My first scratch-built Vacuum Tube Amplifier: "Big Red"

[heekma]

http://imgur.com/a/WryJS#17

Hi folks.  This is my first post here, I was brought here from reddit.com.  Forgive me it this isn't the correct place to post.

If anyone has any questions, ask, I'll do my best to answer.  Bare in mind I'm a hobbiest, not a EE, but I'll do what I can.

Thanks,

Heekma

[c4757p]

While I think you'll find that audio, and particularly tubes, aren't very popular here, I for one like them, and I must say that is beautifully constructed. Nice wiring! You've definitely gilded the lily (Is the volume control really custom? That seems a bit unnecessary...) but you have obviously put a ton of work in here.

[GreyWoolfe]

And it is a shame that tubes have lost favor here.  There is nothing like the sound of a tube amp.  And the glow can't be beat or duplicated.  Don't get me wrong, I love my digital music.  I DO miss my vinyl ( ruined when my 1st wife and I split)  I loved the hiss and pop.  Couple that with the warm wonderful sound of tubes, as people say on this blog, that is sex on a stick.

Tom, NW0lf

[SLJ]

Nice job.  Nothing wrong with tubes.

[Barryg41]

Nice Heekma,

I love working and tweaking on my Heathkit equipment. I can take as long as I want to, it will be there tomorrow.

Thanks for posting your pics.

[TimNJ]

I LOVE the wiring. Awesome job my friend!

[xrunner]

Wow! Nice job and I love the cloth-insulated wire. 

[robbag]

Take my money. That is art.

[c4757p]

I stand correcred

[Radio Tech]

Friggin awesome!
 

[dcel]

  Very nice construction! And yes, a work of art, great job! 

Tell us how it sounds, what inspired you, how long did it take, design decisions, component selection, etc.
Damit, we want details! You cant just post something as cool as this without telling the story.

Chris

[dannyf]

I loved the hiss and pop.

I am sure you can add that to your digital music to make it sound vinyl.

[dannyf]

And the glow can't be beat or duplicated.

There are some tube amps where the tubes are t here purely for decorative purposes and amber leds are used to emulate the "glow".

[grumpydoc]

There are some tube amps where the tubes are t here purely for decorative purposes and amber leds are used to emulate the "glow".

In that case they aren't "tube amps" surely?

[Zero999]

It looks nice.

People love to build copies of old valve amplifiers and play vinyl records for the same reason as why people play with old steam engines: it's fun!

[c4757p]

I loved the hiss and pop.

I am sure you can add that to your digital music to make it sound vinyl.

My take on any of this not-so-scientifically-solid audio stuff: music is art, and emotion and feeling are a perfectly legitimate part of art. It's probably more about the nostalgic element of having listened to it habitually in the past, which would be ruined by knowing it's artificial.

Personally, I find tube amps in general to sound identical to SS if done correctly (the only things that seem to set apart your "average" tube amp are mains hum and poor frequency response....). But if it makes you happy, it makes you happy. I like them for them a "nonsense" reason too: the fact that every single part of them is visible and traceable and even could, in theory, be built by hand with very simple, old techniques (yep, the tubes included) pairs well in my mind with what is the essence of music: simple, pleasing sounds, nothing more than that. No, it doesn't sound any different (again, in my opinion), and I wouldn't even dare try to argue that they are "better", I just like them. Why? Same reason I like vanilla cake better than chocolate - it pleases me more, for completely subjective non-reasons.

There are some tube amps where the tubes are t here purely for decorative purposes and amber leds are used to emulate the "glow".

This is purely pretentious "look how much I spent on something useless". Yuck.

[dannyf]

Same reason I like vanilla cake better than chocolate - it pleases me more, for completely subjective non-reasons.

This is purely pretentious "look how much I spent on something useless". Yuck.

Maybe what's useless is completely subjective non-reasons.

If it floats someone's boat and pleases him/her more, who are we to judge?

[c4757p]

True. And if having a tube sitting on top as an ornament, being lit by LEDs, is what makes you happy, then I guess it makes you happy. But I am willing to bet that more than a few of these are sold by smooth-talking liars trying to play up the vacuum tube/quality connection, to buyers who don't know any better and aren't really getting what they think they are getting. And another significant portion are going to people who will try to insist the very same thing to their friends. If that's not the case, then fine, it's a decoration, and most of us have some sort of decorations; I have no problem with that.

On the flip side, if you can like something for subjective reasons, you can also dislike it for subjective reasons. The idea of an LED-lit tube that does nothing seems a special order of useless to me... Yeah, I dislike it, I think it is very stupid and will happily say so. But that's just me - I'm just not much of a decoration person, in general, so I suppose I'm predisposed not to like it.

[baljemmett]

I loved the hiss and pop.

I am sure you can add that to your digital music to make it sound vinyl.

My take on any of this not-so-scientifically-solid audio stuff: music is art, and emotion and feeling are a perfectly legitimate part of art. It's probably more about the nostalgic element of having listened to it habitually in the past, which would be ruined by knowing it's artificial.

That, plus artificial noise can often be too obviously artificial - see, for example, fake old-film effects on TV programmes.  Sure, it'll go black and white and almost-convincing scratches and dust blobs might appear, but the picture behind it is usually far too crisp and detailed.  (Of course, this is often done as a gag more than anything...)

[zapta]

Very nice constructions. The cloth wires looks realistic. IIRC, the old soldering strips looked like these

http://www.ebay.com/itm/10x-Vintage-Solder-Terminal-Strip-9-lug-2-chassis-Deutschlaender-original-new/181251493093?_trksid=p2047675.m1850&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D11%26meid%3D3198529609349176811%26pid%3D100011%26prg%3D1005%26rk%3D1%26rkt%3D4%26sd%3D181230215342%26

[oldway]

I maked several vacuum tube amplifiers in the sixties and we where not concerned with the appearance of the wiring
The only important thing was to make the shortest possible connections to avoid oscillations and induced hum.
See for example the wiring of a "The Fischer" X100C:
http://classictubeaudio.com/projects/fisher/fisher-x-100-c-see-all-the-new-upgraded-parts/

But if your amplifier is stable and if there is no hum, it's ok.
(to be tested with 1khz square wave and resistive load: if there is no damped oscillations, that's allright.)
We also used to say that a vacuum tube amplifier is as good as his output transformers.

[larry42]

Really nicely constructed!

Being in the electronics industry for 15 years professionally (including designs with mm-wave GaAs FETs and 3000 euro FPGAs) - I like the idea of valve amps. In any case, it's my belief that the weak spots in audio are mainly the speakers and room acoustics... Now if only I had time to finish that EL34 amp and make the chassis for it. Making cases and the mechanics takes me approx. 10^6 times longer than doing the hardware parts on pieces of circuit board...

[N2IXK]

Nice job, beautiful wiring!

Are you having any issues with the 7591s? That was a really advanced type (very high Gm, high plate dissipation for size), introduced toward the end of the tube era, and it took a LOT of manufacturing mojo to get good product.  They were unavailable except as NOS for many years, and the first attempts to restart production (Russian) were really disappointing.  Have the new production tubes gotten more reliable?

[calexanian]

Nice job, beautiful wiring!

Are you having any issues with the 7591s? That was a really advanced type (very high Gm, high plate dissipation for size), introduced toward the end of the tube era, and it took a LOT of manufacturing mojo to get good product.  They were unavailable except as NOS for many years, and the first attempts to restart production (Russian) were really disappointing.  Have the new production tubes gotten more reliable?

Those are old 7591's. Sharp looking amp there.

The imports will never be able to produce the high gm tubes with any reliability for a number of reasons. First and foremost they do not understand grid shadow throttle control. Bud Ringmann was a forefather of that sort of high gm tube design in the 50's. The idea was simple. The screen to grid to cathode distances were so close that screen growth with heat would send the tube into thermal runaway. The solution to this was to stretch the grid (Normal part of grid winding) to a greater degree than the screen. As the screen would heat it would expand more into the shadow of the control grid and intercept less causing an inherent self limiting system. On a 6550 you can see a low freq. oscillation every few seconds in a tube that is working hard. thats this effect. Also for those high gm tubes the tolerances are extremely tight. A 6L6 or EL34 has enough space from cathode to grid to screen to use cut up index cards as spacers. Start with the bottom mica. Add the cathode. Slip a sleeve of paper around the cathode. Drop the grid over. add another paper sleeve. Drop the screen over. add the beam forming plate and fold over the tabs. move to swaging station. swage the grid. then using an optical comparator swage the screen in place where the bottom grid wire aligns with the bottom screen wire. If you look at the top screen wire it will be lower than the top grid wire. Swage the screen. Remove paper sleeves. install crimped plate assembly. Drop on top mica. Grid side rods go in first, the screen side rods, then beam forming plate upper tabs, then plate upper tabs, then cathode, which was held aligned with a pin up the center of it. fold over all tabs. spot weld on screen radiator. spot weld on getter. And.... Congratulations, you just built what is refereed to as a cage!! Now you take your stem. (The glass to metal seal part with the exhaust tubeulation on it) and pre bend and clip the lead in wires to the proper locations. Spot weld the heater to the proper leads and make sure its pointed in the right direction. drop the cage and fit the heater up the cathode. align the grid side rods and plate and beam former tabs by the pre bent stem wires and spot weld all connections. Inspect assembly for straightness and cleanliness. And now you have a mount! Time to put it standing up on a tray with the others and send it to sealing.

You think a worker in a cold damp factory with bad lighting and questionable power and water is going to get that procedure right every time, and the owners will let them take the time to do it? Hell no! I talk all the time with the owner of KR and JJ and even the guys in govt plants in china. They think it was insane that GE and RCA spent so much time cleaning and processing each tube. Its on and off their pumps in under 2 minutes. Chattam used to bake out their tubes for 4 to 8 hours a batch! We will never see that quality again because honestly, we cant afford it anymore.

Ok, where is the advil? hahahahaha

[robrenz]

Excellent work!