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In the Forum: Melquiades Amplifier
In the Thread: Melq 6e5p driver stage for ss?
Post Subject: The drift.Posted by Romy the Cat on: 2/20/2015
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 shannon wrote:
couldnt get "insert iamge from gallary"  to work so i attached it. Had it working for a couple weeks.  Single stage 6e5p testbed.  The B+ rcore and output transformer is underneath.  In the end r23 of 30k worked with 30h choke.  no choke on gas tubes.

A question.  There is a drift of +-10mv on the input.  Do you think that is just my meter is not very good(it drifts on open air)? Is that a problem, it seems to work fine. 
 
Good project. I never was able to get any good full range result from a single stage 6e5p, it was always too stiff sound to my taste but it might means nothing as there is infinite way to do it and you might do something different. It is also a gorgeous Cat, just super cute Cat, congratulations. 
 
About the drift. This is very interesting. Are you sure that the drift does not come from the front end (preamps if you use it). Check it.  If not then pull out the positive gas tube and run it only with negative tube while do not disconnect the connection cable to your preamp. See if you have drift then. If you do then trash the negative supply tube and use another one, if you do not then replace the positive gas tube. Make sure you load the tube with 15-25 mA. If you load the tubes too little they have stability problems and if you do too much then they do the same + they run hot to touch.  Generally you shall not have any drift. I set the balance with +-1mA precision and it stay there for months and months. You might have 1-2mA per year, I never had more. Saying that I need to admit that a minor DC at input affects nothing but very small auditable click when you stitch the cable or in my case change volume (my preamp is DC coupled all the way though). If you have cap or transformer coupled front end or preamp then a few mA at amp input shall not be a problem, even though I would still trace the reason just because my anal retentiveness…

Rgs,
Romy the Cat

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