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Build your own Bass Amp

Discussion in 'Amps and Cabs [BG]' started by jazzcatb17, Sep 5, 2003.

  1. jazzcatb17


    Dec 27, 2002
    Louisville, Ky
    Well i've been searching for the perfect bass amp for quite awhile and haven't found anything thats just right yet. So I thought i might give a shot at building my own. It would be class A tube so no circuit boards or anything, and it would have the most basic controls. I figure how tough can it be? anyways, im looking for some info on schematics, tube manufacters, pots manufacters and whatever else might be helpful, any info would be greatly appreciated.
  2. Just to give you an idea what you're getting into:

    A class A tube amp is going to be four things: heavy, hot, low powered, and highly inefficient. Since you want class A output, you're probably going to want a high powered emitter tetrode, either a transmitter or a large scale inverter tube. To use a ceramic radio transmitter inverter like Kevin O'Connor uses in his London Power Spectrum amp(a pair for 700 watts class AB1) would be relatively cheap for the tube: $40-60 for roughly 30-45 watts class A output. Yep, I said 30-45 watts.

    Here's the fun part. You're going to have to find a power transformer that can supply the 1000+ volts for the plate voltage of the tube, 500+ volts for the control grid (Edit: I'm stuck in push/pull land; single-ended amps are CATHODE biased, so it would be the screen to cathode connection, not the grid) another 300+ volt tap for the preamp, and still be able to supply the filament voltage and do it all at the required current rating for every single tube in the amp. Heyboer could make one for around $800-1000 (my guess).

    Now you'll need an output transformer that can take all that high voltage and connect to a speaker. I'd say that'll be another $500 at least, probably more. Did I happen to mention that the power transformer will weigh 35-50 lbs and the output transformer will weigh 30-40 lbs? You need to know this because that means you'll require a chassis of at least 18 gauge steel or aluminum to support the weight and it will add another 5-10 lbs of weight itself.

    Caps, resistors, sockets, wire, pots, and other assorted goodies probably will be another $200-250, and that's assuming you get the circuit right the first time and don't have any oscillations that could damage the tube/s. A driver for a single ended amp of that size would have to be able to disappate about 5 watts itself, so you're probably also going to have to use a power tube to drive the power section, probably a 6V6GT or a 5881.

    There's still the preamp, but Fender circuits are widely available,and the Dual Showman preamp is THE standard for tube bass preamps (the Mesa 400+, Trace V series, Alembic FX, and a host of others are all based on it) so at least that much will be relatively easy. If you've never done any electronics work, you'll need about $1500 in test equipment just to make sure everything is OK while you're building it. You're looking at roughly $3,300 in parts and equipment alone and probably two to five years of part time building, unless you can devote full time work to it, in which case you're looking at 1 year or a year and half.
  3. Mcrelly


    Jun 16, 2003
    Minnesota, USA
    I forget the TB'er from sweden? he built cabs, amps, effects etc.

    anyone know who I'm talking about? circular clock? ring a bell?
  4. jazzcatb17


    Dec 27, 2002
    Louisville, Ky
    ok, so it might be a little tougher than i thought....:D but anyway im still interested in doing this thing, maybe not class A though. Possibly just build a custom preamp and go QSC for the power amp.
  5. A preamp is a lot more do-able, but I strongly suggest you enlist the help of someone experienced in electronics first. It'll still cost about twice as much as buying a used amp or preamp, but you will have learned what makes them tick.

    I think you'd do better getting a Silverface Bassman or one of those kit amps based on the 50 watt Bassman and go through one of them before you attempt to build something from scratch.

    If you like the tone of an old Sunn look for a 50 watt Dynaco an eBay. The earliest Sunns were simply Dynakit (kits of Dynaco) amps with a preamp on them. They bought the parts FROM Dynaco. Once you hear a 50 watts of tube growl through a resonably efficent cabinet, you'll forget all that high-powered solid state nonsense. ;)
  6. CrawlingEye

    CrawlingEye Member

    Mar 20, 2001
    Easton, Pennsylvania
    I'm not sure if he's from Sweden, I think he's from the Neatherlands, but he would be the person to contact.

    BGavin's knowledgeable on many of the same things as Joris, both are very intelligent and good people to talk to on this subject. :)

    Edit: There's many sources online in regards to the same things, as well.

    I believe one's titled 'diyaudio' or something like that, which is a forum.
    If you head over to headfi.com (a headphone forum, yes) there's many people who build their own headphone amps, and are very good at this type of thing. Jan Meier from meier audio builds a couple amps, and in all probability would not be opposed to giving you some pointers, same with Tangent and many others.

    Good luck. :)
  7. thumbtrap


    Jun 26, 2003

    They're all guitar oriented. But they have tons of information to help you get started.

    Class A is interesting and all that but don't let folks talk you into wierd stuff just because it's hip. The class A amps I've done sounded OK - but I can't really give up my sagging B+ compression. For bass - I'll promise you that you've never heard an all tube class A bass power amp.

    All that said... the other guys are right and trying to help you out.
  8. Psycho is right, as usual. Class A??? WHY???

    If you want to build your own amp, fine, but don't expect to save any money. You can buy a vintage SVT for less than the parts would cost for a conventional push-pull amp of similar power.

    However, for the learning experience, I would suggest going for a small three or four tube guitar amp such as the single ended design found free on the Angela Instruments website. www.angela.com

    http.vintageamps.com also has a forum on amp building. Read through some of the posts and you'll see that getting a good noise-free amp is not as easy as it appears.

    Building tube amps can be a nice hobby, but expensive. And if you aren't electrically inclined or are prone to carelessness, it can be deadly. The voltage supply can easily be over 500 volts. One mistake, one careless touch with a finger or screwdriver, and you're dead. That's D-E-A-D....:eek:
  9. Here's my take.

    First you don't really need to spend that much on equipment. I got by with a multimeter, a soldering iron, and a really crumby oscilloscope I borrowed from my dad. Also, I was REALLY careful about touching high voltage. What I built was a preamp, based on the Ampeg B-25. It still works, and nothing blew up. For the power supply I borrowed the voltage from the tube power amp I already had.

    I had this old heathkit hifi preamp I used for the chassis and parts. Added a couple of switches, and didn't use one of the knobs and next thing you know (actually about 3 years later) I had myself a working preamp. Now I should admit that I'm an EE by training so lots of this stuff made sense to me already, but if you want to have some fun and learn something, go for it!

    Also, there is a magazine called AudioXpress that is written for amateur and DIY builders. Check out AudioXpress for more info. They also run a number of speaker building articles, and some are even geared towards musical instruments.

    Be safe and Stay Low,

  10. thumbtrap


    Jun 26, 2003
    The rule about not saving money still applies here. Especially when you consider what you can find an old Traynor, Sound City, Bassman, etc for.

    The other thing you're not counting on is time. Not just design and construction time. I spent a few weeks getting rid of audible and RF oscillations when I built my amp. Getting the FM (yes FM) radio station out of the system. And I went through about 2 or 3 chassis iterations before I got something functional. (Hint, use an off the shelf hammond box.) Routing and lead dress is important.

    It was fun. I basically built about 3 amps before I got my "amp" finished. Fortunately, I was able to use the same transformers, tubes, and so forth. It's a wonderful hobby. It's a terrible way to try to save a buck. Consider building a small guitar amp or something first. I would hate to see somebody start out trying to build a monster using a Hammond PT-1650W, and a PT-278CX for their first amp. I keep thinking about doing one some day, but it'd be expensive, and the transformers heavy enough that you need to take their weight into account when mounting.
  11. dave_clark69

    dave_clark69 Guest

    Jan 17, 2003
    if you have an electronical shop in america they will most probably have the bits all there, like a shop called maplin in the uk, they do a kit, but it is probably just a 10 watt thing, but you would be able to get the whole idea there are websites that offer schematics, i will have a look for you and find some, i think i have seen one for a marshall head or domething like that
  12. If you buy the parts from your local Radio Shack or even your local electronics parts store, you'll go broke fast.

    Mouser and Digikey are the best sources I've found for many items. Parts Express now carries toroidals for a decent price, too, and they have fair prices on lots of other components. Triode Electronics has some good prices on output transformers, Angela Intruments carries both power and output xformers.

    Since the transformers are the priciest items (other than the power tubes) it's worth trying to find something surplus, though nowadays there's such a high demand for tube stuff that even surplus or used stuff is overpriced IMHO.
  13. You mean me?

    Nah, never built a tube amp. WAY too expensive, WAY too much time-consuming and WAY to dangerous.

    The 2 largest amps I ever built ware 140 and 155 watts. The first was a IC amp (no thinking involved) and the second one a sorta-class-A mosfet kit amp. No thinking involved either.

    Let me ask you a question: you have very little knowledge and technical skill (from what I understand from your post) and you want to build a high power Class A tube amp?

    Would you build a stock car from scratch too....?

    I rest my case.
  14. The only electronics I do is the digital variety in computer systems.

    No amps.


    I buy my QSC amps from eBay and have instant gratification. No building, no getting shocked/killed, no waiting, and much less expensive than building my own.

    I want light weight, non-over driven power. The solid state power amps are just fine for this.
  15. Bgavin, couldn't agree more!

    My main amp is a Yamaha P1600 PA amp. Bought 2nd hand for cheap. It's reliable, has just the power I need (which my homebuilt ones don't!) and is completely worry-free, because whenever I used to play a gig on the 155W mosfet amp, I never took my eyes off it, because I was afraid I would burn my "precious"....

    Take a look at my site. I've done some very nice home-building project (if I may say so, without wanting to sound too proud) but I would NEVER ever build a solid state power amp from scratch, let alone a tube amp.

    Conclusion/advice: don't build an amp yourself, unless you know literally EVERYTHING about it, have the skills, the courage, the patience, the money, the conviction that you can do better than a pro, and the ablility to live with expensive disappointments :D

    Buy second hand gear!
  16. thumbtrap


    Jun 26, 2003
    All true about building vs buying. Anything, but especially amps.

    However, the quote above I have to differ with. I would never build a solid state amp. Tube amps are dirt simple. High schoolers built them a generation or two ago. Solid state OTOH - has pretty well been mass production refined enough that it's pretty silly to build one. (I won't go into any exceptions, because if you meet one of the exceptions, you can't be dissuaded anyway.) Tube amp markups, their ease of construction, etc... make them much easier targets for homebuilt projects. It's not like you can't die from the inside of a ny line fed piece of equipment, be it solid state, tube, or electromechanical.

    I considered making my preamp before I found out about the PB-1, and had I done so it would have likely been tube. Not because of the "magical" properties of the tube, but because They're so simple, I've built them in the past, and it's easy to build compared to a solid state one.
  17. Corwin81


    Mar 18, 2003
    Ames, IA
    I found an Ampeg SVT-100 chassis on eBay that was just missing the power transformer and a couple of components for $75 and restored it. New PT(Marshall JCM800 replacement dropped right in and matched voltage/current), head cab custom built by Rick Sisney(OKRick@aol.com), quad of 6550s that I had from an old Marshall(they last a long time at those low voltages) and some resistors that I already had, and I've restored it.

    Definitely beats building from scratch even though I have the parts to do about 2 or 3 more amps(a 50W(Bassman), a 5W(Champ), and a 15W per channel stereo unit). I've been tempted to sell some of my parts, but not sure yet.
  18. jazzcatb17


    Dec 27, 2002
    Louisville, Ky
    Thanks for all the help folks, still looking into all the resources you all gave me. Im thinkingi'll probaly do a kit and a small project over the school year and when summer comes i'll try to start my own thing, partly so i get a little more experience and partly so i'll have enough time... anyways i've studied up a little on it, and even though it looks like building from the gground-up will be a bit of a headache, im okay with that, i like a good challenge, and how man people can say they have a home-made pre-amp??? But a more imminent thing is the issue of cabs? I know these can be home made without to much trouble and i think im gonna go ahead and go that route, but im looking for some info on tuning the enclosure and also what kinda speaker configurations might work. im running a Ashdown MAG 400 right now through a "full range:rolleyes:" 210, but it lacks a little in the lowend, so if i build a 410 would it make up any? or possibly 1-15 and 210, or 2-12 and 210, or even a 412? Heck, i could even get a little crazy and go with a 16-5, do the Phil Jones thing...... but probally not :D thanks for the help.
  19. Mcrelly


    Jun 16, 2003
    Minnesota, USA
    yes! you! sorry about the country screw-up. I was very impressed my you 'experiments' and the stuff you built. then I also remembered your "don't ask me to help you built something step-by-step" message. :rolleyes:

    what have you built lately?