If it is in the circuit and it's the amp I am thinking of, the valve provides the output drive for the headphones, it doesn't add voltage gain, but provides the current, that's the best way I can think of describing it.
People buy into this like they think a £10,000 push bike will make them into an Olympian, or £10,000 of fishing tackle will make them good at catching fish. Obviously banging records were made in mono in the 60's with reverbs and echos being a speaker and a mic in a cupboard/corridor. Nobody except the BBC had much "gear", studios like Motown made their 4/6 track tape recorders from scratch! It could take 2 years just to buy a tape head! They made good sound/performances and recorded them. Now you slap any old thing down, auto tune it, drag it into time etc - too easy to forget what you're supposed to be doing. A vocal track can have every single syllable processed differently, tuned differently, automated differently - that's what we are fed these days as music - I do it myself - nick vocals off the internet, tune odd words to suit the key, move or stretch/shrink every word and part word to suit my timing etc. It's fun as a hobby - better than watching TV anyway, but what isn't?
So... here's one I did earlier. I'll leave it up for a while for you valve heads. https://soundcloud.com/user-875124689/beautiful-day-2/s-e1p42AjWDy4
I think I’d prefer to stand listening in a sweaty pub reeking of stale beer and fags. That’s proper music.
Knew I'd seen something on this in the past. This fellow reverse-engineers something similar (try and ignore the screechy Aussie voice). The valve just acts as a cathode-follower ie does...nothing. No idea how they get it to work with an HT of 12V. It is, as Mr Jones says, "complete w@nk". The little 8-pin op-amp chip is doing all the work. Folk will buy anything.
24V, but yep, that's a giveaway! The company that makes then is called...Nobsound. ha-ha-ha! I've always known what it was so it's no more problem than if it looked pretty because it had bits of wood on the sides which also don't improve the sound. Pure marketing in each case. Do you really think people believe they are buying a "valve amp"? Silly sausages.
DC-DC converter - 24v in, whatever HT you want out. Valve is probably a 12au7 so HT will be of the order of 100v-200v. 12au7 is a double triode giving L and R amp in one package. There's a healthy market for valves for vintage radios. The radio users hate the audio users because they strip the decent audio valves out of radios and scrap the rest. Just look up the price of a px4 valve on ebay. There is a chap who has bought back the orginal valve manufacturing equipment which was sold off to the Bulgarians for the purpose of making new px4s.
You got me going down the audio rabbit hole on the web . There are apparently folk who buy custom-built op-amps to replace the (perfectly adequate) TI jobs, because apparently they…do something. $50 a pop. An audiophool and his money are soon parted…
PS not unusual for Chinese boards to labelled in English, as that’s what the CAD software they’ve nicked uses.
Cathode followers don't really do nothing, Rich, tho ideally they shouldn't add much of a sonic signature. Some of the Ruski valves were happy with low anode voltages, although you wouldn't be on an ideal part of the curves.
That's the valve in mine. 12AU7. There are 2 trim pots next to it which makes you wonder. there is an 8 pin orange thing with a switch next to it marked "6 series - 12 series" it's set to 12 series. It has a bunch of MOSFET things on quite large heat sinks, a few capacitors, a few resistors and very little else. Best photo I can get of the orange thing. Any idea what it is? The symbol top left looks like 2 diodes, but prob a logo. I'm way out of my depth. [edit] it's a mini power relay. There are definitely no ic chips/op amps. It seems very different to the one in @snotty 's posted video, not that this means much but it does appear to roughly conform to the amusing blurb? Pure Class A Headphone Amplifier & Pre Amplifier Hybrid ! Valve & MOS-FET in Use!! Without any OP amp IC inside!!! Audiophile Performance Design Absolutely!!! Our headphone amplifier is different to others. A/ High grade Caps & DJapan KOA resisters, ALPS volume in use. B/ High cost Large 24V2A low noise adapter with grounding. C/ Precision select 6N11 valve, also match R/L channel within 1dB out put differential. It is a high value and cute headphone amplifier hook up to your PC / Mp3 /MP4/ ipod / any stereo device. You can have a powerful, dynamic and sweet TUBE SOUND from your headphone ! You’ll be astounded at the improvement in sound quality, dynamic range, meticulous transparency, completely demonstrate its high performance and analytical ability, it can also connect with power amplifier such as a high performance pre amplifier to improve your Hi Fi system. New 6N11 tube 1970-1983 made in Peking mark with <J>, but never used. In China <J> means for military use (highest grade) (we have carefully choose and test in Lab). -Using Elna Caps and Dale resistor. The each one of 6DJ8/6922/ECC88 is fully suitable for replacement with much difference musical taste chose by owner. (6DJ8/6922/ECC88 Excluding in this item for sale)!
Orange thing looks like a relay, to me. The three legged jobbies will be regulators for the heaters and, if done properly, a constant current source for the tail of the CF. The 6 and 12 would be the heater voltages. Russian valve-ski generally better than Chinese equivalent. Have a look at duncanamps.com for the Tube Datasheet Locator, for valve equivalents Trimpots are ghastly things, worse than, well don't get me started. Trim pots might be to set the bias of the valves by controlling the current sources.
As above, the orange thing is a relay https://datasheetspdf.com/datasheet/HK19F-DC24V.html. I haven't been able to find a schematic. It's possible that the relay is used as a safety device so the slide switch doesn't make any difference with power enabled.
The best resource I know of for valve equivalents is the valve museum e.g. http://www.r-type.org/exhib/aam0051.htm
This is in for repair, I have been procrastinating, it's likely to kill me, tho some might say that the world would be a better place for that Please excuse the dusty workshop, they do make a rather fine boat anchors, or doorstops, depending upon your point of view, I struggle to lift just one end
Thanks chaps... so is it a valve amp or what? It's not an op amp type amp for sure... there aren't any.
