrument to the breaker panel, it's not just in the amp.
  20. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

    Mar 3, 2021

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