Need Help with PSVANE 6CA7-T

[sdcz]

Guys, I need your expert help. I have a Music Angel EL34 amp which has auto bias and has a very nice sound with the stock Chinese EL34 tubes.

I read that c6a7 tubes are direct replacement to EL34's so thinking that my system would be upgraded, I bought these PSVANE 6CA7-T MarkII tubes.

Upon arrival, I immediately plugged them in replacing the stock EL34 tubes.

Now I the weird thing is that the 6CA7 tubes created a very weird noise just after heating up even when my amplifier is at zero volume. So I just immediately turned off the amplifier and placed back the EL34 tubes which runs normal.

Could it be that these 6CA7 tubes are not compatible?

Thanks in advance..

 

[tinitus]

maybe they are 'recycled' tubes

meaning they might have been returned and shipped again
and maybe more than once

 

[sdcz]

Do you think so? I'm just wondering why they create this distorted sound coming from the left and right speakers.

The supplier claimed that these are brand new premium grade tubes. I sent an email to the supplier and I am waiting for their reply.

Could I file a paypal claim in case they refuse to rectify the problem?

Thanks,

 

[tinitus]

Do you think so?

I have no way to know that, ofcourse not

but I have experienced such with other things
you never know what goes on when money are at stake
not many I would trust when it comes to that

 

[sdcz]

My worry is that maybe my EL34 amplifier is not compatible with 6CA7 tubes.

 

[tinitus]

maybe question whether your stock chinese 'EL34' actually are EL34, or whether those 6CA7 actually are 6CA7

or maybe neither of them are
I would certainly question that
and I don't even know anything either

maybe someone else can help you better

 

[DF96]

6CA7 is equivalent to EL34. However, it may be that some modern 6CA7/EL34 do not exactly follow the parameters of a traditional EL34. This should not be a problem for most amplifiers. A small bias change may be enough; if cathode resistor bias is used than this will be automatic.

 

[TheGimp]

What is the weird noise like?

Possibly it could be an oscillation. This could happen if grid-stop resistors are not used. And, it could be sensitive to what set of tubes is used. In which case nothing is wrong with the tubes, but rather there is a problem with the amp itself.

 

[kevinkr]

I agree with Gimp..

 

[sdcz]

The noise are like scratching sounds.

 

[sdcz]

My amplifier has auto bias. Does it have these resistors built in?

 

[tinitus]

sounds to me like you may have to go see a professional repairman with tube amp experience

 

[sdcz]

I found the problem. I tried placing the tubes one at a time. 3 tubes did not give the noise except for 1 defective tube. So now the amp is playing with 3 6CAT and one EL34 tube.

Now its time to chase for the replacement.
Thanks for all the help!

 

[tinitus]

very good