Creative Anachronism, a Raspberry Pi Vacuum Tube Amp

I really want one of these, though I can’t really justify it. I really have no use for it, or very little. It’s just so bizarre… like a steam locomotive with a computer-generated heads-up display.

It’s a combination of a Raspberry Pi computer and a tube amplifier.

Or, rather, it’s a tube amplifier that bolts onto a Raspberry Pi computer, the latter being ubiquitous.

I’m a big fan of the Raspberry Pi single-board computers, I have several of various generations around, three or four in use, a couple in old projects to be dismantled and a couple in not-yet-completed projects. I’ve written a fair amount about them, though not here yet- they are not just a whole lot of cheap fun, but a force in the entire computer industry. As of this writing they’ve sold over 10 million of them, there are probably hundreds of rivals out there with “me too” boards trying to capture part of that success (almost all missing a good part of the point, one way or another), and- the true measure of modern success- there are tens of thousands of Internet trolls out there loudly insisting that they’re completely useless, a ripoff, and that the ten-million-plus owners are just absolute fools.

My history with tube amplifiers is both shorter and much longer. For many decades I frankly dismissed claims that tube amplifiers sounded better than solid-state as nonsense. I had some understanding of such things, and the capability of solid-state electronics in the hands of those who REALLY understand it is such that it seemed completely unreasonable to assert that they couldn’t make it sound any way they wanted it to, including just like some archaic, obsolete gear with a whole lot of “slop” built into sound reproduction that used to be unavoidable. If you really wanted that “slop” in your reproduction, it seemed to me that it should be easy enough, no more than flipping a switch on a solid-state amp to emulate the older type.

I’ve slowly, slowly, and very reluctantly been forced to think otherwise. Especially reluctant especially since I still don’t have a “working hypothesis”, a mental model as to why it would be so difficult to capture that sound.

I still assume it’s possible, and is being done at higher price-points, based on what I read, but that is beyond my personal experience.

Let’s back up… I have a lot of practice guitar amplifiers of various brands and types. Since I don’t play on stage I rarely if ever need more than a tiny amp. I bought several and got to know their characteristics without ever considering a tube amplifier, for the reasons stated above. Yes, I was aware that in the field of guitar amplifiers especially there is a vocal contingent, perhaps the majority, who insist that tube amplifiers still sound better, but as I’ve said that simply made no sense to me.

One day, there was a considerable sale on a very small Vox tube amplifier, model AC4TV8, one of those steep-discount-for-maybe-a-few-hours things, and I “bit” just out of curiosity.

It took some getting used to. It’s dead simple, unlike inexpensive solid-state amps apparently there’s no temptation to load it with a lot of dubious modes and features. Slowly, though, it’s become my favorite practice amp. It’s hard for me to put my finger on the difference, but it just sounds “better”. Fundamentally better.

Which… leaves me with a whole lot of practice amps I don’t like so much anymore. Sigh.

Over a lot of time I mulled all this over in my mind, trying to make sense of it, but every explanation I came up with sounded a lot like rationalization. Eventually, though, I started thinking about my stereo music.

I’ve been around long enough to have experienced a fair amount of my favorite music in various formats. The first recordings I ever bought were 45 RPM vinyl, then 33 RPM albums. Then there were cassettes for a number of years, which were a step up in portability, durability, and lack of snap-crackle-pop and a step down in constant hiss. I never owned an 8-track, but experienced several. Then there came the CD, the first popular, successful digital format. At first we were thrilled, the detail was incredible, the imaging could be as well, transients were handled like never before, it didn’t hiss or crackle or wear at all, which was something of a miracle.

Problem is, although they could sound IMPRESSIVE, especially for older music it just didn’t sound very GOOD.

I understand the problems of re-mixing for digital, the problem of compressing of the dynamic range CD’s to cater to FM radio broadcast limitations, the orders of the harmonics… whatever it was though, a lot of older albums didn’t sound “right” anymore. And it wasn’t just that I was used to the way they used to sound, they also didn’t impress others with no preconceptions.

The most glaring case-in-point was Abbey Road by the Beatles. This is an album I’ve played thousands of times over my life, and one of the ones I loved dearly. When I got the CD version I played it, I WANTED to love it, and it was just… nasty. Harsh. Wrong. It was so heart-breaking to listen to in the new form (and of course the derivative “ripped” digital formats) that I couldn’t stand to listen to it anymore. I literally quit trying.

I started wondering if there was anything I could do about it, and my experience with the tube guitar amp was nagging at me, so I started idly looking at inexpensive ways to incorporate a tube stage into some system and just try it.

Since I’m a techno-geek I have and have had a lot of generations of stereo gear, some of which are still in storage and I’m about to get rid of, I even had a home theater of sorts for a while (with similar unlovable sound problems for music) but it eventually fell into disuse, and these days virtually all of my stereo music listening is at the keyboard of my computer, with a very modest system. At this writing it’s an S.M.S.L. SA-50 (Tripath chip driven) mini-amp, a couple of Pioneer SP-BS22-LR bookshelf speakers (Andrew Jones and all that, amazing sound for the price then), an Objective DAC and, most recently, a Bravo Ocean tube headphone amp/pre-amp. That last took me a LONG time to break down and buy, but it finally went on sale for a significant discount over normal street price (which is already low) and I “bit the bullet” and took a chance that I might improve my listening pleasure with older music from digital sources. It’s basically a headphone amp, but I rarely use it that way, it also has RCA analog-out that can be piped into another amp, and, surprisingly, doing so doesn’t bypass its own circuitry. I wasn’t even dead sure about that last point when I ordered it, some reviews said it worked that way but it wasn’t in the specs anywhere.

It worked.

Abbey Road sounds like I remembered it, but better. Rumors as well. Cream. Three Dog Night. Even new music sounds “better”, as in, just more pleasant to listen to.

There’s a huge difference between the basic purpose of guitar amplifiers and stereo amplifiers and their fundamental philosophies. “Hi-Fi” is still the holy grail of music REPRODUCTION, it is what everyone ostensibly strives for. With a guitar amp, you aren’t reproducing ANYTHING, you’re making original sound, and as Duke Ellington famously said, “If it sounds good, it IS good”.

For decade after decade I bought into that mindset. Not so much, anymore. After a while, the seeming-fact that the most accurate reproduction may not be the most pleasant to listen to just wears you down. It’s my music, I only listen to it for the pleasure of it, why should I sacrifice a large part of that pleasure for ANY theory? Maybe it’s just my age, but I haven’t got patience for that anymore. If it sounds good, it IS good.

When I bought the Ocean it bothered me that there was no bypass- meaning that playing some music through the tube amplfier (as a pre-amp) and other music directly from the DAC to the amp would be changing wiring around each time. That was a significant reservation. In practice, I just leave it on, everything seems to sound at least a little better, meaning only more pleasant to listen to.

Bravo, the manufacturer of my tube pre-amp who now has my gratitude, also designed the well-regarded “modder’s delight” V2 amplifier that this Raspberry Pi “hat” is based on, so I’m already favorably disposed to it, and I’ve been working on a small Raspberry Pi Internet radio/digital music system (and I hope, Bluetooth audio) for the bedroom… mostly on paper. Thing is, though, this has no RCA output jacks… so it’s really designed as a headphone amp only. I live in a detached single-family home, and although I have a LOT of headphones around I seem to use them very rarely. It would, I think, just be a waste.

It’s still very cool, though, and I can’t help wanting one, at least a little.

– Robert the Wombat

Update:  I’ve copied this update from the comments section (below) just so it won’t be missed by those interested:

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Michael Kelly
pi2design.com

Hi,

I wanted to let you know we have a new and updated version of our Raspberry Pi Tube hat. It’s called the 502HTA (ok, not the most brilliant name, but hey, I’m an engineer). We reduced the noise and increased the power output as well as made the entire design easier to put into a case. In fact we are offering it in it’s own fully enclosed acrylic case:

http://www.pi2design.com/502hta.html

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– Robert the Wombat