Yaqin MC-5881A amplifier improvements

[CityPooh]

Last update...

I inspected main ground wires from -(minus) speaker output on amplifiers plate and the copper was almost black, heavilly corroded with copper oxyde!

Also the main ground spot on amplifiers plate has only two tiny holes!

So i gently ripped off some plate coating around those two holes, so i can solder on, with ETI soldering and a plenty of cello strings colofonium(i still prefer colofonium more), a massive speaker spade on the main ground spot of the plate..

Slight noise or buzz, which was present before, lowered..

I changed those rubbish corroded ground wires for Tempoelectric solid core for speakers, and i also changed + wires from amplifiers plate to the speakers output, for the same Tempoelectrics...
TE Wire costs me around 4 EUs.

This improves positioning of musicians on the stage very well.
Also the depth improves slightly

My next step will be changing wires on the low output signal path and selector, for thinnner Tempoelectrics, suitable for interconnects..
They costs around 10EUs.

[morisleilei]

Hi guys,

I'm looking for a valve amplifier for 3 months so far, I saw a lot reviews regarding the Yaqin 5881A, it looks fantastic. The only one problem is I can only find them from ebay, and they cost a lot for the postage because they are from HongKong, and the delivery time is too long to wait. I'm wondering if I can find this baby in the UK? Many thanks.

[triode_al]

Hi,
I just bought 6L6GC = 6P3S tubes from ebay to replace the 5881A that is provided with the Yaqin 5881A amplifier.

Now I get a blue cloud at the top of the new output tubes I bought. Is this bad for the tube life?
Drtails: I have ensured that the heater voltage is 6.2 AC volts. And Vb to be 360V. The current is 30 mA per tube (10 W anode) and the tube is changed from ultra-lineair to pseudo triode. The 5881 did not give the blue color.

Any suggestions what I should do, anyone?
albert

[Svein_B]

Originally Posted by triode_al

Hi,
Any suggestions what I should do, anyone?

Just listen to some music

Or you may be able to point your finger at the tubes and play with the fluorescent blue glow.

This dark blue glow is normal in some makes of tubes.


SveinB

[Salas]

Blue glow in tube. Is the tube dead or not?

[zbodeoc]

It looks to me that you are fortunate enough to have another visual effect added to the initial one, "magic eyes"... :-)

I've tried 6P3C-E (military grade and shorter than 6P3C) and worked like a charm with no blue effect.

[triode_al]

Thanks for your responses.
Salas, your link is very good to understand the problem. My concerns have gone now!
Interesting is that I have Shuguang 300B tubes too that have blue glass (and I have always suspected the manufacturer to make it blue to avoid seeing such a glow!).

SveinB, the tubes sound like a marvel. Details, crispness, low stage sound.
They measure very well on my test bench too. I had them in my tubetester, all four I bought have the same transconductance like 2100-2150.
All four had this out of the box, so it seems normal for the make.
I had this also on 6550 tubes in the past in another amplifier, and reduced the anode current (fixed bias) until the colour disappeared; but in this amplifier I have auto bias, hard to play around with.

zbodeoc, yes, I saw them too but also needed 6N1P-EB tubes that the seller of the 6P3C-E didn't have.
albert

[CityPooh]

Originally Posted by triode_al

Hi,
I just bought 6L6GC = 6P3S tubes from ebay to replace the 5881A that is provided with the Yaqin 5881A amplifier.

Now I get a blue cloud at the top of the new output tubes I bought. Is this bad for the tube life?
Drtails: I have ensured that the heater voltage is 6.2 AC volts. And Vb to be 360V. The current is 30 mA per tube (10 W anode) and the tube is changed from ultra-lineair to pseudo triode. The 5881 did not give the blue color.

Any suggestions what I should do, anyone?
albert

Hi, Al.
Same happened to me when i changed factory MKP caps for Jantzen Superiors and after some time that nice blue glow dissapears.
Troelsgravesen opinion about caps shows that Superiors are real jam and they are not very expensive, i also use other cap he prefers, russian K42-2 or mixture of both.
K42 after a month of burning in, could be Mundorf SIO killers!
The Grounded Grid preamplifier

My friend told me, there are some amps made to have blue glow and that should be no problem for lifetime expectations of tubes.

Blue Glow in Tubes, Tube Getters, and other Tube Info
Mine is now running on KT77 Genalex Gold Lion.
Signal tubes are JJ E88cc and Vostok 6N1P-EV from 70 ies.(dont buy non "EV" Vostoks!)
KT77 is european invented hybrid tube and it "acts" in 5881 like this is an some kind of bastard between EL34 and 6L6 amp.
Lot more hapenning now in upper mids and highs, bass control remains the same as 6L6.
Almost transistorlike speed and openess.
On signal path i tried 6N6P-ECC99.
Strange, big signal tube for microphones, adviced on Lampizator site..
At first i bought, matched, newer ones, OTK(OTK means the same like EV), Nevz plant, but in that case, ordinary Reflektor from 70ies with no OTK stamp are the real thing.
5881 with 6N6P became sounding like triode amp, much more "civilised" and quieter too.
6N6P are now in my tube DAC, so there is no need to have them in 5881.

So. With that wonderfull and cheap tube is no need to convert 5881 in triode and with Genalex KT77 you get the best from EL34 and 6L6.

[CityPooh]

Originally Posted by zbodeoc

It looks to me that you are fortunate enough to have another visual effect added to the initial one, "magic eyes"... :-)When i was kid, my family had a tube radio with similar magic eye, so i just love that "add on" a lot and i dont care what it supposely do to the sound.

I've tried 6P3C-E (military grade and shorter than 6P3C) and worked like a charm with no blue effect.

I have longer version of those and it is very nice tube.
Could be "softened"(i assume that your russian PIOs caps in 5881 sotfens sound enough without that) with Tesla E88CC and 6N6P Reflektor combo, but the real stuff is 6N1P-EV Voshod-6N6P combo.
And yes. 5881 "likes" a lot JJ E88CC in some combos of signal tubes.
Do you maybe know if there is a particullary reason, why russian fellows are selling shorter version of 6P3C for more money than longer one?
Are they better in some ways?

Shorter?

Google: rezultat iskanja slik za http://tubes-store.com/images/6p3s_e_02.jpg

Longer?

Google: rezultat iskanja slik za http://www.tubemongerlib.com/gallery2/d/10692-1/Russian+Reflector+6p3c-e+Hytron+6L6GB+Label+2+-+USSR.jpg

[CityPooh]

Originally Posted by morisleilei

Hi guys,

I'm looking for a valve amplifier for 3 months so far, I saw a lot reviews regarding the Yaqin 5881A, it looks fantastic. The only one problem is I can only find them from ebay, and they cost a lot for the postage because they are from HongKong, and the delivery time is too long to wait. I'm wondering if I can find this baby in the UK? Many thanks.

I read quite some time ago, that there was once an Yaquin importer in UK.
There is one in France.

Yaqin France

Marc is really a nice guy, very friendly and helpful, and he has two years guarantee on Yaqin products.

There is some, for my personal taste, bit sluggish guy in Slovenija importing them directly from the factory in China -named Tonewin.

Tonewin Electronics Co.,Limited

Maybe the best option is to ask Tonewin sales dept for the price fcco UK and if that is an option, it could the least expensive one.