lust, ecstasy… death!

let’s talk about the weather for a minute…

there was an enormous melt in the arctic last year, and while it may have been cold and snowy in many other places this winter, all that added moisture up north really messed up the weather in Scandinavia. the ocean has absorbed a lot of human made heat recently. and while there was no summer on the ground 2017 where i live, not as i understand summer in any case, and the winter alternated between constant rain and snow cannons, this last winter and summer thus far are the warmest since humans kept track of such things.

march 2018 has been one of the coldest marches on record. and just a few months after, it’s officially a drought now, more than 100 days without rain… and an endless heatwave. in southern Sweden, this is something that happens perhaps once every 1000 years. the new normal isn’t. the new normal is crazy.

it wasn’t either all that different in the world of pop culture either! sandwiched somewhere between directly anti-democratic american celebrity politics and the war in syria-iraq-afganistan-yemen and the proxy wars behind it, all the new displaced people, #metoo, #blacklivesmatter, the gun control “debate”, and all the dead schoolkids, you have the resident gangster narcissist fake president of the usa, his sick buddy benny, the chubby VX luvin thug in north korea, Putin, the GRU, america first – MAGA (wtf!), emperor Xi, fucking erdogan, the Saudis, the fake news press and the oil industry on it’s accelerated trajectory towards taking us all out for cash… and the media has been cheering on the weirdest derivative musical entertainment in fifty years.

there is no message beyond diversion, generally. and when there is, escape, self improvement and misinformation is the top shelf shit. even “gangster rap” has gone zombie (maybe that’s a good thing?). glitzy kitschy consumer bullshit about what matters most. it’s edm backed diva-retro 1970’s luv unlimited… in fake VR, marketing jingles. it’s highly engineered commercial nothingness. we all know that song… and it wasn’t all that great fun the first time around. pass the alcohol and thank goodness for Banksy.

where is the fucking anger? oh right…. facebook.

of course there are exceptions! i do enjoy some Cardi B. (i must admit “Lick”, from “GangsterBitchMusic vol.2 is especially appealing). she’s coquette and hyperbole, and the opposite of deep. her rhythm is fabulously slow. very entertaining/i laugh out loud! the new Cat Power is weirdly excellent (i thought i was all finished with that, if i ever actually was for it?), but Childish Gambino is telling us like it is: our civilization is really over, and it wasn’t ever civil. and it isn’t actually funny, even if that is the only real way to actually deliver news. it’s just amazing some people still want to hear it!

okay, what happens next? Glover, he was also great in the new star wars spin-off. Robot Love! thank goodness for hollywood. did those words actually come out of my mouth?

exceptions aside, there’s notta lotta meat on them potatoes. not even Beyoncé. where the fuck is the anger? is this shit really okay?

if i were to try to describe pop of the moment, it would be hyper predictable electronic soap-opera dreck with overtones of class warfare and undertones of soft drink and cigarette marketing (and alcohol/narcotics), and it’s direct opposite with a hint of hipster licorice. it’s designed to distract from the inevitable death we are rushing towards and promote more consumption. our way of living isn’t sustainable, so turn up the motherfucking volume and dance.

“that’s a bad song, petey! you wrote a bad song…” (flicks his cigarette butt at petey’s head).

sustainable“. it’s such a trendy word. according to real scientists, for us first world homo sapiens to get to something just a bit more sustainable, we would have to reduce our consumption to a third of what it is… minimally. something closer to what it is in the third world. concentrate human life in cities (efficiency), carefully phase out the suburbs (give it back to nature or turn it into city) and give the fauna a break. agriculture needs de-industrialization and re-bio diversification. having many many less babies would just really help a lot. we might also take better care of the ones that are already here! sustainable now is a matter of how to limit the natural resources we exploit to produce consumables that we quickly dump back into nature… which poisons it. leaving less living, and more death.

okay, well sustainable ain’t happening anytime soon is it? farewell and adieu fair codfish! rhino, and bullfrog… i remember bees! rain forest was a great idea… trout was nice. and that quaint chestnut, “penicillin”…

no one is singing those songs yet, but that is definitely coming: to a download near you. i can almost hear the music in my head now…

it should be clear that very few of us is doing anything even close to what is needed… and the message from above is still “buy more now!” do any of you dear readers get the idea anyone wants anything fundamental to actually change. and it would really have to if it were to resemble sustainable.

so let’s forget about sustainable.

let’s talk about death. death by privilege, by overdose, by ignorance, by denial… by design.

you know, civilized death.

no! let’s talk about technology! that comes up like a twitch… i suspect now that i belong to the last generation that grew up believing there was a solution to everything. that death itself would be obsolete, at some point. “there’s a way to fix that!” and technology would save us all. it should be really clear by now, no, there isn’t any way to fix all sorts of things. lots can’t be fixed. just like the living within our means as a species thing. the wealthy plan on and just might get some of that because they seem willing to eat the poor. or just suck on their precious bodily fluids… it makes “fear the walking dead” strangely relevant…

but i am also one of those weirdos that still somehow believes that it isn’t necessary to fuck someone over, in order to survive. because cooperation has ALWAYS proven more durable and less harmful than the more typically civilized investment in coercion at home and conquer abroad. it’s just that cooperation means sharing the spoils and there’s the rub: those accustomed to plenty and privilege don’t ordinarily share. and taking away privilege to make it fair, most often leads to where the usa is right now. let’s face it: fairness is a problem for civilization.

which leads me to my design topic of the day: sustainable analog. wtf!

what the fuck would a more or completely sustainable analog audio be about? how would it happen? is it even possible? and what would it look like?

CLASS A is not GREEN / CLASS D sucks less than it used to.

yes, i just had to admit it. but i’m still not interested in digital amplification. and no it still isn’t as pleasurable. and as a future with less of everything for most of us looms, pleasure is still important!

a new design manifesto?

well, what do you need for sustainable sound design? what are the goals and the ingredients for good long term, upgradable, non-planned-for-obsolescence, in terms of audio debauchery?

by no means will this be comprehensive… but as a start i want to list some basic concepts. many of which are already a strong part of the DIY tubed analog world. we have a head start on this sustainability thing, if you ask me. but why not extend that and look for opportunities? all one needs is an open mind and the willingness to change perspective… but i plan on revisiting this subject from now on, and revising many things…

a) recycle everything: why make the shit it’s made from twice, if we don’t have to?

b) reduce consumption: how much of everything does an audio system really need?

c) make it repairable/up-gradable: no more planned for obsolescence. plan to make it and keep it going… revisions welcome!

d) teach the basic skills necessary to accomplish all of the above to as many as possible, so that even if some aren’t interested in this work, most understand the how and why… and don’t fuck it up for others. if we understand the value our environment, we tend to shit on it less.

e) collective action is always more effective than rugged individualism. especially when it comes to shared experience.

f) it has to be fabulous… attraction is way more powerful than promotion.

okay! that’s a start! how might we turn this into practice?

the I to E converter

what? no one uses this in an analog fashion to do anything these days. except maybe cheap light meters? it is however, extremely popular in the digital domain. there are even power DACs (digital amplifiers) based upon this idea. well, is there something there for us?

I to E converters are also called transimpedance amplifiers because they take a varying current and turn it into a proportionally varying voltage: current in, voltage out. low impedance in, and high impedance out.

yer basic transimpedance amplifier with an op amp. (from wikipedia)
yer basic grounded grid triode

that isn’t all that different from the standard grounded grid operation of any triode… which you see above. driving a cathode takes current, and the output Z at the plate is much much higher. the linearity is good, if the triode has straight plate curves, and because the grid is grounded, the parasitic C between input and output is greatly reduced. although that isn’t going to help much driving a horn speaker, is it?

but what if we were to combine the ideas? a hybrid tube – power operational amplifier might have some interesting characteristics? tubes are still around… even really old ones. surplus is the name of the game. and, it could be made without a coupling transformer, a smaller footprint, and maybe even the op amp could be class AB, to save on power? of course it could be a tubed op amp, and that is something to look at… but to start with, lets start small and antagonistically non-vintage! however, no matter what we do, because the op amp is going to measure the plate current variation in the tube, and output a proportional voltage, we will retain the tube’s transfer characteristic in the final result. how would that look?

it isn’t directly obvious how to sense the plate current in the tube and get it into an op amp… unless we rearrange things a little:

how to get plate current into an op amp: use the virtual ground of the differential inputs

okay. it already doesn’t look like a grounded grid circuit any more…but the current from the tube is converted to a voltage out. of course there will be a voltage drop across Rnfb, because that is doing the I to E conversion. it also determines the feedback ratio. if Rnfb is about the size of a normal cathode resistor, we might be looking at the beginnings of a practical circuit? there is an offset voltage at the input, and the larger Rnfb is, the bigger that will be… also the gain will be quite low if the ratio is small. but a large value Rnfb will both reduce the tube gain/increase the op amp gain and increase output impedance.

what about a choke? plate chokes are beloved by many a skanky tube DIY audio nut… myself very much included. if we use a choke instead of Rnfb, the gain will be really high! but the low DCR will keep the offset voltage less. the gain is peaked actually…and depending upon the supply for the op amp, easily clipped. but now we have a low impedance current in, and high impedance voltage out… not pretty exactly, or even capable of driving the current needed. but an interesting puzzle.

not to mention, a sharp eyed follower of this blog will see an echo of the upside down amplifier here!

I to E with a choke for feedback
801A I to E w/choke sweep
1 Vpp 1 KHz input 801A I to E w/choke

above is a simmed sweep of an 801A vacuum tube in an I to E converter…  with a choke as the feedback element. i can imagine many of you thinking this is pointless on all accounts! it’s not flat… and it’s crazy distorted too! wtf!

but we have gone from a gain of 8 or 10, to a gain 70 dB at the peak… even though it looks a little weird, it’s not that different. well, there’s still no plate resistor and the op amp is in shunt with the cathode choke. actually, the plate voltage doesn’t change at all! only the plate current. and now we can use some regular nfb to get back to something sensible. like this:

compound feedback transimpedance amplifier

there are still problems to be solved before this becomes practical… tubes take a little time to warm up. and the biasing/offset voltages are a bit nutty. i am a rigidly firm believer in basically nothing, except for “no end user adjustments”. it’s against my religion. so it might be worth working some additional circuit features out before testing…. 

isolating the tube voltages from the op amp voltages will prevent fire alarms or fuses… that’s sustainable thinking right there! but how? Stefano Bae suggested a current mirror, and then we can directly couple the plate current to the input of the op amp… without risking the potentially high varying voltages common to tubes. he chose PMOS, so it has a sexy connection to CMOS integrated circuits (hahahhhaha). we both love the IXYS PMOS stuff. nice idea and safety first.

and a servo will insure i can hold on to my all important face, when it comes to user adjustable parts: there won’t be any. there are a few insanely useful op amps for this purpose… the one that comes to mind is the OPA445. up to +/- 45 Volts for the supplies.

practical tubed transimpedance amplifier
1 Vpp 1KHz input 801A I to E with second feedback loop closed


fft sweep of the above circuit

well there you have it: a practical version in a gain of ten size… except it still won’t drive a loudspeaker. fortunately, there are quite a few power op amps that will. i chose the venerable LM3886. it is typical among those that love “chip amps”, and has wonderful built in safety features, such as a mute and thermal shutdown. the above circuit is exactly what you see below, except for the choice of op amp. LT Spice doesn’t have a good model for power op amps… and i don’t need to make a model either, just the real thing.

50 watt hybrid transimpedance amplifier (with +/- 35 volt supplies)

so, to save time, i just used a 5687 so i could use the same supply (+/- 35 volts) as the op amp… for a more finished version i would use a 10 or an RCA 485 (a 5 volt 45, roughly)… or a 71A with 100 to 200 volts B+. but to prove it could be done, it was fun running the tube off the chip supply. remember, the plate voltage doesn’t change… only the plate current. so the plate voltage can be quite low before distortion becomes a problem. an LM3886 with +/- 35 volts can make more than 50 watts into 8 ohms… and it’s small.

hybrid tubed tech is generally ridiculed or hated by tube amp freaks and also by high ended hifi bluffs… they seem threatened by the possibility or condescending about any perceived diminishing of the “purity” of the old or the new. which is partly why it interests me so much! in every great intellectual fear is a good dose of desire, for death as much as love. and anger is just a shitty replacement for desire, in my book. a cop out, actually. but for extending the list of potential ingredients in reusable technology in terms of a sustainable and yet high performance analog application, hybrid can be what it really is all about now, probably from now on. stretching the limits is where imagination gets to play a part. there’s no excuse to stop exploring!

this amp does not “sound” like a solid state amp, nor should it! it is completely defined by the change in plate current natural to the tube of your choice. and the use of feedback is no drawback in this case… i have mentioned before that current feedback resolves differently than voltage feedback. and to me this amp sounds wonderful! is it better? there’s no such thing at this level… it’s in the range of high performance expected from this kind of gear. but it sounds different. and in order to work out the challenges that are part of using an I to E converter as part of a power amplifier, it required some subversive vintage lateral thinking (who uses any of this stuff to make hifi?), a choke!, and cheap mass produced op amps which can be sourced from many places… removed from old gear and reused, or even retrofitted into existing solid state gear. you could even replace the LM3886 with a MacIntosh 275A or a Marantz 9 by opening up the feedback loop, and squeezing the tube and the choke in there instead of the resistors… although i doubt many would! hahahahahhahah

yer basic I to E hybrid tube power amp