You should check the value of the capacitor attached to pin 8 of the 5U4G rectifier tube. Chinese manufacturers often put a capacitor with a value higher than what the tube can handle which is 40uf maximum. A higher value causes the tube to burn out very quickly. A few years ago I built an FU50 amp kit that uses the 5U4G rectifier tube and it was supplied with a 150uf cap that I replaced.
He has identified the choke as transformer, most likely it is a pi filter where a rectifier tube is connected to a smaller capacitor and then the choke and then a large capacitor. The choke's reactance limits the large capacitors effect on the rectifier tube. The tube rectifier also has some resistance which creates a RC filter with excellent overall filtering the ripple, hence the hum.
@@Śiśna3633 I am assuming that they are using a similar schematic to my FU50 amp. There are two 150uf caps In my amp, one before the choke and the second after the choke. It is the one before the choke that can cause the rectifier tube to run hot and burn out.
Ah, the mystery revealed! :D I was surprised its so simple, and the second thing that got me was the component quality. I was expecting (and totally ok with that) cheap caps, cheap wiring etc. And only thing low quality here seems to be the volume pot. And that can be easily fixed :)
Yes, a couple of times in different places, but I never owned any myself before. And in this cases that I've heard them they were good, but there wasn't something like now. I will check that amp with different speakers tomorrow (probably)
I've written you before because I am curious about class A solid state amplifiers, but tube amps have been my obsession for 40 years, especially low wattage single ended triode s (like 300B, 2A3,etc). I must say it looks like a good value. Its simplicity is a good thing, as is point to point wiring. You mentioned $100 worth of tubes with $70 of amplifier, but I'm sure most of the cost was the amplifier. The markup on tubes has become ridiculously high. If any corners were cut, it was the output transformers. They more than anything else determine the quality of a tube amp, and are generally the most expensive part along with the chassis. So, my mind goes to the idea of leaving the tubes and caps alone, but instead improving the output transformers. There are some suitable small manufacturers here in the US l, but that might prove difficult because you sound like you might be in eastern Europe. There is a specialist manufacturer in Greece called Thermionic Labs that makes just the thing. Of course, those transformers will likely cost more than the amp did, but you might end up with something extraordinary for the money. Tubes influence the sound to be sure, but the transformers are what separate the best from the rest. I can't help but laugh at folks who buy $120 amps and put $100 tubes in them. Better to buy a $220 amp and run stock tubes. The current promotion of "tube rolling" isn't helping anyone but tube sellers. Good quality small signal tubes should last for many years. I have some I have run daily for 20 years with little degradation. Output tubes have shorter lives, but not just one to two years! And I've been making a point to tell people that if you buy tubes and they have a purple glow, promptly send them back! Tubes should not glow purple! That glow is gas fluorescing in the tube, and remember, they are VACUUM tubes. There should be no gas! Manufacturers are leaving in a little gas to make them fail prematurely. The only glow should be the orange glow of the filaments. There are exceptions, like thoriated tungsten filaments that glow white, and voltage regulator tubes that intentionally have glowing gas inside, but these are rarely seen except in exotic designs.😅
Thanks for sharing, Im mostly solid state guy, so I am just learning new tricks here. For many years earlier, every tube amp that Ive heard had that warm "blanket on the speakers" like sound so I crossed tubes from my interests. Its just recently that Ive discovered that these can be as transparend and clear as solid states :) As for transformers we have one local very well known manufacturer - Toroidy - and they make excellent gear. Not necessarily cheap, but excellent :) I may try to experiment on that one, its not only about the money, but also about fun and learning!
I now also have the Oatlon speakers, darn you! 😊 I understand the synergy is great and the voices are special. But can you tell me if this combination beats the Cayin MY45-MK3 w the Oatlons for vocals?
yes I need to check that, I wonded if thats synergy or just amp thing: I will check both Oldchen + Logans and Cayin + Oatlons to find out, this will be in full review. And today we will have some sound samples I think - taken via phone, but I couldnt resist and recorded 3 small ugly vids :)
@ Maybe the tonality will come thru! YT listeners on phones still have to take many criteria of sound quality on faith, but maybe we will be lucky and the special qualities will come alive. Thank you!
Another thing to look for is that the IEC earth tab is grounded to the amplifier chassis. Some of these Chinese tube amps don't do this making the amp a potential safety hazard.
I am interested in the FM801 clone. You have it quite some time already but no review yet. Do you think it is worth getting it considering i have the D9?
There is a problem with that one or rather me. I got so weak during covid that I cant move it around now. Its that bad. I used to benchpress 110kg, and now I cant safely lift and move 30kgs :/ I have to get back to shape.stupid thing, really
I had my problems with covid too. After the fever period was finished i got extremely tired and sleepy for about a week and had a bad case of coughing that lasted about 2 months. Take care of your health first. I was just wondering if you thought it is worth the investment. technically speaking i do not need another power amp. I am very curious though lol
I don't know how they can pull that kind of prices. If I would disassemble it for parts I could sell them here in Europe for more in total than I've paid for that amp.
When I bought a TDA1541 dac rated for 220V, the secondary voltages were too high (16V instead of 15V), when running on 230V. Luckily, I found a Polish distributor of the transformer brand used in the DAC and ordered the 230V units. I think that here in Poland it would be safer to buy 240V equipment because of overvoltage risk related to photovoltaics.
My FU50 tube kit amp is also rated for 220v and I have 240v here in OZ. I built a bucking transformer for around $100 that is switchable to output either 220v or 230v depending on need.
@@k4syx I lived in China for many years. If you can reach the manufacturer directly and ask them they will most likely make it for the current you need.
@@jacek_r2701 Yes I've recently measured a couple of times my voltage here (stable as a rock, high quality line near power plant) and its 238 so now if I have a choice I try to get stuff for 240V too A couple of years there were new standarisation regulations for voltage across EU and thats what we have here now. I remeber it was like 219 sometime when I was finishing this apartment ~12 years ago
You should check the value of the capacitor attached to pin 8 of the 5U4G rectifier tube. Chinese manufacturers often put a capacitor with a value higher than what the tube can handle which is 40uf maximum. A higher value causes the tube to burn out very quickly. A few years ago I built an FU50 amp kit that uses the 5U4G rectifier tube and it was supplied with a 150uf cap that I replaced.
Thanks, I will check that!
Well noticed ..I think its like 150uf on this one too. 😵💫
He has identified the choke as transformer, most likely it is a pi filter where a rectifier tube is connected to a smaller capacitor and then the choke and then a large capacitor. The choke's reactance limits the large capacitors effect on the rectifier tube. The tube rectifier also has some resistance which creates a RC filter with excellent overall filtering the ripple, hence the hum.
@@Śiśna3633 I am assuming that they are using a similar schematic to my FU50 amp. There are two 150uf caps In my amp, one before the choke and the second after the choke. It is the one before the choke that can cause the rectifier tube to run hot and burn out.
I am looking forward to the review. Thank you, sir.
Looks interesting for sure. Clean build. Also caught a glimpse of you in the bottom reflection. 😁
Ah, the mystery revealed! :D
I was surprised its so simple, and the second thing that got me was the component quality. I was expecting (and totally ok with that) cheap caps, cheap wiring etc. And only thing low quality here seems to be the volume pot. And that can be easily fixed :)
Have you tried any other single ended tube amps before? I think that is the special quality you are hearing.
Yes, a couple of times in different places, but I never owned any myself before. And in this cases that I've heard them they were good, but there wasn't something like now. I will check that amp with different speakers tomorrow (probably)
I've written you before because I am curious about class A solid state amplifiers, but tube amps have been my obsession for 40 years, especially low wattage single ended triode s (like 300B, 2A3,etc). I must say it looks like a good value. Its simplicity is a good thing, as is point to point wiring. You mentioned $100 worth of tubes with $70 of amplifier, but I'm sure most of the cost was the amplifier. The markup on tubes has become ridiculously high. If any corners were cut, it was the output transformers. They more than anything else determine the quality of a tube amp, and are generally the most expensive part along with the chassis. So, my mind goes to the idea of leaving the tubes and caps alone, but instead improving the output transformers. There are some suitable small manufacturers here in the US l, but that might prove difficult because you sound like you might be in eastern Europe. There is a specialist manufacturer in Greece called Thermionic Labs that makes just the thing. Of course, those transformers will likely cost more than the amp did, but you might end up with something extraordinary for the money.
Tubes influence the sound to be sure, but the transformers are what separate the best from the rest. I can't help but laugh at folks who buy $120 amps and put $100 tubes in them. Better to buy a $220 amp and run stock tubes. The current promotion of "tube rolling" isn't helping anyone but tube sellers. Good quality small signal tubes should last for many years. I have some I have run daily for 20 years with little degradation. Output tubes have shorter lives, but not just one to two years! And I've been making a point to tell people that if you buy tubes and they have a purple glow, promptly send them back! Tubes should not glow purple! That glow is gas fluorescing in the tube, and remember, they are VACUUM tubes. There should be no gas! Manufacturers are leaving in a little gas to make them fail prematurely. The only glow should be the orange glow of the filaments. There are exceptions, like thoriated tungsten filaments that glow white, and voltage regulator tubes that intentionally have glowing gas inside, but these are rarely seen except in exotic designs.😅
Thanks for sharing, Im mostly solid state guy, so I am just learning new tricks here.
For many years earlier, every tube amp that Ive heard had that warm "blanket on the speakers" like sound so I crossed tubes from my interests.
Its just recently that Ive discovered that these can be as transparend and clear as solid states :)
As for transformers we have one local very well known manufacturer - Toroidy - and they make excellent gear. Not necessarily cheap, but excellent :)
I may try to experiment on that one, its not only about the money, but also about fun and learning!
I now also have the Oatlon speakers, darn you! 😊
I understand the synergy is great and the voices are special. But can you tell me if this combination beats the Cayin MY45-MK3 w the Oatlons for vocals?
yes I need to check that, I wonded if thats synergy or just amp thing: I will check both Oldchen + Logans and Cayin + Oatlons to find out, this will be in full review. And today we will have some sound samples I think - taken via phone, but I couldnt resist and recorded 3 small ugly vids :)
@ Maybe the tonality will come thru! YT listeners on phones still have to take many criteria of sound quality on faith, but maybe we will be lucky and the special qualities will come alive. Thank you!
Another thing to look for is that the IEC earth tab is grounded to the amplifier chassis. Some of these Chinese tube amps don't do this making the amp a potential safety hazard.
Good point, I will include that in full review!
@@k4syx Don't forget to mention that tube amps like yours have internal voltages in the 300-400v range.
I am interested in the FM801 clone. You have it quite some time already but no review yet. Do you think it is worth getting it considering i have the D9?
There is a problem with that one or rather me. I got so weak during covid that I cant move it around now. Its that bad. I used to benchpress 110kg, and now I cant safely lift and move 30kgs :/
I have to get back to shape.stupid thing, really
I had my problems with covid too. After the fever period was finished i got extremely tired and sleepy for about a week and had a bad case of coughing that lasted about 2 months. Take care of your health first. I was just wondering if you thought it is worth the investment. technically speaking i do not need another power amp. I am very curious though lol
what a find
I don't know how they can pull that kind of prices. If I would disassemble it for parts I could sell them here in Europe for more in total than I've paid for that amp.
@@k4syx dont say that too loud
Interesting, I thought about it (and others like on double EL84/ch amps just for tweeters in biamp configuration, FM300A for the mid-bass ;)
what would be the freq limit that youd like to push to the tweeters via this amp in such scenario? (just out of pure curiosity?)
@@k4syx Crossover on 2100 Hz 3rd order in my DIY speakers. So the slope is pretty high.
220v would put me off. Our Scottish mains run much higher than this and will probably cause problems in the future.
Yes, you're right, I wonder if they have other (than 110v) versions. Sometimes I saw that I can choose from 220, 230 and 240V when ordering stuff
When I bought a TDA1541 dac rated for 220V, the secondary voltages were too high (16V instead of 15V), when running on 230V. Luckily, I found a Polish distributor of the transformer brand used in the DAC and ordered the 230V units. I think that here in Poland it would be safer to buy 240V equipment because of overvoltage risk related to photovoltaics.
My FU50 tube kit amp is also rated for 220v and I have 240v here in OZ. I built a bucking transformer for around $100 that is switchable to output either 220v or 230v depending on need.
@@k4syx I lived in China for many years. If you can reach the manufacturer directly and ask them they will most likely make it for the current you need.
@@jacek_r2701 Yes I've recently measured a couple of times my voltage here (stable as a rock, high quality line near power plant) and its 238 so now if I have a choice I try to get stuff for 240V too
A couple of years there were new standarisation regulations for voltage across EU and thats what we have here now. I remeber it was like 219 sometime when I was finishing this apartment ~12 years ago
I just bought one from aliexpress hehe