Which Section of The Amp to Plan First?

Discussion in 'Shock Brother's DIY Amps' started by skypn, May 19, 2019.

  1. skypn

    skypn TDPRI Member

    Age:
    56
    Posts:
    23
    Joined:
    May 6, 2019
    Location:
    Dearborn, Mi
    Newbie is back. I have been doing a lot of research and learning on the web since my first post here.
    In my relentless quest to build a 10w to 20w tube bass amp, I keep running into dead ends. I can't seem to find one already made, so I think I will need to bend one to my will.
    What is the first component that determines the rest? Or is it just a house of cards thing?
    I was thinking of nailing down the power section first as (in my limited thinking) without power, how can you test the rest?
    I was going to try building a Traynor YBA1, as I would get more use out of it than the 5F1. In the 5F1's defense, I would have better chances of success, seeing there is SO much info out there on it.

    I cant seem to find the trannys for the YBA1 though. I have parts numbers, but the web doesn't know them.

    PT #78632
    OT #68348
    L1 #68347

    I have a decent schematic that I believe I understand.

    http://www.lynx.net/~jc/661021_YBA1.gif

    The B+ is 450 VDC, guessed by the rating on the caps, and I read an article where one was afraid that the rating of the caps at the B+ left no "wiggle room". The PT has a center tap, so I guess it's 900VDC across the "outside" and the the standard 6.5VDC for the heaters and lamp.
    Am I at least on the right track?
    If not where so I go? (loaded question, I know :))
    TIA
     
    sds1 likes this.
  2. Whatizitman

    Whatizitman Tele-Afflicted

    Posts:
    1,825
    Joined:
    Feb 18, 2018
    Location:
    WV
    The yb1a and 5f1 are vastly different amps. The 5f1 is SE, for starters.

    I’m a noob myself. But I think I would first decide which output design I would want for a the amp. That is, which tube complement and wattage, and output tranny. Also keep in mind that a bass amp requires increased output wattage capacity and headroom to handle the low end.

    That said, I think that pretty much rules out a SE design. The amp in my avatar is an SE ‘bass combo’. I’ve never even tried plugging in a bass in it. It struggles enough with my tele. I replaced the original Jensen 12 inch - it was buzzing bad at anything over 6 or 7 volume. I can’t imagine what my pbass would do to it. Too scared to try.
     
  3. Snfoilhat

    Snfoilhat Tele-Afflicted

    Age:
    38
    Posts:
    1,008
    Joined:
    Apr 8, 2016
    Location:
    Oakland, CA
    If you start an amp project with perfect freedom (budget, design, no parts already in hand), then the place to start is choosing a power tube. Let's say you commit to following the Traynor YBA1. The power section is a pair of 7027s in push-pull configuration. You then download the 7027 data sheet, look at the typical operation, pick a ballpark plate voltage, and write down all the target numbers for things like screen voltage and plate current and the rest.

    Then you choose your power and output transformers based on those numbers. You go to the PT manufacturers' data sheets and calculate B+ in DC volts from the listed AC volts. Some manufacturers have done this for you (like ClassicTone for example). That's where your weird 450V - 900V miscalculation is coming from. Do some reading on rectification, the process of getting DC from AC. PT has to give you the right plate voltage (B+) and the right total current for the amp (most of which is power tube plate current), and have the right heater windings (enough 6.3VAC for all your tubes). OT has to have the right primary:secondary and power handling, which you learned from your data sheet. Here's where you decide what speaker or speakers you will use, so ensure you have the right primary:secondary.

    After that, PT, OT, tubes, and speakers have all been chosen, and so you source a chassis and build the power section, just as you were thinking. Once it is built and tested, you can complete the original design, or mod it, or even go in a different direction, so long as you pick a preamp that is roughly similar. Good luck

    Just for the purpose of illustration (I don't know if 7027s are even made anymore or how much NOS ones cost). Follow the same algorithm for any tube.
    7027.png
     
  4. Silverface

    Silverface Poster Extraordinaire Ad Free Member

    Age:
    67
    Posts:
    9,096
    Joined:
    Mar 2, 2003
    Location:
    Lawndale CA
    Don't think so much about power as volume. The two are NOT necessarily closely related - speaker complement (cone size(s) and number of speakers), cabinet design, and speaker sensitivity are more critical to output level, as is the specific design and tweaking of the output stage.

    Honestly, if you don't know what power transformer to even start with you probably lack sufficient electronics knowledge to *design* an amplifier. A part number is not a hurdle for anyone capable of designing an amplifier, because they understand amplifier specifications and know in advance what they need.

    And as mentioned above, the comparison of two amps of TOTALLY different types is a real concern.

    Designing from scratch is exponentially more complicated than building a kit - even with *basic* electronics knowledge. And it's in a different universe from "assembling" a kit from parts and a layout.

    To design an amp you need to first know what your overall goal is - what its use will be from a practical standpoint. Then it's down to engineering time - starting with the power supply that will handle the output power, the current, and voltage requirements of the types and numbers of tubes you need. Draw up the schematic from back (power supply) - to front.

    If you don't know how to read and interpret details on a schematic fluently - don't even think about designing an amp. Try to find electronics courses, books etc, learn the subject - then build a kit (not just assemble one with no knowledge like a plastic car model).

    I'm not trying to be discouraging - I'm trying to be realistic. It just sounds like what you *want* to do is far beyond your capabilities.
     
    jimytheassassin likes this.
  5. FenderLover

    FenderLover Friend of Leo's

    Posts:
    4,642
    Joined:
    Jun 11, 2009
    Location:
    Minnesota
    Nice tube but expensive. I don't know if they are reproducing them either, but 6L6GC works fine in their place. I had an Ampeg V4 that I put 6L6CG's in 25 years ago, and the friend that bought it still has the same set in the amp.
     
    Paul-T and Snfoilhat like this.
  6. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    7,482
    Joined:
    Dec 29, 2012
    Location:
    United States
    10 to 20 watts = EL84 or 6V6 power tubes.

    Consider doing a Fender 5F6A Bassman kit. It does about 40 watts and was built for bass but as we know is one of the sweetest guitar amps ever built. Use 4 modern, lightweight high efficiency speakers and you got yourself a nice bass amp. It's on the advanced side for a first time build but it can be done, especially if you have a local tech that can come in and save the day if you run into problems.

    If money is an issue you can build the chassis first and use it with an existing cab and then when able purchase the Bassman cab and speakers.
     
    Paul-T, Snfoilhat and sds1 like this.
  7. FenderLover

    FenderLover Friend of Leo's

    Posts:
    4,642
    Joined:
    Jun 11, 2009
    Location:
    Minnesota
    Power and volume are definitely related, of course, volume being more variable (on purpose) for a given amount of power.

    But you design an amp by deciding how much power you want because tubes and transformers are chosen from that criteria.

    Decide on the power you want (based on amplifiers you already know).

    Choose the tube(s) that will get you there (again, based on amps that you already know).

    Determine the PT and OT needed to support it. That can also be done based on amps that you already know. The preamp can be anything you want depending on your style and build constraints.
     
    sds1 likes this.
  8. jhundt

    jhundt Doctor of Teleocity

    Age:
    65
    Posts:
    11,075
    Joined:
    Mar 23, 2003
    Location:
    Netherlands
    I don't want to rain on your parade, but... a 10-20 watt bass amp is going to be almost totally useless for any application. You will be wasting time and money. You could save a lot of both by just buying a little cheapo transistor-powered toy amp.

    If you want a pre-amp for recording, then look at runoffgroove's Ginger flip-top.

    If you want a small amp for home practice - get a little cheap amp as described above, or just use a guitar amp.

    If you want a small amp for rehearsal - 20 watts of bass is never going to be satisfying.
    As a bass player, I can't imagine any kind of reasonable and authoritative tone in a group situation with anything less than 100 watts, even at low-level rehearsal volume.

    I bought a 450-watt Behringer copy of an Ashdown design that sounds really good for $100.

    There is a reason why you can't find an amp like you have described, ready-made or even in kit form. There is no market for such a thing. Nobody in this world needs a 20-watt bass amp.
     
    robrob likes this.
  9. skypn

    skypn TDPRI Member

    Age:
    56
    Posts:
    23
    Joined:
    May 6, 2019
    Location:
    Dearborn, Mi
    Thank all of you for responding.
    Whatiz....I realize that I was comparing two totally different amps, and I guess what I'm asking IS, where do I go from here?

    Snfoilhat...so, with the power tubes being if not the most, at least a major factor, and the 7027 not an option, does this exclude the YBA1 from consideration? Could I simple replace them with 6L6GC's as FenderLover suggested (I don't think I can)? The only reason I was considering the YBA1 was I liked the idea of a single speaker, low wattage Bass tube amp. I am starting to think there is no such animal. If there is, ever was, please tell me. I will start to look at various power tube spec to reduce my basic ignorance.

    Silverface...Please don't be concerned I compared two totally different amps. My comparison was not based on me not knowing the difference, which l do, but on available info about each on the web. It is not my desire to "design" a < or = 20 watt amp single speaker little lug around and not knock the Mrs' teeth out Bass practice amp, at least not at this time. If the 5F1 would fit that bill, with the appropriate Bass speaker (and I'm guessing OT) I would start building it tomorrow. I would love it if someone else had designed one, and I could have the learning experience of building it (studying the schematic, making a turret board), and the added practice of planning the placement of parts, and pots, jacks etc. in the chassis, and building the cab (I am a seasoned woodworker with a nice set of tools), and upholstering it. I want to level up from making a kit.
    Please believe me when I say you are not being discouraging, but I wish you would be more specific than simply saying I don't know enough yet without pointing me where to go learn. I will say, I at least know basic electronics. My ignorance lays in not knowing amp specifics, which is why I am here asking stupid questions. If you truly believe that I am beyond all help here, now, I will go back, start at the very beginning, and try again in 6 months, as to not waste more of anyone's time. I would rather go back and learn (Bass) amp specific things. Again, I don't often express myself well in the written word, and if I sound ungrateful for your input, I assure you, that is not the case, I am just looking for direction.

    Robrob...most of what I have learned so far is from you, and Uncle Doug on YouTube. It is not my desire though to build a four speaker amp at this time. I have already built a big Bass cab, have a decent 400w (SS) head, and if I need power/loudness, I am already covered. All I really want to do is build a little, tiny, Bass amp. Building on that, someday I might build a monster :)

    FenderLover...I haven't found the amp I am looking ...yet.

    Again, I do truly appreciate everyone's input, and hope that I have not offended anyone through my ignorance, inability to express myself, or, as I read and re-read this post, my stubbornness.
     
  10. skypn

    skypn TDPRI Member

    Age:
    56
    Posts:
    23
    Joined:
    May 6, 2019
    Location:
    Dearborn, Mi
    jhundt...well, that settles that. Thank You
     
  11. Paul-T

    Paul-T Tele-Meister

    Posts:
    132
    Joined:
    Nov 23, 2018
    Location:
    London
    speaking as the person who made things more complicated by suggesting the Ampeg B15/portaflex... do what Rob suggests and make a 5F6A bassman.


    It's a really good bass head which will have more bottom end and dynamic range than any 20W amp. You don't have to use 4 x 10... you could build it into a tiny 15 inch combo, or head plus cab. Then if you want to upgrade later... you can sell it on to both guitarists and bassists. Win win!

    The Bassman is known as a great bass amp... but underpowered. But if you're considering a 5F1 or 20w, that's not an issue here. I've hired one for my bassist for recording, it sounded great.

    The 5F6A is well-documented, many people will steer you through. You can buy a chassis and all the parts easily and for not too much money. It's a no-brainer.

    Otherwise you'll be designing your own circuits, pondering multiple variables, and six months from now will still be planning, when you could be playing.
     
    Last edited: May 19, 2019
    Snfoilhat likes this.
  12. Snfoilhat

    Snfoilhat Tele-Afflicted

    Age:
    38
    Posts:
    1,008
    Joined:
    Apr 8, 2016
    Location:
    Oakland, CA
    That YBA1 is essentially a Fender Bassman 5F6a-alike with less available tube selection. But roughly the same physical size and power.

    The historical tweed Bassman might have been released with four 10" speakers but you can choose any speaker setup you want. This is so common that several output transformer manufacturers make reproduction Bassman OTs with multiple secondaries. Single speaker? No problem. Single speaker combo or head and separate cab, it's your choice.

    In the broadest sense, the only difference between guitar amps and bass amps is EQ. The people arguing for a real bass amp are making some educated assumptions about what kind of EQ possibilities you might wish you had. The build a proven guitar amp people are giving you the chance of liking the EQ when you plug a bass in, with the very sound back-up plan that at least it will also be great for guitar if only so-so for bass.

    You, the end user, haven't actually said anything about the EQ you want, just the amp size, leaving too much of the huge design space (or whatever) unresolved.

    The problem with punting questions of EQ to 'proven' bass amps is that there are almost no vintage tube proven bass amps! The long history of them from the beginning to today gives us a few that made history as guitar amps:lol:, a few Ampegs that are quite difficult to pull off and have limited use-cases (B-15 is small, SVT is huge), and a ton of meh amps that are all over the spectrum w/ respect to EQ.

    Edit to say: I would take the fact that you landed by your own process/intuition on the Canadian copy of the exact amp that @robrob recommended to you (with the one useful change for bass of solid-state rectification replacing the rectifier tube, and one bad change you should revert, 7027 -> 6L6GC or 5881, as @FenderLover suggested), as serendipity!
     
    Last edited: May 19, 2019
    Nickfl, robrob and Paul-T like this.
  13. sds1

    sds1 Tele-Holic

    Age:
    42
    Posts:
    967
    Joined:
    May 4, 2017
    Location:
    Orlando, FL, USA
    Don't let him get you down. Notice nobody agreed with him. He's not very DIY-spirited as you may have noticed. You will never seem him actually helping anybody with a build, he's more of the drive-by condescending type.

    Stay the course, plenty of great people to help you along. You are getting great advice otherwise.

    I was going to direct you to this great recent discussion for reference :

    http://www.tdpri.com/threads/help-chosing-first-bass-amp-build.949323/

    But I see it's your thread! :lol:
     
    Last edited: May 19, 2019
    FenderLover likes this.
  14. skypn

    skypn TDPRI Member

    Age:
    56
    Posts:
    23
    Joined:
    May 6, 2019
    Location:
    Dearborn, Mi
    OK Gentlemen...this will be my battle plan. I will first build a 5F1, as I have plenty of of 6 stringers friends who will be more than happy to test drive it for me, and then sell it at cost of materials, the profit being the experience. then I will move on to something like 5F6a. I want this all to be a learning experience. Thank you Paul-T, Snfoilhat and sds1 for the encouragement.
    For the record, my desires for a small Bass tube amp was not driven by need, because I have a Fender SS and Pignose Hog 30, to fill that bill...just want a learning experience.
    I feel that any amp I build will not be a waste of time, if I am learning from it.

    Paul-T...do you think I could get away with a 10" speaker in a 5F6a? just thinking about weight.
    Ever forward....
     
    sds1 likes this.
  15. VintageSG

    VintageSG Friend of Leo's Ad Free Member

    Posts:
    2,949
    Joined:
    Mar 31, 2016
    Location:
    Yorkshire
    https://www.tube-town.net/ttstore/Kits/Verstaerker/TT-Kit-BFlex::8113.html

    Not suggesting you buy a kit from Europe. The shipping would be extortionate, but bass kits do exist. Have a look around the TubeTown website at some of their kits. They have a section ( project page ) with the schematics to pore over.

    I built a Champ-a-like ( WF-55 ) from a British supplier. It has a solid state rectifier in place of a valve. No biggie in a single ended amp. I beefed up the capacitance in the power supply stages and it does OK as a bass amp for noodling. It still farts out as the volume rises, but overall?, it's quite sweet really. Low notes eat power!
     
    Paul-T likes this.
  16. Bendyha

    Bendyha Tele-Afflicted Silver Supporter

    Posts:
    1,883
    Joined:
    Mar 26, 2014
    Location:
    Northern Germany
    The 18W Bassman 20 is about as small and simple as tube bass amps come, with its P-P 6V6 output. The original used a 15" speaker, but that could be changed. With a few changes, it is a very good, basic guitar amp.
    upload_2019-5-19_23-50-5.png
     
    Wally and robrob like this.
  17. skypn

    skypn TDPRI Member

    Age:
    56
    Posts:
    23
    Joined:
    May 6, 2019
    Location:
    Dearborn, Mi
    Bendyha... that certainly is worth a look see. THX
     
  18. jonrpick

    jonrpick Friend of Leo's

    Posts:
    2,237
    Joined:
    Mar 17, 2014
    Location:
    Marietta, GA
    Personally I'd take a blackface Champ (not a 5F1) circuit because of the cleaner preamp (due to the lossy tone stack) and better tone control, and scale it up. Use bigger transformers (both of them) and use a big stout output tube like a KT88.

    Keep the preamp stock.

    Mount the chassis in a taller 1x12 or 2x10 cab and run with it.
     
  19. printer2

    printer2 Poster Extraordinaire

    Posts:
    6,250
    Joined:
    May 24, 2010
    Location:
    Canada
  20. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    7,482
    Joined:
    Dec 29, 2012
    Location:
    United States
    My 5F6A Bassman head cab with a 6" hemp cone practice speaker:
    [​IMG]
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.