Yaqin Tube Valve Amplifiers

Comment from Yves
Time: June 6, 2008, 7:50 pm

Hi, I just purchase a MC 84L. It works but I have a permanent noise on both chanels. Do you have any advise. regards, Yves

Comment from Dan Ashby
Time: June 9, 2008, 9:09 am

Hi Yves, first make sure this is not a ground loop introduced by other equipment. To test I would connect up a source such as a portable cd player or ipod as they will not be earthed. Does it still make a noise? You need to be more descriptive of the noise, is it hum or buzz etc. How sensitive are your speakers? Try reading up on google about these things if you don’t understand the terms.

Good luck, Dan

Comment from Yves
Time: June 10, 2008, 7:13 pm

Hi Dan, I checked the input circuit and there’s no ground loop. Regarding Hum and buzz in fact I have both. On one channel I’ve a smal Buzz on the other one I’ve a hum. I tried different configuration of the delivered EL84 and one is better than all others. But the moises are still present. My speakers are very sensitive >100dB/2,83V/1m so it might be the reason why I’m earing that. Thanks for your interest. Yves

Comment from Dan Ashby
Time: June 11, 2008, 8:51 am

Hi Yves, these amps aren’t designed for speakers of that sensitivity so I would expect the noise floor to be too high. Get some £50 89db speakers and I expect it will be silent!

Dan

Comment from Stuart Leask
Time: December 10, 2008, 10:15 am

Hi there. I have one of these. Had to change the power LED from a headache-inducing hi-bri Blue to a nice warm yellow, but otherwise beautiful tone and looks, feeding some medium-sensitivity speakers.

However… it gets through valves PDQ. I seem to have to replace an EL84 every 6-8 weeks, with a few hours on, couple of days per week. And I’m getting white (heat?) deposits on inside of the grill over some of the EL84s too.

Checking volts, mains around here is 247v, the filament feed 7.3v (not 6.3) , and the HT ~280 (not 245).
Too high. I could perhaps change some of the HT resistors, but that won’t change the filament voltage.

I could put it on an autotransformer* to lower everything. The options here seem to be 240/220/200.

Any thoughts/experiences trying this? Am I right in thinking that dropping the HT by from 1.0 to 0.X simply drops the output power by 0.X squared, or are there also effects from dropping the filament voltage to consider?

(*switch on it draws 150W, soon settling to ~100W… if you play it loud, this drops to just over 90W, the joys of Class A!… but a 200W autotransformer isn’t going to break the bank)

Comment from Dan Ashby
Time: December 10, 2008, 10:29 am

Yes, the LED is awful and covered in my mods on the MC-5881A. 247 Vac is way too high (where are you based). As far as I know the mains transformer will be wound for 220. The heater voltage just needs to be enough to get the valves working properly, it doesn’t affect the output power as long as it is within a sensible working range. Get a 200W 220V auto transformer and I would expect a significant drop in heat and outlay on valves. Let me know how you get on.

Dan

Comment from Richard Floyd-Walker
Time: February 6, 2009, 10:54 am

Hi.
I am thinking of getting one of these amps as a cheap route back into the world of valve based audio. I used to own a set of Quad 2 mono blocks and pre amp wired to a pair of Tower speakers but that was a long time ago and I haven the cash to buy into the Quad thing. But I need to clear up a couple of things.
1: I have been told that Chinese Amps are set up run at 110 volts as opposed to 240 volts. Is this true and if so does it make a difference?
2: I will be be hooking up this amp to a pair of Gale Monitor Gold bookshelf speakers. 6″ Driver, 6ohm Impedance and 89db Sensitivity. Do you think that these will match well?
Also if there is anything else that you feel should be considered before purchasing. I would be grateful to hear of it.
Regards.
Rick.

Comment from Dan Ashby
Time: February 6, 2009, 12:22 pm

Hi Rick,

A1: The ones I have seen were wired for 220v – not 110v. Plugging a 110v device in would certainly fry something! The issues with this are discussed on this page: http://yaqin.slickpepper.org.uk/amplifiers

Various companies are claiming to sell amps wired for 230v (which is our supply standard these days by the way). I haven’t seen any but that doesn’t mean it’s not true.

A2: As far as I know these amps work fine with fairly insensitive (89db is fairly standard these days isn’t it?)speakers – it’s always suck and see I think. I don’t want to get into these kinds of recommendations – I simply don’t know enough about it.

Dan

Comment from Richard Floyd-Walker
Time: February 6, 2009, 1:23 pm

Hi Dan Thanks for the reply.
I’ve just checked the web page you pointed me to. Thanks for that.
What can be done to protect the amp from our higher standard voltage?
Regards
Rick

Comment from Corrado
Time: February 12, 2009, 4:38 pm

The yaqin MC 84L runs at 220v i had an amplifier and cooked the transformers brown and fried the tubes , i then got a custom made step down transformer, to drop the voltage from 240v 250v down to 220v the amplifier runs cool and just warm not hot anymore and it works great.
Corrado

Comment from Richard Floyd-Walker
Time: February 12, 2009, 5:36 pm

Thanks for the reply Corrado (Great name. I had a 16 valve Corrado. Best car I ever owned). Where did you get your step down made? I was thinking of ordering one that runs off 110v volts, which is an official option, and getting a step down from maplins for £40.00.
Regards.
Rick

Comment from Corrado
Time: February 22, 2009, 12:08 pm

Hello i got my step down made custom from a technician. I have known him for many years and he is the only person i trust with my hi end audio. His name is {KIMIL ELETRONICS}

He is located in belmore here is info below

KIMIL ELECTRONICS
ELCTRONICS REPAIR AND SERVICES
220 GEORGES RIVER ROAD
CROYDON PARK NSW 2133
PH:9799 3019 FAX:9799 3688

HIS NAME IS Kimil HE IS THE MOST HONEST AND KINDEST PERSON.

Thank you Corrado

Comment from Chris
Time: April 26, 2009, 10:13 am

Hello,

Does anybody knows if i can use 4 El84 if not matched what will happen ???
What about the bias for thos amp?
Many thanks….

Comment from Corrado infarinato
Time: April 26, 2009, 4:08 pm

Hello Chris

Using el84 unmatched tubes will be ok because the yaqin amplifier, has auto bias for the el84 tubes, so it will automatically match the tubes bias and match them. Just be careful with chinese tubes, they are not very good quality. Try these following tubes MULLARD EL84,JJ ELECTRONICS, TELEFUNKEN. ALSO OTHER TUBES WHICH I FIND VERY GOOD AND CHEAP RUSSIAN 6N14P WORK GREAT IN THE YQIN AMPLIFIER.

Comment from Corrado infarinato
Time: April 26, 2009, 4:14 pm

Hello Chris

Using el84 unmatched tubes will be ok because the yaqin amplifier, has auto bias for the el84 tubes, so it will automatically match the tubes bias and match them. Just be careful with chinese tubes, they are not very good quality. Try these following tubes MULLARD EL84,JJ ELECTRONICS, TELEFUNKEN. ALSO OTHER TUBES WHICH I FIND VERY GOOD AND CHEAP RUSSIAN 6P14P WORK GREAT IN THE YAQIN AMPLIFIER. sorry the tubes are 6P14P not 6n14p

Comment from Chris
Time: April 26, 2009, 5:29 pm

Hello Corrado,

What a good news !!!!!!! Many thanks for the info. The tubes I will received are Russian NOS 6P14P. I will try Mullard later when i get money Thanks again. Regards. Chris.

Comment from Oliver
Time: December 31, 2009, 11:19 pm

Hello I have a new amp and am really enjoying it but the blue LED is driving me mad. Can you tell me where I can find instructions to change it? I would also like to hook up a turntable. Any advice on how I can do this. Mine has a headphone jack too. How can I determine the impedance? Thx.

Comment from Dan Ashby
Time: January 4, 2010, 10:25 am

Hi Oliver. You can tame the LED by putting a resistor in series. You can either calculate the voltage requirement using ohm’s law or an online calculator http://led.linear1.org/1led.wiz or just try some values. As you’ll be increasing resistance and current flow will be minimal the worst than can happen is that it doesn’t get dim enough (increase value). Headphone impedance can be approximately judged by measuring the resistance of the headphone output with an ohmeter. As for turntables, you’ll need a phono preamp of some kind – this is a big subject but to get you started you can but cheap ones for less than £30 on ebay.

Dan

Comment from Kryn
Time: January 10, 2010, 5:44 pm

Just thought I mention. I don’t think the transistor in the design should put off purists. The transistor appears to perform auto bias adjustment (I could be wrong as I am not an electrician by any standards), which can only benefit sound in this case. the alternative i manual adjustment, which is resistors and caps, which to me seems not wise since you have to keep checking your amp on a yearly basis and replace components as the tubes degrades over time…

Comment from Dave Tainer
Time: January 30, 2010, 6:39 pm

In case anyone is interested, I thought I would report my findings on some tube rolling I’ve done on my MC-84L. My previous amp was a MingDa that had come with all Chinese tubes. Changing most of them had no effect except in one slot, and that was when I put in a Russian tube. Since that experience, I have favored Russian tubes because of their quality and low-cost on the market (both eBay and other sources). So when I bought my Yaqin, I purchased 4 x 6n14p to put in immediately, and already owned Sovtek 2 x 12ax7 LPS.

So when it arrived, the first thing I checked was the provenance of the tubes supplied. To my pleasant surprise, it came with Russian 6n14p OTK (military equivalents)! The 12ax7 were Chinese. In this configuration, it sounded great. I kept the Chinese tubes in for several weeks to see if the character would change over time–it did not.

My first switch was to put in the Sovtek LPS. This made a little difference, but mostly very subtle, and mostly in the high end, which was ever so slightly better defined.

After another few weeks with these, I had in the meantime purchased brand new JJ/Tesla ECC803S and two NOS RCA. I next rolled in the NOS RCA (from the codes on them, they appeared to be from the ’70s). I couldn’t really tell much of a difference with the Sovteks. I left them in for a few days and thought that some of that high-end “shimmer” was missing from the sound now.

I next put in the JJ/Tesla ECC803S. These were my new favorite, although again, the sound was still more or less like the original Chinese Tubes, though closer to the Sovtek LPS, but a very slight subtly better high-end. I left these in for a couple of months and enjoyed listening to music.

The last change and current preamp section tubes is with used Telefunkens. I had in my tube stock from my previous amp a single Telefunken ECC83. I finally got a “good” deal on another single on eBay ($20 w/shipping), so now I had a match. Again, there was no amazing difference, but there is definitely a very subtle improvement in overall definition of music. I’ll probably keep these in until they burn out, but I won’t miss them terribly when they do: none of my backups are bad, and the worst are merely good.

As for the power tubes, I tried the Russian NOS 6p14p, brand new JJ/Tesla EL84, and brand new TAD EL84. I could discern no noticeable difference. They were all uniformly excellent and the music sounded the same: same bit of warmth, detail, bass, mids and high end. Of all the tubes rolled, only with the preamp tubes did I get any difference at all, and even that was minimal.

For reference purposes, my sources were: Music Sever > V-DAC; Rega Planar 3 w/Super Elys 2 > Bellari Rolls VP29. My speakers are Klipsch KG2 (91db horn-loaded and passive radiator, 4ohm taps on amp used).