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Old 14th February 2013, 07:02 PM   #71
youngie is offline youngie  United Kingdom
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Default 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
Quote:
Originally Posted by bazouka View Post
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 :
Click the image to open in full size.Click the image to open in full size.
Click the image to open in full size.Click the image to open in full size.
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Old 17th March 2013, 05:58 AM   #72
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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?
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Old 26th May 2013, 07:08 AM   #73
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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"?
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Old 21st July 2013, 07:50 AM   #74
DefQon is offline DefQon  Australia
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Quote:
Originally Posted by Radiola View Post
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.
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Old 21st January 2014, 06:37 PM   #75
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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.
Attached Images
File Type: jpg Take PC Board Out.JPG (415.1 KB, 42 views)
File Type: jpg Step 1.JPG (531.0 KB, 15 views)
File Type: jpg Step 2.JPG (680.0 KB, 18 views)
File Type: jpg Step 3.JPG (620.5 KB, 15 views)
File Type: jpg Step 4.JPG (644.5 KB, 13 views)
File Type: jpg VK-2100_bias.jpg (103.6 KB, 17 views)
File Type: jpg VK2100potsadjust.jpg (131.7 KB, 15 views)
File Type: jpg yaqin01.jpg (56.2 KB, 15 views)
File Type: jpg yaqin02.jpg (64.0 KB, 13 views)
File Type: jpg VK-2100Schematic-input.jpg (144.7 KB, 27 views)
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Old 10th February 2014, 11:59 AM   #76
DefQon is offline DefQon  Australia
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Change your pot.
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