great video on what resistors around vacuum tubes in audio amps do - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: December 25, 2016, 03:22:13 am
content: I just go around learning bits and pieces here and thereResistors, Part 3: Grid Leak, Grid Stopper, and the Fender Input CircuitAnd Uncle Doug always has his cat and/or dog help outI can't post videos yet

author: lordvader88
author_rank: Frequent Contributor
timestamp: December 25, 2016, 03:50:45 am
content: oh I can, here's the other 2 resistorsResistors, Part 4: The Cathode Bias ResistorResistors, Part 5: Plate Resistors

author: Audioguru
author_rank: Super Contributor
timestamp: December 25, 2016, 02:20:35 pm
content: Audio amplifiers that use vacuum tubes are very obsolete.Some amps that have vacuum tubes have a solid state circuit with vacuum tubes on top for "show" and they are not part of the circuit.

author: karoru
author_rank: Regular Contributor
timestamp: December 25, 2016, 05:45:15 pm
content: Quote from: Audioguru on December 25, 2016, 02:20:35 pmThey aren't in one specific application - guitar/bass amps.

author: lordvader88
author_rank: Frequent Contributor
timestamp: December 25, 2016, 05:56:12 pm
content: still very informative on electricity overall, and they're NOT obsolete

author: Circlotron
author_rank: Super Contributor
timestamp: December 25, 2016, 10:01:55 pm
content: When used as a musical instrument amplifier, vacuum tubes can be made to gradually and progressively slide into distortion. This gives the instrument an added dimension of expression, similar perhaps to how the sound of a piano changes when it it played more energetically. It gains a more urgent sound because the harmonic structure of the notes change. In the case of a guitar amplifier, if this distortion is under the control of the musician it can be useful in producing the desired sound.Vacuum tubes may not necessarily be the best way for RE-producing music, but for producing music in the first place, many people like the added flexibility of tone *contributed* by a vacuum tube amplifier. For this purpose at least they are definitely not obsolete.

author: Dan Moos
author_rank: Frequent Contributor
timestamp: December 26, 2016, 01:20:29 am
content: Not obsolete in the guitar amp game. In fact, most pro level amps are tube. Its a completely different animal than the tube hifi thing, which is full of misunderstanding. With guitar, the LAST thing you want is a faithful hifi reproduction of the original guitar.With tube hifi, I think liking tube amps is fine, as long as you are honest with yourself that what you are hearing is a distorted signal, and as long as you are comfortable with realizing that with the expensive commercial tube hifi stuff, you are overpaying for that distortion. It IS a unique and pleasing sound sometimes for some people. If someone likes over priced 2nd order distortion in their sound, who am I to judge?

author: BravoV
author_rank: Super Contributor
timestamp: December 26, 2016, 01:25:53 am
content: So its just the shift in it's functionality as the tube now is valued more as an effect generator, rather than amplifier , CMIIW.

author: Dan Moos
author_rank: Frequent Contributor
timestamp: December 26, 2016, 04:08:03 am
content: Kinda. The amps are built around tubes using circuits that are mostly from the sixties. The side effects of doing so are pretty much the sound we have come to know as electric guitar.Much effort has been made to replicate the tone and response characteristics of tube guitar amps through solid state. It's very much cheaper, uses often 9 volts instead of 400, and is smaller. The closest analog attempt is using JFETS biased such that the dc operating point puts the signal in a part of the curves that is similar to popular triodes used in amps. JFETS are a pretty close solid state tube equivalent, in terms of circuit building.Digital modeling is the other method. The quality of these is fodder for long debate in guitarist circles. I think the better ones do a good job.Tubes are are actually decently linear compared to transistors. Manufacturing spread of parameters is often better also. For instance, current gain is far more predictable.What makes transistors better is that they are small and cheap. A 12AX7 preamp tube has two triodes in it. Think "transistor" when you hear triode. A typical gain stage will use one triode and a handful of passives. It will be far from linear.Done with solid state, you could easily use active load and current sources, cascodes, dif pairs, and use maybe even ten transistors. It will likely be very linear, cheaper, and smaller than the tube version.

author: amirm
author_rank: Regular Contributor
timestamp: December 26, 2016, 04:33:34 am
content: Tube products are hugely popular in high-end audio. And most are very pricey. An example is LAMM ML3 signature monoblock amplifier:The retail for a pair is $139,000!

author: lordvader88
author_rank: Frequent Contributor
timestamp: December 26, 2016, 05:54:15 am
content: I meant to say they are NOT obsolete, and I find VT/values fascinating. I bought 2 old tube radios, haven't messed with them yet though.They are electronics still on a much larger scale. And I love the history of it all.Oh man I had a small like 10" or 13" or so black and white TV growing up, and it was have busted. I remember watching Captain Power and The Soldiers of The Future on it, that was like the 1st TV show with computer graphics every week.But that TV was thrown out, damn I wish I had it now, old radio and TV repair videos are cool.

author: Circlotron
author_rank: Super Contributor
timestamp: December 26, 2016, 09:23:13 pm
content: Quote from: amirm on December 26, 2016, 04:33:34 amThat many dollars worth of vacuum tubes should certainly undo the effects of hundreds of opamps and other solid state stuff in the recording studio.

author: CZ101
author_rank: Contributor
timestamp: December 26, 2016, 11:30:53 pm
content: These "amplifiers" (compressor/limiters) are anything but obsolete (although some very unsavy audio "engineers" around the late 80s thought so and got rid of theirs - along with mics deemed "obsolete" back then - like the Neumann U67 and U47 - funny how things change)http://www.soundonsound.com/reviews/fairchild-660-670

author: amirm
author_rank: Regular Contributor
timestamp: December 27, 2016, 04:16:19 am
content: Quote from: Circlotron on December 26, 2016, 09:23:13 pmMore likely the high output impedance of tube amp interacts with the dynamic impedance of the speaker, changing the final frequency response. This tends to be more liked by many (not me) and possibly brings back how things sounded back in 1960s and 1970s music they grew up on.

author: Loboscope
author_rank: Regular Contributor
timestamp: December 27, 2016, 01:10:17 pm
content: I can understand totally the fascination of the oldfashioned analog tube technology and I still remember those old tube-tv´s I took up from the bulky waste when I was young and the time I disassembled them and tried to construct new items (but I mostly failed - but back then I learned from scratch any safety-rules and never to touch dangerous parts because of the well-known high voltages inside this tv´s!).And from an aesthetic point of view those ¨modern¨ hif-tube-amps are often nice to look at.But as a person who makes recordings in a professional manner, I can only agree that for audio-use tubes are definitely obsolete nowadays (except for example as a sort of effect-equipment as mentioned for guitar-players).To me this belongs more to the ¨audio-phoolery-community¨, comparable to the statements, vinyl-discs will sound better than digital and similar bullshit.

author: CZ101
author_rank: Contributor
timestamp: December 27, 2016, 04:59:39 pm
content: Quote from: Loboscope on December 27, 2016, 01:10:17 pmI guess those late 80s guys are still around.Remember that old effects box known as the LA2A? - nobody uses those anymore.Or those honky old ELAM 251's, or the C12 - "definitely obsolete". ()Oh wait - look what I found on eBay:http://www.ebay.com/itm/NEUMANN-M-269-CLASSIC-VINTAGE-LARGE-DIAPHRAGM-MULTI-PATTERN-AC701-TUBE-MIC-U67-/291910123856?hash=item43f7330150:g:3qQAAOSwqBJXWQZgCan you believe somebody would pay that much for one of those old pieces of junk? It's as though they're in demand or something. I doubt those people who buy something like that actually use it though. (sarcasm alert) And if they do, I doubt they know what they're doing. (more sarcasm alert)But wait a minute, this one is new!https://www.neumann.com/?lang=en&id=current_microphones&cid=m149_descriptionWhat is that company doing making new products that are so definitely obsolete? Golly.(as an analogy - few if any would claim that a wooden violin is "obsolete" - it just is what it is - and can't be replicated in a virtual sense - there are cheap ones, and there are expensive ones, there are old ones, and there are new ones, but they all live in the real world)

author: amirm
author_rank: Regular Contributor
timestamp: December 27, 2016, 05:34:14 pm
content: Quote from: CZ101 on December 27, 2016, 04:59:39 pmI don't know what there is to not believe. Many younger players want to sing into older microphones that were used by the great singers of the time to get the same tonality. I am not a recording guy but a quick search shows this hit on Gearslutz (eevblog for recording people):https://www.gearslutz.com/board/high-end/105100-neumann-m269-how-come-ive-never-heard.html"Stephen Paul once told me the 269 is George Massenburg's go to mic for Linda Ronstadts vocals but the diaphram in his has the .9 micron diaphram."If you don't know him George is one of the top recording engineers out there (Dixie Chicks, Billy Joel, Aaron Neville, etc). He is a multi-grammy award winner too."The M269 is our second choice for trumpet on scoring sessions (after RCA44bx).It is a very good mic. ""i do hip-hop mainly and i think its one of the best mics in the genre- its got this already compressed sound, punch and grit that just kills for rappers. yea the price is a bit of a bitch i wont lie.if anyone has any idea where i can get just the body from. please let me know"My chief designer used to run a home recording studio. He has mics that retail much more than this one and are a handful in the world. He had to buy them because he could not attract certain clientele without them.When it comes to creative aspect of audio, who is to question their choices? They like the sound and there is no other mic or DSP that can replicate it. It is not for me but it is for them.Edit: typo.

author: amirm
author_rank: Regular Contributor
timestamp: December 27, 2016, 05:42:24 pm
content: Quote from: Loboscope on December 27, 2016, 01:10:17 pmWell as a person doing that kind of work you should know then that the audio architecture is completely broken. To wit, the sound you hear most likely is not the sound that anyone using your recordings hear. There are no standards of production. Every producer uses different rooms and speakers to produce their content. And with the same true in home listening spaces, there is no way no how anyone hears the same sound that the talent/engineer heard when they approved the final products.It is this fundamental problem then that allows anything to go in high-end audio including tube amplifiers that change the sound of the speaker to their liking.Since these changes are measurable and readily apparent in double blind tests they don't fall in "audiophoolery" category. They are just preferences people have in the sound they want.The solution is to adopt what video has done which is to calibrate everything from source to playback to a standard. Then we can complain that someone is on purpose changing the sound they are hearing from the standard. No broken display in that manner gets praise.Sadly there is no such initiative in the industry. So we get to live with a broken end-to-end system.

author: razberik
author_rank: Frequent Contributor
timestamp: December 27, 2016, 06:26:39 pm
content: Quote from: Circlotron on December 25, 2016, 10:01:55 pmQuote from: Dan Moos on December 26, 2016, 01:20:29 amNice to say, but many electrical engineers will not understand what are you saying and they will simply not accept it. This is my personal experience when talked to a LOT OF them in various enviroments for many years.Propably it is since many electrical engineers dont know nothing about how guitar sound is created.I have a theory that if you want to describe some non-music person desired distortion of tube, you should avoid any talk about distortion and describe it as "postprocess effect".Quote from: BravoV on December 26, 2016, 01:25:53 amExactly. One should google Marshall JMP-1 preamplifier. There are two 12AX7 with no gain function. It is full of opamps. Tubes are only distorted effect producers.Quote from: Dan Moos on December 26, 2016, 04:08:03 amFractal Audio Axe-FX digital postproscessor is actually extreme close to good tube-effect simulation.Huge amount of guitarists have switched to this last years. 2U rack device for about 2000$ instead of tons of tube gear with investments of K$.

author: Loboscope
author_rank: Regular Contributor
timestamp: December 27, 2016, 09:55:39 pm
content: To avoid any misunderstanding: I dont care about people who want to use tube-devices, may it be tube-microphones, tube-preamps or amps, tube-effects and so on. I am glad to live in a free world and so anyone is free to decide his own preferences.And why should Neumann not offer a modern tube-mic? There is a market and a demand and they can make lots of money this it!But if some of these adepts claim, that only this sort of gear will produce the true and best sound and all hat modern digital stuff will be from the devil I permit myself to call this a bullshit. In my opinion, Geerslutz is not a sort of eevblog for audio, there you can find lots of gurus and audio-mystics. And as long as I could observe, the subject ¨microphones¨ is one of the most esoteric , mystic and non-objective items ever. There are simply really no objective tests which meet for example a standard like double-blind-tests. Only and ever subjective opinions, but mostly they pretend to be scientific but are nothing but opinions, mostly sentiments only.If you are a bit engaged in auditory nerophysiology and the brain-functions of hearing, you will know how easy it is to here great differences also if there are no differences at all!My main profession is (classical) musician and recording is only my secondary business. And I only record classical genres and acoustic ensembles like an orchestra, chorus, chamber music, organ etc. - no pop..And in this genre old technique or tube-technique is nearly irrelevant. You can find these audio-esoterics mostly in other genres like pop etc.I use some Neumanns, some AKG´s, some Sennheiser and Haun-Microphones, all are small-diaphragm. My preamps and interfaces are RME and Behringer (X18 + X32). And I can reproduce the sound of any natural instrument in a quasi neutral manner (within the scope of neutrality a technical reproduction can deliver).My customers are allways satified.

author: retrolefty
author_rank: Super Contributor
timestamp: December 27, 2016, 11:52:40 pm
content: QuoteI would say the same about loudspeakers but on a much larger scale. Speakers and mics are both electromechanical transducers that have pretty large variations in freq response, sensitivity, efficiency (for speakers). I have read over spec sheets for some lab type acoustic calibration microphones so I guess one could use such a 'calibrated lab mic' but I suspect the artist and golden ear crowd would turn their nose up on all but their price.How they 'sound' is pretty subjective and as already stated room layout and surface type have a significant effect. I would say for both kinds of products many buy by brand name or other subjective criteria, rather then choosing from a datasheet like pure electronic components.I'm a believer in the double-blind A/B/X testing method. If a listener can't ID mic X as either mic A or mic B at greater then 50/50 then it's just a subjective preference on the part of the listener.

author: CZ101
author_rank: Contributor
timestamp: December 28, 2016, 12:59:59 am
content: Quote from: amirm on December 27, 2016, 05:34:14 pmWatch out forsarcasm alerts.

author: CZ101
author_rank: Contributor
timestamp: December 28, 2016, 01:31:00 am
content: Quote from: Loboscope on December 27, 2016, 09:55:39 pmExactly. Which highlights the absurdity in proclaiming one or another type to be "obsolete".Quote from: Loboscope on December 27, 2016, 09:55:39 pmOut with the "old technique"! Who needs a Decca Tree nowadays anyway?Here are some crusty old folks making themselves irrelevant -http://www.tube-tech.com/TUBE-TECH-for-Classical-Music-95.html

author: vk6zgo
author_rank: Super Contributor
timestamp: December 28, 2016, 01:31:47 am
content: In the heyday of valve HIFI amplifiers it was never the intent of designers to have such a thing as "valve sound".Their ideal was "a piece of wire with gain",&properly designedvalve amplifiers went a long way towards achieving this.Modern solid state amplifiers do indeed have much more impressive distortion figures when tested using test equipment.Humans,however had the last revision of their inbuilt distortion discrimination many millennia ago,& I sorely doubt that they can tell the difference once distortion becomes below a few tenths of a %.Present day Solid State amplifiers also produce impressive power outputs ( & I'm talking real steady state outputs not the "pretend" stuff),but this is largely necessary to get a reasonable acoustic output from the horrifically inefficient loudspeaker enclosures used.Valve era enclosures (& drivers) were optimised for maximum efficiency--although by the very nature of loudspeakers,it is still lousy.The valve amplifier circuits which pop up on the Internet often use "parallel push-pull" combinations of lower rated power tubes as the large power tubes used as output devices have become "unobtainium".Such circuits have complexities & drawbacks that limit the available performance.I sometimes wonder why nobody has tried 6146 tubes as guitar amp finals--a friend of mine used 807s back in the 1960s!

author: TimFox
author_rank: Super Contributor
timestamp: December 28, 2016, 05:33:48 pm
content: The church where I was baptized used 6146s in the public-address amplifier. 807s are taller.

author: Circlotron
author_rank: Super Contributor
timestamp: December 28, 2016, 10:56:54 pm
content: 6146 or 807 would have been a great choice, with their anode connection on the top cap. No chance of flashover on the base like when pumping a pair of 6CA7s at 100 watts with 1600v peak on the anode pin. Also keeps the high level signal away from low level stuff. Maybe 6146 was simply a bit expensive?

author: Dan Moos
author_rank: Frequent Contributor
timestamp: December 29, 2016, 02:25:37 am
content: I think it's important to differentiate between tube hi fi, and tube guitar and recording equipment.Guitar, and recording are subjective things. It's not math at that level. Sure, old tube compressors are inferior from an engineering standpoint, but to many those flaws sound good. Saying that's not valid is like saying some colors are better than others for art.

author: CZ101
author_rank: Contributor
timestamp: December 29, 2016, 04:01:45 am
content: Quote from: Dan Moos on December 29, 2016, 02:25:37 amYes, and taking this a step further, tube guitar and tube recording equipment are generally on different planets (the latter's traditional goal being linearity).Quote from: Dan Moos on December 29, 2016, 02:25:37 amGood points. I would add that the "soft knee" / "vari-mu" characteristics of tube compressors aresuperiorfrom an engineering standpoint, depending on what one is trying to achieve.

author: lordvader88
author_rank: Frequent Contributor
timestamp: December 29, 2016, 05:28:01 am
content: They can do a hell of a lot more than be used for music, and the size of them really brings electricity up to our scale.

author: Circlotron
author_rank: Super Contributor
timestamp: December 29, 2016, 09:06:32 am
content: Solid state is for achieving a precise end result by a deadline on a weekday.Vacuum tubes are for relaxing and enjoying yourself on the weekend.