Hi- New yaqin 100b owner. I have read everything I could find online.Lots of great information.
Has anyone recently (past year) retested the yaqin 100b to see what, if any updates yaqin may have made since it was originally introduced.
There were certainly some issues, didn't meet power output specs, live caps, mislabeled diagram/components etc.
I would like to upgrade but am reluctant to
since it's been so long since introduced.
I know which tubes I want to roll,but cap upgrades etc.....I'm in the dark.
My experience is limited to having assembled a hafler preamp and power amp kit. I can solder ok, both are still working after @ 30 years.
Anyhow, any info much appreciated.
This is a great site.
Has anyone recently (past year) retested the yaqin 100b to see what, if any updates yaqin may have made since it was originally introduced.
There were certainly some issues, didn't meet power output specs, live caps, mislabeled diagram/components etc.
I would like to upgrade but am reluctant to
since it's been so long since introduced.
I know which tubes I want to roll,but cap upgrades etc.....I'm in the dark.
My experience is limited to having assembled a hafler preamp and power amp kit. I can solder ok, both are still working after @ 30 years.
Anyhow, any info much appreciated.
This is a great site.
Cap mod for this amp are simple. A good portion of the signal path are direct couple. You just need to switch out the two driver to output coupling caps and the splitter cap in the LTP circuit, one set per channel and 6 caps all together. You can use 0.22uF 620V caps. They are the baby blue rectangular caps. Make sure you read the High Voltage handling tread above before you do anything. YMMV on results.
I have the 100B bought a year ago...
I believe this is the latest version as not it doesn't have a ventilation grill on the front side and the circuit board also different will all cables/wires connected at the back side only...
There are few things I wanted to comments...
1. The heater voltage is too high in my unit. With all tubes are plugged in, the voltage reading is 7.1V - 7.2V while the B+ voltage is idle operating point is around 455V.
2. The 4 PSU capacitors (2 for each channels) located in between the transformer must covered all the times. They are in series connection and they have opened (bare aluminum) top. So 1 capacitor at each channel will carry half of B+ voltage (around 270V). This is very dangerous.
3. The front row PSU capacitors turns very hot due to heat from the power tubes. It become very hot even you can't touch them with your fingers.
I am using KT120 to replace the KT88 and bias them slightly higher than KT88 (at 65-70mA) and they sound amazing.
Other mods I did was :
1. Replace all coupling capacitors with Mundorf Supreme and it was a huge improvement to the sound.
2. Remove the cathode bypass for SRPP stage.
3. Reduce the resistor value for the cathode follower to increase the bias current.
4. Experiment with the NFB resistors.
I believe this is the latest version as not it doesn't have a ventilation grill on the front side and the circuit board also different will all cables/wires connected at the back side only...
There are few things I wanted to comments...
1. The heater voltage is too high in my unit. With all tubes are plugged in, the voltage reading is 7.1V - 7.2V while the B+ voltage is idle operating point is around 455V.
2. The 4 PSU capacitors (2 for each channels) located in between the transformer must covered all the times. They are in series connection and they have opened (bare aluminum) top. So 1 capacitor at each channel will carry half of B+ voltage (around 270V). This is very dangerous.
3. The front row PSU capacitors turns very hot due to heat from the power tubes. It become very hot even you can't touch them with your fingers.
I am using KT120 to replace the KT88 and bias them slightly higher than KT88 (at 65-70mA) and they sound amazing.
Other mods I did was :
1. Replace all coupling capacitors with Mundorf Supreme and it was a huge improvement to the sound.
2. Remove the cathode bypass for SRPP stage.
3. Reduce the resistor value for the cathode follower to increase the bias current.
4. Experiment with the NFB resistors.
Solder ok? Humm it may take you over 8 hours or more. Strip all the front out to remove the pcb. Be careful with bottom chassis when you remove the cover , so sharp edge, can cut your finger easily. I used dreamer tool to sand all the edge around
All new 100b coupling caps are .47uF 630v. Some people have old 100b that came with .22uF can be replaced with 0.47uF 630v. The latest version has higher value of other caps too such as 22uF 450v is now 33uF 450v. The PS is a little different. The rest of resistors are pretty much the same. The red wire from output has a fuse before going to B+
I haven't checked heater voltage as aatjitra mention.
aatjitra: bias 65-70 for KT120 ? I set mine at 55 since I am not sure if I can go up that much. I will try your setting later since the manufacture set 65 for KT88. I was worry the KT120 may overload the output.
All new 100b coupling caps are .47uF 630v. Some people have old 100b that came with .22uF can be replaced with 0.47uF 630v. The latest version has higher value of other caps too such as 22uF 450v is now 33uF 450v. The PS is a little different. The rest of resistors are pretty much the same. The red wire from output has a fuse before going to B+
I haven't checked heater voltage as aatjitra mention.
aatjitra: bias 65-70 for KT120 ? I set mine at 55 since I am not sure if I can go up that much. I will try your setting later since the manufacture set 65 for KT88. I was worry the KT120 may overload the output.
Are 122V ok?
Thank you Alllensoncanon aatjitra Alashikata, you posts are very helpful. Have any of you measured the AC line voltage of your homes? My unit is spec'ed at 110v ± 10% and my home ac is about 122v. Is that a concern for the newer units? I did try a variac at 110v but it introduced some hum. Any recommendations?
Thanks much
Repdetect
Thank you Alllensoncanon aatjitra Alashikata, you posts are very helpful. Have any of you measured the AC line voltage of your homes? My unit is spec'ed at 110v ± 10% and my home ac is about 122v. Is that a concern for the newer units? I did try a variac at 110v but it introduced some hum. Any recommendations?
Thanks much
Repdetect
I think it should be fine unless your home voltage is under 110v which it won't have enough power to drive the amp.122V AC line is not unusual here in the US. I see 122V in Northern California too.
It is 11% over what the amp was designed for. They are a problem for most of these Chinese Amp. It changes the bias point (hence one possible source of more distortion). It pushes the operating point to the right side of the tube curve. As a result along with #1, it often resulted in lost of maximum power. It increase the filament voltage and shorten tube life. In your case, your amp has bias adjustment so it take care "some" of the problems in #1 and #2. If you are not using expensive NOS fancy tubes, I would leave it alone (replacement are cheap and plentiful).
It is 11% over what the amp was designed for. They are a problem for most of these Chinese Amp. It changes the bias point (hence one possible source of more distortion). It pushes the operating point to the right side of the tube curve. As a result along with #1, it often resulted in lost of maximum power. It increase the filament voltage and shorten tube life. In your case, your amp has bias adjustment so it take care "some" of the problems in #1 and #2. If you are not using expensive NOS fancy tubes, I would leave it alone (replacement are cheap and plentiful).
the same problem in France but with 10% of 230v = 207v to 253v ... here,i have constantly 245v . to return to your yaqin, already yes at first, control the heating voltage, it will give you an idea of the primary of your power transformer. i have a yaqin mc5881 which was super noisy when i got it, it was almost 7.3v on the heater, i cut the PT insulator, the 6.3v winding is on the surface, i have scratched the varnish of the 4em spire and found 6.2v, so I soldered my heating wire to this place. I then adapted the bias to the voltage B + because my 6p3s-e dissipated too much power at rest, and then I ended up redoing the power supply because it was really **** and since it is silent and runs days whole without turning into a barbecue
another point, the electrolytic capacitors at yaqin are of very poor quality and over-used. it is very limited, even dangerous. on one of my music angel, I read 6500pF on a 130uF / 275v power supply capacitor. Finally, be careful not to draw too much power on your PT and OPT, they are not very well built and it is better a conservative bias.
another point, the electrolytic capacitors at yaqin are of very poor quality and over-used. it is very limited, even dangerous. on one of my music angel, I read 6500pF on a 130uF / 275v power supply capacitor. Finally, be careful not to draw too much power on your PT and OPT, they are not very well built and it is better a conservative bias.
Thanks much everyone, I really appreciate the help. I am running bias at 60. I'll drop down to 50 and listen for awhile and see how it sounds. I'll also keep monitoring the house voltage. As long as it stays at 122v or lower I think I'll be ok. It appears that yaqin has corrected some of the issues that came up early on,e.g. underrated coupling caps, but have not documented them anywhere that I can find. Be great if when someone finds a change on the newer models, say 2017 +, they document on this thread, or somewhere. Considering replacing coupling caps with these. Audyn True Copper Cap 0.22uF 630V Copper Foil Capacitor. Still worth doing with current caps in newer models? Any thoughts?
Thanks all.
Thanks all.
I played around the bias setting from as low as 40mA all the way up to 70mA. I found that bias around 65-70mA make the sound very clean with controlled and tight deep bass.
But if you are not comfortable by setting this bias too high, just stick to the manufacturer default setting (55mA).
Yes I did... my line voltage is 240V.. sometimes go as high as 245V... so for my 100B, I ordered the special 240V transformer.. but still the heater is too high...
yaqin 120b bias
Thanks for the calculation.
I'm going to run at .55 until I get a chance to measure plate voltage.
Thanks for the calculation.
I'm going to run at .55 until I get a chance to measure plate voltage.
Yaqin 100b Caps
I am looking to replace the 6 film capacitors in my Yaqin 100B as many have
done.
Has anyone purchased a yaqin 100b in the past year or so and noted the value of the film caps?
Earlier posts state .22uf, but I want to be sure of the value as I will order caps before I open it up to replace them and want to be sure I get the right value.
Thanks much in advance.
I am looking to replace the 6 film capacitors in my Yaqin 100B as many have
done.
Has anyone purchased a yaqin 100b in the past year or so and noted the value of the film caps?
Earlier posts state .22uf, but I want to be sure of the value as I will order caps before I open it up to replace them and want to be sure I get the right value.
Thanks much in advance.
Why change caps with same value? What do you like to change on the sound?
With 0.1uf the bass will be tighter. With 0.33uf the bass will be deeper but less controll. With same value there will be no much difference. Important is to use right voltage value.
There are a lot of other mods like cut R1 so your input sensitivity will be lower(600mv) on the back inputs. This give less hiss and humm.
Or change input tubes for 5751 type , also less sensitvity. Also lower hiss and humm.
Or put 100k pot in serie with R10/C10 in the feedback, now you can adjust your sound from fluid, easy sound to tight sound.
With 0.1uf the bass will be tighter. With 0.33uf the bass will be deeper but less controll. With same value there will be no much difference. Important is to use right voltage value.
There are a lot of other mods like cut R1 so your input sensitivity will be lower(600mv) on the back inputs. This give less hiss and humm.
Or change input tubes for 5751 type , also less sensitvity. Also lower hiss and humm.
Or put 100k pot in serie with R10/C10 in the feedback, now you can adjust your sound from fluid, easy sound to tight sound.
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Thanks much Koifarm, lots to consider.
I am happy with overall sound. Didn't hear much change in sound when changing tubes.
I haven't installed my final tube selections yet.
I have 2-GL 12ax7, 4- Foton 6sn7 and 4-GL KT-88's.
The 4- Fotons will be replaced with Tung-sol 6sn7.
Bass seemed to get boomy when the Fotons went in. I'm hoping the Tung-sols tighten it up some. I use a sub for 2ch and mch. sources so I don't need very deep bass but I do want tight bass. I'll keep your cap suggestions in mind.
I have an experienced tube modder doing the cap installation, but he hasn't worked on this model amp.
How do I determine the proper voltage of the caps I'm installing?
I am happy with overall sound. Didn't hear much change in sound when changing tubes.
I haven't installed my final tube selections yet.
I have 2-GL 12ax7, 4- Foton 6sn7 and 4-GL KT-88's.
The 4- Fotons will be replaced with Tung-sol 6sn7.
Bass seemed to get boomy when the Fotons went in. I'm hoping the Tung-sols tighten it up some. I use a sub for 2ch and mch. sources so I don't need very deep bass but I do want tight bass. I'll keep your cap suggestions in mind.
I have an experienced tube modder doing the cap installation, but he hasn't worked on this model amp.
How do I determine the proper voltage of the caps I'm installing?
I (got someone else to) put these in mine.
K75-24 630V 0.47uf Hybrid PIO capacitors. Lot of 4 pc. NEW, NOS! | eBay
ciao
K75-24 630V 0.47uf Hybrid PIO capacitors. Lot of 4 pc. NEW, NOS! | eBay
ciao
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