Homebrew Tube Amp - 5881 ultralinear dual mono

[throbbinnut]

@44433391 Ultralinear refers to an output stage that uses a transformer with a primary winding tap for the power tube(s) screen grid(s). It has lower impedance than pentode connection, and higher power output than triode connection. It's like the best of both setups.

[Ursenfuns]

It's wack tube-followers always talking smack bout mp3s. As if they would hear. If they were really into perfect signals, they would buy opamp-driven transistor-devices.

You don't wanna have good signals from a tube amp. You want big glowing tubes sticking out of the case, so the living-room looks more nice and you can prag about it :)

[HiFiReviewer]

LOL thats a "weaksource"

[throbbinnut]

@HiFiReviewer Yep, this was just a test. I'm not too picky, though I realize CD's or vinyl do sound better.

[HiFiReviewer]

@throbbinnut how much does it cost to build something like that?

[throbbinnut]

@HiFiReviewer I used a lot of scavenged parts that I have built up over the years, so I was able to build this for about $200. If you were to buy all of the parts new, it would probably cost about $600-$700 I'd guess.

[donnyab]

name sounds familiar are you on audioasylum

[throbbinnut]

@donnyab Yes, but I haven't posted anything in months.

[enigmaticmindx]

very nice! i notice a lot of people tend to use mp3 players for their tube amps, and the digital into analogue kinda sorta defeats the purpose although it clearly makes it sound better as i have done it myself. But what is the preferred inputs? like phonographs records and such? radio signals? i am trying to learn and am curious.

[throbbinnut]

@enigmaticmindx I use mp3 just because it's convenient. I also use CD's, FM radio, and vinyl. I think most people would say that CD or vinyl sound the best.

[Ihateirans]

Good point you made. I forgot about using 6CG7; an excellent choice. AC coupling has one important advantage over DC coupling. Shifts in operating point on the first stage will not affect the operating point on the second stage as it could quite significantly in a DC coupled amplifier, especially in small signal stages.

[Ihateirans]

Very nice . If I could take a guess at topology, one half 12AT7 is used as a common cathode voltage gain stage DC coupled to a phase splitter driving the push pull grids of your 5881s. If this is the case, you're right in that the design would benefit by adding a push-pull driver stage. 12AT7 is "nasty"; somewhat harsh and hard to tame. Try a 6SN7 as your push-pull driver, or 5687 if you want to keep the miniature nine-pin socket. Type 6SL7 makes a great input stage, or even a 6SN7.

[throbbinnut]

@Ihateirans That's pretty much it. The first 12AT7 triode is actually AC coupled to the second triode stage, which is a split-load phase inverter / driver. Not a lot of voltage swing, but enough for push-pull pentode output stage - not quite enough voltage swing for full power in push-pull ultralinear. Even though the 12AT7 has a bad reputation, I have quite a few of them, so I used them. If I were to do it over again, I would use 6CG7/6FQ7, which has the same curves as a 6SN7.

[Hengilbert]

nice soldiers you got there

[Cesarsound1]

throbbinnut,

Wonderful and well assembled DIY Tube Amp. Clean and warm sound. I also liked your Shack. Congratulations Sir.

[throbbinnut]

@Cesarsound1 Thanks man!

[leshoc]

I'll try it on my NAD integrated amp

[leshoc]

Do the toy soldiers help to increase the depth of the soundstage?

[throbbinnut]

@leshoc Yes, and they look cool.

[thehornypuppy]

And where is the time travel knob?

[throbbinnut]

@thehornypuppy It was removed from the design due to paradox problems.

[thehornypuppy]

@throbbinnut xD Don't get me wrong...it's just that it's really an amazing piece of equipment. i want a little monster like that.

[pikewerfer]

@throbbinnut So you're a son of ether? Cool, man! :-)

[throbbinnut]

@pikewerfer  Not sure what you mean, but yes!

[musmann]

Nice amp! However, I really hope you have some better speakers and a better source than an MP3 player.

[fernando140887]

Very cool man! Congrulations, what is the power RMS of the amplifier??

[throbbinnut]

Well, since I originally designed the driver stage for pentode, and the amp ended up being ultralinear, it's only good for 10 Watts rms. With a proper driver stage it would do 20 Watts rms. Since I only use about 2 Watts rms for my shop, I haven't rebuilt it. Yet.

[synth77]

just curious what do you do for a living is this related to it or is it a hobbie

[throbbinnut]

I build tube amps for my hobby, but I became an electrical engineer because of my love for old electronics. During the day I'm a telecom engineer - all modern digital equipment. At night it's all analog, tubes, high voltage, speakers, etc.

[DLOWSHIT]

COOL

[1runnynose]

I like those speakers!

[throbbinnut]

Thanks.

[donnyab]

nice but why go to all that trouble and then hook an mp3 player to it

[throbbinnut]

I'm not hard to please. MP3's are fine for me. One of the reasons I like tube amps is because they tend to warm up the sound of digital sources with a little bit of tube sweetness. I don't think I can hear above 16kHz anyway.

[VarykGerai]

magic. Ive even heard that some engineers write the ready track onto tape then back to digital.

[Mike82ARP]

Way cool!