Suround Tube Amp?

[gavinzbitz]

Hope I'm Not a Pain by asking "Newb" type questions:

I have good understanding of electrical principles. Built lots of kits and digital electronics but tubes are new to me.

have had a monstrously complex idea which is prob wholly impractical. My solution is to break it down into manageable chunks.

Advice welcomed answers on a postcard.

Large "7.1" surround amp. Done wholly in tubes.
Display devices are to be glassware. Nixies and the like. Dekatrons, tuning eyes and crt's all worth consideration.

Preference is to use cheap readily available components.
Would like reliability and good sound quality.
Seen lots of cheap russian tubes (KW TUBES) any good?


Chunks are as follows:

Media box type PC. High quality 24bit 7.1 soundcard.

Alphanumeric Display module: Using Burrough's nixies. Multiplexed and interfaced with PIC's to a Basic Stamp. Display's information from serial feed from "mediabox" type PC

"Spectrum Analyser" using IN-9's or IN-13's - Russian Bargraph display's. Any ideas?

Stereo channels and centre channels high level of amplification for midrange. Ionising Tweeter Driven By Tube (Have Circuit)

Bass (Subwoofer channel) I have heard valves are not good for low frequency. Is this a myth? Any recommendations for sizeable power?

2 Surround channels. Lower powered.

2 rear Channels. Lower powered.

Pre amps for all the above.

I have seen a valve amp with a CRT display. what does this do? How is it wired? Does it display wave like osclloscope stylee?

This will give me loads of tubes to mount attractively in a massive case!!

Its a nice cocncept which I think for me to tackle as a whole project would be impractical but if I break it up into simpler modules then should be achievable.

Thanks folks for your tolerance.

I have big plans and limited means!!!!

Gavin

[Layberinthius]

So YOU'RE the guy who swiped all those bargraph tubes off ebay!!

Grr, anyway I'm not angry at you just ticked off because I thought I was the only one who came up with it :P

I've got plans for a 4 speaker setup using valves 50 watts per channel 2 at the back about 25w.

yeah, 2 at the back 2 at the front, not sure how it'll go although I intend on using 6L6's for the back channels as they don't need to be as high-powered and dynamically ranged as the frontend which is EH KT90..

But for a P-P setup for each channel you're just asking for trouble in reliability, go for single-ended OTL or straight SE which brings in power requirements.

I was worried about the source as to where I could get the source material from, soundcard or DVD but there are apparently plenty of surround material on the web for download.. and cheap soundcards to suit, however their response over a wide range of frequency is apparently very very poor so I gave up this idea based upon that alone.

Essentially you are limited to soundcards which isn't very vast with all the Creative Crup around...

For making a spectrum analyzer instead of a simple level bargraph display is actually quite dangerous and complex not to mention risky especially as to where you get the schematic for such a device that produces the variying current at differing ranges of frequency to drive the IN-9's and somesuch...

But would look COOL!!!
Very cool! and VERY TALL!!

Valves are excellent bass producers, you just need the proper cabinet design, proper drivers, proper power AND the proper circuit design to make nearly any valve produce only low frequencies, There is also more stress only producing low freq. maybe a schemat can be found that allows maximum efficiency at about 20-100hz

You would more likely need the most amount of power in bass production as it's merely a lower frequency when compared to your upper-hand.

I would go for KT88 or KT90 for Bass however you can get around it by making a very cool bass-rich and mid-rich speaker cabinet, of course placing in more factors like finding a design, driving it properly and of course the final factor, power.

Don't think for one second that this will all fit in the cabinet size of a Pioneer 5.1 or 7.1 setup tho if you're after compactness, punch and response, go for a Pioneer for $400 or around that, they give 50 watts per ch and are good performers...

I would say your front channels will take up 1/3 of your desk space for both channels in the same chassis..

My KT90 amp is proposed to take up 1/3 of my desk and 1m by 1/2 metre of my floor space for the PSU! and be a very good heater

Your bass amp could be built compact if you don't set it on fire. and don't care for looks...

valve amps though aren't really good communicators with CRT monitors, fans, speakers nearby or phones anything magnetic or has an energised coil.

Alphanumeric Display module: Using Burrough's nixies. Multiplexed and interfaced with PIC's to a Basic Stamp. Display's information from serial feed from "mediabox" type PC

I'd be very interested in the high-voltage interface between a Basic STAMP and how you interfaced with software/parallel/serial.

Ie it would be very cool to place a few Nixies to display different voltages like bias, B+. and then title display off winamp/xmms. An independent circuit in a RF tin box soldered to the chassis would be quite cool for just displaying voltages.

I am however very worried (terrified) at the thought of introducing noise from the computer! especially interfacing the computer's grounded chassis to the chassis of the amp!

All I have to say.. Cheers!,Shrug...

[EC8010]

The valve amplifier with a CRT was probably an EMI 555 stereo integrated PP EL84 amplifier. Bizarrely, the CRT was swept horizontally by rectified mains and vertical deflection displayed one channel in one semicircle and the other channel in the other. A far more useful display would have been to have applied one channel to the "X" plates, and the other channel to the "Y" plates, giving a Lissajous figure, which displays phase as well as amplitude. The posh name for this is an audio vectorscope. Making a 7.1 vectorscope is possible (they're available and popular), but not trivial.

[gavinzbitz]

No no no
I wasn't the guy who got the baragraph's from eBay honest. I am looking for some myself, so maybe if you are interested we could bulk buy and geta big discount??? There must be loads still available.

With regards to introducing noise from a computer, I have a solution i believe.

Why not use an external sound card? Using USB it would be possible to have the PC in another room with all its horrible electrical noise and nasty fan sounds pipe the digital audio down the line to the external sound card and from there to the amp.

M-Audio Sonica Theatre looks like a good bet.

I believe it uses the VIA chipset and gives 24kHz sampling and possibility for DVD-Audio quality sound.

I am reassured that Bass is not so much of a problem.

I was looking at using a horn design for the effeciency.

I have a lot to learn but it's nice to know someone else is working on something similar.

[gavinzbitz]

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=2596066519
For some more of the bargraph ones
Im not bidding on any yet
so you are welcome to them....
We should start a cartel and "moderate prices on eBay Sorta like a protection racket!!

With regards to the CRT's what is a lissajous figure?

"Making a 7.1 vectorscope is possible (they're available and popular), but not trivial."

Can you please explain what this means and how it functions?

Many thanks,
Gavin

[EC8010]

Once upon a time, when knights were bold and frequency counters were unheard of, the only way to determine frequency was to compare with another (known frequency). What you did was to apply the known frequency to the "X" plates, and the unknown to the "Y" plates. If the two were identical, and in phase, a straight line inclined at 45 degrees resulted. If they were the same frequency, but 90 degrees out of phase, a circle. If one was almost double the frequency of the other, a pattern with two peaks appeared to rotate about the vertical axis. When exactly twice, the rotation stops. If three times, three peaks appear. Get the idea? You have undoubtedly seen these Lissajous patterns in cheap science fiction or early James Bond films (I think they must be part of the standard laboratory shooting agreement).

For stereo audio, Lissajous figures are very revealing. The CRT is usually rotated by 45 degrees so that mono (identical, in phase) produces a vertical line, whereas out of phase mono produces a horizontal line. Thus, correct stereo produces a messy ball of wool aligned vertically, and its width indicates the amplitude of the stereo component. Lots of regular circles indicates synthesised stereo. (I keep meaning to add a small CRT to my pre-amplifier.)

For 7.1 etc, if you represent the listener in the centre of the CRT, then you could position the loudspeakers around the edges, and a line to one of those positions would represent audio coming from that source, and its length could represent amplitude. Such a line having magnitude and direction is known as a vector, thus the name vectorscope. Vectorscopes were essential for measuring colour information in the days of analogue PAL video.

Manipulating the signals to produce a 7.1 vectorscope display is rather harder than simply applying stereo to the "X" and "Y" plates.

EDIT: As an electrical engineer, vectors and phasors should be meat and drink to you, so you could easily do the required manipulation (all using valves).

[ErikdeBest]

I have nothing to add, just want to wish you good luck with this enormous project.

[Layberinthius]

Enormous is an understatement Enormously worrying is more like it

Go ahead dude grab those off ebay, If i'm right the folk is in Lithuania..

I've seen em go for about $20 per 5 probably costs $20-30 just for money order fees and postage fees ontop...!

That's why -I- backed off (at least for now) I would certianly love to come back sometime down the track and make up a channel level meter with em.

With the VIA chipset, avoid avoid avoid...maybe avoid.

I know VIA are slightly-cool and are apperently 'required' in this world however with what i've heared personally with onboard VIA sound it aint too great.

I guess what i'm saying is I'm worried as the "24kHz" aka "24bit"
96khz box may be cheap as chips... and poorly fried.

Using a USB external box is a /GREAT/ idea provided it has no noise like no-fans etc, replacing that plugpack power supply may be a good idea, if you're up to designing a clean low-voltage psu.

If you want good sound with the PC aka "CPU" from a distance
I myself have opted for an extended VGA cable and audio with KVM...the case is in another room!

I didn't buy an external sound'card' because of the price at the time when I had money..

If you are friendly with USB you can probably have a splitter and place your digicam/keyboard/mouse/sound'card' on one USB line.

Bandwidth issues might creep up tho.

Find something else equivalent, or if you're confident, go for it.:P

[gavinzbitz]

>I guess what i'm saying is I'm worried as the "24kHz" aka "24bit"
>96khz box may be cheap as chips... and poorly fried.

Sorry brain not keeping pace with hands..... Problematico Technico.

There is no external "powerpack" it is all powered from the USB.

Creative have released one which is better, I have found out that you can only use the 96kHz sampling on two channels at once with the M-Audio Big boo boo.

I think that I shal experiment with the amps. If I build them one by one then I can make the system as modular as possible, this way I break the project down into manageable chunks.

I think how I shall proceed with the project is to get 4 amps built to begin with, then invest in the best external audio box at the time, but I shall bear in mind that this technology is liable to improve so keep "upgrading"" the amp as and when. Just a matter of changing the drivers and plugging the new one in.

With regard to using the USB for all it might be a good idea to get a cheap hub. I dont think the bandwidth problems will be evident if using USB 2. Keyboard shortcuts and mousing take up very little bandwidth so I am told.

[Layberinthius]

Nod nod, reason why I didn't buy one cause creative's prices were sky high :P

BUT anyway good luck!! and the keyb/mouse more than likely don't take up too much bandwidth :P