The 'NEW' YAQIN MS-20L Integrated Vacuum Tube Amp Thread - Page 24

just changed the fuse, got right channel again,once again rntlee thank you very much,cheers.

hi, got a problem with the amp. It switched it's input to Aux 2 when a Sony TV remote vol- is pressed.
This is annoying for some.

Got some Gold Lion Kt77's and all ready to install and bias but I am not too sure how to use the multi meter.
I know it is supposed to be set to DC but I am not sure how to do that or how exactly to read the dial. There is a lot
of different info on there and its a bit confusing. Where do I look for .4mv?
Thanks!!!

Depends a bit on your multimeter...some are auto-ranging, some require you to select the range. Is there just one setting for DC voltage? Also, there's probably more than one port on the front for the red probe (+), make sure it's plugged into the voltage port, not the amperage port.

Glad to hear your amps ok arrow!

Thanks for the help! I appreciate all your advice on the subject!
I think I am in over my head on this. The multi meter is super confusing to look at. I am on the hunt for tech or shop locally that
can quickly do it for me.
Just out of curiosity...if I just plug them in and play without biasing what are the consequences? Would they last a week or so
until I can find someone or is it very bad for the amp and I should wait until they can be biased?
Thanks again!

It's not as difficult as you think. What model is your multimeter? I'll find a pic and see if I can help you set it up.

It's a Sperry SP-152A.
Any help would be fantastic.
I just need a basic step by step and I could probably handle it myself.

Does everyone still use the .4mv recommended bias setting?

photo-1.JPG 579k .JPG file

Here is a pic of the multi meter that I have at my disposal.

Here's a pic to help you set up your meter:

SPE-sp-152a.gif 72k .gif file

To set bias on each tube:
Insert the probes into the bias set points, holding them firmly in place. (red to +, black to-)
Insert the torx driver supplied with the amp into the hole for the bias pot, engaging the screw in there. Turn the screw VERY slowly to achieve the required bias setting. You will have to try each direction to see which way to turn it.
Read from the scale that goes to "250".
A reading of "100" would equal 1v, so you want to see a reading of "40".

Wow that is really great!!! Thanks for that!!!
I am going to attempt to do it now.
Quick question:
With the amp off do I take out the old tubes and put in
the new ones and then turn on the amp, warm up and
then adjust the bias?
Thanks again!!

Yes, remove/replace the tubes with the amp off. Allow it to warm up before adjusting. It is also good practice to turn the bias down before removing the old tubes, especially when replacing with a different tube type. Just take a reading on the current tubes and adjust the bias to a low reading, then bring it back up to target with the new tubes in place.

For those that want to get really fussy, also take a reading between the + test points on each side. Adjust one bias pot until you get a reading as close to zero as possible. The cathode resistors are pretty good quality, but still only 5% tolerance. You want an equal amount of current through each tube so there is no offset in the output transformer. Mintchris, i don't think your meter will have sufficient resolution to do this though.
Edited by rntlee - 12/29/12 at 5:45am

Well I am proud to say that I was successful in biasing the amp last night! Definitely easier than I thought and kinda rewarding when it was
all done. I will give a brief review of the Gold Lions later on since I only had some old PSB's hooked up. I can say that from the one
song we played before bed it was a big WOW!!! I am going to hook up a pair of Philharmonics tonight and will let you guys know what I think after
some serious listening!!!
Rntlee I cant thank you enough for all your help! That diagram especially was a massive help!!!
Thanks again!!!

'gratz man!
Looking forward to hearing about the new tubes.

So I am looking at possibly purchasing a tube pre-amp or a tube intergrated. I am just curious as to how you guys think the Yaqin MS-20L compares to some of the higher end brands (would be purchased as used gear, so basically the same price as the Yaqin MS-20L) such as Conrad Johnson, Audio Research, BAT, Cary Audio, ect....Does the MS-20L perform as good as some of those previously mentioned brands/models?

I woul appreciate small help,opinion.Because the volume pot is so sensitive on movement,I had cliping few days ago.The speakers burned and the electrolitic capacitors in crossover damaged - The question is - how big voltage can a cliping produce?Electrolitic capacitors breaking voltage is 70 V so it must be more then 70 v right?

I think you get more for your money with this amp than any other budget tube amp I can think of. Remote control, triode/ultralinear switchable, high tension delay circuit, headphone jack, four inputs and very clean, full sound.


What kind of speakers, FineArts? I can't imagine this amp putting out more than 25-30v to the speakers at most, barring a flashover in the output tranny. Both channels affected?

Bas reflex from Magnat - 3 and half way - 89 db sensitivity.I was listening tape dec Onkyo TA- 2570.This deck has variable output but I forgot to lower the output so while increasing the power of the amp suddenly it was like explosion.I repaired speakers but it was still sounding harsh - then I changed all electrolitic capacitors in crossover and now is again good ols sound.This volume pot is one big minus for constructor of the amp - no metter how short you press the knob on remote it has tremendous effect on power...it's really scary

How are those GL 77's working out for you?

So far they have been really great! Everything is just better. The sound is much sweeter, cleaner and overall BETTER!!!
I will say that a few times I thought I heard a strange buzzing coming from the amp but I haven't heard it in a few days so
I am hoping it was nothing. If it comes back I will update but so far I am very happy with the GL's.
I went right from the stock tubes so I have no idea if something like Mullards would be just as good but for me it was
a nice upgrade to a great little amp!

I have been running my GL for a year now. They really do sound fantastic. It really blows me away, the sound this amp puts through my Energy Veritas 2.4's. This amp has been such a great foundation for my two channel rig!

Jeff

Hi - New here but have read up on most of the comments re: the MS-20L, which has helped me to decide on ordering the "new" MC-30L - This one will come stock with the blue glass Yaqin-stamped (Shuguang-sourced) 6CA7s, and the same 6J1s as have been supplied with the 20L... It should arrive in a few days - Have nothing to compare it to but memories of a recently-departed Grant Fidelity A-348 (KT88 integrated made by Yaqin). Anyone check out this newer model yet?

I own both the Russian 6J1 and the GE JAN preamp tubes. I am getting better clarity on the Russian tubes, less aggressive, no microphonics like the GE tubes. What is everyone's preference? Currently have the Mullard Reissue for the output.

However I am now very careful with this amp.It seems that input tubes like to oscillate.I am not sure but I think when they oscillate some overvoltage peak can harm even devices conected with amp.Lately when my boxes were damaged by huge input signal,my CD player changed the sound as well.I brought it yesterday in service and they found 4 diodes in supply circuit damaged as well.They changed 4 diodes of typ IN4002 and now the sound is again warm and smooth...so handle with care what you conect to this amp..it is great amp but it can be great killer as well...not quite sure if I am right but according to what happened it must be some conection between amount of input signal and described damages

Do you have a conditioned power supply/surge protector for the amp? AC power has a lot of spikes that can really damage sensitive AV equipments

Do you have a conditioned power supply/surge protector for the amp? AC power has a lot of spikes that can really damage sensitive AV equipments

I have power conditioner Furman AC-210 AE so amp must be the sorce of spike.I was told that tubes when oscillating can produce high voltage .I wish I could egzactly know what happened but sure is that spike was there

What mods have you done to the amp, FineArts? I know you changed the coupling caps, same value replacement caps? Did you lose any tubes when the event occurred?

Well,this is very curious.The amp is working fine and phono amp Yaqin MS-12b is working fine.What is damaged is the supplay of lover level - CD player has supply of some 20 volts - there are diodes rated 100v.I persume that diodes in Yaqin amp and phono amp are rated about 1000 v so the spike was bigger then 100 but lower then 1000 v.This is in my head only possible explanation.In that very moment I didn't have Furman conditioner - CD player ,tape deck were conected to a double conversion online UPS while amp was conected to interactive UPS special made for audio amps.Now the second possibility would be that double conversion is not quite customized to use with audio power supply and for some reason it damaged diodes - however this are all my theories.One curiosity more.Even tape deck diodes are damaged and it was not on in this moment - deck was conected with power cord but was not on - so the spike possibly overjumped the switch....again...all my theories and assumptions...I just do not have enough knowledge to realize the facts but I will try to reslove this mistery at any cost...anyway Rntlee and Ktran11 thanks for your kind support ,I really appreciate that,thanks guys