Can I build a Simple amp with a $20 tube console

[bft450]

I am a first time poster and a tube amp newby I am hoping for some guidance on a possible project.

I am a good solderer and I am comfortable working with high voltage electrical devices but tube are totally new to me.

I have plenty of tools but only a multimeter for electrical testing

I have acquired the following items over the last couple years and I think I have enough second hand junk to make something really cool.

Here is what I have

Mid sixties magnavox tube amp and receiver from a console stereo
Includes:
Transformer
4 6v6gt tubes and sockets
2 12ax7 tubes and sockets
1 5u4gb rectifier tube with socket
3 small transformers
tons of various resistors and capacitors

A cheap solid state crate bass amp with a decent 4 ohm 10" speaker and a nice cabinet and a chassis full of solid state electronics

What would be the best circuit to use with the stuff I already have?

Is it worth it?

Am I waisting my time?

[JohnnyCrash]

I'm guessing (though I might be wrong), that the Magnavox is a stereo amplifier.

If this is the case two of those transformers will be output/audio, one will be the power (the big one), and one will be a choke.

Do you have a specific model number on the stereo? Hopefully we can find a schematic to figure out the parts you can use.

--

If it is a dual 2x6V6 stereo amp, you could probably make a 5E3 (and have an extra pair of 6V6's and extra OT for another 5E3).

The major problem then would be in drilling/cutting the old SS amp's chassis to mount the tube sockets and transformers. Second, you might run into problems with space inside the cab - if the tubes hang down and the speaker is in the way, etc.

--

First we have to figure out what parts are useable from the stereo - mainly what the OTs (if it is a 4x6V6 or if it is a dual 2x6V6 setup)... for that we'll either need more in depth photos, or a model number and schematic.

[bft450]

I have found a few numbers on the amp

magnavox console # 1st231L

t-16 and 176-67 are stamped on the chassis

it is still operational so I could take some voltage measurements

[bft450]

I am pretty sure it is a stereo amplifier

[bdgregory]

that magnavox is a stereo amp, and very much in demand by folks who want to use it for stereo audio. There may be better amps to start with, but as Johnnycrash suggests you can get 1 1/2 5E3's out of it. If it were me I'd refurb it for audio use, and get a mono carcass to build a guitar amp from.

[bft450]

Thanks Johnnycrash and bdgregory!

I think I will try to build a 5e3 amp with my existing chassis(from the bass amp) If it works out I will put it in a nice chassis and cab.

I am going to start modding the cab while I source the parts I need.

Is there any way to make sure these transformers have the correct output before I get started?

Thanks for the help!

[bdgregory]

the power transformer will have adequate voltage/output for the filaments, but the secondary hi voltage may be (probably will be) different than the design of your "to be" schematic calls for. You can correct for this with resistor adjustments if it's too far off. The outputs are more than likely 4 ohm, but you can test this using the procedure in this link

it would also help if you had a schematic for your magnavox. It appears to be a Magnavox 175 chassis. You may want to google that . . . there's a lot of discussion on that amp in Audiokarma

[Wally]

Originally Posted by bdgregory

that magnavox is a stereo amp, and very much in demand by folks who want to use it for stereo audio. There may be better amps to start with, but as Johnnycrash suggests you can get 1 1/2 5E3's out of it. If it were me I'd refurb it for audio use, and get a mono carcass to build a guitar amp from.

bft450, you might take note of bdgregory's first observation above.
'verymuch in demand' might well translate into 'someone will pay you enough for that stereo console amp to buy the kit to build a 5E3 amp'?????
Imho, it would be a shame to waste a stereo amplifier like that. IF you have ever heard CD's through a tube amplification system you would understand. Tubes make digital sound so much better. We won't even go into what other forms of recorded music sound like on a tube system.
Building the 5E3 from a kit would be simpler, quicker and.....you would have a 12" speaker in a larger box as opposed to the 10" in that little Crate. BTW, I happen to have the same Crate cab, but it is in stained solid pine wood with dove-tailed joints instead of vinyl covering. You might check the joints on that one. This one I have is a cool little cab in a way. I plan on putting a small...read single 6V6 or EL-84 ....amp in there someday.

[bft450]

Wally- Thanks, I agree.

A fellow member has offered to build me a chassis in trade for the magnavox amp. I think I am going for the deal. My next quest is to build a nice cabinet. I think I will take a smaller bite of the home-brew electronics by building a couple pedal kits and then tackle the amp build later. It is just alot to learn at once!

Thanks for your advice and guidance.

[JohnnyCrash]

An old record player and a stereo tube console sure does sound like a sweet setup... maybe I'll build me one.

If its worth dough, selling or trading is good advice.

You can find tube stereo console kits/instructions as well... so if you still want a nice home audio setup, you could build one :)

[bdgregory]

does this look familiar? Sold for $200 w/i a few days of listing.

I've been doodling with a lot of vintage tube amps over the last year+. I keep the stereo amps for hi fi use (I have a couple of these magnavox console amps and they sound really nice). I've found there's an abundance of vintage Mono tube amps that are easily converted for guitar use (though I haven't perfected my "technique). If you keep your eye open on ebay or Craig's list they can be found for anywhere from $15 - $50 depending on whether they're a brand name or no name, and condition. Conversion can be done by simple mod of the circuit, or you can replace the circuit with a common Fender or other brand off readily available schematics, reusing as many components as possible. Usually this means you need to replace capacitors and a few resistors. Of course if the tubes aren't good you'll need those too. The hard part from a labor point of view is packaging these into a proper cabinet as the chassis are all different.

I'm not sure if this is any cheaper or easier than building from a kit, but most of the kits I've seen are pretty pricey for what you get.

[keithcc]

Converting ANY old console amp these days into a guitar amp is likely to be economically a bad move, because people are buying these things for stereo and paying more than the parts value.

That said they will yield a lot of good parts.

Old mono low power PA amps are probably the best conversion fodder today. Be advised though that if the output transformer has a lot of different output taps it will probably die young in guitar service. I am referring specifically to the ones that had 500 or 600 ohm or 100 or 70 volt distribution outputs. When pushed hard there will be a lot of voltage across this winding and because these transformers are old typically they will fail hypot and arc out.

Larger potted sealed types are an exception.