I tried doing this resistor change in my amp but it didn't like it.
I got hardly any volume at all with a distorted sound so I replaced the old transistors.
I also changed the feedback cap to mkp 68pf I couldn't get 72pf I havnt noticed any difference changing this cap.
I've tested he Jantzen Superior Z in my MC100B. They sounded to my ears a bit "nervous" and little lean and cold. They sounded good on piano though I remember.
I also tested Mundorf Supreme Silver In oil and they had a overall better sound but I didn't like them because they said; "hey come listen to me, here is plenty of detail" type of sound and i couldn't focus on the music at all..
Wima MKP 10 was also in place as a low cost alternative but they sounded flat and dull. I've found them to be much better in other curcuits,
After all this I took a turn to Intertechnics Audyn-Cap Reference and I had them a long time.. All the warmth in the mid I wanted and all the details but i listened to music this time. Just for fun I also decided to try True Copper from same company and yes even more coherent and natural.
I found bypassing poly caps with Silver Mica made them sound better, maybe worth a try to combine different types.
It sounds More open and much louder at the same volume imaging is even more in the room and out of the box away from the speakers type of thing.
There's a down side that bass is less solid on drumming and has less impact but it's only slight.
I fitted switches so I could switch the feedback loop in or out and I now prefere it off.
If you fit switches turn the volume right down or turn the amp off when operating them it didn't like me using the switches with the volume up.
Thanks Martin I will try the Audyn true copper but it will be after Christmas now thanks anyway.
Hello modifiers,
Let me suggest to overcome the low B+ of yaqui by substituting the Kt77/EL34 tube biased to under 50ma. The reason: lower current means higher B+.
When the original poster said he biased the Kt88 at 85mA, I would like to know how low the B+ voltage dropped.
Let me suggest to overcome the low B+ of yaqui by substituting the Kt77/EL34 tube biased to under 50ma. The reason: lower current means higher B+.
When the original poster said he biased the Kt88 at 85mA, I would like to know how low the B+ voltage dropped.
Hi I have got tungsol KT120s set at 120ma but I have not checked my B+.
I did try changing all resistors to the suggested resistors on the circuit diagramme on this thread.
I didn't have the 18k resistors so I used 20k instead but my amp didn't like this at all.
I got a low level distorted sound at full volume no sound until volume was half way so I put the old resistors back.
I have added switches so I can remove my feedback loop and I think it sounds better without feedback loop.
I have replaced all blue capacitors with jantzen silver capacitors which gave me a slightly clearer sound and slightly more bass.
Lower current through output tubes does increase plate voltage, but not much. There is 15-20 volts difference between 50 and 85 mA mostly due to loss in output transformers.
Thanks avp1,
That means the dual power transformers are capable of heavy currents.
If I were you Dave I would measure V of B+, IxV will give your the power dissipated at idle. In class AB want to hit the 30-35 watt of the 60 watts maximum plate dissipation.
That means the dual power transformers are capable of heavy currents.
If I were you Dave I would measure V of B+, IxV will give your the power dissipated at idle. In class AB want to hit the 30-35 watt of the 60 watts maximum plate dissipation.
Thanks avp1,
That means the dual power transformers are capable of heavy currents.
If I were you Dave I would measure V of B+, IxV will give your the power dissipated at idle. In class AB want to hit the 30-35 watt of the 60 watts maximum plate dissipation.
That means the dual power transformers are capable of heavy currents.
If I were you Dave I would measure V of B+, IxV will give your the power dissipated at idle. In class AB want to hit the 30-35 watt of the 60 watts maximum plate dissipation.
I recently purchased a yaqin mc-100b and have some questions. Let me explain my situation.
When I first turned the unit on it sounded great, even with the stock tubes. the third time i turned it on, it blew the circuit breaker in my house and that was a warning sign to me. The next time i turned it on it blew the fuse for the right channel.
I started reading the forums and read about voltage issues. I measured my voltage and it is 125V. So I purchased a APC regulator and set it to 110V and now my voltage is set at that level. After several more listening sessions, the power problem seemed to be fixed. But a new problem started. I noticed that occasionally, (about every 15 minutes on average), I would hear a small popping sound out of the speakers.
I had already learned about tube rolling so that was my next step. Next I rolled all of the stock tubes (gold lion 12ax7, eh 6sn7 and gold lion kt88. The sound from the amp is very good (I assume it will improve after the tubes burn in), but i still have that pop sound.
My question is - what is causing that sound and how can i fix it. Also, does the pop hurt the speakers?
Any help would be greatly appreciated.
Steve
When I first turned the unit on it sounded great, even with the stock tubes. the third time i turned it on, it blew the circuit breaker in my house and that was a warning sign to me. The next time i turned it on it blew the fuse for the right channel.
I started reading the forums and read about voltage issues. I measured my voltage and it is 125V. So I purchased a APC regulator and set it to 110V and now my voltage is set at that level. After several more listening sessions, the power problem seemed to be fixed. But a new problem started. I noticed that occasionally, (about every 15 minutes on average), I would hear a small popping sound out of the speakers.
I had already learned about tube rolling so that was my next step. Next I rolled all of the stock tubes (gold lion 12ax7, eh 6sn7 and gold lion kt88. The sound from the amp is very good (I assume it will improve after the tubes burn in), but i still have that pop sound.
My question is - what is causing that sound and how can i fix it. Also, does the pop hurt the speakers?
Any help would be greatly appreciated.
Steve
There should be no "pop sound" under normal operation conditions. Your amp is likely has a defect, which needs to be corrected. If you do not want or cannot send it back, fund relaible service shop and ask them to look at it.
Need more information - pops on both channels? Do pops disappear if volume set at minimum? Could be a central heating thermostat somewhere doing this. Is the pop coming from the APC unit? Amp should be really quiet.
The I have heard the pops on both channels. They are soft, not loud. After I replaced the tubes they were occuring on average about once every 15 minutes or so. Now they have gone to about once in about 30 minutes or so. Could this just be the new tubes breaking in?
If both channels are popping, power supply is a likely issue - either capacitors or soldering shluld be checked.
Popping - have you installed Full Music 12AX7's as this is a common problem with these. Of course other 12AX7's may exhibit this, have you tried the amp with the 12AX7's pulled? It is quite safe to run the amp with these removed for taking a listen for popping sound.
I have seen several schematics of the MC-100 B on this forum. Has anyone put together a parts list that not only includes values, but the make of the parts?
Is there a consensus about whether replacing caps and resistors with better quality (not different value) parts actually improves the sound?
Is there a consensus about whether replacing caps and resistors with better quality (not different value) parts actually improves the sound?
FYI, I was getting popping and weird noises from my Yaqin. I had an ipod connected to one of the inputs via a dock.... aaaaand the Yaqin was actually picking up the ipod's wifi signals, and giving me random pops and "squiggles" for lack of a better term. This was most noticeable when playing records (on a different input!) but was present for all inputs.
Simply turning off wifi on the ipod fixed the problem.
Dunno if it's the same for you, but sometimes it's the oddest things that cause weird noises. Any kind of bluetooth or wifi device nearby is suspect.
Charles.
Simply turning off wifi on the ipod fixed the problem.
Dunno if it's the same for you, but sometimes it's the oddest things that cause weird noises. Any kind of bluetooth or wifi device nearby is suspect.
Charles.
Resistors are OK there. I would change volume pot to a better one. Also coupling capacitors can be improved. Power supply seems OK unless you want to implement active regulator or add choke.
- Status
- Not open for further replies.