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Old 28th April 2010, 05:31 AM   #1
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Default Help with tube stereo build

I want to build a tube stereo amplifier. I'm done with waiting around for somebody to sell one here in town in the classified ad, and the thrift stores never has any. EBay has tons but they are super expensive and the shipping charge is a beast.
I want to build one for myself. Can anybody help me with an appropriate design? I would like to use it to drive the audio signal from a bunch of goodies, like my Xbox 360, computer, CD player, TV/VCR. I won't be using a record player with this, ever.

I'd like it to have RCA inputs with a selector knob for it. Speaker wire jacks for speakers, two channels A/B. A headphone jack for headphones with a switch. A nice analog volume control with Bass/treble controls.
It will be open on the top to show off the glowing tubes and chassis. The chassis can be aluminum I've seen other tube stereo designs and they have only two tubes plus the rectifier tube for the power supply. This tube stereo amp is going to be a special thing I will have for a long time, I want bunch tubes in the design so it sounds really awesome and looks as good as it sounds. Also it will be grounded and have a fuse in there and anywhere else it needs it.

My hope is to build this bad boy for under $200. Thanks.
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Old 28th April 2010, 05:36 AM   #2
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Originally Posted by CivicProtection View Post
My hope is to build this bad boy for under $200. Thanks.
Not. Gonna. Happen.
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Old 28th April 2010, 05:54 AM   #3
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Originally Posted by Miles Prower View Post
Not. Gonna. Happen.
I forgot to mention that I have a transformer and a bunch of stuff from a scrapped chassis.
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Old 28th April 2010, 07:31 AM   #4
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still unlikely to happen.

However - what have you got??? The transformers especially are the expensive bits and will absolutely dictate the rest of any usable recommendations.
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Old 28th April 2010, 09:59 AM   #5
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Not. Gonna. Happen.
Unless your prepared to drop most of the frills I have to agree with Miles.

Have you considered a very basic kit like the k502 and add the frills later.

How about a donor amp, faulty amps can be had quite cheaply on Ebay and can be rewired according to some of the excellent designs worked out on this forum


Good luck
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Old 28th April 2010, 12:08 PM   #6
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Originally Posted by CivicProtection View Post
Also it will be grounded and have a fuse in there and anywhere else it needs it.
I built a little 2-tube guitar amp a little while ago. The only expensive bit I allowed myself was the Jensen speaker.

I like it, but it's in an unpainted MDF cab without even a carrying handle. The cost of the chassis, parts, shipping, basic cutting of the MDF and excluding the spring reverb, was 120% of the retail cost of an entry-level Fender tube amp with digital effects front end. That's without labour, and I didn't have to buy tools, hook-up wire and other consumables such as solder only because I'd bought them already.

One of the good things about desire is that it makes you raise your sights. If you really want what you've described, then realistically you're gonna need some more money. Therefore you will have to earn it, helping us all out of the recession. (Yes, that much...)

Photograph everything you've got including the chassis IN USEABLE QUALITY and post the photos.

w
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Old 28th April 2010, 04:52 PM   #7
kevinkr is offline kevinkr  United States
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I think you could build a very simple SE amplifier using a pair of Edcor transformers, a small Allied power transformer (The one George/Tubelab recommends) a pair of 6P14P or 6BQ5 and a 6DJ8 driver on an inexpensive aluminum chassis for about the amount of money you propose. No tube rectifier, and no boutique parts whatsoever, however everything you would need is readily and cheaply available from Mouser, Digikey, Edcor, and Allied. The specified iron would eat about $60 - $80 of your budget, leaving plenty for the rest. (Which could include a decent volume control pot, source selector and a couple of inputs, generic binding posts on the outputs.)

The bigger question is do you have the required skills to assemble and debug something like this, and can you live with just a couple of watts of SE power?

Also I think you need to think simple - forgo the tone controls, and a lot of tubes. Your budget will not allow for a fancy high end amp, but you can put together something nice looking and good sounding if you are very careful. Put the most money in the output transformers as this will determine the end result.

Hamfests and eBay are a good source of parts. Ebay for jacks, switches, fuse holders, binding posts, sockets, wire and the like. Hamfests for tube sockets, resistors, and other passive parts, not to mention tools. Get your caps from Digikey or Mouser.

If you can spend more money over time buy one of Tube Lab's Simple SE amps.
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Last edited by kevinkr; 28th April 2010 at 05:00 PM.
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Old 29th April 2010, 12:16 AM   #8
SHiFTY is offline SHiFTY  New Zealand
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I think a simple single-ended EL84 or even EL34 amp should be do-able for that kind of money! You can get quite creative on it...

Thoughts:

1) What is the chassis that you have already, and what is the lineup of tubes was it powering? eg. 5U4, 6L6, etc. Do you have a pic? Also did you keep the old tubes as they rarely go bad; the older ones are pretty rugged actually.

2) Old computer gear (switches, routers, modems etc) can be a good source for a compact high-quality metal chassis. Failing that, a simple wooden box of some kind with a metal top plate is fine. A wine bottle gift box or jewellery box could work nicely.

3) Output transformers- you are best to get good ones as it really is what makes or breaks an amp. Generally the heavier the better. You can get second hand vintage ones for next to nothing off that well-known auction site, just watch the specs are right for what you are building (PP and SE are not interchangeable!) also watch shipping costs. I have seen full transformer sets (power plus choke plus outputs) go dirt cheap. Oh to be closer to Nth America, costs a fortune to ship anything like that down here to the south Pacific.

4) If you want a source of cheap RCA jacks and other bits, see if you can scrounge a dead 1970s/1980s hi-fi amp, before they went to digital control circuitry. Heck see if you can scrounge a broken tube amp, tube reel to reel or large tube radio- lots of useful bits.

5) An input selector switch and headphone jack could easily be rigged up- you might have to see what impedance your phones are though and mess around to get it right. Or buy a separate preamp and build a tube power amp only.

6) You could do a bit of reading- here is a start that got me into it!

Boozhound Laboratories

Last edited by SHiFTY; 29th April 2010 at 12:21 AM.
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Old 29th April 2010, 12:44 AM   #9
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Originally Posted by Miles Prower View Post
Not. Gonna. Happen.
Déjà vu. You don't do flashlights by any chance, or is there something else which moved us both?

CPFMarketPlace - View Single Post - 4Sevens Quark with Piston Drive?

You might try Eli's "Dirt Cheap", which comes in a smidge less than his "El Cheapo". I haven't built it yet, but I'm gonna have one any day now I tell ya.

Audiophiletalk - DIRT CHEAP SE amp
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Old 29th April 2010, 01:13 AM   #10
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Originally Posted by Ty_Bower View Post
Déjà vu. You don't do flashlights by any chance...
No, never saw that site before.

Quote:
...or is there something else which moved us both?
Definitely something else. The OP was asking way too much for way too little.

Quote:
This tube stereo amp is going to be a special thing I will have for a long time, I want bunch tubes in the design so it sounds really awesome and looks as good as it sounds.
I did a stereo VT amp that fits that description quite well, but I sure didn't keep it under $200 despite being able to use the power xfmr from an old color TV, and a few other junk box pickin's (main PS ripple chokes, some Octal VT sockets, a fuse holder, some PS capacitors).

You might be able to make a decent solid state project for under $200, but it would be very difficult to do so with hollow state, even if you had all the equipment to wind your own OPTs since lams and "magnet wire" aren't exactly cheap either.
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