My first scratch-built Vacuum Tube Amplifier: "Big Red" - Page 1
Forum section: electronics / projects

author: heekma
author_rank: Newbie
timestamp: November 14, 2013, 02:11:10 am
content: http://imgur.com/a/WryJS#17Hi folks. This is my first post here, I was brought here from reddit.com. Forgive me it this isn't the correct place to post.If anyone has any questions, ask, I'll do my best to answer. Bare in mind I'm a hobbiest, not a EE, but I'll do what I can.Thanks,Heekma

author: c4757p
author_rank: Super Contributor
timestamp: November 14, 2013, 11:31:28 am
content: While I think you'll find that audio, and particularly tubes, aren't very popular here,Ifor one like them, and I must say that is beautifully constructed. Nice wiring! You've definitely gilded the lily (Is the volume control really custom? That seems a bit unnecessary...) but you have obviously put a ton of work in here.

author: GreyWoolfe
author_rank: Unknown
timestamp: November 15, 2013, 01:07:47 am
content: And it is a shame that tubes have lost favor here. There is nothing like the sound of a tube amp. And the glow can't be beat or duplicated. Don't get me wrong, I love my digital music. I DO miss my vinyl ( ruined when my 1st wife and I split) I loved the hiss and pop. Couple that with the warm wonderful sound of tubes, as people say on this blog, that is sex on a stick.Tom, NW0lf

author: SLJ
author_rank: Frequent Contributor
timestamp: November 15, 2013, 01:42:56 am
content: Nice job. Nothing wrong with tubes.

author: Barryg41
author_rank: Contributor
timestamp: November 15, 2013, 01:45:20 am
content: Nice Heekma,I love working and tweaking on my Heathkit equipment. I can take as long as I want to, it will be there tomorrow.Thanks for posting your pics.

author: TimNJ
author_rank: Super Contributor
timestamp: November 15, 2013, 02:52:50 am
content: I LOVE the wiring. Awesome job my friend!

author: xrunner
author_rank: Super Contributor
timestamp: November 15, 2013, 02:59:29 am
content: Wow! Nice job and I love the cloth-insulated wire.

author: robbag
author_rank: Contributor
timestamp: November 15, 2013, 03:00:16 am
content: Take my money. That is art.

author: c4757p
author_rank: Super Contributor
timestamp: November 15, 2013, 03:03:44 am
content: I stand correcred

author: Radio Tech
author_rank: Frequent Contributor
timestamp: November 15, 2013, 10:13:27 am
content: Friggin awesome!

author: dcel
author_rank: Regular Contributor
timestamp: November 15, 2013, 11:18:57 am
content: Very nice construction! And yes, a work of art, great job!Tell us how it sounds, what inspired you, how long did it take, design decisions, component selection, etc.Damit, we want details! You cant just post something as cool as this without telling the story.Chris

author: dannyf
author_rank: Super Contributor
timestamp: November 15, 2013, 11:58:02 am
content: QuoteI am sure you can add that to your digital music to make it sound vinyl.

author: dannyf
author_rank: Super Contributor
timestamp: November 15, 2013, 11:59:30 am
content: QuoteThere are some tube amps where the tubes are t here purely for decorative purposes and amber leds are used to emulate the "glow".

author: grumpydoc
author_rank: Super Contributor
timestamp: November 15, 2013, 12:01:21 pm
content: QuoteIn that case they aren't "tube amps" surely?

author: Zero999
author_rank: Super Contributor
timestamp: November 15, 2013, 12:17:39 pm
content: It looks nice.People love to build copies of old valve amplifiers and play vinyl records for the same reason as why people play with old steam engines: it's fun!

author: c4757p
author_rank: Super Contributor
timestamp: November 15, 2013, 12:23:01 pm
content: Quote from: dannyf on November 15, 2013, 11:58:02 amMy take on any of this not-so-scientifically-solid audio stuff: music is art, and emotion and feeling are a perfectly legitimate part of art. It's probably more about the nostalgic element of having listened to it habitually in the past, which would be ruined by knowing it's artificial.Personally, I find tube amps in general to sound identical to SS if done correctly (the only things that seem to set apart your "average" tube amp are mains hum and poor frequency response....). But if it makes you happy, it makes you happy. I like them for them a "nonsense" reason too: the fact that every single part of them is visible and traceable and even could, in theory, be built by hand with very simple, old techniques (yep, the tubes included) pairs well in my mind with what is the essence of music: simple, pleasing sounds, nothing more than that. No, it doesn't sound any different (again, in my opinion), and I wouldn't even dare try to argue that they are "better", I just like them. Why? Same reason I like vanilla cake better than chocolate - it pleases me more, for completely subjective non-reasons.Quote from: dannyf on November 15, 2013, 11:59:30 amThis is purely pretentious "look how much I spent on something useless". Yuck.

author: dannyf
author_rank: Super Contributor
timestamp: November 15, 2013, 12:27:53 pm
content: QuoteQuoteMaybe what's useless is completely subjective non-reasons.If it floats someone's boat and pleases him/her more, who are we to judge?

author: c4757p
author_rank: Super Contributor
timestamp: November 15, 2013, 12:34:12 pm
content: True. And if having a tube sitting on top as an ornament, being lit by LEDs, is what makes you happy, then I guess it makes you happy. But I am willing to bet that more than a few of these are sold by smooth-talking liars trying to play up the vacuum tube/quality connection, to buyers who don't know any better and aren't really getting what they think they are getting. And another significant portion are going to people who will try to insist the very same thing to their friends. If that's not the case, then fine, it's a decoration, and most of us have some sort of decorations; I have no problem with that.On the flip side, if you can like something for subjective reasons, you can also dislike it for subjective reasons. The idea of an LED-lit tube that does nothing seems a special order of useless to me... Yeah, I dislike it, I think it is very stupid and will happily say so. But that's just me - I'm just not much of a decoration person, in general, so I suppose I'm predisposed not to like it.

author: baljemmett
author_rank: Unknown
timestamp: November 15, 2013, 03:48:45 pm
content: Quote from: c4757p on November 15, 2013, 12:23:01 pmThat, plus artificial noise can often be too obviously artificial - see, for example, fake old-film effects on TV programmes. Sure, it'll go black and white and almost-convincing scratches and dust blobs might appear, but the picture behind it is usually far too crisp and detailed. (Of course, this is often done as a gag more than anything...)

author: zapta
author_rank: Super Contributor
timestamp: December 06, 2013, 04:44:31 am
content: Very nice constructions. The cloth wires looks realistic. IIRC, the old soldering strips looked like thesehttp://www.ebay.com/itm/10x-Vintage-Solder-Terminal-Strip-9-lug-2-chassis-Deutschlaender-original-new/181251493093?_trksid=p2047675.m1850&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D11%26meid%3D3198529609349176811%26pid%3D100011%26prg%3D1005%26rk%3D1%26rkt%3D4%26sd%3D181230215342%26

author: oldway
author_rank: Super Contributor
timestamp: December 06, 2013, 07:35:41 am
content: I maked several vacuum tube amplifiers in the sixties and we where not concerned with the appearance of the wiringThe only important thing was to make the shortest possible connections to avoid oscillations and induced hum.See for example the wiring of a "The Fischer" X100C:http://classictubeaudio.com/projects/fisher/fisher-x-100-c-see-all-the-new-upgraded-parts/But if your amplifier is stable and if there is no hum, it's ok.(to be tested with 1khz square wave and resistive load: if there is no damped oscillations, that's allright.)We also used to say that a vacuum tube amplifier is as good as his output transformers.

author: larry42
author_rank: Regular Contributor
timestamp: December 06, 2013, 04:33:24 pm
content: Really nicely constructed!Being in the electronics industry for 15 years professionally (including designs with mm-wave GaAs FETs and 3000 euro FPGAs) - I like the idea of valve amps. In any case, it's my belief that the weak spots in audio are mainly the speakers and room acoustics... Now if only I had time to finish that EL34 amp and make the chassis for it. Making cases and the mechanics takes me approx. 10^6 times longer than doing the hardware parts on pieces of circuit board...

author: N2IXK
author_rank: Frequent Contributor
timestamp: December 06, 2013, 05:05:40 pm
content: Nice job, beautiful wiring!Are you having any issues with the 7591s? That was a really advanced type (very high Gm, high plate dissipation for size), introduced toward the end of the tube era, and it took a LOT of manufacturing mojo to get good product. They were unavailable except as NOS for many years, and the first attempts to restart production (Russian) were really disappointing. Have the new production tubes gotten more reliable?

author: calexanian
author_rank: Super Contributor
timestamp: December 06, 2013, 11:15:44 pm
content: Quote from: N2IXK on December 06, 2013, 05:05:40 pmThose are old 7591's. Sharp looking amp there.The imports will never be able to produce the high gm tubes with any reliability for a number of reasons. First and foremost they do not understand grid shadow throttle control. Bud Ringmann was a forefather of that sort of high gm tube design in the 50's. The idea was simple. The screen to grid to cathode distances were so close that screen growth with heat would send the tube into thermal runaway. The solution to this was to stretch the grid (Normal part of grid winding) to a greater degree than the screen. As the screen would heat it would expand more into the shadow of the control grid and intercept less causing an inherent self limiting system. On a 6550 you can see a low freq. oscillation every few seconds in a tube that is working hard. thats this effect. Also for those high gm tubes the tolerances are extremely tight. A 6L6 or EL34 has enough space from cathode to grid to screen to use cut up index cards as spacers. Start with the bottom mica. Add the cathode. Slip a sleeve of paper around the cathode. Drop the grid over. add another paper sleeve. Drop the screen over. add the beam forming plate and fold over the tabs. move to swaging station. swage the grid. then using an optical comparator swage the screen in place where the bottom grid wire aligns with the bottom screen wire. If you look at the top screen wire it will be lower than the top grid wire. Swage the screen. Remove paper sleeves. install crimped plate assembly. Drop on top mica. Grid side rods go in first, the screen side rods, then beam forming plate upper tabs, then plate upper tabs, then cathode, which was held aligned with a pin up the center of it. fold over all tabs. spot weld on screen radiator. spot weld on getter. And.... Congratulations, you just built what is refereed to as a cage!! Now you take your stem. (The glass to metal seal part with the exhaust tubeulation on it) and pre bend and clip the lead in wires to the proper locations. Spot weld the heater to the proper leads and make sure its pointed in the right direction. drop the cage and fit the heater up the cathode. align the grid side rods and plate and beam former tabs by the pre bent stem wires and spot weld all connections. Inspect assembly for straightness and cleanliness. And now you have a mount! Time to put it standing up on a tray with the others and send it to sealing.You think a worker in a cold damp factory with bad lighting and questionable power and water is going to get that procedure right every time, and the owners will let them take the time to do it? Hell no! I talk all the time with the owner of KR and JJ and even the guys in govt plants in china. They think it was insane that GE and RCA spent so much time cleaning and processing each tube. Its on and off their pumps in under 2 minutes. Chattam used to bake out their tubes for 4 to 8 hours a batch! We will never see that quality again because honestly, we cant afford it anymore.Ok, where is the advil? hahahahaha

author: robrenz
author_rank: Super Contributor
timestamp: December 06, 2013, 11:37:30 pm
content: Excellent work!

author: N2IXK
author_rank: Frequent Contributor
timestamp: December 07, 2013, 12:10:56 am
content: Great to see another tube geek here!GE used some 5 layer plate material that helped, too. They used it on their 5AR4s and 8417s, as well. A copper core layer helped conduct the heat away better. Costly stuff, supposedly developed by---Texas Instruments! Manufactured by an explosive welding process. similar to making bimetal for thermostats.Westinghouse really innovated the high Gm close spaced beam tubes. The 7591 and 8417 were both originally Westinghouse designs. GE designed the 6550A, but the plain vanilla 6550 was a Tung-Sol design.Tung-Sol's Chatham division made some really stout tubes, but the ultimate in "cost is no object" tube construction (besides the hand-built submarine repeater stuff) probably has to go to Bendix Red Bank. Ive run a pair of 6384s for hours at 6550-ish condtions (in a Dynaco MK3) with no issue. A few of their types were second sourced by Tung-Sol, Cetron, and most recently a mysterious company called "M U Incorporated", that has a skeletal web presence at:http://www.mu-inc.com/

author: Napalm2002
author_rank: Regular Contributor
timestamp: December 07, 2013, 02:45:19 am
content: Love tubes. And valves.very nicely done. How much do u have invested in the circuitry? Where did u get the transformers?

author: c4757p
author_rank: Super Contributor
timestamp: December 07, 2013, 02:46:24 am
content: Quote from: Napalm2002 on December 07, 2013, 02:45:19 amHmm... tubes are nice, but I really can't stand valves!

author: N2IXK
author_rank: Frequent Contributor
timestamp: December 07, 2013, 03:04:59 am
content: Quote from: c4757p on December 07, 2013, 02:46:24 amHow do you flush your toilet?

author: calexanian
author_rank: Super Contributor
timestamp: December 07, 2013, 03:52:00 am
content: The multilayer material used in plates came in a few different varieties. Originally tubes just had Nickel anodes. An adherent layer of powdery carbon (Referred to as black plat tubes) had a black body radiation of about %80 to %90 in practice. Graphite was also used in early tubes. Molybdenum was used if cost would allow. In transmitting tubes graphite and other materials slowly gave way to zirconium coatings. Zirconium has multiple advantages as it will act as a secondary getter at red heat and has a good heat radiating qualities. Most graphite anodes in good tubes are coated with Zirconium. Early 5881's and other tubes from that series actually had zirconium painted in a strip running down the out side of the anode opposite of the plate from the electron beam strike area. During the war Germany started experimenting with Holland steel plated with nickel and aluminum sputtered in an extremely thin layer on the outside. After processing the aluminum layer becomes a matted Grey and even though aluminum would otherwise melt and sputter in tube conditions it does not. This product was called Aliorn. Most tube manufactures still use it to this day. In the US they added copper over the steel and nickel and aluminum over that. creating a 5 layer product. Actually in the end it was being produced in a plating process and not the explosive cladding process. Some high voltage diodes would have the copper layer bare and exposed on the inside.

author: oldway
author_rank: Super Contributor
timestamp: December 07, 2013, 12:37:35 pm
content: To make a good vacuum tube amplifier, you have to have a lot of experience and knowledge, very good components and mainly good output transformers (the most critical components).If you don't have all this, why loose time and money ?For experience?I don't think such experience would have some interest now and in the future ...A vacuum tube amplifier is very expensive and has very poor energy efficiency.It would have to be very very good to compensate this.What are the power, distortion, frequency response?A lot of people think all the vacuum tube amplifiers are very good, that's wrong.There are still very good available output transformers as thoses:http://www.ringkerntrafo.nl/shop/high-end-audio/uitgangstrafo-s/push-pull-opt.htmlFor good schematic, look for Marantz model 5, of still better, Mc Intosh model 30 or 60.If you have no experience with vacuum tube technology, you should began with guitar amplifiers.It's far more simples, as it needs only limited frequency response and there is no concern with harmonic distortion.

author: N2IXK
author_rank: Frequent Contributor
timestamp: December 07, 2013, 03:37:10 pm
content: In a lot of cases, the use of tubes nowadays is more an aesthetic/artistic decision than an engineering one. Of course, if you are trying to generate huge amounts of RF or pulsed power with a minimal component count and simple circuitry, tubes still represent the state of the art.A well done tube amplifier is a piece of "functional artwork", in a way. Tubes themselves are truly examples of "industrial art". They were largely handmade, to very close tolerances, and formed the basis for the electronics industry for 40+ years. The amount of engineering and material science that went into making good tubes was similar to high-end semiconductor manufacturing today. You can often look at a vacuum tube and understand how it functions, by looking at the arrangements of grids, cathodes, and plates. Solid state devices (particularly ASICs) are literal "black boxes" whose functionality may or may not be considered "proprietary" and/or controlled by copyrighted firmware. Yes, they enable functionality, performance, and space/power efficiency that couldn't be dreamed of using tubes. Imagine a tube equivalent to a barebones cellphone, with a backpack full of tubes and cavity amplifiers, driving a klystron! No thanks...But a vintage piece of tube gear has a "soul" that modern solid state stuff doesn't. A throwback to a simpler time when the average user could maintain their own equipment, and often did. Building with tubes nowadays is more about keeping a part of our industry's history alive, and paying tribute to all the folks who laid the foundations for the stuff we take for granted today.Keep 'em Glowing!

author: calexanian
author_rank: Super Contributor
timestamp: December 07, 2013, 05:00:34 pm
content: Its analogous to people and classic cars. A bone stock Honda is in every measurable sense better. But what is the fun in that? O0

author: oldway
author_rank: Super Contributor
timestamp: December 07, 2013, 05:01:05 pm
content: I agree but in applications where it's not irreplaceable, vacuum tube technology is such an high energy waste that it's perhaps an ecological crime to use it

author: Napalm2002
author_rank: Regular Contributor
timestamp: December 09, 2013, 02:22:09 am
content: Everyone knows that I only threw the valve thing in for all of the non USA bloggers!I also like ball valves. Everyone dabbles in some plumbing sometimes!

author: Zero999
author_rank: Super Contributor
timestamp: December 09, 2013, 04:27:44 pm
content: Quote from: calexanian on December 07, 2013, 05:00:34 pmSame with steam trains.Quote from: oldway on December 07, 2013, 05:01:05 pmAgain, classic cars and steam trains cause horrible amounts of pollution but some people keep them going because they're fun.

author: free_electron
author_rank: Super Contributor
timestamp: December 10, 2013, 01:39:46 am
content: Quoteits a pile of scrap metal enveloped in glass containers interconnected with other bits of metal, carbon and paper. it's got just as much 'soul' as a pile of refined sand with some inmpurities encapsulated in black epoxy..Quotei will take my hat off to the first guy that can make a working ball-valve amplifier .

author: calexanian
author_rank: Super Contributor
timestamp: December 10, 2013, 03:22:52 am
content: Quote from: free_electron on December 10, 2013, 01:39:46 amWell, lets see. If the ball valve has pot metal and any copper on it we can get some zinc oxide and come copper oxide. Can make some crude rectifiers with that. Hmmm.... Nah, I got nothing....