Tube Valve 5.1 Home Theater [Early Research] - Page 1
Forum section: electronics / projects

author: nanogennari
author_rank: Newbie
timestamp: July 23, 2014, 05:08:50 am
content: Hello,I'm researching to make what i am calling "The Ultimate Tube Valve 5.1 Home Theater", i am new here in the forum, but i have some background in electronics, mostly with digital things, never done something so analog.My idea is to make something not so powerful, the focus is in sound quality. I want all digital controls with an analog feeling (some pot knobs connected to an microcontroler). And to complete things i'm thinking to add an Raspberry pi and an HDD or something running an MDP server or something like.I will divide the project in four parts:1. The amplifier electronics.2. The control electronics.3. The speakers.4. The MDP server.I wold love to hear some suggestions, tips and etc. The fist thing i want to decide is the kind of Tube Valve i will use, i have no experience with valves, so... (And unfortunately i live in Brazil and we don't have good suppliers here, most of my things are bough directly from china, there are not a lot of suppliers who ship to Brazil and even less who ship at a fair shipping cost).Sorry if my English bothers you, i still need to enhance it.I will post updates here, and of course it will be opensource/openhardware, see you guys later...

author: nanogennari
author_rank: Newbie
timestamp: July 23, 2014, 05:09:32 am
content: Reserved for future updates.

author: nanogennari
author_rank: Newbie
timestamp: July 23, 2014, 05:09:54 am
content: Reserved for future updates.

author: calexanian
author_rank: Super Contributor
timestamp: July 23, 2014, 05:27:29 am
content: The tube amplifier part is well covered all over the internet. The hard part you are going to get into is finding a suitable high quality 5.1 audio break out system that does not cost a small fortune. That's my two cents. Most of the cheap ones online are of terrible quality from what I understand.

author: nanogennari
author_rank: Newbie
timestamp: July 23, 2014, 06:34:46 am
content: Quote from: calexanian on July 23, 2014, 05:27:29 amI don't plan to put an audio break out (at least not from beginning) i use my PC for everything, including media/TV etc, so i can use the motherboard analog 5.1 output, and in the future i can put a good PCIe soundcard in the pc to enhance sound quality.

author: VK5RC
author_rank: Unknown
timestamp: July 23, 2014, 06:44:43 am
content: Isn't the real killer the impedance matching output /speaker transformers, you will need 6 of them. Linearity/Frequency response will be a real challenge!

author: dannyf
author_rank: Super Contributor
timestamp: July 23, 2014, 02:43:44 pm
content: -The fist thing i want to decide is the kind of Tube Valve i will use,-you typically don't care much about sound quality in an av IE 5.1 system. People tend to invest in sound quality in a stereo ie2.0 system.if I were you, I would think first about output requirement (what impedance, what type of speakers, ...), the topology, then output devices...for topology, google Williamson amplifier. There are also hybrid amps too.

author: calexanian
author_rank: Super Contributor
timestamp: July 23, 2014, 02:47:15 pm
content: Quote from: VK5RC on July 23, 2014, 06:44:43 amYou could skimp on the 4 corner amplifiers. Surround sound limits the low frequency responce to them and rolls off below 100 hz. The center channel should be 30hz to 20khz full power bandwidth and the sub needs to have a low freq roll off at 20 hz. Hammond has suitable output transformers in thier catalog, but you are looking at several hundred dollars worth of them! It may be. Easier and cheaper to buy used tube amplifiers and line them up.

author: SirNick
author_rank: Frequent Contributor
timestamp: July 23, 2014, 06:47:16 pm
content: Why not just use (e.g.) an Outlaw Audio model 975 for the decoding and switching, and build your tube amps as normal power amplifiers? Any time you have to introduce a general-purpose computer, the results are going to be a compromise.

author: dannyf
author_rank: Super Contributor
timestamp: July 24, 2014, 12:12:01 am
content: !Surround sound limits the low frequency responce to them and rolls off below 100 hz.-that's just for some surround sound formats.it is better and more flexible to make all channels identical, other than lfe.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 24, 2014, 12:45:30 am
content: Would tube preamps followed by modern HVIC amps be good enough?

author: jaxbird
author_rank: Frequent Contributor
timestamp: July 24, 2014, 02:22:43 pm
content: Tube amplifiers are interesting and fun, but I really would not recommend them for a living room everyday use system.They are highly inefficient, e.g. I have a pair of 300B SET mono amplifiers, they consume about 75W each side and deliver max 5W with several % distortion!! The single ended ones are pretty much harmonic distortion generators.Besides poor efficiency they generally have very high output impedance meaning the frequency response of your speakers will change according to their impedance.Tubes are expensive, run hot and require lethal level voltages, if you have kids or pets you'll need to make sure they cannot get near them.If you still want tubes, go with something like EL34 or KT88 in push pull configuration and be prepared to spend a lot of money on transformers, both power and output

author: SirNick
author_rank: Frequent Contributor
timestamp: July 25, 2014, 08:58:56 pm
content: Quote from: dannyf on July 24, 2014, 12:12:01 amTechnically, yes and no. I looked at the spectral content of a handful of movies lately and anything goes in modern discrete multi-channel soundtracks. Some rear channels had marginal content down to infrasonic. Some were clearly rolled off at 30-40Hz. None that I found were high-passed at 80 to 100Hz.. HOWEVER... it is common (and usually desirable) for the decoder to have a HPF on all channels (except LFE of course) since nobody has a room that behaves well at sub-bass frequencies. Ideal placement for full-bandwidth speakers is often not the same as ideal placement for subwoofer(s), so best to leave the long-wave stuff to the one box that has a fighting chance of being placed optimally for that frequency range.Although, in reality, people usually seem to stuff the sub anywhere it can't be seen, and then stack all five main speakers up around the TV, so "ideal" placement is pretty much out the window anyway.

author: calexanian
author_rank: Super Contributor
timestamp: July 26, 2014, 07:03:10 am
content: I have found myself enjoying better quality sound, than proper placement, from 5 low cost tinny speakers. I just ran a cable from my TV over to my old mini stereo system and it actually sounds better. Lets just say I don't "Notice" the sound, or rather notice something wrong with it.I would rather have two decent sounding speakers and a sub (Modern movies need a sub) rather than 5 bad sounding ones.

author: Yago
author_rank: Frequent Contributor
timestamp: July 26, 2014, 03:00:05 pm
content: Quote from: calexanian on July 26, 2014, 07:03:10 amI have a stereo system for my PC/movies, and find that the dynamics are all over the place.Richard Crowley said it could be down to poor encoding of the 5:1 to stereo "mix".So, whilst in theory two good channels should win out, in practice they can be difficult to live with IMHE.

author: dannyf
author_rank: Super Contributor
timestamp: July 26, 2014, 03:05:31 pm
content: Over time, I have migrated to stereo listening, even for av materials, through logic 7

author: calexanian
author_rank: Super Contributor
timestamp: July 26, 2014, 05:06:43 pm
content: of course source material and the signal chain be it electronic or software digital decoding makes all the difference. garbage in, garbage out so to speak.

author: dannyf
author_rank: Super Contributor
timestamp: July 26, 2014, 05:31:47 pm
content: I'm sure it differs from person to person . For me, dsp is better turned off.

author: bob808
author_rank: Frequent Contributor
timestamp: July 27, 2014, 10:22:34 am
content: You could go for a push-pull system for better efficiency. With sensible drivers also you don't need much power. But in hot summer days you wish you'd have a solid state systemUsually tube are used for listening sessions not movies but hey...you can do anything

author: calexanian
author_rank: Super Contributor
timestamp: July 27, 2014, 07:44:23 pm
content: More on the philosophical side than technical, but I want to be drawn I to the movie, not think about the sound system.

author: dannyf
author_rank: Super Contributor
timestamp: July 27, 2014, 08:31:35 pm
content: QuoteValves have a considerable advantage over solid state for materials with high crest factors, like dialogues or explosions -> AV content.However, they are not that great in LFE.

author: ampdoctor
author_rank: Frequent Contributor
timestamp: July 27, 2014, 10:10:49 pm
content: Coming from somebody who works with tube audio day in and day out, if I were to design a home theater or actually any home audio system I'd stay with solid state front to back. Why? Tubes are shit when it comes to audio reproduction where you want to accurately hear what the artists and engineers want you to hear. No distortion, coloration of the sound, or generally quirky behavior allowed, or at least reduced to an acceptable minimum.Sitting back and visually appreciating the vibe of the the red and blue glow in blown glass reflected off of polished wood or metal in a beautifully engineered enclosure can be quite satisfying in it's own right but it's a completely different conversation. This is perfectly OK in my book, but it has nothing to do with the quality of the actual audio.Now, where tubes really shine is in the area of audio production. Here you may actually want the distortion products as well as the sound colored in specific ways and impart a "feel" to instrument amplifiers and arguably microphones that are very difficult if not impossible to mimic using digital methods. It's one tool out of many that are used for creating the audio that they want us to hear.

author: dannyf
author_rank: Super Contributor
timestamp: July 27, 2014, 11:26:32 pm
content: QuoteThose may be your criteria for a sound system but hardly everyone else's.

author: mark03
author_rank: Frequent Contributor
timestamp: July 28, 2014, 08:22:06 pm
content: Has anyone characterized tube-amplifier distortion and simulated it in a DSP? I realize part of the fun is in the old hardware (hey, I just built a nixie clock myself), but if it's the "tube sound" someone is after, surely it can't be that hard to just emulate it in software?

author: SirNick
author_rank: Frequent Contributor
timestamp: July 29, 2014, 08:21:27 pm
content: The recording and live sound industries try very hard at this. There are plugins for DAW software, digital modeling amplifiers, stompboxes, and rack units galore. The authenticity of such attempts is under much debate. Some people will tell you it's similar enough to be convincing. Others will tell you there's no comparison. Some of the latter will be influenced by the fact that they're looking at a solid-state box and not glowing tubes, and some of the former might be equally biased.

author: dannyf
author_rank: Super Contributor
timestamp: July 29, 2014, 08:59:59 pm
content: QuoteTwo (potential) sources for "tube sound":1) clipping behaviors: tubes clip gentally vs. hardly by solid state amps. This allows the similarly rated tube amps to handle more peak power without sounding as harsh as ss amps. This part is likely difficult to be characterized by a dsp.2) part of the tube distortion comes from transformers (particularly output transformers). It is fairly doable with a dsp.Multitudes of experiments have shown that when not pushed outside of their performance envelops (not clipping), tube amps are indistinguishable from ss amps.But to remain within its performance envelope, ss amps will need to be rated much higher than ss amps, when content of high crest factor is played.

author: ampdoctor
author_rank: Frequent Contributor
timestamp: July 30, 2014, 05:46:28 am
content: As Nick said, they've been trying to model tubes for decades with very little success until fairly recently. It's close, but it still not quite right. Having said that, once the audio gets past the mixing desk and over to the mastering house, the whole argument becomes moot. At that point the signal has been pushed through so much digital signal processing software that nobody is going to hear the difference. As such, I stand by my original comment that tubes are great for sound production at the front of the chain, but utterly pointless for reproduction.

author: VK5RC
author_rank: Unknown
timestamp: July 30, 2014, 11:26:17 am
content: The Australian popular electronics magazine "Silicon Chip" in its August 2014 out today, publishes a Valve sound simulator, it is described as having some high level clipping with mostly even order harmonics and a "soft' sounding spectrum with a bit of bass resonance circuits built in as well. Uses FET 2N5485.I don't like that "Valve" sound myself but accept others do.

author: ampdoctor
author_rank: Frequent Contributor
timestamp: July 30, 2014, 11:03:38 pm
content: There's so much more to the "valve sound" than just second order harmonics. It's even AND odd order harmonics as well as their ratios and whether or not they're higher or lower order. Depending on the program material you'll get compression and/or hard limiting on the positive excursions depending on the magnitude and the frequency of the signals while the negative going signal remains relatively unadulterated. But that's not always the case as cathode bypass capacitance and local feedback can play havoc with this as well. Add in some sag and ringing from a shit power supply, and poorly designed output transformers, and a truckload of negative feedback on the power amp. Attempts to emulate the effects of all this at the same time is really like trying to hit a moving target and the result is a close approximation at best.

author: SirNick
author_rank: Frequent Contributor
timestamp: July 31, 2014, 12:57:57 am
content: That's probably true, but if you modeled each of those elements individually, the net result would probably be as close to the behavior of any given real tube amp as any other given tube amp is. I.e., it doesn't need to be a perfectly accurate reproduction of exactly one -- just a realistic emulation of any one.I think Peavey's amp sim product tries to do this (simulate the components), but I'm not sure how well they pulled it off. I got a demo a couple years back, but it didn't work very well for some technical reason that I can't remember now. Many of the others (Waves, etc.) seem to follow the "complete signal path" modeling approach. There are, indeed, probably too many variables to make the complete model behave identically to the original, even if a particular demo clip sounds similar, and that might be OK if it sounds good in its own right.

author: bob808
author_rank: Frequent Contributor
timestamp: July 31, 2014, 02:15:19 pm
content: You could also go for a hybrid setup, with tube preamp and SS output. That should give a bit of "warmth" or "tube sound" to the whole setup.

author: Lightages
author_rank: Unknown
timestamp: July 31, 2014, 03:11:17 pm
content: I have yet to see a budget attached to this. The pricing could go from $200 per channel to almost unlimited.You can eliminate the output transformers as there are such things as output transformerless amps, or you can buy off the shelf transformers, or even get them custom made.Do you want to power any random speaker? Are you willing to buy or make speakers specifically made with high efficiency just for this purpose? Is the LFE channel going to be tube also?Do you want to go silly audiophool or practical? How many watts? How many tubes per amp are you willing to manage?The only I see for using tubes is because you like them, rather than they are a better way of reproducing sound. If you agree, then using tubes for such a practical and specific use of a 5.1 theatre sound system is for bragging rights just because you want to. To do a 5.1 system correctly means having some power, and low requirements for maintenance and setup. Tubes rarely offer this at low cost.So what is your cost limit? Why do you really want tubes?