"It's not a bomb!"

aerius · Post by **aerius** » 2006-04-08 10:15am

One of my recurring dreams is coming home to find a SWAT team and bomb squad camped out in my appartment because someone mistook my audio gear for a bomb...

Rye · Post by **Rye** » 2006-04-08 10:43am

So what the hell is it?

muse · Post by **muse** » 2006-04-08 10:52am

An ugly hunk of junk which offends my aesthetic sensibilities.

kheegster · Post by **kheegster** » 2006-04-08 11:39am

Looks like containers of nitroglycerine with an attached timer to me....

Mrs Kendall · Post by **Mrs Kendall** » 2006-04-08 11:41am

What a messy looking home stereo system

I truly feel for J and muse who have to look at that everyday.

Bertie Wooster · Post by **Bertie Wooster** » 2006-04-08 12:07pm

Mrs Kendall wrote:What a messy looking home stereo system
I truly feel for J and muse who have to look at that everyday.

That's nothing. This guy I know has his house filled with gigantic transistor radios. The living room has about a dozen, the den has about a dozen, and the basement has several dozen. And these radios are huge; like the size of small refrigerators.

Imagine how that guy's wife deals with a house full of transistor radios.

TheBlackCat · Post by **TheBlackCat** » 2006-04-08 01:38pm

Rye wrote:So what the hell is it?

Looks like a bunch of massive capacitors and a few big-ass inductors wired to a circuit board and bolted to a piece of a table.

Isolder74 · Post by **Isolder74** » 2006-04-08 01:44pm

TheBlackCat wrote:
Rye wrote:So what the hell is it?
Looks like a bunch of massive capacitors and a few big-ass inductors wired to a circuit board and bolted to a piece of a table.

yep. and those capaciters have a very real possibility to go bang if wired wrong. It may not be a bomb but man put that thin in a box! If only to cover all those bare wires!

Braedley · Post by **Braedley** » 2006-04-08 03:56pm

Can I have the schematics for that?

aerius · Post by **aerius** » 2006-04-08 04:54pm

Rye wrote:So what the hell is it?

It's a vacuum tube headphone and speaker amplifier.

Braedley wrote:Can I have the schematics for that?

Amp schematic
Power supply schematic

The 2.3k resistor on the cathode of the ECC40 is actually a 5k resistor in parallel with a 5k 20-turn trimpot. This lets you adjust the left-right balance in case the tubes don't quite match. Use a straight 2.2k for the prototype build. The output transformer was stolen from another amplifier kit so I have no idea what it is. Look for an audio output transformer that's rated for an 8 Ohm output with a 7200 Ohm primary impedance and a ~10W power rating. The tube filament voltage is 6V, I forgot to put that on the schematic.

The cheapskate method is to order a toroidal power transformer from Digikey (part# 62031), wire together purple & black for the centre tap and put the secondaries in series for the output. Doesn't sound as good but it works.

The capacitors are Aerovox motor run capacitors, but you can use generic electrolytic ones. Just make sure they're rated for at least 250V and don't put them in backwards.

If you want to drive speakers, use a 6BL7 or 6BX7 instead of the 6SN7. Should be good for 3-5W.

BTW, good luck finding a socket for the ECC40 tube. You could use a 6CG7, 6FQ7, 6SN7, or 12AU7, sockets for those are easily available, but the tube pinouts are different so adjust schematic to match. Pinout for the ECC40 can be found here.

Oh yeah, forgot about the power supply notes in case anyone wants to build it. What I have is a complete overkill power supply. For size and practicality purposes, a CRCRCRCRC power supply will do. About 330uF for the first C, 220uF for the next 2, and 100uF for the last 2. Resistors should be about 500 Ohm to 1k, take the power for the output stage off the 3rd C and the input off the final one. The voltage will probably be a bit over 250V, but that's fine.

Ford Prefect · Post by **Ford Prefect** » 2006-04-08 08:20pm

Oh, wow.

Crossroads Inc. · Post by **Crossroads Inc.** » 2006-04-08 08:36pm

Vac-Vacuume tubes? Wow, WOW! My respect for you just soraed, seriously where does one even get Vacuume tubes these days?

Singular Quartet · Post by **Singular Quartet** » 2006-04-08 09:10pm

That's a good question, actually. I'd like to now, since it interests me to actually build a new amplifier, rather than use the pieces of shit I have now...

Spanky The Dolphin · Post by **Spanky The Dolphin** » 2006-04-08 09:47pm

Crossroads Inc. wrote:Vac-Vacuume tubes? Wow, WOW! My respect for you just soraed, seriously where does one even get Vacuume tubes these days?

Vacuum tubes are actually still widely used in many applications, particularly with high-end audio equipment. They're somewhat easy to get.

Plus, my guitar amp has vacuum tubes in it. A digital electric guitar is virtual heresy.

Gee-wiz, Fluke Starbucker!!

aerius · Post by **aerius** » 2006-04-08 10:24pm

Crossroads Inc. wrote:seriously where does one even get Vacuume tubes these days?

Singular Quartet wrote:That's a good question, actually. I'd like to now, since it interests me to actually build a new amplifier, rather than use the pieces of shit I have now...

From VacuumTubes.net of course, and my local electronics surplus stores.

Wicked Pilot · Post by **Wicked Pilot** » 2006-04-08 10:29pm

aerius wrote:It's a vacuum tube headphone and speaker amplifier.

Right. Don't worry, your secret war against Quebec is safe with us. Which part is the detonator?

phongn · Post by **phongn** » 2006-04-08 10:42pm

Ya'know, we have these magic things called transistors now

Spanky The Dolphin · Post by **Spanky The Dolphin** » 2006-04-08 10:50pm

phongn wrote:Ya'know, we have these magic things called transistors now

Tansistors are a rape against art for music electronics.

aerius · Post by **aerius** » 2006-04-08 10:56pm

phongn wrote:Ya'know, we have these magic things called transistors now

I have those too. The circuit board near the top is a Kevin Gilmore headphone amp, and there's another one of those inside the box. But tubes glow in the dark and look cooler.

J · Post by J » 2006-04-08 11:15pm

Mrs Kendall wrote:What a messy looking home stereo system
I truly feel for J and muse who have to look at that everyday.

He says he'll eventually stop tweaking it and build a pretty case for it, unfortunately I don't see that happening anytime soon. I have to admit though, it does sound great.

Alyeska · Post by **Alyeska** » 2006-04-08 11:37pm

Spanky The Dolphin wrote:
phongn wrote:Ya'know, we have these magic things called transistors now
Tansistors are a rape against art for music electronics.

Just like Vynle producers better music then CDs.

Vacume Tubes produce music that is of less quality then a transistor. A Transistor produces music as close to the real thing as possible. People who prefer vacume tubes are the sort who prefer sloppy listening and can't actualy stand to listen to the real thing. You might prefer vacume tubes, but they produce a technicaly lower copy reproduction.

Spanky The Dolphin · Post by **Spanky The Dolphin** » 2006-04-08 11:51pm

Frankly I'd never buy a digital electric guitar setup, that's sure as hell for certain. The amp's use of vacuum tubes is a major aspect to their sound.

Post by **Darth Wong** » 2006-04-08 11:54pm

Spanky The Dolphin wrote:Frankly I'd never buy a digital electric guitar setup, that's sure as hell for certain. The amp's use of vacuum tubes is a major aspect to their sound.

Did you know that people have made processing circuits that can duplicate the distortion products of vacuum tubes in transistor amps? Transistor amps only sound really bad when you drive them past their design limits, and in general, you can make a transistor with far more peak power output than a vacuum tube amp.

aerius · Post by **aerius** » 2006-04-09 12:20am

Alyeska wrote:Vacume Tubes produce music that is of less quality then a transistor. A Transistor produces music as close to the real thing as possible. People who prefer vacume tubes are the sort who prefer sloppy listening and can't actualy stand to listen to the real thing. You might prefer vacume tubes, but they produce a technicaly lower copy reproduction.

Depends. At the power levels required for most speakers, you're right. At the levels needed for headphones or pre-amps (fractions of a Watt), vacuum tubes are better because of their superior low-level linearity. You can see this by comparing the plate voltage curves of a tube and the transistor. The former will have parallel and mostly straight lines all the way down to the cutoff, while the latter has curved lines that become non-parallel near cut-off. Which means tubes perform best at low levels while transistors need to be cranked up a bit to work well. The linearity means you can do away with negative feedback altogether, which means better phase margins, slew rates, much reduced high order harmonic distortion and more natural sound.

Problem is none of the big tube amp companies design things right and they end up with mushy tubey sound because the tubes are being driven past specs and soft-clipping, and the output transformers are made for optimum power transfer instead of maximizing bandwidth. Design a tube amp right and you can have 0.05% THD measurements at up to maybe 5W or so.

Plate curves for 6SN7 tube PDF file, page 3.
Curves for transistor

Mrs Kendall · Post by **Mrs Kendall** » 2006-04-09 10:23am

J wrote:
Mrs Kendall wrote:What a messy looking home stereo system
I truly feel for J and muse who have to look at that everyday.
He says he'll eventually stop tweaking it and build a pretty case for it, unfortunately I don't see that happening anytime soon. I have to admit though, it does sound great.

Haha, the empty promises

Just kidding

Sounds good but looks fugly right