Quick, no brainer solution for $500.00 Blackbird Tube Preamp
This could make a transistor radio amp sound good. There is also a less expensive subminiature model that does fuzz only. Caveat: the tubes will be unavailable forever at some point.
This could make a transistor radio amp sound good. There is also a less expensive subminiature model that does fuzz only. Caveat: the tubes will be unavailable forever at some point.
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That's all very nice, but it's no diyaudio. It is so much more satisfying making something than buying stuff.
Ok, I forgot what planet we were on. One could try using some NOS low voltage tubes, or the subminiatures. Just had an idea. Instead of spending months trying to get something right that is not feasible to begin with, using the P27A preamp, with the addition of just one dual-triode or subminiature "equivalent" the high voltage requirement is not necessary if the clipping diodes are left as is with the tube following, and better with a CF dual-triode after that. Even one tube will add the desired dynamics which will make the amp come alive. Many SS amps use this technique already. Vox, Johnson, Carvin and a bunch more, although I'm pretty sure the tube does the clipping in those. The clipping section could also be modified with say one or both germanium diodes, or a transistor clipping circuit. As a side note, some Marshalls actually have diodes in the preamp.
I know this works since I compared running the Boss MT-2 into the clean channel of a SS amp, and also into an all-tube Hammond organ amp modified for guitar use using the speaker cabinet from the former. Hammonds did not use cathode followers, but it still sounded quite good; certainly night and day difference. Also, the P27A is not a completely fixed model, there are different transistors that may be used, and also a current feedback mod that will simulate rectifier tube droop somewhat and adds sustain.
Okay, reading between the lines, I think you are proposing using a vacuum-tube preamplifier, mated to a solid-state power amplifier. I agree with you that this is certainly a viable way to get acceptable guitar sounds.
Along those lines, a few years ago Anderton's Music had a video demo of a hybrid guitar amplifier built to exactly this recipe. It had real valves (sorry, tubes!) in the preamp, and the power section was a massively powerful solid-state class D beast. I can't find that video now, and I've forgotten the brand and model.
Twelve years ago I bought a Fender Super Champ XD, the first "not nasty sounding" e-guitar amplifier I ever owned. The SCXD design took exactly the opposite approach: the entire preamplifier was solid-state, a mix of analogue and digital, while the entire power amplifier used actual vacuum tubes.
To me, the SCXD had (and still has) excellent Fender "Blackface" clean tones, which come from the actual tube power amp, with the DSP doing nothing but EQ and FX on that channel (clean channel). Meantime, on the "drive" channel, the DSP-simulated overdriven tones were not great, though far better than clipping diodes.
Let's face it, the era of repairable electronic products is virtually gone. As parts shrank and complexity increased, the ability to repair consumer electronics products has dwindled steadily over the last several decades. How many people have ever repaired, say, a cellphone, or a digital camera, or one of the dozens of computers inside their car?
At best we can do trivial repairs like replacing a leaky cap. At worst, we are forced to toss the whole thing into the electronics recycling bin and buy a replacement.
Fortunately for us, modern consumer electronics tends to be extremely reliable.
Agreed. That's the way things are now. I doubt Rod Elliott will be selling PCBs for his project 27 power amplifier n ten years time, either. He is already an old man, and his website has already been around for two decades - how much longer will he have the desire or the health to keep it going?
And if Elliott was somehow still selling PCBs a decade from now, would the necessary power transistors and other discrete semiconductors be available?
I think we have already been shown the future of powerful audio power amplifiers. Class D has already taken over almost the entire field, and is still expanding into the remaining corners of the market.
Speaking for myself, I built my last class B audio power amplifier a long time ago (nowadays it's fashionable to call the same thing class AB). I have no desire to deal with huge, heavy, expensive heatsinks and huge, heavy, expensive power supplies when they are now unnecessary. Class D power modules with switching power supplies have eliminated the need for them.
I don't think this progression is all that common nowadays. Any tube amp is prohibitively expensive now - I don't remember seeing any that cost less than $1000 CAD in recent years. That is a lot of money, especially in this era of small wages and prohibitive cost of living.
A progressing beginner guitarist could get a Boss Katana 50 Mk II for $350 CAD - one third the price of a tube amp - and the Katana includes not only a number of excellent amp models, but also all the built-in FX pedals any sane person could need.
If I was a beginner looking for my next step up in amplifiers today, I would be looking at the Katana line up, not at tube amps.
My favourite electronic product of the last few years is the little Flamma FS06 Preamp, a collection of 14 excellent digitally modelled tube amps in a little effects-pedal sized enclosure. It's amazing how touch-sensitive some of the amp models are, and yes, they have very realistic-sounding "tubey" compression, too.
I remember those - they were called Korg NuTubes. They were basically a modified VFD (Vacuum Fluorescent Display).
I did look up some data on the NuTube, and they are very different from old-fashioned 12AX7s and the like. Internal plate resistance (Ra, Rp) is insanely high, for example, so these can't drive any sort of load (not even a volume pot).
VOX sold a few tiny "lunchbox" guitar amps using a NuTube or two. None of those sounded good to me.
To be clear, I'm not disagreeing with anything you've said. I think we both see the same thing - the future of giant all-valve guitar amps is bleak. Something else will replace them.
Many viable replacements are already available today, and already popular today, including hybrid with tubes in the preamp, hybrid with tubes in the power amp, and digitally modelled tube amp emulators.
That last category already dominates, at both ends of the price spectrum, and everywhere in between as well. I don't think that is about to change.
-Gnobuddy
Interesting. I wonder what's actually inside one of those? More important, I wonder how close they are to sounding like real tubes?
SS devices like this, packaged and sold as direct plug-in tube replacements, have come and gone many times.
A very clever Russian engineer who goes by the online handle KMG has already shown us, years ago, how to make a MOSFET behave almost exactly like a half-12AX7.
-Gnobuddy
I think this is the last remaining niche reason to try and coax analogue solid-state devices to sound like vacuum tubes.
Until someone open-sources DSP code for creating good-sounding digitally modelled tube amps, we DIY types are stuck with the analogue approach.
Big corporations will never do this (they make tonnes of money from their secret-sauce DSP tube models).
If open-source DSP tube models eventually arrive, it will most likely be from the world of university researchers. They are full of smart young people with the technical knowledge, and the urge to use their intelligence, creativity, and knowledge to create new things. The same group of people who have created the wonderful ecosystem we now know as Linux.
-Gnobuddy
I agree that there are lots of alternatives, and I think even looking at discrete JFet stages can be very useful in a mixed solid state / hollow state guitar preamp.
One doesn't necessarily preclude the other, it`s just nice to consider alternates to op-amp designs. One of those Nixie tube voltage multiplier boards can power up the plate supply to a 12AX7, you could have a nicely overdriven tube stage with a JFET front end.
I agree entirely.
There are now some really interesting options for off-the-shelf, inexpensive, SMPS that generate enough voltage for tube amps.
For less than $15 CAD, you can get a 400-volt-capable SMPS board: https://www.amazon.ca/Converter-45V...g/dp/B08KWFDLSJ/ref=sr_1_5?crid=2YSWDZ2JK489J
One diyAudio member posted in a long-ago thread that he was successfully powering a Champ-like tube amp from one of these boards, i.e. a 12AX7 or two, as well as a 6V6.
I also found a few threads on various forums about the use of automotive AC inverters as SMPS for tube amps.
We're talking about the little inverters that plug into a 12V cigarette lighter socket in your car, and generate AC that lets you run some household 120V AC devices in the vehicle.
These little inverters can be found cheap up to more than a hundred watts of output power capability. Complex internal circuitry first generates a stable high-voltage DC rail, then a MOSFET bridge chops that to deliver AC output. But the HV DC rail can be used directly to power a tube amp, either by simply ignoring the bridge chopper, or by removing those chopper FETs by desoldering them from the board.
IIRC, "120V AC" versions of these inverters have about 170 volts DC on the internal rail (1.414 times 120 V), while "240 V" versions of auto inverters have the really good stuff - around 340 volts DC internally, quite enough to run a pair of 6V6 beam tetrodes on!
I've never tried to actually get at the HV DC inside one of these. Without a schematic, it's a little scary. But it's been on my long list of "things I should try one day" for a while.
-Gnobuddy
Yes I recall that thread, it was an interesting project indeed. As we had discussed, the Bloc 100G has a very good discrete preamp based on Jfets and Jfet/BJT stages. What fell a bit short to me is the diode clipper on the distortion channel. The clean side IMHO is great, and I think with some tweaking it could get some nice overdrive on it`s own, but for sure feeding a couple of triode stages along the signal path could make it really great.
Take a listen to the attached MP3 file, and see what you think. (Just remove the ".pdf" at the end of the file name; it's really a short MP3 clip, not a PDF file.)
Moderators: the file is a few seconds of crude guitar playing, not a copyrighted song or other audio performance.
The guitar playing in the clip is - ummm - not so good. But set aside the playing, and listen to the sound. What do you think of the tone (timbre) of the sound?
This is supposedly a sound sample created by a very simple two-transistor circuit, created by one Tiago Charters de Azevedo in 2012.
Azevedo called his circuit "2BJTE" for "BJT Tube Emulation with 2 transistors".
Azevedo's Web presence seems to have disappeared in the ten years since 2012, along with his schematic and sound clip. But I have a copy of both on my PC.
The "2BJTE" circuit has many bizarre component values, indicating a "design by plugging parts into the breadboard until it sounds good" approach was taken.
There is an additional complication. Azevedo said he had obtained this sound sample by plugging his guitar into a well-known Boss overdrive pedal, the output of which he connected to his 2BJTE circuit. Azevedo's post said that the Boss was set to provide only clean gain, and no overdrive.
If that was correct, then the sound sample really does represent only the sound of the 2BJTE circuit. But it almost sounds too good to be true to my ears...two transistors, no EQ, and what I hear as quite a rich and dynamic overdriven sound.
It's possible that part or all of the rich overdrive tone came from the Boss pedal, and not Azevedo's circuit. But it's so simple a circuit that it's probably worth building and testing, just to find out.
If anyone is interested, I'll post Azevedo's schematic. Let me know in your posts.
-Gnobuddy
Some off-the-cuff of opinions: Opamps are your friends here, especially for buffering high and low impedance components !! They are much easier to work with than transistors when testing new circuits, and some are extremely quiet and operate almost Class A. The opamp could also be used for clipping which sounds very "squeaky/buzzy" and unwieldy to play with, thus needs to be filtered. The lead in Bruce Springsteen's "Badlands" sound like it could be that.
Yamaha makes some really inexpensive tube guitar amps which could be used for testing and modding.
Class D power output should be ok in the distortion realm for driving the speakers. Believe it or not, very few people can tell the difference between Class A, A/B, B, D or anything else when distortion is on. Same goes for DSP.
The P27A is Class A/B (if I recall correctly) and has adjustable bias (that does not drift), to put it in almost the Class A realm at the expense of a little more power wastage, but much less than true Class A which is almost double. Turning the bias up is useful in only a few circumstances, but the option is there at the turn of the trimpot.
If anyone is worried that ESP boards and projects will at some time be unavailable, when you find out which projects suit your needs, simply acquire several bare boards, and make digital copies of the commentary and assembly instructions. Same goes for all the components; none are expensive. This goes for tubes/valves as well. I would almost bet my life that R.E. already has a contingency plan in the event of his departure.
The HT module cited above on eBay will work but is not reliable. A simple flyback driven by an opamp is much more reliable--the one that uses an inductor and diode. This is good for low current and not too high voltages. Another option I found was using two 120/240 transformers with the 12v secondaries connected to each other. The first transformer primary winding is the input, the 12v "junction" provides the heater power, and the 240 winding is for the HT. This gives isolated power with ~300v HT. In the 220/240 countries both transformers will be identical. The example I saw used "wall wart" transformers feeding a two-stage fuzz box, i.e., one 12AX7. More stages=more current, especially the heaters. No wallwarts? Small, torroidal PCB mount transformers may be used, and higher VA ratings are available.
Still, after many decades of attempts, there is nothing that can replace the original tube designs from the 1930s exactly, and nothing on the horizon that I know about. Don't expect the preamp tubes and even the power bottles and tube rectos to disappear anytime soon. My best guess is humanity will disappear first, with all that glass taking millenniums to disintegrate, as a testimony to the cosmos.
Food for thought: Norman Greenbaum has lived off the one song, "Spirit in the Sky" since 1970 using a cheap fuzz box. He never had to work since.
More food: Recordings made at studios with producers and sound engineers are--very frequently--pieces of work that never existed, or are too difficult to perform live, e.g., Boston.
Yamaha makes some really inexpensive tube guitar amps which could be used for testing and modding.
Class D power output should be ok in the distortion realm for driving the speakers. Believe it or not, very few people can tell the difference between Class A, A/B, B, D or anything else when distortion is on. Same goes for DSP.
The P27A is Class A/B (if I recall correctly) and has adjustable bias (that does not drift), to put it in almost the Class A realm at the expense of a little more power wastage, but much less than true Class A which is almost double. Turning the bias up is useful in only a few circumstances, but the option is there at the turn of the trimpot.
If anyone is worried that ESP boards and projects will at some time be unavailable, when you find out which projects suit your needs, simply acquire several bare boards, and make digital copies of the commentary and assembly instructions. Same goes for all the components; none are expensive. This goes for tubes/valves as well. I would almost bet my life that R.E. already has a contingency plan in the event of his departure.
The HT module cited above on eBay will work but is not reliable. A simple flyback driven by an opamp is much more reliable--the one that uses an inductor and diode. This is good for low current and not too high voltages. Another option I found was using two 120/240 transformers with the 12v secondaries connected to each other. The first transformer primary winding is the input, the 12v "junction" provides the heater power, and the 240 winding is for the HT. This gives isolated power with ~300v HT. In the 220/240 countries both transformers will be identical. The example I saw used "wall wart" transformers feeding a two-stage fuzz box, i.e., one 12AX7. More stages=more current, especially the heaters. No wallwarts? Small, torroidal PCB mount transformers may be used, and higher VA ratings are available.
Still, after many decades of attempts, there is nothing that can replace the original tube designs from the 1930s exactly, and nothing on the horizon that I know about. Don't expect the preamp tubes and even the power bottles and tube rectos to disappear anytime soon. My best guess is humanity will disappear first, with all that glass taking millenniums to disintegrate, as a testimony to the cosmos.
Food for thought: Norman Greenbaum has lived off the one song, "Spirit in the Sky" since 1970 using a cheap fuzz box. He never had to work since.
More food: Recordings made at studios with producers and sound engineers are--very frequently--pieces of work that never existed, or are too difficult to perform live, e.g., Boston.
Op-amps are wonderful things, in a lot of applications, for a lot of good reasons.
That said, I really dislike op-amps used in e-guitar preamps. See this recent thread of mine for the reasons why: https://www.diyaudio.com/community/...pping-in-solid-state-e-guitar-preamps.391513/
Got a link to share? I've never seen anything really inexpensive from Yamaha, though IME everything they make is good quality.
Not to go down that rabbit hole, but once THD is below 0.1% and frequency response is flat from 30 Hz to 15 kHz, all the evidence is that nobody can tell the difference between any of those as long as they're kept out of clipping...though many people believe they can!
Technically, class B means each output device in a push-pull pair conducts for exactly 180 degrees of phase of each sinewave cycle. Class AB means the devices are biased further into conduction than that, so each device conducts over considerably more than 180 degrees of phase.
With valve output stages, they really do have to be biased to conduct for well over 180 degrees (both devices may conduct over, say, 250 degrees of phase), and the term "Class AB" is quite technically correct.
With transistor output stages, too much bias is just as bad as too little. There should be no region when neither transistor conducts, causing crossover distortion (technically, that's class C). Neither do you want too much bias (class AB), which raises the transconductance of the output stage in the crossover region, causing the opposite problem - too much gain in the crossover region, rather than too little.
So with transistor output stages, they really need to be biased to that exact point that ensures that there is almost a constant transconductance through the crossover region, as operation shifts from one device to the other of a push-pull pair. Each device really only conducts for 180 degrees, with maybe a tiny tail of current for a few degrees more. That really is class B operation. But for the last decade or two it has come to be called class AB on Internet forums, for no good technical reason.
Until just a few years ago, I could definitely tell the difference between affordable DSP tube emulation, and actual tube amps. All the affordable tube emulator devices had crude distortion sounds, and too-clean clean tones. They had a harsh quality to the overdrive that caused me significant ear-fatigue after a few minutes. I tried a bunch of them, wasted a lot of money, and kept having my nose rubbed in the same unpleasant lesson: they did not sound like real tubes, not by a long shot.
At the time, you had to spend well over $2000 USD before you got good enough DSP modelling in hardware form to have trouble telling that it wasn't real tubes. At that price, why bother? You could buy a real tube amp for less.
For me, all that changed for the first time with the Boss Katana series. IMO overdriven sounds still sound too grainy to be really tube-like, but for the first time, "clean tone" really sounded "tubey". My Katana 50 cost around $475 CAD, IIRC. Not exactly cheap, but considerably less than Kempers and Axe FXs.
Much more recently, Flamma Innovations started selling an unassuming little purple box (the Flamma FS06 Preamp). It contains seven DSP tube amp models, each with a clean and drive channel (14 models in all). It's a guitar FX pedal-sized enclosure. Plug into a flat-response powered speaker, P.A. system, mixer, or DAW to use.
I was blown away by Brett Kingman's demo of the Flamma Preamp on You Tube. I got one, and it sounds more "tubey" than my actual Fender Princeton Reverb reissue tube amp does. I can't hear any digital artifacts fom the Preamp - this is the first time I've had a DSP hardware tube amp emulator that really does erase the line between real tubes and simulated tubey sounds.
And the kicker is that this pedal costs under $100 USD.
For me, this little gadget took away most of my motivation to tinker with DIY guitar amps, whether tube or solid state. Simply put, it sounds much better, and is more versatile, than anything I can build. And it costs less, too.
This is exactly the same as every decent discrete power amp of this type designed since the 1970s. More bias is not better; as mentioned above, too much bias causes more distortion, and so does too little bias. There is a very fine margin in between, an exact bias point where crossover distortion of the output stage is minimized.
There is a better option - a 230V:120V AC isolation transformer. Wired backwards, and with the 230V winding fed to the usual silicon diode bridge rectifier, you can expect to get something around 330 VDC - 340 VDC from it. Quite enough for modestly powered tube amps.
If 50 watts is enough for you, the Triad N68X is probably value-for-money king here: https://www.digikey.ca/en/products/detail/triad-magnetics/N-68X/1887210
The N68X has big brothers if you really need more than 50W. (Remember heater power has to come from something else - there are no 6.3V AC heater windings on these affordable isolation transformers.)
Do you really believe new-production vacuum tubes will continue to be manufactured to the end of humanity's days on earth?
Glass is long-lived, so yes, there will be traces left of vacuum tubes and incandescent light bulbs for a long time. Like Roman coins buried in today's Britain, they won't be of much significance to guitar players. (If there are still guitar players; that depends on how quickly our species reaches its end.)
But affordable new-production vacuum tubes to be used in new-production tube guitar amplifiers? IMO, those clearly have one foot in the grave, and the other on a banana peel.
In 2019 there were only three factories in the world that still manufactured new tubes. The Chinese one (Shuguang) shut down permanently after a big factory fire.
That left JJ Electronic in Slovakia, and Reflektor in Russia (Reflektor is owned by Mike Matthews, also owner of Electro Harmonix).
When Putin started his war with Ukraine, Russian tube exports to the rest of the world were shut down by international sanctions for a while. Tube stocks in North America plunged, prices soared, and there was much panic among people with large collections of expensive tube guitar amps. Mike Matthews issued a statement about his inability to import tubes from his Russian factory.
The shutdown of tube exports from Reflektor left only one single factory in the entire world - JJ Electronic in Slovakia - still making and shipping tubes suitable for e-guitar amps.
If you don't recall the geography of Europe very well (I can never remember all those little countries), look at a map of Europe, and you'll see that Slovakia is very much in the line of fire from Russia's war on Ukraine. Slovakia shares a border with Ukraine, and if Putin's toxic war heats up, JJ Electronic will almost certainly shut down as well.
To recap: this very year, we had a period when there was one single factory in the entire world still manufacturing and shipping new tubes. That factory was under threat from a nearby war.
So yes, I would say that ongoing manufacture of new vacuum tubes suitable for use in electric guitar amplifiers already has one foot in the grave, and the other on a banana peel.
Sounds like material for a thread over in the "Everything Else" forum.
You might like the book "Perfecting Sound Forever". I found it fascinating. Here's a link : https://www.amazon.com/Perfecting-Sound-Forever-History-Recorded/dp/0865479380
-Gnobuddy
If true, and I highly suspect it is, pretty impressive. I just saw someone win a bid on a Ibanez compressor SB, for $220. A_single_ compressor pedal. Sounds like you can do better for that kind of money. Some of the old things just...have a stunning resale value. Unsure why, when there's newer alternatives, such as you describe that can meet or beat them in the $ / performance ratio.
My mistake; I didn't really look into the Yamaha too deeply. What I had in mind was something like this Bulgara 50w Two Channel Head
A used copy is one option for experimenting with hybrids. I ordered a custom aluminum chassis and it cost over $100 8 years ago. No holes, no components, and no cabinet; today $200. Used Bulgara $300, a little more than what you could pay for a stripped, dented, rusty vintage tube chassis.
Some of the vintage stuff sells (or at least asks for) megabucks. Seems the interest is more for nostalgia than actual use. I wouldn't mind one of those old tape echos, though. One that works, that is. At the end of the day however, the modern echo units make more sense in performance/options/reliability vs. cost.
"Do you really believe new-production vacuum tubes will continue to be manufactured to the end of humanity's days on earth?"
Yes, as long as there are guitar players.
A used copy is one option for experimenting with hybrids. I ordered a custom aluminum chassis and it cost over $100 8 years ago. No holes, no components, and no cabinet; today $200. Used Bulgara $300, a little more than what you could pay for a stripped, dented, rusty vintage tube chassis.
Some of the vintage stuff sells (or at least asks for) megabucks. Seems the interest is more for nostalgia than actual use. I wouldn't mind one of those old tape echos, though. One that works, that is. At the end of the day however, the modern echo units make more sense in performance/options/reliability vs. cost.
"Do you really believe new-production vacuum tubes will continue to be manufactured to the end of humanity's days on earth?"
Yes, as long as there are guitar players.