Custom Amp Build - what do I need to know?

Discussion in 'Glowing Bottle Tube Amp Forum' started by Geniustoogs, Mar 15, 2019 at 11:52 AM.

  1. Geniustoogs

    Geniustoogs Tele-Meister

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    Hello everyone!

    I’ve been thinking about making myself an amp lately, and I thought I would post a thread to get some advice. I’m not sure if this is the right forum for this so if not I apologize!

    Basically I want to build a 1x12 tube amp with a master volume, pre gain, post gain, and standby switch. This seems like it would be fairly simple but I know little to nothing about the amp world.

    I know for the power tubes I would like to use EL84’s

    And I also know the risks involved in amp building and electricity, I have family members who are experienced who will be helping me as well.

    Thanks for any and all help! :)
     
  2. telex76

    telex76 Doctor of Teleocity Silver Supporter

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    You can study for a few years, or you can get a paint by numbers kit, be very thorough and careful as you go, and hope you get lucky.
     
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  3. jimgchord

    jimgchord Tele-Holic

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    That's a tall order for a first build. Good luck!
     
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  4. Geniustoogs

    Geniustoogs Tele-Meister

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    Thank you! If I may ask, which aspects make it a tall order? I thought it was a rather simple layout.

    Thanks!
     
  5. jimgchord

    jimgchord Tele-Holic

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    Not sure what you mean by pre gain and post gain and why you feel you need a standby.
     
  6. boredguy6060

    boredguy6060 Friend of Leo's

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    Shock Bros, is probably the best forum for amp builds.
    Have you studied any of the circuits that contain all those features you’re looking for?
    That would be a good first step. Unless you plan on designing a custom circuit, which is a huge first step for a newbie.
    Almost everyone will recommend that you do a simple circuit first, mostly a 5F1 or 5F2.
    Starting a complex amp as a first build usually ends badly, meaning the new builder just gives up on the project after spending a lot of time and money.
    Good luck with it,
     
  7. AlbertaGriff

    AlbertaGriff Tele-Holic

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    I had to look up what you meant by pre and post gain.

    Wouldn't post gain be the same as a master volume?

    I've never built an amp, but it seems to me like you should be thinking more about what you want the amp to sound like than what knobs it has?
     
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  8. toomuchfun

    toomuchfun Tele-Holic

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    Building an amp is a great experience, especially when it works.

    In my case I had a bunch of '60's & '70's Fender amps and started looking at them. With the help of Gerald Weber's books I started doing simple mods like biasing an amp, changing caps, adding reverb to both channels and such. I then took the plunge and built a tweed Twin clone from a kit. Lucky me, it worked the first time I fired it up. I finished a tweed Deluxe for a friend from a kit he started and had success with that too.

    If you don't already, you need good soldering skills. That's soldering and desoldering (there's a tool for that). You should have a good variable temperature unit or a number of irons with different temperatures.

    You should have a multi-meter and a capacitor meter is handy too.

    Building a current limiter (mine is a light bulb type) for initial fire up should be done too. I have a variac too, but you can get by without one.

    Still with me?

    If you understand all of the above you're well on your way.

    I would still recommend a kit. That way all the components match for good chance of success the first time. There are probably a lot of kits in your area of interest, I would consider a 18 watt Marshall kit. You may know of another style that will fit you better.

    Now, please indulge us. Tell us why you want a master volume, pre gain and post gain. If you can't explain that in a post then I don't think you should try to build an amp. Not trying to be a richard head, just trying to be real. Notice I didn't mention the standby, I like them myself and like my amps to have them (Champs excluded).
     
    Last edited: Mar 15, 2019 at 7:22 PM
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  9. Geniustoogs

    Geniustoogs Tele-Meister

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    I do have a lot of experience with soldering, so that won’t be an issue. And I have everything else you mentioned other than a current limiter.

    As for why I chose master volume, pre, and post gain was for what I thought would be simplicity. What I’ve realised since (partially from reading some of the replies from this thread) is that post gain is really no different than a master volume.

    Also, anythjng I do in terms of choosing components to match will be done with my cousin who has repaired and rebuilt many amps
     
  10. clintj

    clintj Friend of Leo's

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    You might like an 18W build with a lead channel like Tube Depot sells kits for.

    Another advantage to kits is you're not spending a fortune on shipping by ordering transformers from one place, chassis and hardware from another, resistors and caps from a third, and a few more random orders because you missed a part or three when you were building up a parts list. Been there, done that a few times. It really does add up after a few rounds.

    You also get some nice documentation from someone who's taken the time to figure out layout, lead dress, grounding, and they may have even predrilled the chassis to hold your finished eyelet or turret board safely. Those alone go a very long way to not getting a hot mess of an amp that hums and shrieks at turns.

    Sent from my Pixel 2 using Tapatalk
     
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  11. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    ^^This

    "Layout" is pretty meaningless. Amps are not plastic model kits or paint by numbers sets - especially with he variables you included in the mix.

    Do you understand electronics? Voltage, resistance, current, impedance, inductance? The function of transformers? Chokes? resistors? Different types of capacitors? what the different types of potentiometers are and where they are used?

    How and where to test voltages? At what build stages tests should ideally be performed - and what stages are built and tested first? Do you own a quality multimeter and an LCR meter? Do you know how to ensure tubes are matched and how to bias them? Different types of tone circuits? Preamp gain - and gain vs noise, what types of tubes to use to reduce noise? Ground schemes and how many/where specific grounds need to be located? Lead dress and how to properly rout and cross wiring; which wires need to be twisted; which need to be separated from which?

    I this seems like overkill, it's not based on what you stated you wanted to build.

    Many of us recommend at least basic electronics knowledge, lead dress understanding and parts types and functions before attempting even a simple Champ build. A few months of study - specific to electronics AND tube amp design - makes the whole job go much more smoothly with a FAR higher chance of building a functional low-noise amp. And THAT is with purchase of a simple, complete kit. VERY few come with anything other than "assembly" instructions. That's not "building" an amp. That's an electronics version of a plastic model kit - but if it doesn't work - then what?

    But the amp you want to build doesn't exist - you need to DESIGN it. And amp design requires electronics knowledge. Most amp techs don't design amps - it's a specialized skill.

    That's what makes it a "tall order".
     
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  12. TequilaCaster

    TequilaCaster Tele-Meister

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    Go to ax84.com and build yourself a P1.
    http://ax84.com/p1.html

    The P1 is a single 12AX7 and single EL84. Gain, bass, mid, treble, master, power, and standby controls.

    It is about as simple of a great useable tube amp that there is...good documentation... it is the perfect first build. You may never need to build a bigger amp.

    Through a 12" efficient speaker, it will get half as loud as a 50 watt tube amp... it's loud enough for most small gigs, and larger gigs when mic'ed.

    It take pedals well... reverb, delay, tremolo, etc.
     
  13. thechad

    thechad TDPRI Member

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    I’m not sure what your budget is or what you are looking for. But I can highly recommend looking into “trinity amplifiers” if you decide to go with a kit. They have an excellent forum on the website and they also provide excellent support and guidance to customers. If it’s your first build you will surely learn a few things and likely not end up with a pile of soldered junk at the end. After you gain some confidence from a kit build, you could then try an amp build from scratch and probably be a little more prepared, get a better idea what you want etc.
    Best of luck whatever you decide!

    But if you plan to build your own design, you need to know a lot! For starters, are you planning to build a single ended amp or push pull? If you want to use EL84 power tubes you probably want to go with a push pull amp, so you’ll need the appropriate transformers and a phase inversion stage. If you want something simple with EL84 tubes maybe look at the orange “tiny terror” schematic and go from there. If you have some help and you know a thing or 2, it would be a good starting point. I think your question is a little too vague for anyone to actually help give you a complete answer.
     
    Last edited: Mar 16, 2019 at 1:06 AM
  14. toomuchfun

    toomuchfun Tele-Holic

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    Well sir, there is no reason not to take the plunge. The point I was trying to make is there are a lot of things you need for your first build which is an investment and you already have them.

    I feel a master volume is another link in the chain that can muddy up an amp. I know people like Ken Fischer made master volumes that didn't suck tone but I have little experience with them. I'm a fan of simple circuits myself. One of my favorite amps is a '55 tweed Pro, it is a 2 channel amp that has 2 volumes and a tone. It needs nothing else (well, maybe a spring reverb pedal).
     
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  15. cgharrison

    cgharrison TDPRI Member

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    I say go for it. I’m all self taught, and have been building amps for about 10 years now. IMHO, people are pretty exaggerated in these sorts of threads about the difficulty and dangers of building tube amps. If you’re an intelligent person with common sense, read a lot, take your time and be careful, you can totally do this. Remember, this is 1950’s technology we’re talking about - not rocket science! My 2 cents is that you look for a kit, and adapt it to your needs. I’d suggest an 18 watt kit from somewhere - maybe Triode Electronics or Mojo. Then you know you’ve got most of the components, tubes, sockets, correct transformers, etc, and can just sub in extra parts as needed. Make your own faceplate based on the controls you choose, and use it to cover any chassis holes you don’t use. Study the circuits you want to base your design on, start drawing layouts, and get feedback from people online. Some will be dicks, but hey - it’s the internet. Most will be helpful. Lastly, listen to the opinions of others - people who build a lot of amps have good ideas about more than just technical stuff. Their thoughts on how a given circuit will sound are often right on - even if they’ve never heard it. Good luck!
     
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  16. Geniustoogs

    Geniustoogs Tele-Meister

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    Thank you all for your responses! I really appreciate all the help and reccomendations. I think I’m going to take some time and design my own circuit. I know it’s a tall order, but I would rather spend extra time to do it my way.

    The only thing I’m really confused about at this point is the circuit board itself. I generally understand how the rest of the amp functions (I will solidify that understanding before attempting anythjng) but in terms of capacitors, resistors, etc I don’t know what to do. I can’t seem to find any sources online that discusses that aspect. Does anyone have any good sources I should look at to learn about what values to choose, and how each component on the board feeds into each other and the amp?

    Again, I’m sorry if I’m asking loaded/redundant questions

    Thanks!
     
  17. Snfoilhat

    Snfoilhat Tele-Holic

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    This is a great set of questions. Being honest about the gaps in your knowledge is the best way to move forward.

    Anyone with an internet connection can learn as much electronics theory as they might need to safely build a unique(-ish) and well-functioning guitar amp in a fairly short amount of time. I'm going to leave that thread there, though others may disagree.

    What you can't learn from just reading the best resources is 1) how all the parts will work together. Most resources are reductive -- they break down the concepts into circuit blocks and even into the behaviors of individual components, and that's a time-tested way to learn fundamentals. But all the components in the amp work together in a way that is very hard to predict from the individual parts.

    2a) many (many!) guitar players know what kind of sounds they like, and have a pile of associations in their minds and on the forums. I got this great tone with these great pickups and pedals and amp and this tube set and that speaker. Even really granular stuff like I got this great tone with this modification to the power supply on my 1970 Princeton and it's just the best.

    Almost all of that is useless in designing amps for yourself. Market research surely influences designers of production equipment, but when you are your own critic there has to be something concrete behind the old 'takes pedals great' claim. Very seldom can people can leap from what they hear or want to hear to what part or parts are the main contributors to that desired sound.

    2b) if you don't know very well what you want a custom amp to do, then how do you even know you want a custom amp? Designers have been churning new stuff out since the 1940s and who has played everything? When I read your first post I thought, Oh, Matchless Lightning. Or maybe one of the simple Dr. Z amps. Or Robrob's Blackvibe based on the Vibroverb. Not saying don't build something, but don't ignore all the shoulders of giants to stand on. Everyone starts somewhere. I don't care one bit about the Fender Deluxe 5E3, but I've read pretty much everything https://robrobinette.com/Amp_Stuff.htm has written about it. That was valuable to me.

    If you're at the stage of "why are there two resistors here instead of just one?" (it might be a voltage divider) or "why is this coupling cap 0.022 microfarads but this one is 500 picofarads?" (it might be part of a high-pass filter) then you could do a lot worse than reading everything about the Deluxe and the Bassman, and then checking out specific resources like https://learn.sparkfun.com/tutorials/voltage-dividers/all and http://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php

    Theory should answer specific questions, not be some enormous block of knowledge you master before ever being allowed near electricity. Not even professional EEs are taught that way.

    Good luck
     
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  18. Geniustoogs

    Geniustoogs Tele-Meister

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    Thank you all for your responses! I really appreciate all the help and reccomendations. I think I’m going to take some time and design my own circuit. I know it’s a tall order, but I would rather spend extra time to do it my way.

    The only thing I’m really confused about at this point is the
    Wow! Lots of detail, thanks! I understand what you mean when you ask how I know I want a custom amp. Personally, it’s not necessarily a sound I’m looking for. It’s mostly the desire to create something, and if I’m going to make an amp I want to make it my own
     
  19. Old Deaf Roadie

    Old Deaf Roadie Tele-Meister

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    Being in the same boat as you: a guy who has the technical skills & likely aptitude to build an amp but hasn't actually done so, my approach would be a decent kit for a 1st build. After a deeper understanding of the beast, you will have a better go with a custom design.
     
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  20. bblumentritt

    bblumentritt Tele-Afflicted Platinum Supporter

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    Read RobRob's site in it's entirety, and the Valve Wizard, before you embark.
     
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