Sound Review : Yaqin MC-100B (6th August 2012) I bought this 100B without tubes, then I bought the valves I wanted to use. So I can’t tell you how it compares to a standard setup. The pre tubes (12AX7) are TJ Full Music so are the 6SN7’s, all new. While I waited for the Psvane KT88-T’s (reference series) to arrive I used the Eletro Marmonix’s 88’s from my Bewitch amp,these have hundreds of hours on them & are a known sound. So with all the bottle’s installed & after a 15minute warm up the Bias was set to .55v Then a record was played ……………… the sound was truly Awful ! It was really bad! All very shape treble, with some min range & almost no bass. (It sounded like an early small handheld transistor radio that used a PP9 battery, you know the type.) This was down to the Full Music 6SN7’s, they have a reputation for having a very pronounced sharp top end until they burn in! Clearly I had to get some hours on these tubes, but it sounded so bad I couldn’t listen to the music ! So I unplugged the TV from the Alto amp & plugged it into the 100B. The TV has tone controls built into it’s menu, so the treble was dialed way down & the bass turned up, now it was bearable to listen to using the TV & DVD (played through the TV). I got 7 hours on the tubes that night. Later the next day I tried again with a record (same one) My God was this the same amp! It sounded so much better, there was Bass, Bass!!!!!!!!!!!! and mid range. 7 hours on the 6SN7’s had done the job, after 15 hours I would say the 100B it was out performing my Bewitch amp, no easy task. Then the Psvane 88’s arrived, what joy! I couldn’t fit them quickly enough, Straight out of their Big Box they sounded great, so smooth with a firm well controlled bass & great clarity. The Bias was set after a 15 minute warm up & all was well. The sound was so good I canceled an evening out to stay in & play my records ( who needs a girl friend anyway). However after an hour there was a load hum from the right channel & I noticed the V3 tube was glowing bright orange!!!!!! I quickly powered the amp down (still using a Variac) I gave it 1 minute then slowly powered it back up to full voltage, all was well. I guessed the problem could be down to the Bias, when checked that valve (V3) it was well low (.41v) the others were also all over the place, remember I had set them only an hour ago! I guess the control grid on the V3 valve had failed due to the low Bias voltage which allowed the valve to run wild. The Bias was reset & all was well. I checked the Bias ever hour, (sounds excessive I know, but very necessary) they were swinging about all over the place. After about 5 hours they were starting to stabilize, in the next two hours they changed very little on the Bias voltage, now all seemed well. The amp sounds so good, very accrete, firm solid bass well controlled, instruments sound so real, I play a “Rickie Lee Jones” LP (180gram) & it sounded like she was in the room, I looked behind the sofa for the band, but no sign of them! nor could I find where Diana Krall had hidden her Grand piano in my lounge? The amp now has about 50 hours on it & seems well settled down, she sounds just wonderful a delight to hear, I’ve had a lot of good quality amp’s some costing three times what I’ve spent on this & I heard some expensive amps on top set up, but none can match my 100B. Remember with a valve amp it’s only as good as the valves you use!, dump the stock Shuguang valves & invest in top quality valves if you want the best performance this amp can give you.