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The 'NEW' YAQIN MS-20L Integrated Vacuum Tube Amp Thread - Page 14

post #391 of 796
2/26/12 at 6:43pm
Quote:
Originally Posted by rntlee View Post

The only schematic of this amp I'm aware of is this one(I got it from Song @ Canadian Hifi Online):

Attachment 238521

It's possible there are errors, I haven't had my amp open yet to check.

My only concern with posting/encouraging internal modifications is the danger to inexperienced modders. Tube amps utilize very high (ie. deadly) voltages. There's 450V at hand inside the MS-20L that will give anyone who comes into contact with it a very bad day.

That said, one modification I did need to do with mine was to place a bucking transformer between the amp and the mains voltage. I'm in Canada and my measured household voltage is 126-127VAC. This is a little high for this amp, which seems to be designed for a voltage of around 115VAC. The heaters on the tubes are to be run at 6.3v for maximum tube life. Mine were at about 6.9v, which would have shortened the tube life by about half:
Attachment 238526
I bought a boost/buck transformer from ebay and it drops my 126VAC to 115VAC. This amp also uses a SRPP for the input stage, which is pushing the heater to cathode voltage in the top 6J1 to the max allowable. I may have even been exceeding it with my high mains voltage.

Good point about modding these amps, I was a TV repairman in the 70s, remember tube TVs? I "lit myself up" more than once back in those days
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post #392 of 796
2/26/12 at 7:19pm
Its a low amp load though, couldnt exactly be deadly.

I recall a thoroughly enjoyable experience I had years back when I was a structural welder. Hit with the arc welder set at 140 amps. Never forget that one, good thing I was working on an addition for the fire dept.!
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post #393 of 796
2/27/12 at 5:35am
The four B+ filter caps form a 330uf bank charged to 450VDC. This is around 30 joules of stored energy that can be discharged instantly. The average Taser discharges <0.5 joules. As little as 10 joules across your heart can induce ventricular fibrillation.
That's why you should always keep one hand in your pocket when working with high voltage equipment.
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post #394 of 796
2/29/12 at 12:23am
Hi all, well after a lot of research I decided to purchase MS-20L. Hoping to receive it next week. I'm now really into female vocal jazz, so thought that tube sound should compliment this kind of music. Really looking forward to experimenting with it. I have Vienna Acoustics Beethoven hopefully the amp will be able to drive them. Also, waiting to receive Audio Research vs115 from one of the high-end dealers that I can use at home for a few days. It would be very interesting to compare $600 amp with $6,5000 amp. I will post my impressions as I get them both.

I'm planning to do some tube rolling with Yaqin. One thing I can't figure out from the postings, there are 8 small tubes of the same type. Should I try to replace all 8 of them or only 4 that are for preamp make difference and the rest of them wouldn't. I'm very new to the tube world, so please pardon my ignorance.

Also, has anybody experimented with Shuguang Treasure Vacuum Tubes 6CA7-Z? How do they compare to Gold Lion KT77? Are those tubes approaching point of diminishing returns?
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post #395 of 796
3/1/12 at 5:16am
I don't see the MS-20L in Canadian HiFI's eBay store? Out of stock?

I was all set to order today.
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post #396 of 796
3/1/12 at 10:35am
I think I bought the last one Here is Song's email, you might want to ping him and ask about availability: sgao8@rogers.com
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post #397 of 796
3/1/12 at 12:44pm


I emailed him and he says he expects more by the end of March.


Quote:
Originally Posted by nick-seattle View Post

I think I bought the last one Here is Song's email, you might want to ping him and ask about availability: sgao8@rogers.com
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post #398 of 796
3/2/12 at 5:02am
Quote:
Originally Posted by nick-seattle View Post

Hi all, well after a lot of research I decided to purchase MS-20L. Hoping to receive it next week. I'm now really into female vocal jazz, so thought that tube sound should compliment this kind of music. Really looking forward to experimenting with it. I have Vienna Acoustics Beethoven hopefully the amp will be able to drive them. Also, waiting to receive Audio Research vs115 from one of the high-end dealers that I can use at home for a few days. It would be very interesting to compare $600 amp with $6,5000 amp. I will post my impressions as I get them both.

I'm planning to do some tube rolling with Yaqin. One thing I can't figure out from the postings, there are 8 small tubes of the same type. Should I try to replace all 8 of them or only 4 that are for preamp make difference and the rest of them wouldn't. I'm very new to the tube world, so please pardon my ignorance.

Also, has anybody experimented with Shuguang Treasure Vacuum Tubes 6CA7-Z? How do they compare to Gold Lion KT77? Are those tubes approaching point of diminishing returns?

I would replace all 8 of the 6J1 tubes
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post #399 of 796
3/2/12 at 6:15am
How does the MC-100B compare to MS-20L? I am ready to buy and not sure I want to wait a month. I might opt for the 100B
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post #400 of 796
3/2/12 at 7:59am
Quote:
Originally Posted by TKYR1967 View Post

How does the MC-100B compare to MS-20L? I am ready to buy and not sure I want to wait a month. I might opt for the 100B

MC-100B uses KT88 tubes vs MS-20L uses EL34 tubes. KT88 are more powerful, so the first amp has more juice. I bought 20L because of the tubes. EL34 have very specific sound to them that works fantastically for vocal jazz with very sweet mids. I already have a great SS system, so this one for specifically for jazz. So it really depends on what you are listening to.

here is an excerpt from another thread: On sound quality, the consensus seems to be that the '34 has more lushness or richness in the mid-range than almost any other mid- to hi-power output tube while being a little soft at the frequency extremes. The '88 (and its very close cousin the 6550) is more balanced across the frequency band, exhibiting more-extended and -controlled bass and better-quality treble than the '34 while lacking the '34's (euphonic?) mid-range richness. These differences probably can be swamped by the extremes of different brands of the 2; the above is average or typical.
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post #401 of 796
3/2/12 at 8:50am
Quote:
Originally Posted by cytowing View Post

I would replace all 8 of the 6J1 tubes

Be sure to put a matched pair in the phase splitter...I ordered 2 matched quads of 6j1p-ev's for mine, and used the two closest pairs from each set in the phase splitters.
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post #402 of 796
3/2/12 at 9:56am
Thanks Nick, I will wait for Song to get more MS-20Ls in stock. That rich, lush midrange is what I want most.
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post #403 of 796
3/4/12 at 7:19pm
Looked a little further into the caps in this amp. The only caps in the signal path are the coupling caps between the phase splitter and the power tubes.
Here's a pic with the 4 coupling caps circled in red.
Yaqin chose an interesting capacitor for this job. They used Pilkor (Philips) PCX2 337 MKP caps, which are an EMI supression cap usually used in things like power supplies. These caps are rated as a "safety capacitor", which means they will withstand pretty large spikes above their rated voltage, won't catch fire if they fail and they will fail open, rather than shorted like most caps do.
Not really considered an audio cap, but does have the benefit of protecting the grids on the El34B's from receiving the anode voltage from the 6j1's in the previous stage in the event the coupling cap fails. (because these will fail "open circuit")
I don't know that changing these out for so-called audio caps would yield enough sonic improvement to be worthwhile. You would also probably lose the safety aspects these caps have been tested for.
I think I'm just going to enjoy my Yaqin "as is".
If anyone decides to try other caps in theirs, I'd be interested to hear how it affected the sound of their amp.
I checked the schematic for obvious errors, and found only a couple. "R120" is placed in the wrong spot in the schematic, and "R107" should actually be labeled "R127". There may be others, but I didn't see any more that this.
I measured some voltages in a few places in the left side and labelled them on this partial schematic. It also shows where R120 should have been drawn.
Attachment 239376

Yaqin did a pretty nice job with this circuit, it's a much improved version over the MC-10L (which is itself pretty highly regarded as a budget tube amp). The more I look into this amp, the more it impresses me!
LL
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post #404 of 796
3/5/12 at 6:31am
Quote:
Originally Posted by rntlee View Post

Looked a little further into the caps in this amp. The only caps in the signal path are the coupling caps between the phase splitter and the power tubes.
Here's a pic with the 4 coupling caps circled in red.
Yaqin chose an interesting capacitor for this job. They used Pilkor (Philips) PCX2 337 MKP caps, which are an EMI supression cap usually used in things like power supplies. These caps are rated as a "safety capacitor", which means they will withstand pretty large spikes above their rated voltage, won't catch fire if they fail and they will fail open, rather than shorted like most caps do.
Not really considered an audio cap, but does have the benefit of protecting the grids on the El34B's from receiving the anode voltage from the 6j1's in the previous stage in the event the coupling cap fails. (because these will fail "open circuit")
I don't know that changing these out for so-called audio caps would yield enough sonic improvement to be worthwhile. You would also probably lose the safety aspects these caps have been tested for.
I think I'm just going to enjoy my Yaqin "as is".
If anyone decides to try other caps in theirs, I'd be interested to hear how it affected the sound of their amp.
I checked the schematic for obvious errors, and found only a couple. "R120" is placed in the wrong spot in the schematic, and "R107" should actually be labeled "R127". There may be others, but I didn't see any more that this.
I measured some voltages in a few places in the left side and labelled them on this partial schematic. It also shows where R120 should have been drawn.

Yaqin did a pretty nice job with this circuit, it's a much improved version over the MC-10L (which is itself pretty highly regarded as a budget tube amp). The more I look into this amp, the more it impresses me!

I opened my mc-100b last weekend and found the same caps. I also entered schematic into Spice simulator, and I didn't like resuts at all. It looks like there are several ways to improve this amp. I will try to tweek it based on on what I found in simulation.
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post #405 of 796
3/5/12 at 11:35am
Hi all, I got my MS-20L on Saturday. Very quick shipment – it was shipped by Song on 2/28 and I got it in Seattle on 3/3 – made my weekend so much more fun.

Unboxed it - nice job packing tubes. It would take a drop from a very significant height to damage them in the package. I think the amp would fall apart before the tubes would be damaged. I plugged my Viennas into the amp. For the input I used Sonos connect to play my collection of FLAC 24/96 files. Turned the map on, waited for 20 seconds for it to come alive. And started playback.... What can I say. The whole music scene came alive - I felt the band in the room - incredibly realistic, incredibly warm – complete sonic nirvana. Superb reproduction of Vocal Jazz!!! It's still burning in and I can hear harsh notes, but overall very impressive. I tried my Emotiva XPA-3 in the same setting with the same speakers with the same music and it can't be even compared to MS-20L for vocal jazz. Rock on the other hand... I strongly prefer Emotive with my B&W 804s. But that's exactly the reason I got a second set up. One in HT room with 1000W sub, another in the library with just Viennas and 20L.

Stock tubes sound great, but I know that I'll be forced by my alter ego to purchase Premium set from Captain Bob . http://www.ebay.com/itm/160558268499

Still waiting for AR 115 to arrive. Will post the comparison as I A/B test them.
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post #406 of 796
3/10/12 at 7:38pm
If someone considers MC-100B as more powerful, do not expect miracle. I recently tested this amplifier. At 1 kHz I was able to squeeze 32 watts (to 8 ohm load) before clipping. But at 8 kHz and higher the limit was just 22 watts. This is all you can get from it. I do not know if MS-20L is overrated too (I didn't see any published measurements). So be cautious if your speakers are not very efficient.
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post #407 of 796
3/11/12 at 6:37pm
out of all my readings about yaqin amps not once have i read where the amps are overrated in their power ratings. are you sure you are doing your tests correctly or do you work for jolida or one of the other tube amp manufacturers?
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post #408 of 796
3/11/12 at 9:10pm
Anyone have any experience with Primaluna and how the MS-20L compares to the Prologue Classic or One? The Prologue Classic is $1800 vs $529 for the Yaqin, both are made in China.
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post #409 of 796
3/11/12 at 11:17pm
Well. That didn't last long I was so impressed with the sound of Yaqin (it being my first tube amp) that I decided to upgrade and sell my Yaqin. I just got McIntosh 275. As you should expect MC is better in many respects (especially with complex music), but not by 6x. Yaqin still outperformed MC in midrange (for slow vocal jazz), which is expected due to EL34 vs KT88 tubes. It was fun while it lasted, but I'm a new tube convert - although I still like my Emotiva for Movies - the power that it can master into B&W 804s is amazing.

So if somebody is looking for a slightly used (less then 100 hours) Yaqin MS-20L in Seattle area, ping me.
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post #410 of 796
3/12/12 at 6:31am
Quote:
Originally Posted by mboldda1 View Post

out of all my readings about yaqin amps not once have i read where the amps are overrated in their power ratings. are you sure you are doing your tests correctly or do you work for jolida or one of the other tube amp manufacturers?

I am sure did correct measurements. And no, I do not work for any competitor or even in audio industry. Audio/video field is just one of my hobbies, which I enjoy. I posted detail techinical analysis of MC-100B on another forum, so if you are interested in it, do Internet search for a reference (I do not want to post a link to that forum here).
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post #411 of 796
3/18/12 at 10:10pm
anyone try eh 6ca7's in the 20l yet?
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post #412 of 796
3/22/12 at 5:42pm
I'm currently running Tung-Sol EL34B's in mine, and I've gotta say I'm really impressed with them, especially for the price (~$90 shipped for a matched quad). Very clean mid-range!
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post #413 of 796
3/22/12 at 5:57pm
Quote:
Originally Posted by ap1 View Post

If someone considers MC-100B as more powerful, do not expect miracle. I recently tested this amplifier. At 1 kHz I was able to squeeze 32 watts (to 8 ohm load) before clipping. But at 8 kHz and higher the limit was just 22 watts. This is all you can get from it. I do not know if MS-20L is overrated too (I didn't see any published measurements). So be cautious if your speakers are not very efficient.

Tube amps typically have low slew rates, and I doubt most people would notice the difference between 32W and 60W output (< 3dB) ...Though that's a bit dishonest of Yaqin if it's typical of the 100B.
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post #414 of 796
4/20/12 at 4:36am
Everyone still happy with their MS-20L? This post hasn't had any action in a while. I see that Song has them back in stock and I'm about to order.
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post #415 of 796
4/20/12 at 4:42am
Still loving mine after a tube roll to electro harmonics tubes.
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post #416 of 796
4/20/12 at 4:55am
still happy with mine, stock tubes and all...
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post #417 of 796
4/20/12 at 2:33pm
Still enjoying mine every night.
My curiosity got the better of me and I decided to remove the cover from one of the output transformers, just to see what's hiding under there. I was pleased to see that Yaqin didn't scrimp on the iron. Good sized transformers in there...pretty much fill the covers:
Attachment 244072

I kinda wish Yaqin had added a little ventilation to the mains transformer cover. My cover gets pretty warm if I'm giving the amp a workout, so I wonder how hot the transformer actually is getting? I was going to remove it and add some grills or something but it looks to be a fairly intensive job getting it off. The screws are all under the circuit board, and I'm not really feeling like disassembling the entire amp...not yet anyway.
LL
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post #418 of 796
4/21/12 at 1:22am
This thread has compelled me to consider purchasing the MS-20L. Hoping I could get some help with a couple of questions. Can I use this without being a tube expert or audiophile? Are their speakers under $1,000 that would work best (classical, jazz, classic rock)? Lastly, i was considering the Marantz PM 8004 if the Yaquin was too labor intensive. Thoughts? Would welcome your advice!
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post #419 of 796
4/21/12 at 4:25am
There's not a lot of maintenance with these amps, just an occasional bias adjustment (you need a voltmeter to measure voltage at the test points on top of the chassis). It'll drive most speakers without issues.
Just the same, tube amps aren't for everybody. If you were wanting one to play around with, this amp is a great way to test the waters without dropping a ton of cash.

Regarding the Marantz, have you also considered the HK 3490? For under $500 you get a lot more features.
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post #420 of 796
4/21/12 at 5:30am
Quote:
Originally Posted by Gatsby1965 View Post

This thread has compelled me to consider purchasing the MS-20L. Hoping I could get some help with a couple of questions. Can I use this without being a tube expert or audiophile? Are their speakers under $1,000 that would work best (classical, jazz, classic rock)? Lastly, i was considering the Marantz PM 8004 if the Yaquin was too labor intensive. Thoughts? Would welcome your advice!

sure, you'll be fine... i am far from a tube expert (as noted earlier, mine still has the stock tubes in it), and we get a lot of enjoyment out of ours... my wife uses it a lot, it's set up in our bedroom...

as far as speakers go, that's more up to you than to us... what have you heard that you like? since mine is in a bedroom setup, and i wanted something a little different, i had a pair of single drivers custom made (jordan's from jim salk, if anyone is curious)...

but the yaqin should drive pretty much anything you hook up to it, as long as you sren't trying to reach ridiculous spl's in a huge room....
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