Tube preamp budget kit test and review
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- Опубліковано 27 лип 2024
- Special thanks to a viewer who sent this in with a bunch of other electronics. It gets my usual battery of tests to see what I think of it.
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Email: johnaudiotech@gmail.com
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Some asshole tried to sell me this Chineseum as a phono preamp, this reviews are super important, keep up the good work!
Keep up the good work and I hope the kitty stays around a while longer.
So Glad to see Snickers feeling a bit better - And quite chatty! Big hugs Mr. Snickers.xx
Mine was noisy but I found a threat on diy audio website explaining how to add some capacitors in one of the resistors, also removed the pot and cut the coper trails as they go close to the heaters power. That little change removed all the hiss. Good video, thanks John.
Ha! 'Hungry?' The first and last phrase every cat learns.
Hi John, I built and reviewed this little preamp on my channel about 2 years ago. The valve is in fact a RF valve, not really made for audio. The Chinese do not seam to have any low cost valves made for audio at all. I did not find hum or buzz on mine, quite surprisingly but it did pick up noise from my bench.
Regarding the low frequency response, I started testing with an amplifier with a 10 K pot on the input, like you I found the low response very poor. On switching to my main amplifier, the L12/2 with it's 50k input pot, the low end was much better but did end up replacing the input caps to 2.2 mF. With this combo I ended up with -1db at 25 Hz. which is OK.
Overall I did not like the sound, quite coloured and lacking detail, but it is a valve and silly cheap. Does anyone expect HiFi really? A number of people asked me if it's OK for a mag cartridge. The answer of course, diffidently NOT. No RIAA eq and quite noisy with just 3mV input. My review here if anyone's interested in a second opinion. ua-cam.com/video/ZpdBQ-MwqrM/v-deo.html
Russian 6n6p or 6n2p would work in this application very well, of course need to adjust resistors values. SRPP works best, but not by this plate voltage. These tubes need min 100v plate U
Man...
This channel is so far away the best one in audio specs. Subscribed.
Thanks for the wet food suggestion. He never seemed to like it before but he sure did today. I'm glad to hear snickers is eating. We have our appointment Saturday morning
So happy for Snikers!
So happy for you and Snickers. The tube amp on the other hand, not so much.
Stay well John.
Your UA-cam channel is so good and underrated.. keep it up one day you will be have 1 million subscribers
Glad your kitty is better !
Let me go in and feed my cat. He's about Snicker's age. He has his moments.
I put that together a few years ago for kicks and thought the negative output was odd as well. I put an old 18vac 800mA I had from an obsolete daw I used to use for recording.
Meoww to Snickers, he knows what I mean. Thanks for the entertaining and interesting vid John!
Happy to hear snickers is back to his old self.
I've watched a few other vids about this tube preamp and maybe if they'd actually put much better hardware on it I'd splurge and build one for fun. Thanks for the great info! I hope your cat is still doing well. I just lost my 18-year-old tuxedo cat last month. He used to howl during some of my videos!
So it wasn't just my imagination that the tube amp I just put together last week seemed bright/tinny compared to putting the signal directly into the class D 7498e amp.
I'll try switching out the 1uf caps for some larger value ones, nice timing on this vid.
Something I noticed with mine was that the 12.5V AC transformer I used was actually putting out 13.5V and the voltage across the heater elements was 13.4V and on the edge of too high for them (6.3V +-10%), but the 28V ended up at 33.5V. There's a 2.2Ω resistor that I could switch out to bring it back to 12.6V (the elements are 36 ohm each) by my calculation a 6Ω resistor should do it. Unfortunately my kit is full of 35V caps so I cant push for higher input voltages without switching out all the 470uf caps to 50V rated ones and I don't have a 6ohm resistor though a 4ohm resistor in series with the 2.2 ohm should do the trick and I have plenty of 5W one's of those, it'll just look messy.
I have had one of these things for a while now, mine has a green PCB, I remember looking into its power supply to figure out how they were getting the tubes to run off 12V, at the time I didn't know that it was possible to run tubes below a few hundred volts and this got me to learn how it was possible, I learned from the process that there once was a time when tubes were used in car audio! That was fascinating... Anyway, I didn't get any of the noise that you got with yours, I didn't really notice the bass rolling off, I will be looking at mine to see if it's the same thing with it....
I predominantly use mine for when I need to connect my android phone to my hifi when I need to record to compact cassettes! The phones output is hopeless but this thing works wonders for gain... I was amazed when you took it up to 100khz and it was still flat, I was kinda hoping that you would take it higher in the frequency to see where it was going to start giving up, sure! It's not like it's usable for audio all the way up there but it's pretty impressive considering that it's vacuum tube and it's a $10 Chinese unit, those provided tubes aren't anything special but they work, most people tend to go for the 12AX7 but I prefer the EF86 for hifi, the 12AX7 seems to be heavily used in guitar amps but I guess that's just personal taste talking there... Actually the Mullard datasheet for the EF86 is one of those datasheets that have a plenty to say about those tubes and hifi, I think that Mullard specifically designed them for hifi... It's a real good read if you can get your hands on it....
I hope that you can work out why yours is humming, might have forgotten the words or something LoL...
Great to hear that snickers is better! He's a fighter!
Hi Peter, yes valves that are used in preamps quite often run on low anode voltages, ie 50/100 volts. The EF86 is a good example. Mullard often used it in what they called starvation conditions, low HT and only a mA or 2 in current, claiming low distortion and noise. The EF86 was made for use in real HiFi amplifiers of it's day. The ECC83 being a double triode was favoured in tone control circuits using negative feedback between the 2 triodes. Guitar amps liked them to cut the tube count down, noise not being an issue.
Car radios did use valves but not really on a low HT as they used a vibrator to step us the 12 volts to about 200/250, higher in fact than many American all 5 domestic radios.
The valve in this kit is really an RF valve, not meant for audio at all, probably why it's HF just keeps on going up...and up.
I have a soft spot for these cheap DIY kits of these hybrid tube amps because they are pretty straight forward and people have actually been modifying the circuit in online forums and making it better, by showing how to bypass some traces and re-routing them. It's definitely possible to fix a few design mistakes and i'm sure with audiograde resistors, these little amps sound even better. I got myself a few of these as solder practice kits and work on combining 2 of these to a little guitar Amp. Keep in mind that these kits are really only using the tubes as a audiosignal pass-through. Which for some of us is exactly what we need to get somewhat of a tube-sound on a budget and at much lower voltages. So this Transistor / Tube combo is pretty nice. The more common sold pre-made models usually come with OpAmps instead of transistors. However the standard tubes that come with these are usually not really audiograde level but military grade tubes.
Funniest thing is imagining all the audiophiles screaming in pain when they see you touching the tubes with your bare hands ...
Hi, looking at Snickers made me think of cats we've had over the years that experienced kidney problems. It's quite typical for a cat of that age. Symptoms include dehydration, weight loss and loss of appetite. Did you notice if he drinks more than usual? There are special foods out there, but it would be important to get him a blood test first to confirm. Wet foods are much better than kibbles, but the higher the protein, the worse it's going to be for his kidneys. This cat can keep you company for years to come, but a timely response may be crucial. Best of luck to you both, from myself, my wife, and our three furry family members.
I took him in a couple weeks ago and he had a blood test. Doctor thought it is something with his bowels, but I'm not so sure. Now that he's eating, his poop looks normal and he needs less water (cats get most of the moisture from their food). I now think he was just malnourished because he was eating little canned food and barely touching the dry. The vet really drove home the point about getting him off the dry food totally and getting a quality wet food. I could not get him to eat most of the expensive stuff, but the stuff he likes isn't too bad. catinfo.org has lots of good food info.
I have this preamp. Upgraded it with GE5654 tubes. This circuit by itself is rubbish induces all sorts of noises (AC) to the amp ruins the entire fun. But then I added lots of good quality caps, Inductors, changed coupling capacitors to WIMA that started sounding amazing. Most noises were gone. But still it needs to leave it at low gain since its gain has increased considerably after all the new caps. But we just need that distortion thingy you know :P But yes enjoying it since 2 years.
I’ve built a few of those and I use it as a guitar distortion effect. I rewired one with two pots and fed one tube into the other to overdrive the other and with two pots you can control the gain stage 😎
I use it as a guitar preamp too, but it's quite noisy, what did you do to solve that problem? If you did
I did it too ,it’s nice sounding
Ive been waiting for this lmao.
I would love to see your modifications to this board in a second video. I have an FX-Audio preamp using the 6K4 that sounds incredible with the cheap Russian 6J1p-EV surplus military tubes you can get on ebay $20/10 shipped. It makes my $75 class D amp sound like my fathers old KRELL amp that cost well over $1000. With what these cheap tube buffers do for audio on the cheap, they will be getting more and more popular esp with a near endless supply of NOS military grade sharp cutoff pentodes available for a dollar or two each on ebay
Haven't tried the J1p-EV's .. probably my next try but I ordered a pair of Jan5654W from Riverstone on Amazon with excellent results for the Fx Audio 03 that also came w/6k4's. I thought the shipped tubes sounded ok until I received the Jan5654W's. Way more linearity, better bass and better mid and upper range. Since the case and tubes are so microphonic I used some cable ties as tube dampers and put a piece of high density foam with a weight on the back part of the case and that eliminated all the anomalies in the sound (wooly bass and diffused midrange). On my system w/Martin Logans I was floored at how good this little preamp sounded. Next move is cap replacement.
C'mon Snickers we all love you.
I have this kit! It arrived with one of the tubes smashed however ... I got some replacements. No instructions and labeled in Chinese! 😂 I started out by powering it with DC and getting the inputs and outputs swapped. I did some "troubleshooting" and removed the 104 caps (mine were not like yours). Finally figured out my mistake and put 'em back in. Seems to be working? I had to power it with a transformer I have that is suppose to output 12V6 but I was getting +/-36V at the test points on the back, the ones that should be +/-28V. I am going to order an AC wall wart off Amazon next month for it I think ...
I was getting high voltage as well and had to use a variac. Get a small 12 volt transformer of no more than 500ma so that the amp loads down the transformer so the voltage is not so high.
I recently got a kit with one of the tubes smashed too. I got a refund for most of the order and have ordered some new tubes for it with the money. After some of these reviews I've been watching, I'm wondering if I shouldn't have bothered ordering the kit in the first place lol. But I'll solder the kit together and see if it's any good or not. There seems to be plenty of info online for modifications of the circuit
I love the kit because it's basically fool proof. For a beginner like me; it's good practice. Since prototype boards are so cheap now, you should offer your own board or kit. I searched for a better kit but none really do the job. Or you build from a schematic, which is beyond my skill level.
Those harmonics are whats gonna make that tube amp sound good lmao
Where did u connect the capacitor that u connected accross
Just one question.When you changed frequency in the response test did you maintain constant generator through out?Great explination.Thank you.
I bought and assembled this kit, but have yet to run audio through it. The schematic you show has 5 diodes, but on the main board there was only marked locations for 4. My kit came with 5 diodes. Looking at the board from the front with the potentiometer, on left side,, there is a diode. Looking closely at the PCB, there are two unmarked holes that have PCB traces on either side of that diode. Does the 5th diode go there, and if so, which direction is it oriented?
Good information
Hey man. You should do a mod video where you fix all the little things you mention. Put that resistor in the right place and swap out those caps, and the 10k output resistors. Post a schematic with your changes. Then conduct all your tests to show the differences. See if your can take that $10 Chinese junk amp, and make it a decent entry audiophile amp.
Snickers looks and sounds strong there. "John, my dish is empty"... "Dish is still empty, John"... "John, dish"... "John"...
...after the STARE doesn't work!
Trying to find a transformer to power this with. Any idea what Wattage it should be at?
Hi nice informative videos keep it up. Can you make a video regarding blocking the 48v phantom from a mixer going to a phone via 2 xlr male (L & R) to balance 3.5mm jack but still get the full frequency from 20hz to 20khz? Hope you’d be interested on this small project.
Hi, John. I bought the same preamp but it's difficulty to find a 12vca transformer.... I have two 110vca-15vca .... Do you believe I can use 15vca instead 12vca in this circuit? Thanks for all
Regarding your comment on the 28V being potentially dangerous to things hooked up to the output - since the voltage coming in is DC, the 0.1uf cap should stop it and only the AC voltage from the signal should pass through? My circuits 101 knowledge may be lacking though.
I think d4 and d5 are drawn backwards. do tr1-4 just limit the current to 15 mA?
edit again: I see what they do. R2 and C3 form a low pass filter (72 mHz cutoff) and TR1 is an emitter follower for that average output. guess that will work if the ripple is not greater than Vbe of TR1 (negative can't be less than Vavg - Vce sat). TR2 and R4 are the current limit
edit again again: oops the diodes are correct
So it is true, not to put ceramic caps on signal path.. Been once tried one on a tone control or something like that, and the audio output goes dirty, got some noise, speakers sounded like pouring corn / nuts onto the speaker membrane. Power it off, change the caps to MKM, and the corn went away.
IM having the exact opposite problem, only bass is coming through. Power amp input impedance is about 20k ohm. I replaced the crap ceramic coupling caps with 2uf WIMA and it made the problem even worse. Kinda at a loss what to do with it. Ordered a second, exact same problem. I was expecting a lack of bass going in, not ONLY bass,
Aren't the tubes just acting as a buffer and the transistors are actually doing the amplification?
No those transistors are voltage stabilisers, the valve does provide all the gain
Since this is a tube device, you need to use the correct audiophile words and phrases. I have "borrowed" some text from a popular "stereo-lover" review site:
"amplifier made music sound effortless, direct, and emotionally accessible ... most notable weakness was a slight veiling-a misty, second-harmonic softness that muted detail and diminished rhythmic drive ... more muscular presentation-with sharper focus, greater transparency, and more distinctly punctuated momentum surrounded by its own personal volume of air" etc etc
This is a typical Headphone Amp. 6J1 is very common tube.
Hi John, Iv'e looked around the internet trying to find a definitive answer to this question. When measuring the output of a pre-amplifier, what resistance should be across its output?
In this video you use 10K, is that a standard or just for this tube pre-amp? I have seen some posts suggesting 100K per channel. I would prefer your advice if possible.
On another kit assembled which has 4 dual triodes, I started testing with 10K on each channel. After reaching 10 clean VAC on each output I decided to stop the test and ask you.
It depends on its use. If you're going to connect it to an amplifier with a 10k input impedance, test at 10k. If it's going to be a product released to the public, I'd test down to 1k.
@@JohnAudioTech Nice one John. I was worried I could do damage to the pre-amp by pushing for maximum output, even though I did the same tests on an op-amp based pre-amp and it was fine. The tubes on this kit cost a lot more than the op-amp kit.
Looks like a lot of trouble with 12V AC and a voltage doublers instead of using a low power switching boost converter to make 250V from the 12V input.
They probably put the filaments in series - 12V supply and 6V filaments. The issue is you can get uneven heating.
Many old radios that ran directly from the mains did put all the valves heaters in series without issue. The issue here is cheap nasty valves. The word CRAP comes to mind.
Great John! Tubes are warmer - literally. Heh [Great to hear about Nick.]
Cats are very interesting animals. Some time ago, our local cat savior who takes cats from area pounds called my daughter, who is a cat lover. Seems she had this little white cat that was picked up in a neighboring city. They could not find a home for the cat so were going to put it down, she took it, seems it was attacked by a dog and one of it's ears was deformed from the attack and nobody seemed to want it because of that. So we took it in. Now it was a small kitten, you could hold it in your palm when we got it, and the lady said it was going to be a regular cat. NOT SO, we discovered as it grew, and grew, and grew some more that it was any thing but normal. Now some 3 months later the cat weighs in at 24 pounds, he is over 3 feet from nose to tail and still behaves like a very, very smart kitten. He can understand most of our command words now, although we have never tried to train him, and his markings are remarkable. My daughter took a photo and sent it to a cat fancier web forum only to be told we had a Turkish Van cat. A rather rare breed believed to be the cat that was aboard Noah's ark. It has all the markings of the breed and behaves as described in the documentation of the breed. He was neutered before we got him, so his value is low even though he is a rare breed and nobody can understand how such a rare cat was found on the streets of a city in the oil patch of North Dakota since the cost of such a kitten is very high, well over a thousand bucks. Ah well, we call him Max (after Maxwell Smart as he was very clumsy when young) and he has adopted me as his person, I am the only one who can pet him without being nipped, and he listens to me and surprisingly obeys commands much like a dog, never had a cat that acted like that. At any rate, I understand this is not a cat video, but thought it interesting at any rate. I just ordered 2 of these kits, they were being sold 2 for 6 bucks which indicates the lack of demand for them. I intend on replacing all the caps with quality made Jap caps that I have a good supply of, and as said, perhaps go up a bit to acquire a better base. I intend to pair them up with WIFI radio's that I have been building and if my aging body allows me to work in my wood shop a bit, will be building a nice wooden case to house the setup. I will be using 4 X 16 displays to show the channel to make it a bit more like the old radios and intend on playing both music and OTR shows on the sets. I am in hopes the tube sound will aid in bringing these old forms of radio back to what I remember when I grew up with old tube radios running off battery packs for our only entertainment back in the 50's on our old home place where power never came, and running water was we children running from the windmill to the house with pails of water for our needs.
On minute 17:55 the noise comes from the diodes 2,3,4,5. . . . if these are bridged with capacitors then the sirring goes down. . . . these diodes are too fast for this kind of use, that’s the reason.
what is the problem of letting the audio run through a ceramic at the input ? i guess that was higher value one .....
and also the hum was kinda annoying on my kit, which i found a little improved when used twister pair/ shielded input cables and probably used a 1000uf filament cap.
I guess it's because they are microphonic, they have a piezoelectric effect.
@@Gengh13 i see, thanks. may be i will change them to electrolytics then.
@@Gengh13 2.2uf at i/p & 4.7uf at o/p electrolytics sounding a bit mushy. i may change the i/p ones to 1uf box caps probably.
I'm not to good at Electronics but it don't stop me watching and trying to figure stuff out. One thing I thought about tubes was they need a high voltage like 80v+ and I normally thought it was 200v+ but looking at this diagram it's only 12v but the tube input is 28v. Can you get low voltage tubes? I have seen on the net that tube stuff shouldn't be done by beginners because of the high voltage it uses, it can bite you! Is this a true assumption?
Thanks!
Tubes work with electric fields and very roughly more voltage > bigger electric field > larger curent and curent is what you are controlling in a tube. This does work at low voltages as well but the margins are just so slim and since tubes were mostly run off mains might as well make it high voltage.
However, many tubes will run far below their intended voltage, especially high gain tubes like the 12ax7 famously work even at 12V, since they have electrodes very close together, increasing electric field (if i remember stuff correctly) though at that point you are so far out of spec, so don't expect any performance. I have a distortion pedal that runs a 12ax7 at just 9V and it certainly does create a lot of distortion. In the amp in the video they are actually run at +/- 28V so 56V in total, wich is a range where you certainly can start to get proper performance.
But actual low voltage tubes do/did exist, mostly inteded for battery powered or car radios. They are mostly direct heated pentodes like the 1T4, that work nice at 45V (5 9V batteries in series) and a single AA for heater, it is also still super easy to get. There is also a series of russian pencil/rod tubes, super tiny tubes that also work nice in the 20-60V range, like the 1J24b, also easy to get and lots of projects already out there. And for the super low voltage range you have space charge tubes, those are really made to run 30V and less, the ECC86 for example is designed to run off a car battery at 12V. These are quite rare and expensive but you can still get them.
And yes, a proper high voltage tube amp can and will kill you if you don't know what you are doing, but safety can be learned and if you follow proper precautions you will be safe. But it is good to have respect of high voltage, know what you are capable off. If you are not comfortable working on a live mains circuit I wouldn't recommend working on an active tube circuit, but the low voltage stuff i mentioned is a good place if you want to get started, 50-60v is quite safe (but still can quite whack you so caution is still necessary) and easily gotten from a voltage multiplier like in the circuit in the video, from basic power supplies (lots of network equipment uses 48V to 58V psus and since tubes need low current, a 15$ 48V 500mA supply for a poe switch is easy to get), boost converters or even batteries (9Vs in series). Or just see what runs at 12-20V. Look into the tubes i mentioned, there are quite a few projects with them and simmilar tubes out there. Stay safe and have fun.
@@uzmeyer1752 Thanks for the detailed response :-) Much appreciated!
Hello mister John, quite coincidentally I also bought this amplifier!
can't you tell us/me a little more about how this Tube preamp could be improved?
I understand replacing one or two of the capacitors?
.
apart from that i experimentally put the output of one tube into the input of the other to get some more gain,
can you give an opinion on that?
.
Healthy and Friendly Greetings from the Netherlands!
Rob
For line level, gain is the last thing more that is needed. Definitively upgrade the output capacitors. I'd have to tinker with the board to solve the hum problem.
@@JohnAudioTech
When I bought this I thought it won't be the best but wanna see what it does
But it disappoints me!
Had hoped for a bit more Amplification but no.
In that respect, I should not have bought it and built an ECC83 myself, for example,
I have quite a few tubes lying around here and also transformers.
But you are a bit misled that it looks pretty nice!
It was true that if I did the exit from one half to the other half entrance it was slightly louder!
(I don't need stereo but mono)
Kind regards again from NL area Rotterdam!
Rob
@@hobbyrob313 Hallo Rob. I have made this preamp in mono. And it's loud. I have added two potmeters and there are not past noon too loud. Also due to the microphonic of the tubes they are feedbacking. But i.m.o. this preamp is loud. Groetjes ook uit Rotterdam. Paul.
what happens if instead of AC, you use DC to power the preamp?
it doesnt work.
Hi bro .. I want hifi (high end) tube preamp kit .. from where I can get .. plz share link .. thank bro.. for nice videos I watch its regularly..
Tubes. Of course tubes. This is YouTUBE. 🤔
Nice video. 👍
So, what if you increase the output caps?
He did.
how old is Snickers? Is he doing better?
I built one of these kits. I'm afraid to power it up.
Man you need some batter lights. Put one light on the right side and you will be good . There are to much shadows . 😇😁
Interesting, I got a kit with exactly the same PCB, but in mine there where axial film caps. Some chinese eBay seller apparently also figured that problem out. On the other hand one of the tubes was dying on arrival so yeah....
Glad to see Snickers is feeling better. No answers from the blood work? Get a fountain, makes a big difference.
Vet took sample and thought maybe it was inflamed bowels. I think he was was just starving. Now that I fixed up his diet, he is doing better. I'll have more to say in my next reply video in March.
@@JohnAudioTech Patrol your floors for debris a cat might try to eat, they will do after the strangest things like string, rubber bands, etc.
Кондензаторите в близост до лампите? Кой пян човек е проектирал това чудо на техниката? Колко водка е изпил?
By the way your voice sounds I thought you were in your 20's, looking at the oscilloscopes reflection turns out I was wrong 😀
Age brings experience and knowledge, at 20 your still in the silly stage thinking you know everything.
There's a video of him talking about himself.
the chinese part is just input at the side and output in the middle.
I think twice about tubes in audio applications. They high voltages compared to signal voltage levels, they have high inner circuit impedances, requiring impedance matching means for power amps und the circuits dont have enough open loop amplification to apply negative feedback. So their distortion levels are pretty high. They don't clip very hardly because of their highly nonlinear behavior close to the voltage rails, but this is not really an advantage over semiconductor devices.
I would try TELEFUNKEN Space Charge Vacuum tubes not the Japanese vacuum tubes.
Design "mistakes" like this are why I always have an input blocking cap on my amplifiers.
Could you fix this amp? Old Snick looks exately like it should look for a grandpa cat ...it is normal he is very old now.
Wish Snicker get better, cats can live long if not crossbred too much, but he's thin.
Find an interesting part: John fixes cripple design and explain why, so we can buy cheap boards and fix them, in order to enjoy cheap but nice sound, rather than go the 10 grands grade equipment.
can you make your own better version of it and sell it?
Yes you could, but it already exists, it's called a 5532. Better in every possible way.
The electrolytics are going to get too hot being so close to the tubes
Iv'e seen fleabay photos both with the caps mounted on the top with the tubes and with them mounted on the underneath of the board. I guess it's up to the one soldering the kit in to decide what side what goes in
Hi, you must get thousands of questions but I would like to ask one and will make it brief, I want to build my own headphone amp, I will design the PCB and enclosure myself but would like a known good schematic ( tried and liked ) to work from, highest possible sound quality for my old ears (55 years, I had them from new ) I won't scrimp on the quality of components and probably run it from my apple MP3 player or laptop with an external DAC, I would love for you to make a recommendation of some designs to look at but I have no experience with the subtleties of design that's why I would like your help or help from your viewers ! my headphones will be entry to mid range decent brand like Sennheiser ...cheers!
The diyaudio forum is the best place for advice. Lots of helpful experienced builders there. I get a lot of questions and can only provide short answers like this.
@@JohnAudioTech Cheers, I will check that out.
Don't even think about valves for headphones. Valves are high impedance devices, most headphones are low impedance, perfectly suited to solid state devices.
@@MichaelBeeny Thanks, I've seen cheap devices where they put blue LEDs under the valve,exactly what I'm gonna avoid ! any thoughts on my question Sir ?
@@andymouse Take a look at this -- it's simple, has been around for years, has been built by many people, and sounds quite good in my experience. tangentsoft.net/audio/cmoy/
Sorry to note that his cat "Snickers" also passed on not long ago.
Meow :)
we want boiled fish...😊
Great work but Cat rules!
dc filament is much better for hum.. ;-)
I doubt at the gain this is running at it would make a difference, considering that even 4&5 stage high gain amps often run AC heaters, shielding is more important or you'll suddenly be listening to radio :p Though who knows how shitty those chinesium tubes are, may still be worth a try.
they look like tantalum caps an the pot.
The 6J1 is complete trash. Make your own actual preamp circuit with a 12AU7/12AX7 and build a high voltage supply with two 12.6vct 1A filament transformers.
An even better choice would be the EF86, higher gain also. Almost any valve is better than the 6J1.
Like
Haha
Mister flimsey.
Snickers is a talker.
Without shots from vets and non store made cat foods I've had friends cats and mine live over 20 years.
15 is young.
Man made foods and medicines arnt healthy for humans or animals in the long run.
Nature gave us a we needed. But there no money in healthy humans. And things that last like cars and such amps or whatever..
Just the way our system is. Money money money to withl health and life.
Chinese mindset, thats good enough. American mindset, if your gonna do it, do it right. Generally
it is annoying to see people touching the glass of the valves with fingers, don't do it!
It's a valve, piece of glass. Have you looked in side of an old radio? The valves are covered in muck, they don't care.
@@MichaelBeeny I've been looking in valve radios since 1965, when I was 7yo
it seems like you had your mind made up about this preamp going into the review, and thus are fairly biased (pun intended) just weird how you seem disappointed when it performs in an area better than you thought and get excited when it fails... weird. kinda racist tbh
Just one question.When you changed frequency in the response test did you maintain constant generator through out?Great explination.Thank you.