Yaqin MC-100B - not as powerful as advertised, but still a good value. - Page 2 - diyAudio
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Old 13th August 2012, 01:32 PM   #11
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Join Date: Feb 2009
I'd like to bring my view on the Yaqin MC100-B. I have this amplifier for over 4years now and I have had the opportunity to compare it with many solid states and tube amps from different price range.

I can now say that IMO, once properly customised this amplifier gives a very good sound and at least as good as famous market amps up to 6x or 7x its original price.

The mods that I've made on mine:
- Mundorf silver oil 1uf caps
- Shuguang GEKT88 (bias at 45ma max)
- 2x 6SN7 Sylvania NOS
- 2 x 6SN7 Russian NOW
- 2 x 12AX7 Psvane treasure
- HV delay (1min20)
- Amp mounted on spikes
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Old 31st August 2012, 08:08 PM   #12
Aleks1 is offline Aleks1  United Kingdom
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Join Date: Nov 2004
Location: Manchester, Uk
Hi Everyone, thought i would share my experience with this amplifier. I got it off Ebay delivered including taxes for £500. Ordered it thursday midnight and it was at my front door midday the following monday. Wow was quick.

Anyway i connected it up and had a listen. It sounded terrible to be honest. I reached for my soldering iron and got a circuit diagram. I removed the feedback loop completely. Got rid of the volume control and selector switch from the circuit. I then wired the front set of phono sockets to the grids and added a 47k grid stopper in series. I then noticed that the grid leak resistor was actually 510k and not 39k as per the drawing. I fitted 47k instead. I then removed the capacitor across the input stage cathode and made the two cathode resistors one value.

I threw away the ecc83s and 6sn7s that came with the amplifier and fitted mullard and sylvania respectively. I switched on and biased the output stage to 65ma having measured an anode voltage of approx 420Vdc.

Time to listen. I was gobsmacked by the sound I heard coming from my B&W683s. Sublime is the word. Amazing imaging and depth, with massive space around all the vocals and instruments. I played disc after disc and the hours flew by. I didn't want to switch it off. The sound continued to improve as the amplifier burnt in. Sounding good on CD and Vinyl.

6 months on and i'm still grinning. I have since replaced the ECC83s with Russian 6n2ps and modifed the PCB to take into account the different heater arrangement. I split the track between pins 4 and 5 with a junior hacksaw blade and moved the heater supply wire from pin 9 to the now spare pin 5. I've also replaced the 6 0.22uf caps with wima MKP 10s. This has added another dimension again. The amplifier sounds so fluid and natural and makes listening a real pleasure.

I use it with a Conrad Johnson PV10a and a heavily modded Mission PCM4000 and Technics 1210 with SME V.

My only wish is that the amplifier had more power, but for the money I can't complain. I punches well above it's weight.

I will post any further mods I make. Next mod is to use a bunch of Elna Cerafines leftover from another project in the power supply. Should spice things up a bit more.

Bye for now
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Old 24th December 2012, 04:15 PM   #13
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It's great to read about such mods. Would you have a schematic showing your mods?
I'm using this amp as integrated amp so can't get rid of the volume pot.
My mods: caps replaced by 1uf silver oil mundorf, high voltage 1min20 delay, amp on spikes, tubes: GEKT88, 6SN7GT Raydon and CV181Z, 12AX7 Shuguang Treasure.
What other mods would recommend?

Cheers :-)

Sent from my GT-N7100 using Tapatalk 2
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Old 31st January 2013, 02:49 PM   #14
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I have an MC-100B, and haven't done any modifications to it (I know little about electronics and circuits, I'm a software guy).

I'm wondering if I can just drop some KT77s in and have it work without circuit modifications. The KT77 is a beam tetrode just like the KT88, and they're less than half the price of KT88s, which is low enough to be worth experimenting with. The EL34 is a pentode, not a beam tetrode, so I'm curious that you think it might be compatible. (Again, I know little about audio circuits and the differences between tubes)

If either of these are swappable, what would I run the bias adjustment at after installing them?

Thanks!

Charles.
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Old 31st January 2013, 02:53 PM   #15
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I do plan some minor mods to this thing. For starters, I intend to remove the volume pot from the signal path of the front input. For the integrated part, it makes sense. But for the front input, I would rather have a clean input from my phono stage (which has its own volume control)

Also, after 5 years of ownership the super bright blue LED burned out, so I'll probably replace that with a nice (dim) orange one. But that's really the extent of my ability.

Charles.
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Old 6th January 2014, 07:24 PM   #16
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Default Help asked upgrading yaqin MC-100b caps and resistors

Greetings from Spain and happy new year¡¡¡
I am the proud owner of a Yaqin MC-100b. So far I am fully satisfied with the amp, it sounds incredible good to me, much better than expected. Let me start by saying that I am not a technician at all. I just have very elementary electricity concepts, some soldering skills and of course lots of care. When adjusting bias for the first time I realized one of the pots was broken. Therefore, with some Christmas holidays ahead I decided to take the PCB to replace it and, once being there, I thought it would be worth upgrading the amp caps (I’ve read very good reviews about the Murdoff/Solen oil films and the Wima caps) and ceramic resistors as suggested by many of you in this forum. Which brand and specs should I use to get more bass and if possible greater definition?. The amp does currently have 6 PILKOR X2 0.22uF(220nK) 275v OFC caps and four 5 watts 10 ohms ceramic resistors (regardless of the PCB legend saying that they should be 3 watts 10 ohms¡¡¡). Should I change all the 6 caps to get the best possible results? What about the resistors, any suggestions? Should I go for 3 watts? I am very sorry to post such an elementary question to you guys, but as said before I am a newbie in this world.

I will try to post some pics for further clarification,
Kindest regards, Marianom
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Old 6th January 2014, 08:31 PM   #17
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Default Couples/Pairs 6SN7 are specular: V1-V4 and V2-V3 ??

Hi The couples of 6SN7 are specular: V1-V4 and V2-V3 ???
or the pairs are V1-V3 and V2-V4

That's in order to use 2 different couples of 6SN7

And someone knows the plate voltage of KT88 in the MC100-B (for 230VAC) ??
That's to calculate the bias adjustment;
the 0.55 V suggested by manufacter at what % of plate dissipation put the point of work for the tube??

Thanks

Last edited by Achi70; 6th January 2014 at 08:36 PM.
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Old 6th January 2014, 08:33 PM   #18
avp1 is offline avp1  United States
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Location: Central NJ
Quote:
Originally Posted by marianom View Post
Greetings from Spain and happy new year¡¡¡
I am the proud owner of a Yaqin MC-100b. So far I am fully satisfied with the amp, it sounds incredible good to me, much better than expected. Let me start by saying that I am not a technician at all. I just have very elementary electricity concepts, some soldering skills and of course lots of care. When adjusting bias for the first time I realized one of the pots was broken. Therefore, with some Christmas holidays ahead I decided to take the PCB to replace it and, once being there, I thought it would be worth upgrading the amp caps (I’ve read very good reviews about the Murdoff/Solen oil films and the Wima caps) and ceramic resistors as suggested by many of you in this forum. Which brand and specs should I use to get more bass and if possible greater definition?. The amp does currently have 6 PILKOR X2 0.22uF(220nK) 275v OFC caps and four 5 watts 10 ohms ceramic resistors (regardless of the PCB legend saying that they should be 3 watts 10 ohms¡¡¡). Should I change all the 6 caps to get the best possible results? What about the resistors, any suggestions? Should I go for 3 watts? I am very sorry to post such an elementary question to you guys, but as said before I am a newbie in this world.

I will try to post some pics for further clarification,
Kindest regards, Marianom
Do not chanve capacitors and high power resistors. There is very little value in it. Try mods I described in my three posts here. You will be much better satisfied with results than simpy swapping components to a different type.
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Old 6th January 2014, 08:35 PM   #19
avp1 is offline avp1  United States
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Join Date: Oct 2010
Location: Central NJ
Quote:
Originally Posted by ChopperCharles View Post
I have an MC-100B, and haven't done any modifications to it (I know little about electronics and circuits, I'm a software guy).

I'm wondering if I can just drop some KT77s in and have it work without circuit modifications. The KT77 is a beam tetrode just like the KT88, and they're less than half the price of KT88s, which is low enough to be worth experimenting with. The EL34 is a pentode, not a beam tetrode, so I'm curious that you think it might be compatible. (Again, I know little about audio circuits and the differences between tubes)

If either of these are swappable, what would I run the bias adjustment at after installing them?

Thanks!

Charles.
You will better use KT90 and set idle current to 100mA. It will indeed improve sound.
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Old 11th January 2014, 01:13 AM   #20
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Join Date: Jan 2014
Default Couples of 6SN7 in yaqin mc100b - plate voltage

Hi

The couples of 6SN7 are specular: V1-V4 and V2-V3 ???
or the pairs are V1-V3 and V2-V4

That's in order to use 2 different couples of 6SN7

And someone knows the plate voltage of KT88 in the MC100-B (for 230VAC) ??
That's to calculate the bias adjustment;
the 0.55 V suggested by manufacter at what % of plate dissipation put the point of work for the tube??

Thanks
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