Hello DIY. This is my first post and also my first tube amp.
I hate joining a new forum and starting right out looking for assistance, but I don't know where else to go. I recently purchased a Music Angel Mini, L4 using EL84 tubes. So far, Im satified with the performance and sound of this amp but my concern is Bias.
The amp came with no Owner manual and I havent been able to find any information on how to bias the amp or what settings. I emailed the seller and was told it was biased at factory with the factory installed tubes. However, I have a set of EL84M Sovteks I'd like to try but don't dare until I know more about how to bias this amp.
Can someone maybe point me in the right direction, maybe where to obtain the information I need? Im not really a DIYer but bias adjustment I think, anyone that used tube amps is something that needs to be known.
I'd surely appreciate any help or assistance,
Thanks
Ed
I hate joining a new forum and starting right out looking for assistance, but I don't know where else to go. I recently purchased a Music Angel Mini, L4 using EL84 tubes. So far, Im satified with the performance and sound of this amp but my concern is Bias.
The amp came with no Owner manual and I havent been able to find any information on how to bias the amp or what settings. I emailed the seller and was told it was biased at factory with the factory installed tubes. However, I have a set of EL84M Sovteks I'd like to try but don't dare until I know more about how to bias this amp.
Can someone maybe point me in the right direction, maybe where to obtain the information I need? Im not really a DIYer but bias adjustment I think, anyone that used tube amps is something that needs to be known.
I'd surely appreciate any help or assistance,
Thanks
Ed
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Most push/pull EL84 amps are cathode biased, so there is no adjustment. Of course there are EL84 amps with fixed bias, and some with Dave's EFB. If nooone has a manual to verify, you might have to open it up. Make sure it's unplugged first.
Hi.
A schematic would help...
It is probably cathode biased with a common resistor shared by two EL84, bypassed by an electrolytic cap, or, better, with an individual resistor + cap for each cathode.. In this case you don't need to worry about it, just buy matched EL84's.
You can measure the voltage across this cathode resistor and divide it by the resistor value to get the current (which should be somewhere between 35 and 45 mA for one EL84 - double that for two tubes if there's a single shared resistor, and the two/four currents should be very close).
A schematic would help...
It is probably cathode biased with a common resistor shared by two EL84, bypassed by an electrolytic cap, or, better, with an individual resistor + cap for each cathode.. In this case you don't need to worry about it, just buy matched EL84's.
You can measure the voltage across this cathode resistor and divide it by the resistor value to get the current (which should be somewhere between 35 and 45 mA for one EL84 - double that for two tubes if there's a single shared resistor, and the two/four currents should be very close).
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Appears to be a variation on the Meng Yue Mini. Same board layout and parts:
http://www.diyaudio.com/forums/tubes-valves/157134-meng-yue-mini-schematic.html
jeff
http://www.diyaudio.com/forums/tubes-valves/157134-meng-yue-mini-schematic.html
jeff
If that's the schematic, then the good news is that each EL84 has its own cathode resistor, which prevents the pentode from self-destructing in case of current drift.
The bad news is that the voltage amplifier/phase splitter stage is cr*ppy, you'll need balanced 6N2 tubes and/or the 50k pot shoud be adjusted for minimum distortion when you change the input tubes. BTW, ditch the chinese 6N2 and get some russian 6N2P-EV.
The bad news is that the voltage amplifier/phase splitter stage is cr*ppy, you'll need balanced 6N2 tubes and/or the 50k pot shoud be adjusted for minimum distortion when you change the input tubes. BTW, ditch the chinese 6N2 and get some russian 6N2P-EV.
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Amazing. Thank you all for all this information. I will be ordering the Russian 6N2P-EV very soon. It really does sound alot better then I expected. Once I learn what to do, maybe a few mods will make the amp even more satisfying. I followed the link in Vinylkids post and alot of good reading there. I'll be back to read more tomorrow. Never got into tubes in my 40+years in the audio hobby but I think Im gonna like them
I opened up the bottom of my amp to do some investigatin, Seems there is a ground wire hooked from the chassis to the ground on the IEC so that takes care of one concern.
Looking at the solder joints, it looks as if 1/2 way through, someone got in a hurry for some reason. 1/2 look real good and the rest looked hurried. Seem to apprea solid just not nice and smooth like you'd expect. I think next rainy day, I'll clean up the solder that needs it.
Other then that, I'm pretty impressed with the over all performance. I think it's a decent amp for this price. Much more then i expected, thats for sure. I've actually given it a permanent spot on the rack so it's a keeper.
Thanks everyone for all the help. I shurely appreciate it
Ed
Looking at the solder joints, it looks as if 1/2 way through, someone got in a hurry for some reason. 1/2 look real good and the rest looked hurried. Seem to apprea solid just not nice and smooth like you'd expect. I think next rainy day, I'll clean up the solder that needs it.
Other then that, I'm pretty impressed with the over all performance. I think it's a decent amp for this price. Much more then i expected, thats for sure. I've actually given it a permanent spot on the rack so it's a keeper.
Thanks everyone for all the help. I shurely appreciate it
Ed
It looks like the original driver tubes are 6N3. I bought a pait of JAN-5670W to swap in and when i did, I got a wicked loud hummming. What would cause that?
I wanted to ask, would going with a different brand 6N3 change the sound, performace and if so, what should I expect?
I cant tell what brand the original 6N3's are. Even with using a magnifying glass, I cant seem to find a name.
I started looking for some 6N3's but still not sure which brands to try and which, if any to avoid. Any recommendations?
Thanks
I cant tell what brand the original 6N3's are. Even with using a magnifying glass, I cant seem to find a name.
I started looking for some 6N3's but still not sure which brands to try and which, if any to avoid. Any recommendations?
Thanks
The stock 6N3P's are surely Chinese. Try some Russian 6N3P-EV's, they're pretty cheap, even on ebay. Most say they are a sonic upgrade, although I don't have any exp. with these particular tubes.
jeff
jeff
Well I ordered some 6N3P-EV's from the tube store. Minimum order there is $10 so I had to order 8 of them. Guess Ill either keep em all or sell off 4 of them. Should be here soon. I hear that driver tubes make the biggest difference in SQ so we will see. Thank you Jeff.
I heard there is some modifications that can be done to this amp also. Maybe I'll look into that soon too.
I heard there is some modifications that can be done to this amp also. Maybe I'll look into that soon too.
I got the 6N3P-Ev's and they are ding the same as the 5670W's.ud humming. Id sure like to find a schematic, maybe get this modded so i can eliminate those 6n3 driver tubes.
Ive searched everywhere i can think of and can not find a schematic.
Ive searched everywhere i can think of and can not find a schematic.
The Mengyue Mini schem shows a 500R pot across the heater winding. Does your amp have this?
Eliminating the 6N3P's probably means rebuilding the amp P-P and throwing the PCB in the trash. I did see a Mini somewhere that had been rebuilt.
jeff
well, I know why I was having so many isseues swapping the 6n3's. I found out this amp has 6N1's not the 6n#'s that was stated in the description. Now i know why the 5670W's didnt work out too good. I just ordered some EH 6922's for the driver replacements. I've been told that Id notice a bigger difference swapping driver tubes then I will swappin power tubes. Guess Ill find out soon enough.
What have others experienced, bigger difference in driver tubes vs. power tubes?
What have others experienced, bigger difference in driver tubes vs. power tubes?
Well, the Mengyue schematic shows 6N2P tubes... :\
If you are absolutely sure your amp is supposed to use 6N1, buy russian 6N1P-EV tubes off ebay, they are excellent. The 6922/E88CC is NOT a direct substitute for 6N1P, even if most tube sellers say so! They are quite different tubes.
If you are absolutely sure your amp is supposed to use 6N1, buy russian 6N1P-EV tubes off ebay, they are excellent. The 6922/E88CC is NOT a direct substitute for 6N1P, even if most tube sellers say so! They are quite different tubes.
Pinout difference??
I have an amp that came with Chinese 6n3 and putting 5670W instead improved it drastically. Later got some Soviet 6n3p-ev and they sound about the same as 5670w (but are not as pretty).
Be careful with tube swapping as 6n3p(or 5670) has different pinout than 6n1p - heater is on 1&9 and for 6n1p on 4&5 so if 5670 lights-up then your amp is definitely made for 6n3p and not 6n1p.
I have an amp that came with Chinese 6n3 and putting 5670W instead improved it drastically. Later got some Soviet 6n3p-ev and they sound about the same as 5670w (but are not as pretty).
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I dont know but for some reason, my amp ended up with 6N1's. I know another guy has the same one as mine and his has 6N3's. Maybe they had an over abundance of 6N1's that day. I just ordered a pair of Sovtek 6N1P hat should be here by weeks end. Ill give those a try for a week or so and maybe ill get a pair of EH-6922's. I have a friend in another forum that tells me the 6922's should work just fine. He's been an audio tech for years and specializes in tube rebuilds. We will soon see I spose.
Thanks for the help fellers, I do appreciate it. Im still open for any and all suggestions too.
Thanks for the help fellers, I do appreciate it. Im still open for any and all suggestions too.
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