Yaqin VK-2100 mods

[bazouka]

Waww this is some serious job you've done.
More pictures please !

 

[fantacrazy]

hello this is my first post on this forum, I greet and thank everyone for the help
i have a question ... I am going to apply changes to the 2100 just arrived, I immediately noticed that my amp has no louness but is prepared, I have an output of 14 volts to the right where nothing is connected from the photos on the forum. Tips for the loudness and the lack of such a link?
said this is my real question is: better to replace the 0.47 uf capacitors with 0.33 uF or replace leaving 0.47?. under the I-circuit capacitors or other components to be replaced? I have not taken apart ...

 

[acerjac]

Hey guys I just received the 2100 yesterday. I am impressed with this things sound quality! Mine does not have the loudness button either. It also has a standard power supply instead of the toroidal that I have seen on line. Does anyone know why this is. Is the one with the loudness button a later version? I am new to any kind of tubes and modding an amplifier. I am looking forward to squeezing as much sound out of this thing I can.

Mark

 

[DefQon]

Just fyi guys, the newer revisions (without the loudness button) have a slight circuitry change and use of better components to those from the pictures provided on the previous pages in this thread.

Depending on which seller or distributor you buy from, my one came preinstalled with 2 12AU7 tubes on the outer sides and 2x 12AT7 in the middle. This brings a lot more options to add to tube rolling to get the sound preference required rather then the older VK-2100 that only accepted 6v tubes.

 

[HornTube]

Hi,
Stock Shuguang is really Too smooth and shy, week on highs, and more important, bass is boomy, on complex music everything becomes relatively messy very rapidly.

With the 6N1P-EV, everything is much clearer in the highs but the biggest improvements was the bass, more slam, much less boomy, but everything keeps a lot of sweet, no aggressiveness, it is impossible you didn't notice the difference it is really an upgrade !!!


For the Bias just look to the DOC

So true. I experienced the same bloated boomy bass problem. The dynamics went through the roof with the 6N1P. The russian 6N1P did transform this not that bad amp to a quite good amp. I love soviet tubes so much, they kill every Telefunken, Valvo or US tube. Oh, one thing more: Please change the 4 coupling caps, they contribute a lot to the boomy sound. If you want ultimate speed and save money go for the Sparague orange drops, if it is too dry for your taste you can use DynamiCap or ...

 

[djn]

I have a 2100 that has issues. I have a couple questions.

Which caps are the coupling caps??? I figure I would replace them since I am there anyway.

My PCB is marked for both the 6XX and 12XX tubes. Can I just drop in a 12XX without rewiring the heaters?

When I checked the DC offset on the speaker terminals, I got a fairly steady 287mv on the left and on the right I got 1v, then a quick drift down to 244mv. I did not have a load on across the terminals.....should I have had one?

 

[HornTube]

The big blue ones - Siemens or Philips both sound awful, slow, bloated, muddy transient killers, no detail & no air. With fullrangers I use Jensen, I don't recommend them in the first place but better than the big blue crap. For "normal" speakers I do recommend Sprague, Jantzen, any Mundorf & MIT RTX.

 

[djn]

Thanks Horn. I have a carvar M1.5T and Carver TFM45 on the bench that both need parts. Seem like a good time to bundle an order to mouser!

Has anyone compared the 6N1P with the 12XX tubes?

 

[HornTube]

As I said, even Telefunken & Valvo don't have a realistic chance against the communist tubes The 6N1P are rhythmically like a Soviet train, injecting speed, dynamics & life to the music. The bass alone is so much better, it is a transformation.

 

[djn]

I just went to the bay and found gobs of 6N1P tubes for not much money. I'll be giving them a try. Thanks Horn.

 

[youngie]

will just this part of the upgrade be any good or will i need to do all of them. chee

The biggest difference to the previous state, was by replacing the 10000uf filtering caps by better 15000 ones, Bass is faster (I love fast bass) but more interestingly, this amplifier as all amplifiers tend to sound thinner (treble goes high) when you push it into high power zones, and it loses separation between instruments, anyway Upgrading those caps really keeps the amp more balanced whey listening to (VERY) high sound levels .thank you all lee. oh and i have bais it with not much luck keeps changing all the time any help on this mate would be great 2 cheers all lee

Hello
I think I finished doing all the tweaks on my amp, I'll sit and listen now.

My Speakers are French Cabasse MT3 Antigua, they are Great for my taste..

I've put the link for the bias manipulation in this tread before and here it is again: Let me google that for you

Last modifications where :
Replacement of the 47uf 450V capacitors by better 82uf 400v ones, decoupled with some Russians I had in my desk (not a big gain).
Replacement on the lousy Nichicon LK 10000uf capacitors by NCC KMH 15000uf ones (they fit just right, specially the hight)
I added an ERO1840 0.33 cap under each row of blue capacitors, to bring back the whole capacitance to near origine (0.33uf x5 in place of 0.47ufx4)
I replaced the signal connection with some silver coated Coax Cable RG316, Not a Necessary mod but I wanted to test It..

The biggest difference to the previous state, was by replacing the 10000uf filtering caps by better 15000 ones, Bass is faster (I love fast bass) but more interestingly, this amplifier as all amplifiers tend to sound thinner (treble goes high) when you push it into high power zones, and it loses separation between instruments, anyway Upgrading those caps really keeps the amp more balanced whey listening to (VERY) high sound levels .

And really changing the stock Chinese tubes by russian 6n1p-ev in my case (and many others on the French forum for the vk2100) brought in a more Flat sound, and a much better résolution, I tried them again for some hours this W.E., No way I am keeping the Chinese tubes in !!
It is nearly impossible you haven't heard any gain by doing the same, but what counts more is how this amp suits your ears.

also I have to say that I change the 4 tubes every year, old 6n1p tubes loses trebel and liveness, I keep tha amplifier on for long periods of time, I evaluated the useful life of tubes for me to be under 2000 hours,
please note I have not chacked the tube section for the voltages etc, so mabe my amp is burning tubes, I dont care because the tubes are about 7 dollars for the 4, and I have 10 on them at home, but maybe I will check that in the near future.

Here are some new pics from my amp, after mods :

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An externally hosted image should be here but it was not working when we last tested it.

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An externally hosted image should be here but it was not working when we last tested it.

 

[kneedeepinit]

I just installed some 6N1P-EV tubes and it created a hum. I have never adjusted bias or offset with the stock tubes because it worked perfectly.

Can I do any adjustment to use the new tubes or am I stuck with stock tubes?

 

[tt64]

Hello
Did somebody pay attention on the tube part? SRPP is very strange.
Grid ot the load tube (second part of triode) is connected not after, but before resistor R4 or R8, pins 2 and 3 are closed.
I checked it on my amp, it is really done, as in drawing.
Does sombody know about that "SRPP"?

 

[DefQon]

Hello, everyone!

I apologize if I am going to sadden some of the people with my comments but I think you should know some facts about this amplifier; they will come from somebody, who is working with analog electronics for last 20 years and at least it will bring some technical clarity on a number of topics here. Or so I hope.

Also, TOSHIBA is not manufacturing the output transistors of that type for, maybe 10 years now. What is used in VK-2100 is Chinese knock-offs.

FAIRCHILD manufactures replacements to 2SC5200/2SA1943, they are FJL4215/4315, they are quite inexpensive and they also have better linearity. I purchased a handful from DIGIKEY, matched two pairs and replaced the output transistors. That greatly improved the stability of DC offset with temperature and now it is running at 3-5 mV of DC offset at all times.

Indeed all 0.47 uF capacitors need to be replaced; mine were from a Korean manufacturer, who makes no secret that these are from low cost computer grade family.

Just revisiting this thread again, although this post is an old one it is most ill-informed post made. What's funny is the original poster of this failed to deliver any straight through facts and I'd thought for any new posters still reading through this thread don't be put off by the above crap.

First off, the Toshiba 2SC5200/2SA1943 are not discontinued and haven't been over the past decade. You can buy the original genuine deal (i.e proper part codes and Made in Japan) over from Mouser. The 2SA1943 works as a complementary transistor with the 2SC5200.

Fairchild also makes 2SC5200's which have a slightly higher voltage rating of 250v and 2% higher current rating of 17a compared to the original Toshiba's of 230v working voltage and 15a at max DC rating.

Do note that not all VK-2100 come installed with Korean 0.47uf coupling mkp cap's, all VK-2100 after 2011-11-1 come installed with Vishay MKP's of the same rating which imho sound better than the Russian PIO junk you see used quite alot. The only coupling caps that sound slightly better "sounding with a bit more body and authority" are the ultra expensive Mundorf Gold or the higher grade Auricaps.

Another thing to add from myself is that unless the VK-2100 you're buying is old stock (before 2011-11) or second hand, the two big cap's are not 10000uf 63v ones, they 12000uf 63v Samwha's but changing it out to 150000 yields very little to no improvement depending on the tubes you roll and the speakers/source components of the chain.

Current mods I recommend is leaving the Vishay MKP caps alone, replace the electrolytics for better brands (higher ripple, lower esr, same(or high) voltage and higher farad rating only for the two big 10000/12000uf caps). Tube rolling the 12AT7's have a bigger sound affect than rolling 12AU7's.

 

[Kknight]

My vk-2100 only lasted a couple years before problems. One channel louder than the other even though bias and DC offset have been set. Probably transistors going bad already.

I will post all the pics and info I have and wanted to state that no matter what's printed on the circuit board, your vk-2100 is only wired for 12x pre amp tubes based on the year it was manufactured. DO NOT REPLACE OR ROLL TUBES UNTIL YOU CAN DETERMINE WHAT YEAR MODEL YOU HAVE. I have 12AU7 and 12AT7 printed right on the board, but mine is only wired for 6N1 tubes. According to my distributor and seller (Song in Canada- tabnac on Ebay), Yaqin never bothered changing board markings.

 

[DefQon]

Change your pot.

 

[draftex]

12V or 6V?

My vk-2100 only lasted a couple years before problems. One channel louder than the other even though bias and DC offset have been set. Probably transistors going bad already.

I will post all the pics and info I have and wanted to state that no matter what's printed on the circuit board, your vk-2100 is only wired for 12x pre amp tubes based on the year it was manufactured. DO NOT REPLACE OR ROLL TUBES UNTIL YOU CAN DETERMINE WHAT YEAR MODEL YOU HAVE. I have 12AU7 and 12AT7 printed right on the board, but mine is only wired for 6N1 tubes. According to my distributor and seller (Song in Canada- tabnac on Ebay), Yaqin never bothered changing board markings.

I am a little confused. After rewiring the tubes the way you have illustrated, is it going to be suitable for 12AU7/12AT7 tubes or 6N1? Please clarify. Mine is wired same as your first pic (pre-mod) I have two 12AT7 tubes installed at middle and two 6N1 tubes on the sides. It works great but 12AT7s dont glow at all while 6N1s glow orange beautifully

 

[Radiola]

Just revisiting this thread again, although this post is an old one it is most ill-informed post made. What's funny is the original poster of this failed to deliver any straight through facts and I'd thought for any new posters still reading through this thread don't be put off by the above crap.

First off, the Toshiba 2SC5200/2SA1943 are not discontinued and haven't been over the past decade. You can buy the original genuine deal (i.e proper part codes and Made in Japan) over from Mouser. The 2SA1943 works as a complementary transistor with the 2SC5200.

Hi buddy

Just noticed that I got a response from you. So, to make sure there is no crap indeed, please download the Toshiba datasheet on 2SC5200 where you could find out that Toshiba restarted production on Aug 2012, which is, what, a year from the time of my post?

 

[50jess]

Are the 6N1’s compatible with both 12AU7 and 12AT7? I plan to substitute the 6N1’s.

 

[DefQon]

Are the 6N1’s compatible with both 12AU7 and 12AT7? I plan to substitute the 6N1’s.

Absolutely not.