yaqin mc100b upgrades

There are many thoughts about various Chinese amplifier designs, some have a habit of using too many resistors or people feel the best option in some cases is to remove some resistors altogether, or replace certain resistors with small capacitors.
With Yaqin’s 100B I think they generally got it right, no doubt it’s possible that small improvements can be made in some area’s, but you must be real sure of what your doing! If people want improvements then the first step is to dump those Shugang bottles & buy some decent one’s, that’s the best route for improvement, as you have already done this I would say just sit back & enjoy your amp.

many thanx for that drastic88. i did make one more change to the tubes. i bought a pair of golden dragon E83cc/12ax7A and they gave me the same gorgeous bass that i love but added more detail and textures throughout the frequencies. the funny thing is the golden dragons are the cheapest by far 12ax7`s i have used in this amplifier. with the sound i have now i don`t feel that bothered by making any further upgrades. the only upgrade i will be making is to the speaker cables that i use. at the moment i`m using chord company oddessey 2 cables and i will be going up a notch by using the same companies epic speaker cables which will apparently enhance and improve on the sound i`m getting now. oh happy days! long live tube amps!

I feel that I obtained a big improvement in sound when I had my tech change six capacitors to 4-Silver Oil Mundorf's (in the audio signal path) and 2-Jantzen Silver (not directly in the audio signal path). Another significant improvement in my opinion was obtained when I changed out my Treasure Series KT88's with Tung-Sol KT120's and increased the bias based upon my plate voltage using Ohm law. I also prefer the sound of using Sylvania 5751 black plate gold bands over the sound achieved using Telefunken 12AX7's smooth plates. However, the Telefunken's may have been technically more neutral sounding. Bypassing the preamp stage by using the RCA inputs on the front while switching to .6v gain provided a small improvement as well. Using the KT120's increased the dynamics and sound stage and provided a deeper,tighter more defined bass. I use KenRad VT-231 6SN7's (Black Glass) in V1 through V4 but often switch or mix them up with Sylvania 6SN7W (Short Bottles). The Sylvania short bottle tubes are very dynamic and provide more punch to the sound. I also really like the sound produced from using Shuguang Treasure Series CV-181's, although you will need to obtain a tube adapter since the stock base of the CV-181's will not fit tightly into the recessed tube sockets due to their larger diameter base. I actually use socket savers generally used with tube testers and they work fine.

One thing I have now done that gave a nice lift to the performance is to change the four input cap's. They are too small, wrong shape, low quality. I fitted some Russian PIO job's, of the same value (.22uf 275v min) go up a little if you wish to add more bass, say .47uf max, but I found .22uf was just right.