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Help with finding vintage valve amplifier circuits (amplifiers for a rock band)

  1. Apr 26, 2017 #1

    wolram

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    Can any one help please, I have been searching for vintage valve amplifier circuit diagrams and components.
    I need help in finding valves, transformers, and diagrams.
    I intend to build amplifiers for a rock band so i would like to build one with a 3KW output if that is feasible.
    Thanks for any help no matter how little.
     
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  3. Apr 26, 2017 #2

    Averagesupernova

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  4. Apr 26, 2017 #3

    wolram

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  5. Apr 26, 2017 #4

    berkeman

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  6. Apr 26, 2017 #5

    jim hardy

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    My honest advice is

    1. Search on terms guitar amp tube circuits, it'll return scores of sites with varying degrees of credibility

    2. buy a copy of RCA Receiving Tube Manual (they're all over Ebay) from mid 1960's and build the fifteen watt hi-fi amplifier in their "Projects" section in back of the book. It has great tube sound(i built it one 1963) and will make a great guitar amp. It uses the 7199 low noise preamp which will "WOW" audiophiles.
    Real reason to build it is to get your feet wet. Reading the tube manual will educate you in how tube amps work so you will be able to tell the internet wheat from chaff.
    Get one 1960 or newer, you'll be better able to find those not so ancient tubes.


    old jim
     
    Last edited: Apr 26, 2017
  7. Apr 26, 2017 #6

    jim hardy

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    I'm away from home right now so without my books. But last year i downloaded a copy of the RCA tube manual , from an archive site. RC30 is the version i have, about 35 megabytes.

    Here's that amplifier schematic
    very simple, good starter project.
    https://archive.org/details/RCA_RC-30_1975
    RCA15watthifi.jpg

    its rich sound will astonish you.

    Be aware though you can buy a good transistor amp with better specs for less than the cost of a 7199....

    old jim
     
  8. Apr 26, 2017 #7

    davenn

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    unless you are an extremely experienced tech, forget building anything over ~ 100W

    Jim has given an excellent example of a medium power amp in the post above


    Dave
     
  9. Apr 26, 2017 #8

    jim hardy

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    Thanks Dave
     
  10. Apr 27, 2017 #9

    wolram

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    Thank you for your replies, you have given me a great starting point.
     
  11. May 3, 2017 #10
    Jack Darr's "Electric Guitar Amplifier Handbook" (1971) is chock full of schematics, and still in print (4th edition).
     
  12. May 8, 2017 #11
    Does that hifi amp have riaa EQ on the input?........assuming it's a phono input.

    For a guitar amp, best not to start with a "HIFI amp" since many brochures of old HIFI amps had lines like "can pass square waves without ringing".......meaning....very little coloration of the sound.

    Try www.triodeelectronics.com and check out the amp section..........plenty of pictures and the site has tons of parts.
     
  13. May 9, 2017 #12

    analogdesign

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    If you're looking for something that will take you through all the electronics required for guitar players (power supplies, pickups, amps, effects) I can't recommend "Electronics for Guitarists" enough but Denton Dailey enough. It strikes that balance where it is accurate and useful, but doesn't read like an engineering text (and you don't need a degree in Electrical Engineering to understand it). It starts from the beginning and goes from there.

    You can get the second edition from Amazon for about $50: https://www.amazon.com/Electronics-Guitarists-Denton-J-Dailey/dp/1461440866
     
  14. May 9, 2017 #13

    jim hardy

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    It's a "line level" input
    Magnetic phono cartridges are barely audible through it due to their millivolt level signal. . One should precede it with a RIAA preamp and tone control for use with them.
    Ceramic cartridges because they approach a volt and don't really need RIAA equalization sound pretty good through it as -is.


    http://www.lh-electric.net/tutorials/phono.html

     
    Last edited: May 9, 2017
  15. May 10, 2017 #14
    @wolram - if you really think what you need are schematics of vintage tube guitar amps, there are loads of web sites that host all the schemos you could want; just start Googling; or else buy a copy of The Tube Amp Book by Aspen Pittman; it includes a CD with a massive amount of vintage schemos: https://www.amazon.com/Tube-Amp-Boo...6&sr=8-1&keywords=guitar+amplifier+schematics

    However from searching your profile page and your previous posts to find out how much electronics work you do, I found this recent post which suggests you are pretty much a beginner on soldering; this suggests you are also a beginner in electronics work in general: https://www.physicsforums.com/threads/lead-free-solder.901042/

    If so I don't advise trying to work just from a schemo. Especially with high voltage tube amps, the circuits tend to be very noisy unless the lead dressing is very very good; and very dangerous to the end user unless constructed up to a given country's safety standards, e.g. proper strain relief for the power cord, proper means of fastening the earth wire from the power cord to the chassis, an understanding of earthing principles, etc. etc. etc. Even experienced tube amp builders often have to troubleshoot their builds to fix problems with noise or with cold solder joints or other build problems. And working from a schemo, you'd have to design your own layout - a huge task for a beginner and one you'd probably get wrong unless you are an autodidact on the scale of Leonardo da Vinci.

    Instead, from a beginner's building standpoint, I would suggest you look for and build a kit amp - a low-power kit amp to begin with. Kit makers assemble all the parts you will need & the favored designs tend to be vintage or close to vintage, e.g. a change to the schematic to ensure proper earthing. Kit makers include mainstream vendors such as Weber and Mojotone, as well as slightly smaller "boutique" vendors such as Allen Amps or Boot Hill. Note that Weber and Mojotone also sell components, along with many other vendors. Hammond (already mentioned) sells only transformers, and are very reputable; another excellent transformer source is ClassicTone. However most non-tube parts (passive, solid state, etc. ) are more cheaply obtained, and often of better quality, from industrial suppliers. In the U.S. this is chiefly Mouser and DigiKey; there are surely equivalents in the U.K.

    However there is a further wrinkle here. When you say this -
    - what on earth do you mean? A 3,000W output? That is meaningless in the context of tube guitar amps: club players tend to put mics on their small vintage guitar amps; the mics feed into a PA system and that is how sound reaches the audience; the amps themselves are low-watt, e.g. 15W, 25W, 50W, 100W, sometimes 200W. Some of the big stage shows such as ZZ Top do it differently; from what I've read, they tend toward advanced multi-component solid state systems to replicate the sound of small tube amps pushed into overdrive - nothing you could build yourself.

    Can you state what the actual goal is in terms of what sort of rock band or bands and what you believe their needs to be and where you would fit in?

    Lastly, if you're committed to exploring this further, this forum is not the place. Go to tube/SS guitar gear forums. We have EEs here, including many highly skilled builders; but guitar amps are a specialized field, so you need go to the well instead of quaffing bottled water.

    The best and most accessible of the lot is The Gear Page - their home page is https://www.thegearpage.net/board/index.php and their tech page for amplifiers and speakers is https://www.thegearpage.net/board/index.php?forums/amps-cabs-tech-corner-amplifier-cab-speakers.11/ Lots of EEs and electronics techs/repair shops on the tech page, but also lots of idiots; moderators tend to intervene far less so if you ask a naive question you may get a large number of stupid replies, a large number of semi-ignorant replies, and a small amount of courteous, excellent replies. If you can ignore the stupid replies and separate the wheat form the chaff, it's an excellent source; I've gotten tons of help there. Two of their best EE members are in the U.K.; a third is in Argentina.

    Also very good is Music Electronics Forum (MEF) - again, a mix of EE guitar amp buffs, plain old guitar amp buffs, small amp builders, kit builders, etc. MEF tends to be a bit more polite aside from a few crazy types, so you might like that aspect better: http://music-electronics-forum.com/forum.php Again, they have a number of U.K. members who could certainly tell you good U.K. sources for parts.
     
    Last edited: May 10, 2017
  16. May 11, 2017 #15

    wolram

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    Wow, I thought this thread was done, Thanks for all the great advice, as for my ability, I started life as an electrician and I have worked with electronics before, mainly transistor circuits. And I did get my radio armature licence, but that was yeas ago.
     
  17. May 11, 2017 #16
    That would certainly make a difference. A key thing with high-voltage DC circuits crammed into tight space = lotsa noise potential! So layout is a "craft" issue as much as it is understanding how noise propagates, e.g. capacitive conductance, radiation, etc.

    But if you know transistors, valve theory is "same only simpler", basically - biasing etc. One nice thing is that graphical analysis of load lines, which apparently is not useful for most semiconductor circuits, is quite useful for valves; I have done a lot of that with help from Merlin Blencowe's books & articles (see my next paragraph) and some additional tips from a couple of EEs on The Gear Page forum.

    A really good source if you have interest in actual circuit design is a fellow called Merlin Blencowe, a.k.a. "The Valve Wizard", who (again) is also in the U.K.; he is an EE who at some point feel in love with valves as a hobbyist & then as an author. He's written two very nice books that very highly regarded in the valve guitar amp community, one on valve preamps for guitars and the other on valve preamps for high fidelity. I have both books & think they're terrific. I built my own small prototyping efforts at a low-voltage, single-ended guitar amp via adapting some of his example designs & also with help from tutorial articles on his web site - e.g., he doesn't address the power amp section in his books, but he does have several articles on the web site that walk you through how to calculate both single-ended and push-pull power amps to go with whatever preamp you build.

    Here's Blencowe's web site - note the "grounding" page includes a downloadable PDF which is the chapter from one book that addresses not only earthing but also noise reduction - a real treasure: http://www.valvewizard.co.uk

    As for the two books - here's the guitar preamp book on amazon UK: Designing Valve Preamps for Guitar and Bass, Second Edition
    And here's the hi fi preamp book ditto: Designing High-Fidelity Valve Preamps

    Note that even if you are just going to do guitar amps, the hi-fi book is worth getting as it has extra chapters near the back on power supplies - many sorts of neat circuits.
     
  18. May 11, 2017 #17

    f95toli

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    Reading this thread it is quite obvious that most people here are assuming that you are talking about a guitar amplifier (=the amplifier directly connected to the guitar). These are VERY different in design than normal amplifiers since a lot (most) of the "character" of the sound of an electrical guitar comes from the amplifier. This in turns means that the amplifiers are far from "transparent" and they are usually (for rock) driven so hard that there is a LOT of distortion. This in turn explains why guitar amplifiers are usually only 5-200W (note that even a 5W amplifier can be VERY loud if you allow it to distort). This also means that there is not "correct" way to build a guitar amp; it is just personal preference.

    3kW would be more typical for a large PA system where you need a "clean" signal to amplify the whole band and also need a lot of headroom for EQ, feedback cancellation etc. However, modern PA amplifiers are -AFAIK- never built with valves. Back in the "olden" days before the advent of transistors they simply did not have very powerful amplifiers (for sound) which is why they sometimes ended up using large horne-based speakers; the latter have high sensitivity meaning you don't need a lot of power.
     
  19. May 11, 2017 #18
    You are right about everything you say; however I thought I would expand just a bit on this one point. Of course someone building from scratch can do whatever they like; but probably they're going to end up (a) learning by necessity about the craft of valve audio circuits, and (b) borrowing from historically well-known valve guitar amp designs.

    Regarding (a), there is a known body of craft that will help someone designing, building, or repairing valve audio amplifiers, whether for guitar or hi-fi. The craft for valves differs in particular ways from that for solid state, so even a good SS designer will have to learn some new things.

    As for (b), as you have already indicated, there is a tradition going back by now for over 60 years if not longer of valve circuits being designed & built for very particular sounds that both guitarists and their audiences are now accustomed to hearing & preferring - see for example this page on "10 Classic Guitar Amps & Their Sounds." Typically the sound is shaped by how much clipping, and what type, is going on or not going on in the preamp; ditto the power amp; how much abuse the output transformer and speakers are getting; also various flavors of passive filters; plus finally the interaction of all of this with the different sorts of electric guitar pickups and different sorts of pedal effects. When the OP asks for "vintage" schematics, he is in effect nodding toward this long history of existing preference on the part of rock guitarists and audiences for these sorts of circuits. You can of course mix and match different flavors of preamp and power amp - that's what I've done myself.

    What's interesting is that way back when Leo Fender was building his first designs, he apparently did a lot of unorthodox things - e.g. reasonably quiet lead dressing was achieved not by following best practices, but via endless trial and error. Same with VOX, Marshall, and many other companies that did the early designs that are now copied and repeated, including repetition via solid state and digital emulator circuits. Part of this is that if distortion (clipping) is good, many designs that would have flunked the standards of the old valve hi-fi stereo companies got by just fine in Leo's hands - if I remember, he was just a small-time radio repair guy when he started out.

    The little world of valve guitar amps is neat in a way, and claustrophobic in other ways. The belief that valve guitar amps have a special sound that is superior to solid state is a fetish among many guitar enthusiasts - especially those who don't know much about electronics, and who share with each other myths and misconceptions about valves, transformers, capacitors, etc. etc. Meanwhile, there is virtually no work being done by anyone to invent valve guitar amplifiers that produce new kinds of sounds. Solid state, MIDI, digital platforms such as Ableton, and to some extent digital pedals have taken over the task of inventing new sounds.
     
    Last edited: May 11, 2017
  20. May 11, 2017 #19

    jim hardy

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    That's how the reflex design came about. When 15 watts from push-pull 6V6's was considered a lot of power the audio guys figured out how to make the sound from the back side of the speaker cone come out the front of the enclosure and reinforce not cancel that from its front..
    Search on Reflex Speaker Enclosure, Thiele, and "Electro Voice" . There are some fascinating papers out there.

    Also the classic 1940 RCA book on "Acoustics"
    https://www.google.com/search?q=1940+book+"Acoustics"+.&ie=utf-8&oe=utf-8
     
  21. May 11, 2017 #20

    dlgoff

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    @Planobilly made good use of this forum doing it. e.g. https://www.physicsforums.com/threads/my-latest-crazy-amp-project-photos.894868/ and https://www.physicsforums.com/threads/new-amp-build-photos.891627/
    just sayin'
     
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